### Goal

A Common Understanding of the Environment Over Time, and the Limitations
of

Our Understanding of this Environment.

# Table 2

The following table lists some of the morphologic and physiologic
characteristics of an aorta where an endovascular graft has been placed
for treatment of an AAA, with or without iliac involvement, that may
change from pre-treatment to post-treatment and over time. The work
assignment involved suggesting characteristics that could affect the
function or performance of an endovascular graft, identifying the range
of the values, rating the importance of the characteristics from a
clinical standpoint and providing comments. The discussion at the
workshop centered on the compiled work assignment. Both the compiled
work assignment and workshop comments are included in the table.

**Table 2 Morphologic and Physiologic Characteristics Post-Placement and
Over Time**

+----+----------+---+---+---+---+---+----------------------------+--------+
| ** |          | * |   |   |   |   | **[Comments]{.smallcaps}** | **[R   |
| [C |          | * |   |   |   |   |                            | eferen |
| ha |          | [ |   |   |   |   |                            | ces]{. |
| ra |          | C |   |   |   |   |                            | smallc |
| ct |          | r |   |   |   |   |                            | aps}** |
| er |          | i |   |   |   |   |                            |        |
| is |          | t |   |   |   |   |                            |        |
| ti |          | i |   |   |   |   |                            |        |
| c] |          | c |   |   |   |   |                            |        |
| {. |          | a |   |   |   |   |                            |        |
| sm |          | l |   |   |   |   |                            |        |
| al |          | i |   |   |   |   |                            |        |
| lc |          | t |   |   |   |   |                            |        |
| ap |          | y |   |   |   |   |                            |        |
| s} |          | ] |   |   |   |   |                            |        |
| ** |          | { |   |   |   |   |                            |        |
|    |          | . |   |   |   |   |                            |        |
|    |          | s |   |   |   |   |                            |        |
|    |          | m |   |   |   |   |                            |        |
|    |          | a |   |   |   |   |                            |        |
|    |          | l |   |   |   |   |                            |        |
|    |          | l |   |   |   |   |                            |        |
|    |          | c |   |   |   |   |                            |        |
|    |          | a |   |   |   |   |                            |        |
|    |          | p |   |   |   |   |                            |        |
|    |          | s |   |   |   |   |                            |        |
|    |          | } |   |   |   |   |                            |        |
|    |          | * |   |   |   |   |                            |        |
|    |          | * |   |   |   |   |                            |        |
+====+==========+===+===+===+===+===+============================+========+
|    |          | 1 | 2 | 3 | 4 | 5 |                            |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| ** |          |   |   |   |   |   |                            |        |
| An |          |   |   |   |   |   |                            |        |
| eu |          |   |   |   |   |   |                            |        |
| ry |          |   |   |   |   |   |                            |        |
| sm |          |   |   |   |   |   |                            |        |
| C  |          |   |   |   |   |   |                            |        |
| ha |          |   |   |   |   |   |                            |        |
| ra |          |   |   |   |   |   |                            |        |
| ct |          |   |   |   |   |   |                            |        |
| er |          |   |   |   |   |   |                            |        |
| is |          |   |   |   |   |   |                            |        |
| ti |          |   |   |   |   |   |                            |        |
| cs |          |   |   |   |   |   |                            |        |
| ** |          |   |   |   |   |   |                            |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
|    | Endoleak |   |   |   |   |   |                            |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Type I   |   |   |   | 1 | 1 | -   Critical failure mode. | Jacob  |
| -1 |          |   |   |   |   | 0 |     Primary means of       | owitz, |
|    |          |   |   |   |   |   |     addressing is with a   | 1999;  |
|    |          |   |   |   |   |   |     device / mechanical    |        |
|    |          |   |   |   |   |   |     solution.              | White, |
|    |          |   |   |   |   |   |                            | 1998;  |
|    |          |   |   |   |   |   | -   Pressure increases to  |        |
|    |          |   |   |   |   |   |     systolic               | Co     |
|    |          |   |   |   |   |   |     instantaneously.       | hnert, |
|    |          |   |   |   |   |   |                            | 2000;  |
|    |          |   |   |   |   |   | -   The first priority in  |        |
|    |          |   |   |   |   |   |     design.                | Sch    |
|    |          |   |   |   |   |   |                            | urink, |
|    |          |   |   |   |   |   | -   Equates to lack of     | 1999;  |
|    |          |   |   |   |   |   |     seal, procedural /     |        |
|    |          |   |   |   |   |   |     device failure.        | Buth,  |
|    |          |   |   |   |   |   |                            | 2000;  |
|    |          |   |   |   |   |   | **[Workshop                |        |
|    |          |   |   |   |   |   | comments:]{.underline}**   | Midor  |
|    |          |   |   |   |   |   |                            | ikawa, |
|    |          |   |   |   |   |   | **Persistent leaks need to | 1999   |
|    |          |   |   |   |   |   | be treated.**              |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Type II  | 2 | 1 | 2 | 5 | 1 | -   Critical failure mode, | Same   |
| -2 |          |   |   |   |   |   |     although not readily   | as     |
|    |          |   |   |   |   |   |     addressed through      | above  |
|    |          |   |   |   |   |   |     device/mechanical      |        |
|    |          |   |   |   |   |   |     solutions. Adjuvant    |        |
|    |          |   |   |   |   |   |     procedures become      |        |
|    |          |   |   |   |   |   |     necessary solutions.   |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Does not affect        |        |
|    |          |   |   |   |   |   |     endograft performance. |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Device independent.    |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Easier to fix but      |        |
|    |          |   |   |   |   |   |     harder to diagnose.    |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Likely to also be      |        |
|    |          |   |   |   |   |   |     related to, and        |        |
|    |          |   |   |   |   |   |     influenced by, all     |        |
|    |          |   |   |   |   |   |     other types of         |        |
|    |          |   |   |   |   |   |     endoleaks (i.e., if    |        |
|    |          |   |   |   |   |   |     Type I, III, IV are    |        |
|    |          |   |   |   |   |   |     present, collaterals   |        |
|    |          |   |   |   |   |   |     may never clot off and |        |
|    |          |   |   |   |   |   |     seal).                 |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   IMA or accessory renal |        |
|    |          |   |   |   |   |   |     to lumbar is           |        |
|    |          |   |   |   |   |   |     significant,           |        |
|    |          |   |   |   |   |   |     lumbar-lumbar usually  |        |
|    |          |   |   |   |   |   |     is not.                |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   May result in dampened |        |
|    |          |   |   |   |   |   |     pressure so probably   |        |
|    |          |   |   |   |   |   |     will not reach         |        |
|    |          |   |   |   |   |   |     systolic.              |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | **[Workshop                |        |
|    |          |   |   |   |   |   | comments:]{.underline}**   |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **With respect to      |        |
|    |          |   |   |   |   |   |     whether type II        |        |
|    |          |   |   |   |   |   |     endoleaks need to be   |        |
|    |          |   |   |   |   |   |     incorporated into      |        |
|    |          |   |   |   |   |   |     pre-clinical models,   |        |
|    |          |   |   |   |   |   |     the consensus was that |        |
|    |          |   |   |   |   |   |     the loads on the       |        |
|    |          |   |   |   |   |   |     device are highest     |        |
|    |          |   |   |   |   |   |     with a completely      |        |
|    |          |   |   |   |   |   |     excluded aneurysm, so  |        |
|    |          |   |   |   |   |   |     this characteristic    |        |
|    |          |   |   |   |   |   |     does not need to be    |        |
|    |          |   |   |   |   |   |     included in the        |        |
|    |          |   |   |   |   |   |     modeling.**            |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | ```{=html}                 |        |
|    |          |   |   |   |   |   | <!-- -->                   |        |
|    |          |   |   |   |   |   | ```                        |        |
|    |          |   |   |   |   |   | -   **There is a question  |        |
|    |          |   |   |   |   |   |     as to what impact the  |        |
|    |          |   |   |   |   |   |     pressure gradient      |        |
|    |          |   |   |   |   |   |     could have on device   |        |
|    |          |   |   |   |   |   |     performance, however,  |        |
|    |          |   |   |   |   |   |     this was thought to    |        |
|    |          |   |   |   |   |   |     probably be an         |        |
|    |          |   |   |   |   |   |     academic question.**   |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Type III |   |   | 1 | 2 | 8 | -   Critical potential     | Same   |
| -3 |          |   |   |   |   |   |     failure mode over      | as     |
|    |          |   |   |   |   |   |     chronic intervals of   | above  |
|    |          |   |   |   |   |   |     time.                  |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Important only if it   |        |
|    |          |   |   |   |   |   |     persists.              |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Device failure. May be |        |
|    |          |   |   |   |   |   |     fixable by additional  |        |
|    |          |   |   |   |   |   |     intervention.          |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Critical given         |        |
|    |          |   |   |   |   |   |     post-implant           |        |
|    |          |   |   |   |   |   |     morphological changes. |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Pressure increases to  |        |
|    |          |   |   |   |   |   |     systolic               |        |
|    |          |   |   |   |   |   |     instantaneously.       |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Type IV  |   |   | 2 | 6 | 2 | -   Controllable failure   | Same   |
| -4 |          |   |   |   |   |   |     mode that can be       | as     |
|    |          |   |   |   |   |   |     addressed at the       | above  |
|    |          |   |   |   |   |   |     design level.          |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Important only if      |        |
|    |          |   |   |   |   |   |     persists.              |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Not a major acute      |        |
|    |          |   |   |   |   |   |     issue; major if        |        |
|    |          |   |   |   |   |   |     chronic.               |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Graft is there to      |        |
|    |          |   |   |   |   |   |     provide seal. It's     |        |
|    |          |   |   |   |   |   |     failure equates to     |        |
|    |          |   |   |   |   |   |     pressure transmission. |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   If increased porosity  |        |
|    |          |   |   |   |   |   |     persists, then could   |        |
|    |          |   |   |   |   |   |     have potential         |        |
|    |          |   |   |   |   |   |     systolic pressure.     |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Long     |   |   | 5 | 4 | 2 | -   May produce end shear  | H      |
| -5 | itudinal |   |   |   |   |   |     between implant and    | arris, |
|    | s        |   |   |   |   |   |     vessel walls=\>        | 1999   |
|    | hrinkage |   |   |   |   |   |     migration, leak,       |        |
|    |          |   |   |   |   |   |     compressive loads in   |        |
|    |          |   |   |   |   |   |     device =\> fatigue     |        |
|    |          |   |   |   |   |   |     failures,              |        |
|    |          |   |   |   |   |   |     buckling/kinking.      |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Depends on graft type. |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Kinks and angles       |        |
|    |          |   |   |   |   |   |     possible.              |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Change in morphology   |        |
|    |          |   |   |   |   |   |     may lead to fabric and |        |
|    |          |   |   |   |   |   |     stent relative motion  |        |
|    |          |   |   |   |   |   |     or                     |        |
|    |          |   |   |   |   |   |     kinking/obstruction.   |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Should accommodate     |        |
|    |          |   |   |   |   |   |     morphological changes, |        |
|    |          |   |   |   |   |   |     but not loose seals.   |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Significant potential  |        |
|    |          |   |   |   |   |   |     source of post-implant |        |
|    |          |   |   |   |   |   |     complications not      |        |
|    |          |   |   |   |   |   |     readily addressed by   |        |
|    |          |   |   |   |   |   |     device/mechanical      |        |
|    |          |   |   |   |   |   |     solutions.             |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Conflicting data in    |        |
|    |          |   |   |   |   |   |     literature. May affect |        |
|    |          |   |   |   |   |   |     certain graft designs  |        |
|    |          |   |   |   |   |   |     more than others.      |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | **[Workshop                |        |
|    |          |   |   |   |   |   | comments:]{.underline}**   |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **Does longitudinal    |        |
|    |          |   |   |   |   |   |     shrinkage occur? There |        |
|    |          |   |   |   |   |   |     was no consensus. 24%  |        |
|    |          |   |   |   |   |   |     decreased length of    |        |
|    |          |   |   |   |   |   |     \>5mm. There is some   |        |
|    |          |   |   |   |   |   |     shortening and some    |        |
|    |          |   |   |   |   |   |     lengthening.**         |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | ```{=html}                 |        |
|    |          |   |   |   |   |   | <!-- -->                   |        |
|    |          |   |   |   |   |   | ```                        |        |
|    |          |   |   |   |   |   | -   **If there is          |        |
|    |          |   |   |   |   |   |     longitudinal           |        |
|    |          |   |   |   |   |   |     shrinking, is it       |        |
|    |          |   |   |   |   |   |     related to device      |        |
|    |          |   |   |   |   |   |     failure as an isolated |        |
|    |          |   |   |   |   |   |     variable? The question |        |
|    |          |   |   |   |   |   |     was raised, with no    |        |
|    |          |   |   |   |   |   |     conclusion drawn.**    |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Pressure |   | 2 | 1 | 6 | 3 | -   Higher the pressure -- | Baum,  |
| -6 | inside   |   |   |   |   |   |     worse the scenario.    | 2001;  |
|    | the      |   |   |   |   |   |                            |        |
|    | aneurysm |   |   |   |   |   | -   Probably not an issue  | White, |
|    |          |   |   |   |   |   |     if sac pressure does   | 1999   |
|    |          |   |   |   |   |   |     not ever increase      |        |
|    |          |   |   |   |   |   |     above systemic         |        |
|    |          |   |   |   |   |   |     diastolic; but major   |        |
|    |          |   |   |   |   |   |     issue with increased   |        |
|    |          |   |   |   |   |   |     aneurysm size.         |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Subtle failure mode    |        |
|    |          |   |   |   |   |   |     that has potentially   |        |
|    |          |   |   |   |   |   |     catastrophic           |        |
|    |          |   |   |   |   |   |     consequences. Due to   |        |
|    |          |   |   |   |   |   |     association with       |        |
|    |          |   |   |   |   |   |     retrograde perfusion,  |        |
|    |          |   |   |   |   |   |     more of a diagnostic / |        |
|    |          |   |   |   |   |   |     follow-up issue than a |        |
|    |          |   |   |   |   |   |     device issue.          |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Impact not             |        |
|    |          |   |   |   |   |   |     well-understood;       |        |
|    |          |   |   |   |   |   |     affects clotting       |        |
|    |          |   |   |   |   |   |     study, porosity        |        |
|    |          |   |   |   |   |   |     assumptions.           |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Pressure = force =     |        |
|    |          |   |   |   |   |   |     failed protection of   |        |
|    |          |   |   |   |   |   |     sac. What's more       |        |
|    |          |   |   |   |   |   |     important, mean        |        |
|    |          |   |   |   |   |   |     pressure or pulse      |        |
|    |          |   |   |   |   |   |     pressure?              |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Shape    | 1 | 2 | 3 | 2 | 2 | -   Localized enlargement  | White, |
| -7 |          |   |   |   |   |   |     reflects pressure.     | 2001;  |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Saccular vs.           | Resch, |
|    |          |   |   |   |   |   |     Concentric.            | 2000;  |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Device performance is  | S      |
|    |          |   |   |   |   |   |     largely independent of | ingh-R |
|    |          |   |   |   |   |   |     post-implant AAA       | anger, |
|    |          |   |   |   |   |   |     shape.                 | 2000;  |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Angles, size of        | M      |
|    |          |   |   |   |   |   |     "waist" (distal        | alina, |
|    |          |   |   |   |   |   |     aorta), fusiform /     | 1997   |
|    |          |   |   |   |   |   |     saccular has           |        |
|    |          |   |   |   |   |   |     modularity             |        |
|    |          |   |   |   |   |   |     considerations. Iliac  |        |
|    |          |   |   |   |   |   |     take-off angles and    |        |
|    |          |   |   |   |   |   |     bends are important.   |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Different etiology may |        |
|    |          |   |   |   |   |   |     impart differing       |        |
|    |          |   |   |   |   |   |     post-graft implant     |        |
|    |          |   |   |   |   |   |     physiology.            |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Size     | 1 |   | 5 | 5 | 1 | -   Change in size is most | Wolf,  |
| -8 |          |   |   |   |   |   |     important.             | 2000;  |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Criticality = 3,       | May,   |
|    |          |   |   |   |   |   |     assuming size refers   | 1995   |
|    |          |   |   |   |   |   |     to diameter.           |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Device performance can |        |
|    |          |   |   |   |   |   |     be monitored /         |        |
|    |          |   |   |   |   |   |     characterized via its  |        |
|    |          |   |   |   |   |   |     ability to induce a    |        |
|    |          |   |   |   |   |   |     reduction in           |        |
|    |          |   |   |   |   |   |     aneurysmal diameter /  |        |
|    |          |   |   |   |   |   |     volume.                |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Correlation to necks   |        |
|    |          |   |   |   |   |   |     is more important.     |        |
|    |          |   |   |   |   |   |     Also, largest sizes    |        |
|    |          |   |   |   |   |   |     with or without        |        |
|    |          |   |   |   |   |   |     significant shrinking  |        |
|    |          |   |   |   |   |   |     may expect greatest    |        |
|    |          |   |   |   |   |   |     post-implant           |        |
|    |          |   |   |   |   |   |     morphological changes. |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   It takes less force to |        |
|    |          |   |   |   |   |   |     further expand and     |        |
|    |          |   |   |   |   |   |     complicate a larger    |        |
|    |          |   |   |   |   |   |     aneurysm.              |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | To       |   | 1 | 2 | 4 | 5 | -   Can produce load       |        |
| -9 | rtuosity |   |   |   |   |   |     concentration in       |        |
|    | /        |   |   |   |   |   |     implant. Can increase  |        |
|    | an       |   |   |   |   |   |     loads on vessel        |        |
|    | gulation |   |   |   |   |   |     attachment and modular |        |
|    |          |   |   |   |   |   |     component joints.      |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Fatigue and            |        |
|    |          |   |   |   |   |   |     thrombosis.            |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Critical to access,    |        |
|    |          |   |   |   |   |   |     seal fixation,         |        |
|    |          |   |   |   |   |   |     migration resistance.  |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   After initial          |        |
|    |          |   |   |   |   |   |     placement, criticality |        |
|    |          |   |   |   |   |   |     decreases.             |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Post-implant AAA       |        |
|    |          |   |   |   |   |   |     angulation is          |        |
|    |          |   |   |   |   |   |     significant only if it |        |
|    |          |   |   |   |   |   |     affects patency and    |        |
|    |          |   |   |   |   |   |     mechanical             |        |
|    |          |   |   |   |   |   |     performance. It is     |        |
|    |          |   |   |   |   |   |     anticipated that       |        |
|    |          |   |   |   |   |   |     device performance is  |        |
|    |          |   |   |   |   |   |     largely independent of |        |
|    |          |   |   |   |   |   |     post-implant AAA       |        |
|    |          |   |   |   |   |   |     angulation.            |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Quality of anchorage   |        |
|    |          |   |   |   |   |   |     and flexibility match  |        |
|    |          |   |   |   |   |   |     with graft; impart     |        |
|    |          |   |   |   |   |   |     dynamics on the        |        |
|    |          |   |   |   |   |   |     post-implanted graft.  |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | **[Workshop                |        |
|    |          |   |   |   |   |   | comments:]{.underline}**   |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **Angulation in the    |        |
|    |          |   |   |   |   |   |     device is created by   |        |
|    |          |   |   |   |   |   |     changes in volume,     |        |
|    |          |   |   |   |   |   |     shape and size of the  |        |
|    |          |   |   |   |   |   |     aneurysm.**            |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | ```{=html}                 |        |
|    |          |   |   |   |   |   | <!-- -->                   |        |
|    |          |   |   |   |   |   | ```                        |        |
|    |          |   |   |   |   |   | -   **Device needs to be   |        |
|    |          |   |   |   |   |   |     able to accommodate    |        |
|    |          |   |   |   |   |   |     such changes.**        |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2- | Volume   | 1 | 1 | 5 | 1 | 2 | -   How does this relate   | Rhee,  |
| 10 |          |   |   |   |   |   |     to rupture?            | 2000   |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Discriminator of       |        |
|    |          |   |   |   |   |   |     depressurization &     |        |
|    |          |   |   |   |   |   |     helpful to define      |        |
|    |          |   |   |   |   |   |     significance of leak   |        |
|    |          |   |   |   |   |   |     or no change in        |        |
|    |          |   |   |   |   |   |     diameter               |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   More important than    |        |
|    |          |   |   |   |   |   |     diameter.              |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Ongoing investigation  |        |
|    |          |   |   |   |   |   |     of this attribute.     |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Device performance can |        |
|    |          |   |   |   |   |   |     be monitored /         |        |
|    |          |   |   |   |   |   |     characterized via its  |        |
|    |          |   |   |   |   |   |     ability to induce a    |        |
|    |          |   |   |   |   |   |     reduction in           |        |
|    |          |   |   |   |   |   |     aneurysmal diameter /  |        |
|    |          |   |   |   |   |   |     volume.                |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | **[Workshop                |        |
|    |          |   |   |   |   |   | comments:]{.underline}**   |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **When the centerline  |        |
|    |          |   |   |   |   |   |     angles are great and   |        |
|    |          |   |   |   |   |   |     associated with volume |        |
|    |          |   |   |   |   |   |     changes this is        |        |
|    |          |   |   |   |   |   |     associated with        |        |
|    |          |   |   |   |   |   |     increases in stresses  |        |
|    |          |   |   |   |   |   |     on the device.**       |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Thrombus |   |   |   |   |   | -   No thrombus=\> Type II |        |
| -1 | in sac   |   |   |   |   |   |     leak may be less       |        |
| 0a |          |   |   |   |   |   |     likely to seal.        |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | **[Workshop                |        |
|    |          |   |   |   |   |   | comments:]{.underline}**   |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **Thrombus is not      |        |
|    |          |   |   |   |   |   |     stable in volume or    |        |
|    |          |   |   |   |   |   |     physiologic            |        |
|    |          |   |   |   |   |   |     characteristics, but   |        |
|    |          |   |   |   |   |   |     this cannot be modeled |        |
|    |          |   |   |   |   |   |     on the bench.**        |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Long     |   |   | 1 |   |   |                            |        |
| -1 | itudinal |   |   |   |   |   |                            |        |
| 0b | len      |   |   |   |   |   |                            |        |
|    | gthening |   |   |   |   |   |                            |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | A        | 1 |   |   |   |   | -   Asymmetry can force    |        |
| -1 | symmetry |   |   |   |   |   |     unusual fits which     |        |
| 0c | of       |   |   |   |   |   |     must be explored and   |        |
|    | iliacs   |   |   |   |   |   |     tested (often outside  |        |
|    |          |   |   |   |   |   |     of ideal IFU           |        |
|    |          |   |   |   |   |   |     conditions).           |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | **[Workshop                |        |
|    |          |   |   |   |   |   | comments:]{.underline}**   |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **Pressure is the      |        |
|    |          |   |   |   |   |   |     overriding factor and  |        |
|    |          |   |   |   |   |   |     flow forces            |        |
|    |          |   |   |   |   |   |     negligible.**          |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | ```{=html}                 |        |
|    |          |   |   |   |   |   | <!-- -->                   |        |
|    |          |   |   |   |   |   | ```                        |        |
|    |          |   |   |   |   |   | -   **Static forces are    |        |
|    |          |   |   |   |   |   |     dominant. Whether they |        |
|    |          |   |   |   |   |   |     are important depends  |        |
|    |          |   |   |   |   |   |     on the device          |        |
|    |          |   |   |   |   |   |     design.**              |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Volume,  |   | 2 |   |   |   |                            |        |
| -1 | absolute |   |   |   |   |   |                            |        |
| 0d |          |   |   |   |   |   |                            |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Volume,  |   |   |   |   | 1 | -   Trend is more          |        |
| -1 | trend    |   |   |   |   |   |     important than         |        |
| 0e |          |   |   |   |   |   |     absolute numbers.      |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
|    | **Vo     |   |   |   |   |   | **[Workshop                |        |
|    | lumetric |   |   |   |   |   | comments:]{.underline}**   |        |
|    | change   |   |   |   |   |   |                            |        |
|    | in sac   |   |   |   |   |   | -   **Could you model      |        |
|    | with     |   |   |   |   |   |     change in diameter,    |        |
|    | changes  |   |   |   |   |   |     shape,...?**           |        |
|    | in shape |   |   |   |   |   |                            |        |
|    | and      |   |   |   |   |   | -   **Angulation change    |        |
|    | size**   |   |   |   |   |   |     and shape change that  |        |
|    |          |   |   |   |   |   |     results from volume    |        |
|    |          |   |   |   |   |   |     change are vectors.**  |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | ```{=html}                 |        |
|    |          |   |   |   |   |   | <!-- -->                   |        |
|    |          |   |   |   |   |   | ```                        |        |
|    |          |   |   |   |   |   | -   **Is it necessary to   |        |
|    |          |   |   |   |   |   |     test dynamic changes   |        |
|    |          |   |   |   |   |   |     or extremes? Should    |        |
|    |          |   |   |   |   |   |     they be evaluated      |        |
|    |          |   |   |   |   |   |     separately or          |        |
|    |          |   |   |   |   |   |     combined?**            |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| Ne |          |   |   |   |   |   |                            |        |
| ck |          |   |   |   |   |   |                            |        |
| C  |          |   |   |   |   |   |                            |        |
| ha |          |   |   |   |   |   |                            |        |
| ra |          |   |   |   |   |   |                            |        |
| ct |          |   |   |   |   |   |                            |        |
| er |          |   |   |   |   |   |                            |        |
| is |          |   |   |   |   |   |                            |        |
| ti |          |   |   |   |   |   |                            |        |
| cs |          |   |   |   |   |   |                            |        |
|  - |          |   |   |   |   |   |                            |        |
| *  |          |   |   |   |   |   |                            |        |
| *[ |          |   |   |   |   |   |                            |        |
| Wo |          |   |   |   |   |   |                            |        |
| rk |          |   |   |   |   |   |                            |        |
| sh |          |   |   |   |   |   |                            |        |
| op |          |   |   |   |   |   |                            |        |
| co |          |   |   |   |   |   |                            |        |
| mm |          |   |   |   |   |   |                            |        |
| en |          |   |   |   |   |   |                            |        |
| ts |          |   |   |   |   |   |                            |        |
| :] |          |   |   |   |   |   |                            |        |
| {. |          |   |   |   |   |   |                            |        |
| un |          |   |   |   |   |   |                            |        |
| de |          |   |   |   |   |   |                            |        |
| rl |          |   |   |   |   |   |                            |        |
| in |          |   |   |   |   |   |                            |        |
| e} |          |   |   |   |   |   |                            |        |
| Sh |          |   |   |   |   |   |                            |        |
| ou |          |   |   |   |   |   |                            |        |
| ld |          |   |   |   |   |   |                            |        |
| t  |          |   |   |   |   |   |                            |        |
| he |          |   |   |   |   |   |                            |        |
| ne |          |   |   |   |   |   |                            |        |
| ck |          |   |   |   |   |   |                            |        |
| ch |          |   |   |   |   |   |                            |        |
| an |          |   |   |   |   |   |                            |        |
| ge |          |   |   |   |   |   |                            |        |
| in |          |   |   |   |   |   |                            |        |
| t  |          |   |   |   |   |   |                            |        |
| he |          |   |   |   |   |   |                            |        |
| m  |          |   |   |   |   |   |                            |        |
| od |          |   |   |   |   |   |                            |        |
| el |          |   |   |   |   |   |                            |        |
| ov |          |   |   |   |   |   |                            |        |
| er |          |   |   |   |   |   |                            |        |
| t  |          |   |   |   |   |   |                            |        |
| im |          |   |   |   |   |   |                            |        |
| e? |          |   |   |   |   |   |                            |        |
| Is |          |   |   |   |   |   |                            |        |
| t  |          |   |   |   |   |   |                            |        |
| he |          |   |   |   |   |   |                            |        |
| an |          |   |   |   |   |   |                            |        |
| sw |          |   |   |   |   |   |                            |        |
| er |          |   |   |   |   |   |                            |        |
| to |          |   |   |   |   |   |                            |        |
| th |          |   |   |   |   |   |                            |        |
| is |          |   |   |   |   |   |                            |        |
| qu |          |   |   |   |   |   |                            |        |
| es |          |   |   |   |   |   |                            |        |
| ti |          |   |   |   |   |   |                            |        |
| on |          |   |   |   |   |   |                            |        |
| de |          |   |   |   |   |   |                            |        |
| vi |          |   |   |   |   |   |                            |        |
| ce |          |   |   |   |   |   |                            |        |
| sp |          |   |   |   |   |   |                            |        |
| ec |          |   |   |   |   |   |                            |        |
| if |          |   |   |   |   |   |                            |        |
| ic |          |   |   |   |   |   |                            |        |
| (e |          |   |   |   |   |   |                            |        |
| .g |          |   |   |   |   |   |                            |        |
| ., |          |   |   |   |   |   |                            |        |
| b  |          |   |   |   |   |   |                            |        |
| al |          |   |   |   |   |   |                            |        |
| lo |          |   |   |   |   |   |                            |        |
| on |          |   |   |   |   |   |                            |        |
| -e |          |   |   |   |   |   |                            |        |
| xp |          |   |   |   |   |   |                            |        |
| an |          |   |   |   |   |   |                            |        |
| di |          |   |   |   |   |   |                            |        |
| ng |          |   |   |   |   |   |                            |        |
| ve |          |   |   |   |   |   |                            |        |
| rs |          |   |   |   |   |   |                            |        |
| us |          |   |   |   |   |   |                            |        |
| s  |          |   |   |   |   |   |                            |        |
| el |          |   |   |   |   |   |                            |        |
| f- |          |   |   |   |   |   |                            |        |
| ex |          |   |   |   |   |   |                            |        |
| pa |          |   |   |   |   |   |                            |        |
| nd |          |   |   |   |   |   |                            |        |
| in |          |   |   |   |   |   |                            |        |
| g; |          |   |   |   |   |   |                            |        |
| mo |          |   |   |   |   |   |                            |        |
| re |          |   |   |   |   |   |                            |        |
| or |          |   |   |   |   |   |                            |        |
| le |          |   |   |   |   |   |                            |        |
| ss |          |   |   |   |   |   |                            |        |
| ra |          |   |   |   |   |   |                            |        |
| di |          |   |   |   |   |   |                            |        |
| al |          |   |   |   |   |   |                            |        |
| f  |          |   |   |   |   |   |                            |        |
| or |          |   |   |   |   |   |                            |        |
| ce |          |   |   |   |   |   |                            |        |
| )? |          |   |   |   |   |   |                            |        |
| ** |          |   |   |   |   |   |                            |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2- | Neck     |   |   | 1 | 3 | 8 | -   Load concentration,    |        |
| 11 | angles   |   |   |   |   |   |     kink potential,        |        |
|    |          |   |   |   |   |   |     sealing challenge.     |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Threatens length of    |        |
|    |          |   |   |   |   |   |     fixation.              |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Important for          |        |
|    |          |   |   |   |   |   |     anchoring and sealing. |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   May lead to unstable   |        |
|    |          |   |   |   |   |   |     graft attachment.      |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | **[Workshop                |        |
|    |          |   |   |   |   |   | comments:]{.underline}**   |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **There was agreement  |        |
|    |          |   |   |   |   |   |     that 2-11, 2-12, and   |        |
|    |          |   |   |   |   |   |     2-13 are the most      |        |
|    |          |   |   |   |   |   |     important attributes   |        |
|    |          |   |   |   |   |   |     to consider.**         |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2- | Neck     | 1 |   |   | 2 | 8 | -   Short length -         | May,   |
| 12 | lengths  |   |   |   |   |   |     potential loss of      | 1996   |
|    |          |   |   |   |   |   |     seal.                  |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Important for          |        |
|    |          |   |   |   |   |   |     anchoring and sealing. |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Impact on seal.        |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Difficult to measure.  |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2- | Neck     | 1 | 1 |   | 6 | 3 | -   Reverse cones --       |        |
| 13 | shape    |   |   |   |   |   |     potential leaks.       |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Concentric; Ellipse;   |        |
|    |          |   |   |   |   |   |     Irregular; Beveled;    |        |
|    |          |   |   |   |   |   |     Tapered; Flared.       |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Difficult to measure.  |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Post implant neck      |        |
|    |          |   |   |   |   |   |     shape is not expected  |        |
|    |          |   |   |   |   |   |     to have a critical     |        |
|    |          |   |   |   |   |   |     bearing on device      |        |
|    |          |   |   |   |   |   |     performance. This      |        |
|    |          |   |   |   |   |   |     consideration is       |        |
|    |          |   |   |   |   |   |     better addressed at    |        |
|    |          |   |   |   |   |   |     the time of            |        |
|    |          |   |   |   |   |   |     patient/device         |        |
|    |          |   |   |   |   |   |     selection.             |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Impact on seal.        |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2- | Neck     |   |   | 3 | 3 | 5 | -   Size change more       | Wever, |
| 14 | size     |   |   |   |   |   |     important.             | 2000   |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Very large \>30mm may  | Mats   |
|    |          |   |   |   |   |   |     have increased         | umura, |
|    |          |   |   |   |   |   |     potential for further  | 1998   |
|    |          |   |   |   |   |   |     enlargement, requiring |        |
|    |          |   |   |   |   |   |     increased              |        |
|    |          |   |   |   |   |   |     surveillance.          |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Important, if          |        |
|    |          |   |   |   |   |   |     changing.              |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Criticality = 5,       |        |
|    |          |   |   |   |   |   |     assuming size refers   |        |
|    |          |   |   |   |   |   |     to diameter            |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Time-dependent changes |        |
|    |          |   |   |   |   |   |     in neck diameter can   |        |
|    |          |   |   |   |   |   |     have negative patient  |        |
|    |          |   |   |   |   |   |     consequences.          |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Impact on quality of   |        |
|    |          |   |   |   |   |   |     neck. Large necks are  |        |
|    |          |   |   |   |   |   |     invariably pre-dilated |        |
|    |          |   |   |   |   |   |     through disease and    |        |
|    |          |   |   |   |   |   |     other factors.         |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | **[Workshop                |        |
|    |          |   |   |   |   |   | comments:]{.underline}**   |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **This characteristic  |        |
|    |          |   |   |   |   |   |     is important for       |        |
|    |          |   |   |   |   |   |     pre-clinical *in vivo* |        |
|    |          |   |   |   |   |   |     testing.**             |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Neck     |   |   |   | 1 |   | -   Devices are usually    |        |
| -1 | cross-s  |   |   |   |   |   |     considered as a round  |        |
| 4a | ectional |   |   |   |   |   |     shape, all patients do |        |
|    | shape    |   |   |   |   |   |     not present with       |        |
|    |          |   |   |   |   |   |     perfect circular       |        |
|    |          |   |   |   |   |   |     proximal neck.         |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| H  |          |   |   |   |   |   |                            |        |
| em |          |   |   |   |   |   |                            |        |
| od |          |   |   |   |   |   |                            |        |
| yn |          |   |   |   |   |   |                            |        |
| am |          |   |   |   |   |   |                            |        |
| ic |          |   |   |   |   |   |                            |        |
| R  |          |   |   |   |   |   |                            |        |
| el |          |   |   |   |   |   |                            |        |
| at |          |   |   |   |   |   |                            |        |
| ed |          |   |   |   |   |   |                            |        |
| C  |          |   |   |   |   |   |                            |        |
| ha |          |   |   |   |   |   |                            |        |
| ra |          |   |   |   |   |   |                            |        |
| ct |          |   |   |   |   |   |                            |        |
| er |          |   |   |   |   |   |                            |        |
| is |          |   |   |   |   |   |                            |        |
| ti |          |   |   |   |   |   |                            |        |
| cs |          |   |   |   |   |   |                            |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2- | Blood    |   | 4 | 5 | 1 |   | -   Pathway may change as  |        |
| 15 | flow     |   |   |   |   |   |     morphology of          |        |
|    | pathway  |   |   |   |   |   |     stent-graft changes.   |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Potential sign of      |        |
|    |          |   |   |   |   |   |     thrombosis?            |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   How the graft fits /   |        |
|    |          |   |   |   |   |   |     pathway compare to     |        |
|    |          |   |   |   |   |   |     blood flow.            |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2- | Blood    | 2 | 3 | 4 | 2 |   | -   Interrelated to 2-20.  |        |
| 16 | flow     |   |   |   |   |   |                            |        |
|    | rate     |   |   |   |   |   |                            |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2- | C        | 1 | 2 | 3 | 4 | 1 | -   Depends on what is     |        |
| 17 | orrosive |   |   |   |   |   |     being degraded.        |        |
|    | env      |   |   |   |   |   |                            |        |
|    | ironment |   |   |   |   |   | -   Pitting is not a major |        |
|    |          |   |   |   |   |   |     problem.               |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Known factors.         |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   pH, electrolytes,      |        |
|    |          |   |   |   |   |   |     temperature.           |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | **[Workshop                |        |
|    |          |   |   |   |   |   | comments:]{.underline}**   |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **Standards are not    |        |
|    |          |   |   |   |   |   |     well defined. It is    |        |
|    |          |   |   |   |   |   |     unclear how to         |        |
|    |          |   |   |   |   |   |     evaluate corrosion.    |        |
|    |          |   |   |   |   |   |     How to test is in      |        |
|    |          |   |   |   |   |   |     ASTM. Interpretation   |        |
|    |          |   |   |   |   |   |     of results is not      |        |
|    |          |   |   |   |   |   |     standardized. No       |        |
|    |          |   |   |   |   |   |     threshold has been     |        |
|    |          |   |   |   |   |   |     established. The data  |        |
|    |          |   |   |   |   |   |     need to be considered  |        |
|    |          |   |   |   |   |   |     in comparison to other |        |
|    |          |   |   |   |   |   |     devices, that is this  |        |
|    |          |   |   |   |   |   |     parameter is           |        |
|    |          |   |   |   |   |   |     relative.**            |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **Corrosion is not     |        |
|    |          |   |   |   |   |   |     defined in a           |        |
|    |          |   |   |   |   |   |     biological sense.**    |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **Has corrosion lead   |        |
|    |          |   |   |   |   |   |     to a clinical problem  |        |
|    |          |   |   |   |   |   |     or device problem?**   |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **Martin King reported |        |
|    |          |   |   |   |   |   |     that in Eurostar they  |        |
|    |          |   |   |   |   |   |     have seen corrosion.   |        |
|    |          |   |   |   |   |   |     Specifically in        |        |
|    |          |   |   |   |   |   |     Nitinol and it has     |        |
|    |          |   |   |   |   |   |     been pitting           |        |
|    |          |   |   |   |   |   |     corrosion. The         |        |
|    |          |   |   |   |   |   |     corrosion is due to    |        |
|    |          |   |   |   |   |   |     the chemical           |        |
|    |          |   |   |   |   |   |     environment and the    |        |
|    |          |   |   |   |   |   |     interaction of         |        |
|    |          |   |   |   |   |   |     dissimilar metals.     |        |
|    |          |   |   |   |   |   |     Corrosion has been     |        |
|    |          |   |   |   |   |   |     associated with        |        |
|    |          |   |   |   |   |   |     failure of the wire.** |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **Is there a test to   |        |
|    |          |   |   |   |   |   |     predict whether there  |        |
|    |          |   |   |   |   |   |     will be corrosion?**   |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **For pre-clinical     |        |
|    |          |   |   |   |   |   |     testing it is          |        |
|    |          |   |   |   |   |   |     important to consider  |        |
|    |          |   |   |   |   |   |     other materials        |        |
|    |          |   |   |   |   |   |     interacting with       |        |
|    |          |   |   |   |   |   |     graft.**               |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **It is known that     |        |
|    |          |   |   |   |   |   |     non-electropolished    |        |
|    |          |   |   |   |   |   |     surfaces get           |        |
|    |          |   |   |   |   |   |     pitting.**             |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **Processing is        |        |
|    |          |   |   |   |   |   |     critical.**            |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | ```{=html}                 |        |
|    |          |   |   |   |   |   | <!-- -->                   |        |
|    |          |   |   |   |   |   | ```                        |        |
|    |          |   |   |   |   |   | -   **The difference       |        |
|    |          |   |   |   |   |   |     between corrosion and  |        |
|    |          |   |   |   |   |   |     crazing must be        |        |
|    |          |   |   |   |   |   |     considered.**          |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2- | Impact   | 2 | 3 | 3 | 3 |   | -   Dynamic (impact)       | See    |
| 18 | forces   |   |   |   |   |   |     forces are likely      | Com    |
|    |          |   |   |   |   |   |     small compared to      | ments, |
|    |          |   |   |   |   |   |     pressure forces.       | below  |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Pulse pressure; loads  |        |
|    |          |   |   |   |   |   |     may increase.          |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Force = movement. No   |        |
|    |          |   |   |   |   |   |     force = no movement.   |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2- | Kinetic  | 1 | 2 | 3 | 4 |   | -   Inertial forces are    | See    |
| 19 | (i       |   |   |   |   |   |     likely small compared  | Com    |
|    | nertial) |   |   |   |   |   |     to pressure forces.    | ments, |
|    | forces   |   |   |   |   |   |                            | below  |
|    |          |   |   |   |   |   | -   Blood flow             |        |
|    |          |   |   |   |   |   |     pathway-related.       |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Shear, impact, kinetic |        |
|    |          |   |   |   |   |   |     are in same category,  |        |
|    |          |   |   |   |   |   |     but different loads    |        |
|    |          |   |   |   |   |   |     than post-implant      |        |
|    |          |   |   |   |   |   |     morphological changes. |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Force = movement. No   |        |
|    |          |   |   |   |   |   |     force = no movement.   |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2- | Shear    | 1 | 4 | 3 | 3 |   | -   Hemodynamic (viscous)  | See    |
| 20 | forces   |   |   |   |   |   |     shear forces are small | Com    |
|    |          |   |   |   |   |   |     compared to pressure   | ments, |
|    |          |   |   |   |   |   |     forces. Shear forces   | below  |
|    |          |   |   |   |   |   |     acting on              |        |
|    |          |   |   |   |   |   |     device-vessel wall     |        |
|    |          |   |   |   |   |   |     interface (not         |        |
|    |          |   |   |   |   |   |     hemodynamic) may be    |        |
|    |          |   |   |   |   |   |     quite large in some    |        |
|    |          |   |   |   |   |   |     situations.            |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Interrelated to 2-16.  |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Small compared to 2-18 |        |
|    |          |   |   |   |   |   |     and 2-19.              |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Occur at points of     |        |
|    |          |   |   |   |   |   |     impedance mismatch.    |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Cyclic   |   |   |   |   | 1 | -   Critical factor in     |        |
| -2 | loads    |   |   |   |   |   |     device design and      |        |
| 0a | arising  |   |   |   |   |   |     durability. May        |        |
|    | from     |   |   |   |   |   |     produce axial tension, |        |
|    | pulse    |   |   |   |   |   |     compression, or        |        |
|    | pressure |   |   |   |   |   |     bending in device      |        |
|    |          |   |   |   |   |   |     depending on design    |        |
|    |          |   |   |   |   |   |     and anatomy.           |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Pulse    |   |   | 1 |   |   |                            |        |
| -2 | pressure |   |   |   |   |   |                            |        |
| 0b | (sys     |   |   |   |   |   |                            |        |
|    | tolic/di |   |   |   |   |   |                            |        |
|    | astolic) |   |   |   |   |   |                            |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Pressure |   |   | 1 |   |   |                            |        |
| -2 | Pulse or |   |   |   |   |   |                            |        |
| 0c | dP/dt    |   |   |   |   |   |                            |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Forces   |   |   |   | 1 |   |                            |        |
| -2 | due to   |   |   |   |   |   |                            |        |
| 0d | pressure |   |   |   |   |   |                            |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
|    | ###      |   |   |   |   |   | **[Workshop                |        |
|    | # Forces |   |   |   |   |   | comments:]{.underline}**   |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **There was            |        |
|    |          |   |   |   |   |   |     disagreement as to the |        |
|    |          |   |   |   |   |   |     importance of forces   |        |
|    |          |   |   |   |   |   |     other than pressure.** |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **Some felt that it is |        |
|    |          |   |   |   |   |   |     necessary to consider  |        |
|    |          |   |   |   |   |   |     as a positive feedback |        |
|    |          |   |   |   |   |   |     loop, quasi-static,    |        |
|    |          |   |   |   |   |   |     but cyclic.**          |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **The importance or    |        |
|    |          |   |   |   |   |   |     effect depends on the  |        |
|    |          |   |   |   |   |   |     curve. Resistance to   |        |
|    |          |   |   |   |   |   |     outflow factor should  |        |
|    |          |   |   |   |   |   |     be considered. Due to  |        |
|    |          |   |   |   |   |   |     the torque factor on   |        |
|    |          |   |   |   |   |   |     top of the cyclic      |        |
|    |          |   |   |   |   |   |     forces, grafts will    |        |
|    |          |   |   |   |   |   |     lift out from the      |        |
|    |          |   |   |   |   |   |     bottom.**              |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | ```{=html}                 |        |
|    |          |   |   |   |   |   | <!-- -->                   |        |
|    |          |   |   |   |   |   | ```                        |        |
|    |          |   |   |   |   |   | -   **Others noted that    |        |
|    |          |   |   |   |   |   |     these forces are small |        |
|    |          |   |   |   |   |   |     compared to pressure   |        |
|    |          |   |   |   |   |   |     (1). That is, internal |        |
|    |          |   |   |   |   |   |     pressure compared to   |        |
|    |          |   |   |   |   |   |     pressure in an         |        |
|    |          |   |   |   |   |   |     aneurysm sac. Both     |        |
|    |          |   |   |   |   |   |     static and dynamic     |        |
|    |          |   |   |   |   |   |     pressure must be       |        |
|    |          |   |   |   |   |   |     considered. Pressure   |        |
|    |          |   |   |   |   |   |     is more important than |        |
|    |          |   |   |   |   |   |     flow going around the  |        |
|    |          |   |   |   |   |   |     curve. Hemodynamic     |        |
|    |          |   |   |   |   |   |     forces are not what    |        |
|    |          |   |   |   |   |   |     are causing the        |        |
|    |          |   |   |   |   |   |     motion. The pressure   |        |
|    |          |   |   |   |   |   |     is reoriented to       |        |
|    |          |   |   |   |   |   |     modify the             |        |
|    |          |   |   |   |   |   |     configuration based on |        |
|    |          |   |   |   |   |   |     the pressure           |        |
|    |          |   |   |   |   |   |     differential.**        |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | ```{=html}                 |        |
|    |          |   |   |   |   |   | <!-- -->                   |        |
|    |          |   |   |   |   |   | ```                        |        |
|    |          |   |   |   |   |   | -   **There is a pressure  |        |
|    |          |   |   |   |   |   |     at the distal end.**   |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **Distortion/bending   |        |
|    |          |   |   |   |   |   |     is more important      |        |
|    |          |   |   |   |   |   |     under cyclic load.     |        |
|    |          |   |   |   |   |   |     This is related to     |        |
|    |          |   |   |   |   |   |     continued bending,     |        |
|    |          |   |   |   |   |   |     rather than sheer or   |        |
|    |          |   |   |   |   |   |     kinetic energy.**      |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **The 'firehose        |        |
|    |          |   |   |   |   |   |     effect' is due to      |        |
|    |          |   |   |   |   |   |     large mass flux, with  |        |
|    |          |   |   |   |   |   |     no distal attachment.  |        |
|    |          |   |   |   |   |   |     There is no associated |        |
|    |          |   |   |   |   |   |     pressure drop. Firemen |        |
|    |          |   |   |   |   |   |     need to sit on fire    |        |
|    |          |   |   |   |   |   |     hoses because of the   |        |
|    |          |   |   |   |   |   |     construct of the       |        |
|    |          |   |   |   |   |   |     hose.**                |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **May need to test     |        |
|    |          |   |   |   |   |   |     different designs      |        |
|    |          |   |   |   |   |   |     differently and are    |        |
|    |          |   |   |   |   |   |     testing different      |        |
|    |          |   |   |   |   |   |     things in various      |        |
|    |          |   |   |   |   |   |     tests.**               |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | ```{=html}                 |        |
|    |          |   |   |   |   |   | <!-- -->                   |        |
|    |          |   |   |   |   |   | ```                        |        |
|    |          |   |   |   |   |   | -   **If non-cylindrical   |        |
|    |          |   |   |   |   |   |     applications, there    |        |
|    |          |   |   |   |   |   |     may be much higher     |        |
|    |          |   |   |   |   |   |     local forces.**        |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| Ve |          |   |   |   |   |   |                            |        |
| ss |          |   |   |   |   |   |                            |        |
| el |          |   |   |   |   |   |                            |        |
| Wa |          |   |   |   |   |   |                            |        |
| ll |          |   |   |   |   |   |                            |        |
| C  |          |   |   |   |   |   |                            |        |
| ha |          |   |   |   |   |   |                            |        |
| ra |          |   |   |   |   |   |                            |        |
| ct |          |   |   |   |   |   |                            |        |
| er |          |   |   |   |   |   |                            |        |
| is |          |   |   |   |   |   |                            |        |
| ti |          |   |   |   |   |   |                            |        |
| cs |          |   |   |   |   |   |                            |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2- | Co       |   | 1 | 4 | 4 | 2 | -   Radial and axial       | M      |
| 21 | mpliance |   |   |   |   |   |     forces may change      | alina, |
|    | /        |   |   |   |   |   |     somewhat with change   | 1998   |
|    | el       |   |   |   |   |   |     in compliance.         |        |
|    | asticity |   |   |   |   |   |                            |        |
|    | (axial   |   |   |   |   |   | -   Impact of compliance   |        |
|    | and      |   |   |   |   |   |     on fatigue life /      |        |
|    | circumfe |   |   |   |   |   |     durability is a        |        |
|    | rential) |   |   |   |   |   |     critical parameter for |        |
|    |          |   |   |   |   |   |     long-term device       |        |
|    |          |   |   |   |   |   |     performance.           |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Difficult to measure.  |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Extent and progression |        |
|    |          |   |   |   |   |   |     of disease. Can it     |        |
|    |          |   |   |   |   |   |     hold the graft?        |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   Range 1-10%.           |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | **[Workshop                |        |
|    |          |   |   |   |   |   | comments:]{.underline}**   |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **Should run tests at  |        |
|    |          |   |   |   |   |   |     5% compliance and      |        |
|    |          |   |   |   |   |   |     don't worry about      |        |
|    |          |   |   |   |   |   |     damping. That is, a 5% |        |
|    |          |   |   |   |   |   |     change in internal     |        |
|    |          |   |   |   |   |   |     diameter.**            |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **We need to define    |        |
|    |          |   |   |   |   |   |     compliance. It is      |        |
|    |          |   |   |   |   |   |     defined in ISO and     |        |
|    |          |   |   |   |   |   |     AAMI as the % change   |        |
|    |          |   |   |   |   |   |     in diameter per 100    |        |
|    |          |   |   |   |   |   |     mmHg.**                |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **There may be some    |        |
|    |          |   |   |   |   |   |     non-linearity in the   |        |
|    |          |   |   |   |   |   |     range of 100 mmHg.**   |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **If measure by        |        |
|    |          |   |   |   |   |   |     volume, rather than    |        |
|    |          |   |   |   |   |   |     diameter, you get      |        |
|    |          |   |   |   |   |   |     about twice the        |        |
|    |          |   |   |   |   |   |     number.**              |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **Pulsatility is not   |        |
|    |          |   |   |   |   |   |     compliance.**          |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **Oscillating strain   |        |
|    |          |   |   |   |   |   |     that the structure     |        |
|    |          |   |   |   |   |   |     sees is the most       |        |
|    |          |   |   |   |   |   |     important question.    |        |
|    |          |   |   |   |   |   |     This needs to be       |        |
|    |          |   |   |   |   |   |     combined with what the |        |
|    |          |   |   |   |   |   |     endurance is of the    |        |
|    |          |   |   |   |   |   |     product. Strains from  |        |
|    |          |   |   |   |   |   |     diameter changes and   |        |
|    |          |   |   |   |   |   |     from other causes      |        |
|    |          |   |   |   |   |   |     (e.g., longitudinal    |        |
|    |          |   |   |   |   |   |     bending forces) must   |        |
|    |          |   |   |   |   |   |     be considered.**       |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **Some do not believe  |        |
|    |          |   |   |   |   |   |     that this is what      |        |
|    |          |   |   |   |   |   |     causes problems. There |        |
|    |          |   |   |   |   |   |     can be TF 6 month to 1 |        |
|    |          |   |   |   |   |   |     year, with no          |        |
|    |          |   |   |   |   |   |     oscillating strain.**  |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **Some think that      |        |
|    |          |   |   |   |   |   |     compliance of the tube |        |
|    |          |   |   |   |   |   |     is critically          |        |
|    |          |   |   |   |   |   |     important, even if the |        |
|    |          |   |   |   |   |   |     stent does not move.   |        |
|    |          |   |   |   |   |   |     There is still a load, |        |
|    |          |   |   |   |   |   |     even without motion.   |        |
|    |          |   |   |   |   |   |     There is cyclic        |        |
|    |          |   |   |   |   |   |     pressure inside, as    |        |
|    |          |   |   |   |   |   |     well as compliance as  |        |
|    |          |   |   |   |   |   |     defined above. Need to |        |
|    |          |   |   |   |   |   |     control the tube and   |        |
|    |          |   |   |   |   |   |     must know what         |        |
|    |          |   |   |   |   |   |     pressures you are      |        |
|    |          |   |   |   |   |   |     dealing with.**        |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | ```{=html}                 |        |
|    |          |   |   |   |   |   | <!-- -->                   |        |
|    |          |   |   |   |   |   | ```                        |        |
|    |          |   |   |   |   |   | -   **There are loading    |        |
|    |          |   |   |   |   |   |     difference if the      |        |
|    |          |   |   |   |   |   |     stent is on inside or  |        |
|    |          |   |   |   |   |   |     outside or within the  |        |
|    |          |   |   |   |   |   |     graft wall. Sizing     |        |
|    |          |   |   |   |   |   |     makes a huge           |        |
|    |          |   |   |   |   |   |     difference. There is a |        |
|    |          |   |   |   |   |   |     different              |        |
|    |          |   |   |   |   |   |     stress-strain          |        |
|    |          |   |   |   |   |   |     relationship depending |        |
|    |          |   |   |   |   |   |     on the sizing.**       |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **There was a question |        |
|    |          |   |   |   |   |   |     as to whether the      |        |
|    |          |   |   |   |   |   |     diameter relationship  |        |
|    |          |   |   |   |   |   |     for fully expanded vs  |        |
|    |          |   |   |   |   |   |     constrained stents     |        |
|    |          |   |   |   |   |   |     should be discussed.** |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **We need to make a    |        |
|    |          |   |   |   |   |   |     model that behaves     |        |
|    |          |   |   |   |   |   |     much like the aneurysm |        |
|    |          |   |   |   |   |   |     responds. \[Then model |        |
|    |          |   |   |   |   |   |     what actually          |        |
|    |          |   |   |   |   |   |     happens.\]**           |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **What is              |        |
|    |          |   |   |   |   |   |     physiologic?**         |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **Compliance is        |        |
|    |          |   |   |   |   |   |     important,\...**       |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | -   **There are mean and   |        |
|    |          |   |   |   |   |   |     alternating strains.   |        |
|    |          |   |   |   |   |   |     If there is a low mean |        |
|    |          |   |   |   |   |   |     strain, the device can |        |
|    |          |   |   |   |   |   |     handle the cyclic      |        |
|    |          |   |   |   |   |   |     strain.**              |        |
|    |          |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   | ```{=html}                 |        |
|    |          |   |   |   |   |   | <!-- -->                   |        |
|    |          |   |   |   |   |   | ```                        |        |
|    |          |   |   |   |   |   | -   **In identifying the   |        |
|    |          |   |   |   |   |   |     range feasible to test |        |
|    |          |   |   |   |   |   |     within, must correlate |        |
|    |          |   |   |   |   |   |     to the range expect to |        |
|    |          |   |   |   |   |   |     see physiologically.** |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| I  |          |   |   |   |   |   |                            |        |
| li |          |   |   |   |   |   |                            |        |
| ac |          |   |   |   |   |   |                            |        |
| c  |          |   |   |   |   |   |                            |        |
| ha |          |   |   |   |   |   |                            |        |
| ra |          |   |   |   |   |   |                            |        |
| ct |          |   |   |   |   |   |                            |        |
| er |          |   |   |   |   |   |                            |        |
| is |          |   |   |   |   |   |                            |        |
| ti |          |   |   |   |   |   |                            |        |
| cs |          |   |   |   |   |   |                            |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Common   |   |   |   | 1 |   |                            |        |
| -2 | iliac    |   |   |   |   |   |                            |        |
| 1a | diameter |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   |                            |        |
|    | 10-204   |   |   |   |   |   |                            |        |
|    | mm       |   |   |   |   |   |                            |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Common   |   |   |   | 1 |   |                            |        |
| -2 | iliac    |   |   |   |   |   |                            |        |
| 1b | length   |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   |                            |        |
|    | 5-41 mm  |   |   |   |   |   |                            |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Landing  |   |   |   | 1 |   |                            |        |
| -2 | site     |   |   |   |   |   |                            |        |
| 1c |          |   |   |   |   |   |                            |        |
|    | common   |   |   |   |   |   |                            |        |
|    | or       |   |   |   |   |   |                            |        |
|    | external |   |   |   |   |   |                            |        |
|    | iliac    |   |   |   |   |   |                            |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Distal   |   |   |   |   | 1 |                            |        |
| -2 | seal     |   |   |   |   |   |                            |        |
| 1d | site     |   |   |   |   |   |                            |        |
|    | diameter |   |   |   |   |   |                            |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Distal   |   |   |   |   | 1 |                            |        |
| -2 | seal     |   |   |   |   |   |                            |        |
| 1e | site     |   |   |   |   |   |                            |        |
|    | length   |   |   |   |   |   |                            |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Hyp      |   |   |   |   |   |                            |        |
| -2 | ogastric |   |   |   |   |   |                            |        |
| 1f | artery   |   |   |   |   |   |                            |        |
|    | location |   |   |   |   |   |                            |        |
|    |          |   |   |   |   |   |                            |        |
|    | Involved |   |   |   |   |   |                            |        |
|    | or not   |   |   |   |   |   |                            |        |
|    | involved |   |   |   |   |   |                            |        |
|    | in iliac |   |   |   |   |   |                            |        |
|    | aneurysm |   |   |   |   |   |                            |        |
+----+----------+---+---+---+---+---+----------------------------+--------+
| 2  | Renal    |   |   |   | 1 |   | Consequences of inadequate | M      |
| -2 | Artery   |   |   |   |   |   | renal perfusion can be     | alina, |
| 1g | Obs      |   |   |   |   |   | profound in recipients of  | 1997   |
|    | truction |   |   |   |   |   | endovascular therapies.    |        |
|    |          |   |   |   |   |   |                            | W      |
|    |          |   |   |   |   |   |                            | alker, |
|    |          |   |   |   |   |   |                            | 1998   |
+----+----------+---+---+---+---+---+----------------------------+--------+

OTHER COMMENTS

Pressure in the aneurysm sac: Is it equal everywhere? Does monitoring of
the pressure interventionally preclude an accurate measurement?

I know we struggle with trying to define the geometry and physiologic
properties in a simple method but we have to start viewing these in 3-D
space (angles and vectors).

How various physiologic and anatomic (calcification, Marfan's....)
characteristics null effect the hemodynamic stresses of the system.

**Training Considerations** - The learning curve of the doctors and the
need for adjuvant procedures were independent risk factors of operative
device-related and arterial complications. **The importance of proper
instruction during an institution\'s initial phase with this treatment
is emphasized by these observations**; per Buth and Laheij. J Vasc Surg
2000 Jan; 31 ( 1 Pt 1) 134 -- 146.

COMMENTS SPECIFIC TO ITEMS 2:18, 2:19, 2:20

AXIALLY-DIRECTED, FLUID-RELATED FORCES ACTING ON AAA STENT-GRAFTS

Part I: Major PxA Force :

> The axially-directed longitudinal force of principal concern is a
> function of blood pressure. This force is developed as a result of the
> flow restriction imposed by the terminal vascular beds, and
> theoretically would be transmitted back along the length of aorta. It
> would act on a AAA graft only because the aneurysm, with the device in
> place, can be considered a discontinuity in the aorta that is bridged
> by the graft. In order to balance the force in the system, some
> tensile force is applied to the device to counteract the load created
> by the blood pressure.
>
> This force, F, representing peak load, can be approximated simply by
> multiplying the peak pressure times the area over which it acts:
> F∼3lbf/in^2^)(∼1 in^2^)=3lbf. The actual F however is far less than
> 3lbf due to a combination of factors; also, the other axial forces
> developed by the fluid flow (see attachment) are negligible with
> respect to F.
>
> Perhaps most importantly, all of the force is not transmitted back
> along the aorta to the site of device placement; instead, most of this
> load is transferred from the vasculature to the surrounding
> peri-vascular structures to which it is attached via the adventitial
> layer, thus reducing the magnitude of F.
>
> Another important force-reducing feature of the system is load
> sharing. The reduced force F that is actually transmitted to the site
> of device placement would be borne by the device only if a gap in the
> aorta were present, and bridged by the device. Instead the aorta,
> which bore the entire load of F prior to device placement, remains in
> place; thus, F is shared by both the aortic wall and the device,
> leading to a further reduced force, F, acting on the device.
>
> Most of the longitudinal load is transferred to the device through the
> interference fit described as "oversizing" in which a larger device is
> placed than the luminal diameter of the aorta.

A confirmation of the arguments presented here was provided by an
inspection of 400+ sets of patient radiographs; in roughly 1% of the
patients were the anchors deployed into the aortic wall. In the
remainder, the anchors had not entered the wall as would occur with
forces acting to move the device distally.

## Conclusion

F\< F\< F

Part II: Other fluid derived forces

[Estimation of the inertial force, Force~1~]{.underline}

Force~1~ is that which arises from the directional change of the fluid
flow at, and distal to, the bifurcation.

Eq 1: P~1~A~1~-P~2~A~2~(cosR~x~=V~1~A~1~~~(V~2~cosV~1~)

And similarly, in the Y direction,

Eq2: P~2~A~2~-P~1~A~1~(sinR~y~+W=V~1~A~1~~~(V~2~sin)

Where:

P=pressure

A=cross-sectional area

V=mean fluid velocity

=fluid density

R~x~=reaction force in the x direction.

=angular change of fluid flow

For the purposes of this analysis of [other]{.underline} forces, the PxA
term will be ignored (see description in the body of this text) though
it is by far of the greatest magnitude. Also, we are interested only in
the axial force, so that we can ignore the Y forces. Further, with the
assumption that the fluid flow turns 90 at the bifurcation,  is
90and the trigonometric terms drop out. Another set of simplifying
assumptions for the estimation of the inertial load is that the flow is
frictionless and adiabatic. The inertial component then becomes,

Eq 3: R~x~=V~1~^2^A~1~~~

Q=flow rate6liters/min=366in^3^/min

V~1~=Q/A~1~in^3^/min/(in^2^/4)/60sec/min=7.77in/sec=0.65ft/sec

~~65lbm/ft3


Rx=F~1~=(0.65ft/sec)^2^(0.0055ft^3^)(65lbm/ft^3^)/32.2ftlbm/lbfsec^2^=0.0047lbf

[Estimation of PxA, Force~2~]{.underline}

The second component of the axial force to be estimated arises from the
change in pressure along the length as the flow velocity increases
distally in the leg zone. Force~2~ is entirely separate from the PxA
force that arises from blood pressure.

From conservation of mass:

eq4: mass flow rate= V~1~A~1~~~ V~2~A~2~~~

# Once again making the assumptions of adiabatic, frictionless, incompressible flow,

Eq5: P~1~/~~+ V~1~^2^/2g~c~= P~2~/~~+ V~2~^2^/2g~c~ where ~~~~

# Solving eq 4. And eq5. simultaneously yields P

Eq 6: P~1~-P~2~=V~2~^2^2g~c~x-(A~2~/A~1~)^2^

The diameter of each leg is 12.5mm, so the combined area is 2x(.49
inch)^2^/4=0.38in^2^,

A~2~=0.38in^2^, A~1~=in)^2^/4=0.82 in^2^

V~2~=Q/A~2~=366in^3^/min/.38in^2^=963in/min=80ft/min=1.34ft/sec

(A~2~/A~1~)^2^=(0.38/0.82)^2^=.46^2^=0.22

P~1~-P~2~=1.34ft/sec)^2^65lbm/ft^3^/2(32.2lbmft/lbfsec^2^)x1.21lbf/ft^2^=0.0084lbf/in^2^

The area upon which this force is acting represents the reduction in
cross-sectional area from trunk to legs:

A~p~=area projection=A~1~-A~2~=0.82in^2^-0.38in^2^=0.44in^2^

# And the total force acting on this area, F~2~=PxA~p~=(0.0084lbf/in^2^)( 0.44in^2^)=0.0037lbf

[Estimation of shear force, Force~3~]{.underline}

Force~3~ is that which arises from fluid shear interaction with the
device surface. For this reason, the assumption of frictionless flow is
no longer made.

From Newton's viscosity law: eq7: V/r)

Where r=radius=1/2D at center of tube

From above we know that for Q=6L/min, then V~2~=1.34ft/sec

For a parabolic flow profile, peak flow velocity is twice the mean
velocity. For purposes of a conservative estimate, assume that velocity
in the entire bifurcation is that of the legs, so V~max~2.68ft/sec

# To simplify, assume a straight line flow profile: V=0@r=0, and V=Vmax@r=1/2 D

Then

Eq8: V=2rV~max~/D

And

Eq9: V/r=2V~max~/D

Where D=twice the diameter of one leg=25mm=0.082ft

V/r=2(2.68ft/sec)/0.082ft=65.3sec^-1^

from Mark's

@37Cx10^-5^lbfsec/ft^2^

=x10^-5^lbfsec/ft^2^)(65.3sec^-1^)=0.00131lbf/ft^2^=0.00001lbf/in^2^

by inspection of magnitude, F~3~ is negligible with respect to F~1~ and
F~2~

## Conclusion

F~1~+F~2~=0.0047lbf+0.0037lbf=0.0084lbf\<\<F(of PxA) . Forces F~1,~ F~2~
and F~3~ will be ignored.

## References

Baum RA; Carpenter JP; Cope C; Golden MA; Velazquez OC; Neschis DG;
Mitchell ME; Barker CF; Fairman RM. Aneurysm sac pressure measurements
after endovascular repair of abdominal aortic aneurysms. **J Vasc
Surg**. 2001 Jan; 33(1): 32-41

Buth J; Laheij RJ. Early complications and endoleaks after endovascular
abdominal aortic aneurysm repair: report of a multicenter study. **J
Vasc Surg**. 2000 Jan; 31(1 Pt 1): 134-46.

Cohnert TU; Oelert F; Wahlers T; Gohrbandt B; Chavan A; Farber A;
Galanski M; Haverich A. Matched-pair analysis of conventional versus
endoluminal AAA treatment outcomes during the initial phase of an aortic
endografting program. **J Endovasc Ther**. 2000 Apr; 7(2): 94-100.

Harris P; Brennan J; Martin J; Gould D; Bakran A; Gilling-Smith G; Buth
J; Gevers E; White D. Longitudinal aneurysm shrinkage following
endovascular aortic aneurysm repair: a source of intermediate and late
complications. **J Endovasc Surg**. 1999 Feb; 6(1): 11-6.

Jacobowitz GR; Rosen RJ; Riles TS. The significance and management of
the leaking endograft. **Semin Vasc Surg**. 1999 Sep; 12(3): 199-206

Malina M; Ivancev K; Chuter TA; Lindh M; Lanne T; Lindblad B; Brunkwall
J; Risberg B. Changing aneurysmal morphology after endovascular
grafting: relation to leakage or persistent perfusion. **J Endovasc
Surg**. 1997 Feb; 4(1): 23-30.

Malina M; Lanne T; Ivancev K; Lindblad B; Brunkwall J. Reduced pulsatile
wall motion of abdominal aortic aneurysms after endovascular repair. **J
Vasc Surg**. 1998 Apr; 27(4): 624-31**.**

EVT Investigators. EndoVascular Technologies, Inc., Matsumura JS;
Chaikof EL. Continued expansion of aortic necks after endovascular
repair of abdominal aortic aneurysms. **J Vasc Surg**. 1998 Sep; 28(3):
422-30; discussion 430-1

May J; White GH; Yu W; Waugh RC; Stephen MS; Harris JP. A prospective
study of changes in morphology and dimensions of abdominal aortic
aneurysms following endoluminal repair: a preliminary report. **J
Endovasc Surg**. 1995 Nov; 2(4): 343-7.

May J; White G; Yu W; Waugh R; Stephen M; Harris J. A prospective study
of anatomico-pathological changes in abdominal aortic aneurysms
following endoluminal repair: is the aneurysmal process reversed? **Eur
J Vasc Endovasc-Surg**. 1996 Jul; 12(1): 11-7.

Midorikawa H; Hoshino S; Iwaya F; Igari T. Graft-wall endoleak 18 months
after successful endoluminal AAA repair. **J Endovasc Surg.** 1999 Aug;
6(3): 251-5.

Resch T; Ivancev K; Brunkwall J; Nirhov N; Malina M; Lindblad B. Midterm
changes in aortic aneurysm morphology after endovascular repair. **J
Endovasc Ther**. 2000 Aug; 7(4): 279-85.

Rhee RY; Eskandari MK; Zajko AB; Makaroun MS. Long-term fate of the
aneurysmal sac after endoluminal exclusion of abdominal aortic
aneurysms. **J Vasc Surg**. 2000 Oct; 32(4): 689-96.

Schurink GW; Aarts NJ; van-Bockel JH. Endoleak after stent-graft
treatment of abdominal aortic aneurysm: a meta-analysis of clinical
studies. **Br J Surg**. 1999 May; 86(5): 581-7.

Singh-Ranger R; McArhur T; Lees W; Adiseshiah M. A prospective study of
changes in aneurysm and graft length after endovascular exclusion of AAA
using balloon and self-expanding endograft systems. **Eur J Vasc
Endovasc Surg**. 2000 Jul; 20(1): 90-5

Walker SR; Yusuf SW; Wenham PW; Hopkinson BR. Renal complications
following endovascular repair of abdominal aortic aneurysms. **J
Endovasc Surg**. 1998 Nov; 5(4): 318-22.

Wever JJ; de-Nie AJ; Blankensteijn JD; Broeders IA; Mali WP; Eikelboom
BC. Dilatation of the proximal neck of infrarenal aortic aneurysms after
endovascular AAA repair. **Eur J Vasc Endovasc Surg**. 2000 Feb; 19(2):
197-201.

White GH; May J; Petrasek P; Waugh R; Stephen M; Harris J. Endotension:
an explanation for continued AAA growth after successful endoluminal
repair. **J Endovasc Surg**. 1999 Nov; 6(4): 308-15.

White GH; May J; Waugh RC; Chaufour X; Yu W. Type III and type IV
endoleak: toward a complete definition of blood flow in the sac after
endoluminal AAA repair. **J Endovasc Surg**. 1998 Nov; 5(4): 305-9

White RA; Donayre CE; Walot I; Woody J; Kim N; Kopchok GE. Computed
tomography assessment of abdominal aortic aneurysm morphology after
endograft exclusion. **J Vasc Surg**. 2001 Feb; 33(2 Suppl): S1-10.

Wolf YG; Hill BB; Rubin GD; Fogarty TJ; Zarins CK. Rate of change in
abdominal aortic aneurysm diameter after endovascular repair. **J Vasc
Surg**. 2000 Jul; 32(1): 108-15.

## Abstracts for Selected References (from above)

Baum RA; Carpenter JP; Cope C; Golden MA; Velazquez OC; Neschis DG;
Mitchell ME; Barker CF; Fairman RM. Aneurysm sac pressure measurements
after endovascular repair of abdominal aortic aneurysms. **J Vasc
Surg**. 2001 Jan; 33(1): 32-41

OBJECTIVES: The goal of endovascular grafting of abdominal aortic
aneurysms (AAAs) is to exclude the aneurysm sac from systemic pressure
and thereby decrease the risk of rupture. Unlike conventional open
surgery, branch vessels in the sac (eg, lumbar artery and inferior
mesenteric artery \[IMA\]) are not ligated and can potentially transmit
pressure. The purpose of our investigation was to evaluate the
feasibility of various interventional techniques for measuring pressure
within the aneurysm sac in patients who had undergone endovascular
repair of AAAs. METHODS: Sac pressure measurements were performed in 21
patients who had undergone stent graft repair of AAAs. Seventeen of 21
patients had endoleaks demonstrated on 30-day computed tomographic (CT)
scans. Access to the aneurysm sac in these patients was through direct
translumbar sac puncture (5 patients), through a patent IMA accessed via
the superior mesenteric artery (SMA) (9 patients), or by direct
cannulation around attachment sites (3 patients). Four patients had
perioperative pressure measurements obtained through catheters
positioned along side of the endovascular graft at the time of its
deployment. Two of these catheters were left in position for 30 hours
during which time CT and conventional angiography were performed.
Pressures were determined with standard arterial-line pressure
transduction techniques and compared with systemic pressure in each
patient. RESULTS: Elevated sac pressure was found in all patients. The
sac pressure in patients with endoleaks was found to be systemic (15
patients) or near systemic (2 patients) and all had pulsatile waveforms.
Elevated sac pressures were also found in patients without CT or
angiographic evidence of endoleak (2 patients). Injection of the sacs in
two of these patients revealed a patent lumbar artery and an IMA.
CONCLUSIONS: It is possible to measure pressures from within the
aneurysm sac in patients with stent grafts with a variety of techniques.
Patients may continue to have pressurized AAA sacs despite endovascular
AAA repair. Endoleaks transmit pulsatile pressure into the aneurysm sac
regardless of the type. It is possible to have systemic sac pressures
without evidence of endoleaks on CT or angiography.

Buth J; Laheij RJ. Early complications and endoleaks after endovascular
abdominal aortic aneurysm repair: report of a multicenter study. **J
Vasc Surg**. 2000 Jan; 31(1 Pt 1): 134-46.

> OBJECTIVE: The aim of this study was the identification of risk
> factors for adverse events and the assessment of the early success
> rate in 1554 patients with abdominal aortic aneurysms (AAAs) who
> underwent treatment with endovascular technique between January 1994
> and March 1999. For this purpose, the clinical and procedural data
> were correlated with observed complications and endoleaks. METHODS:
> The data were collected from 56 European centers and submitted to a
> central registry. Patient characteristics, aortoiliac anatomic
> features, operative technical details, types of devices used, and
> experience of the teams of physicians were correlated with the
> occurrence of complications and endoleaks. The technical success rate
> was assessed according to the Society for Vascular
> Surgery/International Society for Cardiovascular Surgery, North
> American Chapter, guidelines. For the assessment of correlations
> between risk factors and adverse events, a multivariate logistic
> regression analysis was used. RESULTS: The operative complications
> were grouped into three categories: failure to complete the procedure
> (39 patients, of which 27 underwent a conversion to an open AAA
> repair; 2.5%); device-related or procedure-related complications (149
> patients; 10%); and arterial complications (51 patients; 3%). The most
> important risk factors for failure to complete the procedure included
> an aneurysm diameter of 60 mm or more and the need for adjuvant
> procedures. The factors that predicted device-related and arterial
> complications were the experience of the team with endovascular AAA
> treatment and the need for adjuvant procedures. Forty patients (2.6%)
> died within 30 days after operation. American Society of
> Anesthesiologists III and IV operative risk classification results
> predicted higher mortality rates than did American Society of
> Anesthesiologists operative risk classification I and II results. The
> patients who underwent operation in 1994, the first year documented in
> this registry, and those who required adjuvant procedures also had an
> increased risk of perioperative death. The incidence rate of systemic
> complications within the first 30 days (279 patients; 18%) was higher
> in patients aged 75 years or more, in patients with an impaired
> cardiac status, and in patients considered unfit for an open
> procedure. An endoleak was detected at the completion of the procedure
> in 16% of the cases and was still present after 1 month in 9%. The
> risk factors for primary endoleaks were female gender and age of 75
> years and older. The observed technical success rate in this patient
> series was 72%. CONCLUSION: The learning curve of the doctors and the
> need for adjuvant procedures were independent risk factors of
> operative device-related and arterial complications. The importance of
> proper instruction during an institution\'s initial phase with this
> treatment is emphasized by these observations. Although the
> endovascular management of AAAs is less stressful than open surgery,
> systemic complications were still the most common adverse events
> during the first postoperative month. These complications were
> associated with several patient-related factors, including advanced
> age, impaired cardiac status, and poor general medical condition.
> These observations may be a guide for improved patient selection for
> endovascular AAA repair.

Cohnert TU; Oelert F; Wahlers T; Gohrbandt B; Chavan A; Farber A;
Galanski M; Haverich A. Matched-pair analysis of conventional versus
endoluminal AAA treatment outcomes during the initial phase of an aortic
endografting program. **J Endovasc Ther**. 2000 Apr; 7(2): 94-100.

> PURPOSE: To investigate whether endovascular stent-grafts implanted
> during the early phase of an aortic endografting program have
> advantages over conventional surgical procedures for treatment of
> infrarenal aortic aneurysm (AAA). METHODS: In the first months of an
> endografting program, 37 patients (36 men; mean age 67.9 +/- 7.1
> years, range 55 to 86) underwent AAA repair with endovascular
> implantation of a Vanguard (n = 17) or Talent (n = 20) bifurcated
> stent-graft. Data collected during the perioperative period and in
> follow-up were compared retrospectively to a matched group of 37
> elective surgical patients. RESULTS: All endograft implantations were
> completed. Two type I and 6 type II endoleaks (21.6%) were seen
> postoperatively. Five type II sealed without intervention; 1 type I
> endoleak was corrected with an additional stent, but 1 type I and 1
> type II endoleaks persisted despite attempts with coil embolization.
> Two (5.4%) endograft patients died during the perioperative period;
> however, this was not significantly different (p = 0.15) from the
> control group. In the mean follow-up of 12 +/- 6 months for both
> groups, 1 (2.7%) late conversion was necessary at 2 years for aneurysm
> expansion in an endograft patient with an unsealed type I endoleak.
> CONCLUSIONS: In our learning curve experience with aortic
> endografting, postoperative morbidity and mortality were higher in
> endograft patients compared to conventionally treated controls. Only
> in the endograft group was reoperation required during follow-up.
> Careful monitoring with periodic imaging studies is mandatory after
> endoluminal AAA treatment.

Harris P; Brennan J; Martin J; Gould D; Bakran A; Gilling-Smith G; Buth
J; Gevers E; White D. Longitudinal aneurysm shrinkage following
endovascular aortic aneurysm repair: a source of intermediate and late
complications. **J Endovasc Surg**. 1999 Feb; 6(1): 11-6.

> PURPOSE: To report the incidence of delayed complications following
> endovascular abdominal aortic aneurysm (AAA) repair and the
> relationship of these sequelae to morphological changes in the sac and
> endograft. METHODS: Twenty-six AAA patients treated with Vanguard
> endografts had completed \> or = 1-year follow-up. Postoperative
> angiograms and spiral computed tomographic (CT) scans with
> 3-dimensional reconstruction were compared to the 1-year images to
> determine morphological changes in the aneurysm sac and the
> endograft.These changes were then related to complications occurring
> between 1 and 12 months postoperatively in the study group. RESULTS:
> Comparison of angiograms uncovered endograft buckling in 18 (69%)
> patients and acutely angled or kinked endografts in 10 (38%).
> Measurements from the CT scans found that undistorted endografts had a
> mean change in sac length of +6.6 mm. Mean sac length change in
> buckled endografts was -3.1 mm, while kinked endografts displayed a
> mean change of -6.2 mm (p \< 0.002, Student\'s t-test). Five (19%)
> patients, all with distorted endografts, demonstrated late (1 to 12
> months) complications (4 endoleaks and 1 graft limb thrombosis) owing
> to component separation, distal stent migration, and acute angulation.
> No movement in the proximal stent was observed. Elongation of the
> endograft (flow line measurement) was observed in one tube graft only.
> CONCLUSIONS: In this study, longitudinal shrinkage of the sac
> following endovascular aortic aneurysm repair led to buckling or
> kinking of the endograft within 1 year in 69% of patients. This
> appears to be an important source of delayed complications.

Jacobowitz GR; Rosen RJ; Riles TS. The significance and management of
the leaking endograft. **Semin Vasc Surg**. 1999 Sep; 12(3): 199-206

> Endoleak is the persistence of blood flow outside the lumen of an
> endograft, but within an aneurysm sac or adjacent vessel being treated
> by the graft. Diagnosis may be difficult, and treatment remains
> somewhat controversial. The purpose of this article is to discuss the
> clinical significance and appropriate management of endoleaks within
> the context of our current understanding of this phenomenon. The
> diagnosis of an endoleak can be made by conventional angiography,
> duplex ultrasound, intravascular ultrasound (IVUS), and computed
> tomography (CT) angiography. All of these modalities are effective,
> although CT angiography may be the most sensitive. Endoleaks can be
> categorized into 5 classes: (1) perigraft flow around the proximal end
> of the endograft; (2) perigraft flow around the distal end of the
> endograft; (3) flow through a defect in the body of the endograft; (4)
> flow between segments of a multicomponent endovascular graft; and (5)
> flow between arterial branches within an aneurysm sac. The first 4
> classes have been shown to represent a clinical situation in which
> systemic arterial pressure is transmitted to an inadequately excluded
> aneurysm sac, placing the sac at risk of rupture. In contrast,
> branch-flow leaks do not appear to carry an increased risk of rupture,
> provided there is no increase in aneurysm sac diameter. However, an
> increase in the diameter of an aneurysm sac after endograft
> implantation may be a sign of occult endoleak, even if not visualized
> by current imaging techniques. Thus, we believe that collateral branch
> leaks with no associated aneurysm sac expansion may be observed with
> regular follow-up by CT angiography. All other endoleaks should be
> treated with adjunctive endovascular maneuvers or explanation of the
> endograft with standard open repair-in short, routine follow-up
> imaging on endografts to detect the presence of late endoleaks or
> aneurysm sac expansion.

Malina M; Ivancev K; Chuter TA; Lindh M; Lanne T; Lindblad B; Brunkwall
J; Risberg B. Changing aneurysmal morphology after endovascular
grafting: relation to leakage or persistent perfusion. **J Endovasc
Surg**. 1997 Feb; 4(1): 23-30.

> PURPOSE: To relate changing abdominal aortic aneurysm (AAA) morphology
> after endovascular grafting to the presence of leakage, collateral
> perfusion, and other factors. METHODS: Thirty-five patients who
> underwent successful AAA endovascular grafting were evaluated.
> Self-expanding Z-stents and Dacron grafts were applied in bifurcated
> and aortomonoiliac systems. Postoperative diameter changes were
> calculated from repeated spiral computed tomographic scans,
> angiograms, and ultrasonic phase-locked echo-tracking scans during a
> median 6-month follow-up (interquartile range \[IQR\] 3 to 12).
> RESULTS: At 12 months, the diameters of completely excluded aneurysms
> had decreased 6 mm (IQR 2 to 11; p = 0.006). The proximal
> graft-anchoring stents had dilated 2 mm (IQR 0.5 to 3.3; p = 0.01).
> The aortic diameters immediately below the renal arteries but above
> the stents had not changed. Endoleakage and collateral perfusion (n =
> 13) were each associated with preserved aneurysm size and a 12 times
> higher risk of aneurysm dilation. After the leakage or the collateral
> perfusion had been treated, the aneurysm size decreased. Aneurysms
> with extensive intraluminal thrombi presented a reduced risk of
> leakage or perfusion. CONCLUSIONS: The diameters of endovascularly
> excluded AAAs decrease, except in cases of leakage or perfusion.
> Careful follow-up of patients with aortic endografts is necessary.

Malina M; Lanne T; Ivancev K; Lindblad B; Brunkwall J. Reduced pulsatile
wall motion of abdominal aortic aneurysms after endovascular repair. **J
Vasc Surg**. 1998 Apr; 27(4): 624-31**.**

> PURPOSE: The reduced size of abdominal aortic aneurysms (AAAs) after
> endovascular repair suggests lowered intraaneurysmal pressure. In the
> presence of endoleaks, the size is not decreased. Although
> postoperative intraaneurysmal pressure is difficult to record, the
> pulsatile wall motion (PWM) of aneurysms can be measured
> noninvasively. The aim of this study was to assess the PWM of AAAs
> before and after endovascular repair and to relate the change in the
> PWM to aneurysmal size and presence of endoleaks. METHODS: Forty-seven
> patients underwent endovascular repair of an AAA. The aneurysm
> diameter and PWM were measured with the use of ultrasonic
> echo-tracking scans preoperatively; at 1, 3, and 6 months; and
> thereafter biannually. Fifteen aneurysms developed endoleaks, whereas
> 32 were completely excluded. The leaks were characterized with the use
> of computed tomographic scanning and angiography. Median follow-up was
> 12 months (interquartile range, 5 to 24 months). RESULTS: The
> preoperative PWM of the aneurysms was 1.0 mm (range, 0.8 to 1.3 mm).
> After complete endovascular exclusion, the PWM was 25% (range, 16% to
> 37%) of the preoperative value (p \< 0.001), and aneurysm diameter
> decreased by 8 mm (range, 6 to 14 mm) (p \< 0.001). After 18 months,
> no further diameter reduction occurred. In three patients without
> endoleaks but with enlarging aneurysms, the postoperative PWM showed
> less reduction (p \< 0.05). Aneurysms with endoleaks showed no
> diameter decrease, and the postoperative PWM was 50% higher than that
> in the totally excluded cases (p \< 0.01). In five patients with
> transient endoleaks, the PWM was reduced after leakage ceased (p \<
> 0.05). Leaks of various sources displayed similar PWM. CONCLUSION: The
> size and PWM of aneurysms are reduced after endovascular repair. The
> diameter reduction may cease after 1.5 years. Endoleaks are associated
> with higher PWM than expected. Pressure may be transmitted without
> evidence of leaks.

Malina M; Brunkwall J; Ivancev K; Lindh M; Lindblad B; Risberg B. Renal
arteries covered by aortic stents: clinical experience from endovascular
grafting of aortic aneurysms. **Eur J Vasc Endovasc Surg**. 1997 Aug;
14(2): 109-13

OBJECTIVES: During the endovascular repair of abdominal aortic aneurysms
(AAAs), effective anchoring of the stent-graft is difficult in the
presence of a short infrarenal aneurysm neck. The aim of this study was
to investigate renal artery patency and renal function after deployment
of graft anchoring stents across the renal arteries. DESIGN:
Retrospective open study. PATIENTS: Twenty-five renal arteries, in 18
patients treated by endovascular exclusion of an AAA, were intentionally
covered with the Gianturco Z-stent to ensure stent graft attachment.
METHODS: Renal artery patency was assessed by repeated spiral computed
tomography (CT) scans and angiography. Creatinine levels, blood pressure
and antihypertensive medication were recorded. Follow-up was a median 6
months (2-9). RESULTS: All 25 stent-covered renal arteries remained
patent. CT showed a small infarct in one kidney. Creatinine was 108
mumol/l (89-133) before intervention and 98 mumol/l (87-127) at
follow-up. Blood pressure was 150/80 mmHg on both occasions.
Antihypertensive therapy was intensified in one patient whose creatinine
level remained stable and whose separate renin sampling was normal.
CONCLUSIONS: Covering the renal arteries with the Gianturco Z-stent does
not seem to affect renal function within 6 months. Further follow-up is
needed before suprarenal stent deployment can be advocated.

EVT Investigators. EndoVascular Technologies, Inc., Matsumura JS;
Chaikof EL. Continued expansion of aortic necks after endovascular
repair of abdominal aortic aneurysms. **J Vasc Surg**. 1998 Sep; 28(3):
422-30; discussion 430-1

> BACKGROUND: Longitudinal studies have revealed that the aortic segment
> proximal to an infrarenal abdominal aortic aneurysm (AAA) is at risk
> for continued enlargement after a standard aneurysm repair. Similarly,
> preliminary reports have shown expansion of one or both aortic necks
> after endovascular repair. Although some investigators have suggested
> that this may be a transient effect, continued dilatation at the
> endograft attachment site could effect the overall device stability.
> METHODS: As part of a multi-institutional trial of endovascular
> grafting for the treatment of AAA, 59 patients were successfully
> implanted with straight endografts between February 1993 and January
> 1995. A morphometric analysis of aortic neck size was undertaken with
> serial review of computed tomography scans available through April
> 1997. The neck sizes at both graft attachment sites were measured,
> with investigators blinded to patient identity and date of scan.
> Changes in minor diameter were defined, annual interval expansion
> rates were calculated, and the data were correlated with endoleak,
> device migration, aneurysm size change, endograft diameter, attachment
> system fractures, and initial preimplant neck size. RESULTS:
> Significant aortic neck enlargement, particularly at the level of the
> distal neck, was observed for at least 24 months after AAA repair. The
> annual interval dilation rates of the proximal aortic neck were 0.7
> +/- 2.1 mm/year (P = .023) and 0.9 +/- 1.9 (P = .008) mm/year during
> the first and second years, respectively. Enlargement of the distal
> neck during the observation period was more marked, with corresponding
> annual expansion rates of 1.7 +/- 2.9 mm/year (P \< .001) and 1.9 +/-
> 2.5 (P \< .001) mm/year. In 5 patients (14%), the minor diameter of
> the distal neck was at least 6 mm larger than the preimplant diameter
> of the graft. Migration of the distal attachment system was observed
> in 3 of these 5 patients. Expansion rates did not have a statistically
> significant correlation with initial neck size, endograft dimensions,
> aneurysm size change, presence of endoleak, or attachment system
> fracture. CONCLUSIONS: Aortic neck enlargement was observed for at
> least 2 years after endovascular grafting. Close patient follow-up
> remains mandatory in lieu of the potential risk of late failure as a
> result of continued aortic expansion. The relative contribution of
> device design to this phenomenon will need to be defined.

May J; White GH; Yu W; Waugh RC; Stephen MS; Harris JP. A prospective
study of changes in morphology and dimensions of abdominal aortic
aneurysms following endoluminal repair: a preliminary report. **J
Endovasc Surg**. 1995 Nov; 2(4): 343-7.

PURPOSE: The aim of this prospective study was to analyze early changes
in morphology and dimensions of abdominal aortic aneurysms (AAA)
following endoluminal repair. METHODS: Forty-two of 62 patients
undergoing endoluminal repair of AAAs between May 1992 and November 1994
were potentially available for follow-up at 6 months or longer after
operation. After excluding patients with failed endoluminal repairs,
patients who died within 6 months of operation, and patients with
anastomotic aneurysms, a study group of 30 patients remained.
Contrast-enhanced computed tomography (CE-CT) was performed
preoperatively, within 10 days of operation, and at 6 and 12 months
postprocedure. Based on the postoperative CE-CT findings, patients were
divided into two groups: those with no extravasation of contrast into
the aneurysmal sac (group I; n = 26), and those in which there was
contrast extravasation (\"leak\") into the aneurysmal sac (group II; n =
4). RESULTS: The mean maximum diameters of AAAs in group I diminished
progressively at 6 and 12 months, while those in group II increased.
Twenty-three (88%) patients in group I had decreased diameter of AAA,
while all patients in group II had progressive increase in AAA diameter.
Patients who had an increase in AAA diameter had a significantly higher
incidence of leak compared with those who had a decrease in diameter (p
= 0.001). CONCLUSIONS: The majority of AAAs in which the sac has been
excluded from the general circulation diminish in size following
successful endoluminal repair. An increase in size occurs in those AAAs
in which a communication exists between the aortic lumen and the sac.
These results suggest that successfully excluded AAAs that continue to
increase in size should be suspected of having an undetected leak.

May J; White G; Yu W; Waugh R; Stephen M; Harris J. A prospective study
of anatomico-pathological changes in abdominal aortic aneurysms
following endoluminal repair: is the aneurysmal process reversed? **Eur
J Vasc Endovasc Surg**. 1996 Jul; 12(1): 11-7.

AIM: The aim of this prospective study was to analyse early
anatomico-pathological changes in abdominal aortic aneurysms (AAA)
following endoluminal repair to determine if the natural history of
continued expansion of AAA is reversed. MATERIALS AND METHODS:
Sixty-seven of 85 patients undergoing endoluminal AAA repair between May
1992 and August 1995 had their operations prior to the end of February
1995 and were potentially available for follow up at 6 months or longer
after operation. Excluded were: patients with failed endoluminal repairs
(n = 14), patients who died within 6 months of operation (n = 5),
patients with anastomotic AAA (n = 1), leaving 47 patients in the study
group. Based on contrast enhanced CT performed preoperatively, within 10
days of operation and 6, 12 and 18 months after operation patients were
divided into two groups: those in whom the AAA maximum transverse
diameter (MTD) decreased Group I (n = 39) and those in which it
increased Group II (n = 8). The following parameters were analysed:
diameter of the supra coeliac aorta, MTD and the dimensions of the
proximal and distal necks of the AAA plus extravasation (\"leak\") of
contrast into the aneurysmal sac. RESULTS: Leak of contrast was seen in
0 of 39 patients in Gp I and 5 of 8 patients in Gp II. Patients in Group
I experienced a progressive diminution in AAA mean MTD. The diameters of
the proximal and distal necks increased but there was no shortening of
the length of the necks in this group. In Group II the AAA MTD was
dependent on whether or not the aneurysmal sac was isolated from the
circulation. The diameter of the proximal and distal necks increased
irrespective of this fact. CONCLUSION: We conclude that in early follow
up AAA which diminish in diameter following endoluminal repair remain
isolated from the general circulation. Co-incident with this decrease in
AAA diameter, the proximal and distal necks increase in diameter but do
not undergo any shortening in length. This paradoxical increase in neck
diameter, was not progressive in the period of follow-up.

Midorikawa H; Hoshino S; Iwaya F; Igari T. Graft-wall endoleak 18 months
after successful endoluminal AAA repair. **J Endovasc Surg.** 1999 Aug;
6(3): 251-5.

> PURPOSE: To describe a case of graft-wall endoleak 18 months after
> successful endoluminal repair of an abdominal aortic aneurysm (AAA).
> METHODS AND RESULTS: A 71-year-old man with infrarenal AAA was
> successfully treated with an endoluminal aortomonoiliac graft and
> femorofemoral crossover bypass with surgical ligation of the right
> external iliac artery. The stent-graft was made from 2 Gianturco
> Z-stents and a tapered thin-walled (0.1-mm) Dacron graft. Eighteen
> months after endografting, the patient complained of a pulsatile
> abdominal mass. Angiography and computed tomography showed graft-wall
> endoleak. Aneurysmectomy was performed, and the aneurysm was
> successfully replaced with a Y-shaped knitted Dacron graft. A hole in
> the graft wall was found 3 cm from the proximal edge of the
> stent-graft. CONCLUSIONS: This case suggests that the use of
> thin-walled graft material in endografts may not be sufficiently
> durable.

Resch T; Ivancev K; Brunkwall J; Nirhov N; Malina M; Lindblad B. Midterm
changes in aortic aneurysm morphology after endovascular repair. **J
Endovasc Ther**. 2000 Aug; 7(4): 279-85.

> PURPOSE: To study midterm changes in aortic aneurysm morphology after
> endovascular aneurysm repair. METHODS: Of 94 patients with abdominal
> aortic aneurysms (AAAs) treated with endografts between November 1993
> and August 1998, 84 were available for follow-up. Patients were
> evaluated preoperatively by spiral computed tomography (CT) and
> aortography; in follow-up, spiral CT scanning was performed at 1, 3,
> and 6 months and semiannually thereafter. Measurements of the aneurysm
> neck diameter, maximum aneurysm diameter, and the distance from the
> lowermost renal artery to the aortic bifurcation were made
> preoperatively and in follow-up. RESULTS: Mean follow-up was 17.5 +/-
> 1.1 months; 56 (67%) patients were followed for 1 year and 28 (33%)
> for \> or = 2 years. There was a median 2-mm increase (interquartile
> range \[IQR\] 0 to 3) in neck diameter at 18 months. However, a \> or
> = 3-mm increase was seen in 18 (46%) of 39 patients examined at 18
> months (median 4 mm, IQR 3 to 4, p = 0.0001). The maximum AAA diameter
> decreased by 9 mm (IQR 4 to 16, p = 0.0003) at 24 months, but after 18
> months, no further interval decrease was seen. Aneurysms with a
> persistent endoleak showed either increasing or unchanged AAA
> diameters. There was no change in the renal artery to bifurcation
> distance. CONCLUSIONS: The infrarenal aortic neck appears to dilate
> after AAA endografting, but only in a subset of patients. Shrinkage of
> aneurysms after successful stent-grafting seems to stop after 18
> months, implying that the only indication of late failure in the
> absence of endoleak might be aneurysm enlargement. Graft-related
> endoleaks are often associated with an increase in aneurysm diameter.

Rhee RY; Eskandari MK; Zajko AB; Makaroun MS. Long-term fate of the
aneurysmal sac after endoluminal exclusion of abdominal aortic
aneurysms. **J Vasc Surg**. 2000 Oct; 32(4): 689-96.

> PURPOSE: Shrinkage of an abdominal aortic aneurysm (AAA) is the
> hallmark of successful endoluminal treatment. Our goal was to
> prospectively assess the midterm to long-term shrinkage of the AAA sac
> after endovascular repair. METHODS: A total of 123 patients with AAA
> underwent endoluminal treatment with the Ancure device at our
> institution between February 1996 and February 2000. At least a 1-year
> follow-up was available for 70 of the 123 patients. AAA sac size,
> presence of endoleaks, calcifications, and outcome data were collected
> on these patients at 6, 12, 24, and 36 months after repair and
> compared with the preoperative AAA size and characteristics. All
> endoleaks found at the 6-month follow-up visit were treated
> aggressively with embolotherapy. An AAA sac regression of 0.5 cm or
> more was considered the minimum measurable decrease. Regression of the
> sac diameter to 3.5 cm or less was considered a complete collapse of
> the sac. RESULTS: Successful endoluminal repair was accomplished in
> 119 of 123 patients. The mortality rate was 0.8% (1/123). There was a
> steady decrease in AAA sac size from baseline (5.56 +/- 0.1 cm), to 6
> months (5.0 +/- 0.14 cm, P =.0006), to 12 months (4.65 +/- 0.13 cm, P
> =.04), and to 24 months (4.26 +/- 0.16 cm, P =.03). At 24 months, 74%
> (29/39) had a decrease in sac size of 0.5 cm or more, with 28% (11/39)
> complete collapse. Patients with initial endoleaks had the same
> likelihood of regression of sac size (\> or = 0.5 cm) when compared
> with the group of patients with no endoleaks at the 24-month
> evaluation (64% vs 76%, P =.09). CONCLUSION: Endoluminal AAA repair
> resulted in a significant reduction in sac size that continues up to 2
> years. Significant shrinkage occurs as early as 6 months after
> placement. The initial presence of endoleaks does not predict the lack
> of sac regression.

Schurink GW; Aarts NJ; van-Bockel JH. Endoleak after stent-graft
treatment of abdominal aortic aneurysm: a meta-analysis of clinical
studies. **Br J Surg**. 1999 May; 86(5): 581-7.

> BACKGROUND: Endoleak is the major complication after endovascular
> treatment of abdominal aortic aneurysm (AAA) and its incidence seems
> to remain significant. Little is known about the association of device
> type and configuration with respect to the incidence, location, time
> of onset and fate of endoleakage. METHODS: A meta-analysis was
> performed via a Medline search of clinical studies after 1995 dealing
> with the endovascular treatment of AAA. Details of number of patients
> treated, configuration and type of endovascular device were collected.
> Data concerning site of origin, time of occurrence and fate of the
> endoleak were retrieved, along with information on change in diameter
> of the aneurysm with time. RESULTS: The 23 publications included
> reported on 1189 patients. The 1118 patients with successfully
> inserted transfemoral endovascular grafts experienced 270 endoleaks
> (24 per cent). The majority arose from the distal stent attachment
> site (36 per cent), were present immediately after stent-graft
> placement (66 per cent) and were persistent in time (37 per cent).
> Tube grafts were more frequently affected by endoleakage (35 per cent;
> P \< 0.0001), especially at the distal stent attachment site (51 per
> cent), than bifurcated grafts (18 per cent; P = 0.004) and
> aortounilateral devices (20 per cent; P = 0.70). Self- expandable
> stent-grafts were more frequently associated with endoleaks (25 per
> cent) than balloon-expandable stent-grafts (17 per cent) (P = 0.037).
> CONCLUSION: Endovascular treatment of AAA is an evolving field. Even
> after the initial learning curve and attention to device-related
> problems, it is still accompanied by a significant number of
> endoleaks. Uniform presentation of results of treatment is necessary
> for analysing the effect of differences between patients, aneurysm
> morphology and device type.

Singh-Ranger R; McArhur T; Lees W; Adiseshiah M. A prospective study of
changes in aneurysm and graft length after endovascular exclusion of AAA
using balloon and self-expanding endograft systems. **Eur J Vasc
Endovasc Surg**. 2000 Jul; 20(1): 90-5

> PURPOSE: Longitudinal shrinkage of aneurysms post-endovascular repair,
> employing unvalidated measurement techniques has been held to account
> for endograft disruption. In this study we record changes in aneurysm
> length, diameter and volume using the gold standard of calibrated
> spiral CT angiography (SCTA). METHOD: From 179 patients with AAA
> scanned by SCTA, 68 were selected for endografting. Twenty-seven had
> PTFE home-made prostheses while 41 patients had Talent endografts.
> SCTA was performed on the fifth postoperative day and 6-monthly
> intervals thereafter. The distance between the lowest renal artery and
> the aortic bifurcation (VBL - vertical body length) and the luminal
> centre line length (LCL) were measured. Maximal sac diameters and
> volumes were recorded using 3DCT reconstruction. RESULTS: Significant
> increase was noted in VBL (3.2) mm for PTFE-treated patients
> accompanied by an increase in sac volume at day 5 (12.5 ml). No
> changes in LCL or maximal diameters were evident. At 1.5 years further
> lengthening of both VBL (6.4 mm) and LCL (9.3 mm) was unaccompanied by
> sac diameter/volume changes. Talent patients - no changes in VBL or
> LCL were evident. Volumes and maximal AP and transverse diameters
> showed marked shrinkage: AP -11. 2 mm; transverse -2.6 mm; volumes by
> -35.5 ml at 6 months. CONCLUSION: With PTFE increase in VBL but not
> graft length, without concurrent changes in maximal diameters at day
> 5, is commensurate with increase in sac volume; after 1.5 years graft
> lengthening overtakes aortic lengthening. In Talent patients VBL/graft
> length remained unchanged. There is no evidence for longitudinal
> aneurysmal contracture. Volumes and maximal diameters for the Talent
> endograft but not for PTFE show shrinkage

Walker SR; Yusuf SW; Wenham PW; Hopkinson BR. Renal complications
following endovascular repair of abdominal aortic aneurysms. **J
Endovasc Surg**. 1998 Nov; 5(4): 318-22.

PURPOSE: To investigate the renal complications associated with
endovascular repair of abdominal aortic aneurysms (AAAs). METHODS: Data
were prospectively collected on 164 AAA patients (154 males; median age
72 years; interquartile range 51 to 88) undergoing endovascular
grafting. Any history of renal failure and diabetes mellitus was
recorded. Serum urea and creatinine levels were measured preoperatively
and at regular intervals postoperatively. Renal impairment was defined
as serum creatinine \> 130 micromol/L. RESULTS: There were no
significant differences in pre- and 1-day postoperative serum urea and
creatinine levels. Among 15 (9.1%) patients with preoperative renal
failure, 7 (47%) died, 4 (27%) in the perioperative period. Of the 149
patients with normal renal function preoperatively, 4 (2.7%) developed
renal failure as part of multisystem organ failure. Another 9 (6.2%)
developed significant postoperative elevations (\> 20%) in their
creatinine levels compared to baseline; 4 of these patients died, 2 in
the perioperative period. There was no significant difference in the
median dose of intravascular contrast used for those patients that did
and did not have a deterioration in their renal function (250 mL versus
300 mL). CONCLUSIONS: In this study, approximately 6% of patients with
normal preoperative renal function who undergo endovascular AAA repair
develop renal dysfunction. For patients with preoperative renal
impairment, the perioperative mortality rate is high, 27%, following
endovascular aortic aneurysm repair.

Wever JJ; de-Nie AJ; Blankensteijn JD; Broeders IA; Mali WP; Eikelboom
BC. Dilatation of the proximal neck of infrarenal aortic aneurysms after
endovascular AAA repair. **Eur J Vasc Endovasc Surg**. 2000 Feb; 19(2):
197-201.

> OBJECTIVES: to assess size changes of the proximal aortic neck after
> endograft placement. METHODS: since 1994, 54 consecutive patients have
> undergone abdominal aortic aneurysm (AAA) repair with the Endovascular
> Technologies (EVT) endograft. The study group comprised the 33
> patients who had completed at least six months of the prospective
> follow-up protocol. The pre-, postoperative and follow-up helical
> computed tomography (CT) angiograms (CTAs) were processed on a
> workstation. The proximal neck dimensions were measured perpendicular
> to the central lumen line of the aortic neck. The cross-sectional area
> was measured at the proximal attachment system and at 1 cm proximal to
> the renal arteries. RESULTS: while the dimensions of suprarenal aorta
> did not change, a significant dilatation of the proximal neck was
> found. The median increase was 10.3% at 6 months and 15.5% at 12
> months. No correlation could be found between the amount of dilatation
> and pre- or postoperative neck-size, graft diameter and amount of
> graft-oversizing. CONCLUSION: the infrarenal aortic neck demonstrates
> continued dilatation during follow-up after endograft placement.

White GH; May J; Petrasek P; Waugh R; Stephen M; Harris J. Endotension:
an explanation for continued AAA growth after successful endoluminal
repair. **J Endovasc Surg**. 1999 Nov; 6(4): 308-15.

PURPOSE: To present and analyze several cases that illustrate persistent
sac pressurization following endovascular abdominal aortic aneurysm
(AAA) repair. METHODS AND RESULTS: Four patients with successful
endovascular AAA exclusion presented in follow-up with an expanding
aneurysm. Two had initial sac diameter decrease, but by 18 and 24
months, respectively, the AAA had enlarged and become pulsatile. There
was no endoleak evident, but the proximal attachment stents had mig
rated distally in both cases. One patient developed endoleak with
aneurysm expansion at 6 months; contained rupture occurred at 12 months.
The last case had slowly evolving aneurysm expansion over 36 months but
no endoleak. All endografts were removed and successfully replaced with
conventional grafts. Intrasac thrombus was implicated as the means of
pressure transmission that precipitated AAA expansion in these cases.
CONCLUSIONS: Excluded AAAs can increase in size owing to persistent or
recurrent pressurization (endotension) of the sac even when there is no
evidence of endoleak. One proposed mechanism is pressure transmission
via thrombus that lines the attachment site. Endotension may also
represent an indiscernible, very low flow endoleak that allows blood to
clot at the source of leakage.

White GH; May J; Waugh RC; Chaufour X; Yu W. Type III and type IV
endoleak: toward a complete definition of blood flow in the sac after
endoluminal AAA repair. **J Endovasc Surg**. 1998 Nov; 5(4): 305-9

In this document the authors continue to refine their seminal
categorization of endoleak, a major complication of endovascular
aneurysm repair. In addition to type I (related to the graft device
itself) and type II (retrograde flow from collateral branches) endoleak,
they propose two new categories: endoleak due to fabric tears, graft
disconnection, or disintegration would be classified type III, and flow
through the graft presumed to be associated with graft wall \"porosity\"
would be categorized as type IV endoleak.

White RA; Donayre CE; Walot I; Woody J; Kim N; Kopchok GE. Computed
tomography assessment of abdominal aortic aneurysm morphology after
endograft exclusion. **J Vasc Surg**. 2001 Feb; 33(2 Suppl): S1-10.

> OBJECTIVES: Assessment of the long-term function of endografts to
> exclude abdominal aortic aneurysm (AAA) includes determination of
> aneurysm dimensions and morphologic changes that occur after
> implantation. This study reports the dimensional analysis of patients
> treated with AneuRx bifurcated endoprostheses with postintervention,
> 1-year (n = 51), 2-year (n = 28), and 3-year (n = 10) postimplantation
> contrast computed tomography data. METHODS: Maximal diameter (D) and
> cross-sectional area (CSA) of the AAA were measured from axial
> computed tomography images. Total volume, AAA thrombus volume (AAA
> volume minus the volume of the device and luminal blood flow),
> diameter of the aorta at the level of the renal arteries and within
> the device, distance from the renal arteries to the device, length of
> the device limbs, and the angle of the proximal neck were also
> determined at the same follow-up intervals after deployment with
> computed tomography angiograms reconstructed in an interactive
> environment. RESULTS: Fifty-one of 98 consecutively treated patients
> with the AneuRx bifurcated prosthesis (29 \"stiff\" and 22
> \"flexible\" body devices) had complete data from the postprocedure
> and follow-up computed tomography studies available for analysis. Max
> D, CSA, total volume of the AAA, and AAA thrombus volume decreased
> sequentially from year to year compared with the postimplantation
> values. D and CSA decreased or were unchanged in all except four
> patients, two who had unrestricted enlargement of the aneurysm with
> eventual rupture and one who had surgical conversion for continued
> expansion despite four diagnostic angiograms and attempted
> embolizations. Total volume of the AAA increased in 11 of 51 patients
> at 1 year, eight of whom had endoleaks at some interval during the
> follow-up. Thrombus volume increased more than 5% in four of these
> patients, including the two with eventual rupture and the one
> conversion. Patients with endoleaks who had spontaneous thrombosis or
> were successfully treated either remained at the same volume or had
> decreased volume on subsequent examinations. D at the renal arteries
> increased an average of 0.9 mm during the first year, with a
> concomitant increase of 2.8 mm within the proximal end of the device
> related to the self-expanding nature of the Nitinol suprastructure.
> Subsequent enlargement of the proximal neck continued at a slow rate
> in some cases but never exceeded the diameter of the endoluminal
> device. The distance from the renal arteries to the device increased
> by an average of 3 mm over the first year, with the greatest increases
> occurring in patients with a \"stiff\" body device and those with
> rapid regression (\>10% total volume) in 1 year. As regression of the
> AAA occurred, the angle of the proximal neck varied from -5 degrees to
> +25 degrees from the original alignment. Limb length varied from -8 mm
> to +10 mm, with no consistent pattern for the change, that is,
> ipsilateral or contralateral limb. CONCLUSION: Significant variation
> in the quantitation of aneurysm size occurs depending on the technique
> of computed tomography assessment used. In most patients diameter
> assessment is adequate, although volumetric analysis appears to be
> very helpful in certain patients who do not show aneurysm regression,
> or in whom the diameter increases or where endoleaks persist.
> Three-dimensional reconstruction and volumetric analysis are also
> useful to assess the mechanism by which the endovascular device
> accommodates to morphology changes and to determine criteria for
> reintervention.

Wolf YG; Hill BB; Rubin GD; Fogarty TJ; Zarins CK. Rate of change in
abdominal aortic aneurysm diameter after endovascular repair. **J Vasc
Surg**. 2000 Jul; 32(1): 108-15.

> OBJECTIVE: Untreated abdominal aortic aneurysms (AAAs) enlarge at a
> mean rate of 3.9 mm/y with great individual variability. We sought to
> determine the effect of endovascular repair on the rate of change in
> aneurysm size. METHODS: There were 110 patients who underwent
> endovascular AAA repair at Stanford University Medical Center and who
> were followed up for 1 to 30 months (mean, 10 months) with serial
> contrast-infused helical computed tomography (CT). Maximal aneurysm
> diameter was determined using two independent methods: (1) measured
> manually, from cross-sectional computed tomography (XSCT) angiograms
> and (2) calculated from quantitative three-dimensional computed
> tomography (3DCT) data as orthonormal diameter. RESULTS: Maximal
> cross-sectional aneurysm diameter measured by hand (XSCT) and
> calculated as orthonormal values (3DCT) correlated closely (r = 0.915;
> P \<.001). The XSCT-measured diameter was larger by 2.3 +/- 3. 75 mm
> (P \<.001), and the 95% CI for SE of the bias was 1.85 to 2.75 mm.
> Preoperative aneurysm diameter (XSCT 59.1 +/- 8.4 mm; 3DCT 58.1 +/-
> 9.3 mm) did not differ significantly from the initial postoperative
> diameter. Considering all patients, XSCT diameter decreased at a rate
> of 0.34 +/- 0.69 mm/mo, and 3DCT diameter decreased at a rate of 0.28
> +/- 0.79 mm/mo. Aneurysms in patients without endoleaks had a higher
> rate of decrease, an XSCT diameter by 0.50 +/- 0.74 mm/mo, and 3DCT
> diameter by 0.46 +/- 0.84 mm/mo. In these patients, mean absolute
> decrease in diameter at 6 months was 3. 4 +/- 4.5 mm (XSCT) and 3.3
> +/- 5.9 mm (3DCT) and at 12 months, 5.9 +/- 5.7 mm (XSCT) and 5.4 +/-
> 5.7 mm (3DCT). Aneurysms in patients with persistent endoleaks did not
> change in mean XSCT diameter, and 3DCT diameter increased by 0.12 +/-
> 0.52 mm/mo (not significant). Aneurysm diameter remained within 4 mm
> of original size in 68% (3DCT) to 71% (XSCT) of patients. In one
> patient, aneurysm diameter increased (XSCT and 3DCT) more than 5 mm.
> Four patients who had a new onset endoleak had a much higher expansion
> rate than those with a chronic endoleak (P \<.05). CONCLUSIONS: The
> rate of decrease in aneurysm size (annualized 3.4-4.1 mm/y) after
> endovascular repair of AAA approximates the reported expansion rate in
> untreated aneurysms. However, individual aneurysm behavior is
> upredictable, and the presence of an endoleak is unreliable in
> predicting changes in diameter. New onset endoleaks are associated
> with an enlargement rate greater than that of untreated aneurysms.