# Summary of Safety and Effectiveness Data

#### WALLSTENT Venous Endoprosthesis with Unistep Plus Delivery System

# 

# 1. General Information

Device Generic Name: Intravascular Stent

> Device Trade Name: WALLSTENT Venous Endoprosthesis with Unistep Plus
> Delivery System

Applicant's Name and Address: Boston Scientific Scimed Inc.

One Scimed Place

Maple Grove MN 55311-1566

PMA Number: P980033

Date of Notice of Approval to the Applicant: Novermber 16, 2001

# 2. Indications for Use 

The Wallstent Venous Endoprosthesis is indicated for improving central
venous diameter following unsuccessful angioplasty in patients on
chronic hemodialysis with stenosis of the venous outflow tract.
Unsuccessful angioplasty is defined as:

> • residual stenosis [\>]{.underline} 30 percent for a vein
> [\<]{.underline} 10 mm in diameter or [\>]{.underline} 50 percent for
> a vein \> 10 mm in diameter;
>
> • a tear which interrupts the integrity of the intima or lumen;
>
> • abrupt lesion site occlusion or refractory spasm.

The vessels that can be treated with the Wallstent Venous
Endoprosthesis are the innominate and subclavian veins ranging from 8 mm
to 15 mm in diameter.

# 3. Device Description

The Wallstent Venous Endoprosthesis is comprised of two components: the
implantable metallic stent and the Unistep Plus Delivery System.

• The stent is composed of biomedical superalloy wire with a radiopaque
core braided in a tubular mesh configuration.

• The delivery system is composed of co-axial tubes which allow
reconstrainment as indicated by the limit marker and has radiopaque
marker bands which aid in accurate placement of the stent.

The Wallstent Venous Endoprostheses is available in the following
diameters: 10, 12, 14, 16 mm. See Table 1 for stent sizing information.

Stent diameter selected should be approximately 1 mm to 2 mm larger than
the vessel diameter desired. Deployed lengths reflect expansion to
desired vessel diameter. Constricting the stent to a smaller diameter
will cause a longer deployed length, depending on the degree of
constriction. On average, a 0.5 mm change in diameter yields a 10-15
percent change in length. Once the desired vessel diameter is reached,
no additional reduction in stent length should occur.

# Table 1: Stent Sizing Specifications

+-----------+--------+---------+----------+---------+----------+-----+
| ### WALLS |        |         |          |         |          |     |
| TENT® Ven |        |         |          |         |          |     |
| ous Endop |        |         |          |         |          |     |
| rosthesis |        |         |          |         |          |     |
|           |        |         |          |         |          |     |
| ###       |        |         |          |         |          |     |
| Vessel Di |        |         |          |         |          |     |
| ameter an |        |         |          |         |          |     |
| d Approxi |        |         |          |         |          |     |
| mate Impl |        |         |          |         |          |     |
| anted Ste |        |         |          |         |          |     |
| nt Length |        |         |          |         |          |     |
+===========+========+=========+==========+=========+==========+=====+
|           | Fully  |         | WA       |         |          |     |
|           | Opened |         | LLSTENT® |         |          |     |
|           |        |         | Venous   |         |          |     |
|           | Stent  |         | Endopr   |         |          |     |
|           | Di     |         | osthesis |         |          |     |
|           | ameter |         |          |         |          |     |
|           | /      |         | When     |         |          |     |
|           | Length |         | I        |         |          |     |
|           |        |         | mplanted |         |          |     |
|           |        |         | in       |         |          |     |
|           |        |         | S        |         |          |     |
|           |        |         | pecified |         |          |     |
|           |        |         | Vessel   |         |          |     |
|           |        |         | Diameter |         |          |     |
+-----------+--------+---------+----------+---------+----------+-----+
| Order     | Diam.  | Length  | Vessel   | Stent   | Vessel   | Len |
| Number    |        |         | Diam.    | Length  | Diam.    | gth |
|           | \(mm\) | \(mm\)  |          |         |          |     |
|           |        |         | \(mm\)   | \(mm\)  | \(mm\)   | \(m |
|           |        |         |          |         |          | m\) |
+-----------+--------+---------+----------+---------+----------+-----+
| 71-132    | 10     | 20      | 8        | 33      | 9        | 27  |
+-----------+--------+---------+----------+---------+----------+-----+
| 71-134    | 10     | 42      | 8        | 54      | 9        | 48  |
+-----------+--------+---------+----------+---------+----------+-----+
| 71-136    | 10     | 68      | 8        | 77      | 9        | 69  |
+-----------+--------+---------+----------+---------+----------+-----+
| 71-138    | 10     | 94      | 8        | 115     | 9        | 103 |
+-----------+--------+---------+----------+---------+----------+-----+
| 40210     | 12     | 20      | 10       | 31      | 11       | 26  |
+-----------+--------+---------+----------+---------+----------+-----+
| 40211     | 12     | 40      | 10       | 51      | 11       | 47  |
+-----------+--------+---------+----------+---------+----------+-----+
| 40212     | 12     | 60      | 10       | 73      | 11       | 66  |
+-----------+--------+---------+----------+---------+----------+-----+
| 40213     | 12     | 90      | 10       | 110     | 11       | 100 |
+-----------+--------+---------+----------+---------+----------+-----+
| 40310     | 14     | 20      | 12       | 33      | 13       | 27  |
+-----------+--------+---------+----------+---------+----------+-----+
| 40311     | 14     | 40      | 12       | 50      | 13       | 46  |
+-----------+--------+---------+----------+---------+----------+-----+
| 40312     | 14     | 60      | 12       | 72      | 13       | 65  |
+-----------+--------+---------+----------+---------+----------+-----+
| 40313     | 14     | 90      | 12       | 107     | 13       | 98  |
+-----------+--------+---------+----------+---------+----------+-----+
| 40330     | 16     | 20      | 14       | 28      | 15       | 23  |
+-----------+--------+---------+----------+---------+----------+-----+
| 40331     | 16     | 40      | 14       | 49      | 15       | 45  |
+-----------+--------+---------+----------+---------+----------+-----+
| 40332     | 16     | 60      | 14       | 70      | 15       | 64  |
+-----------+--------+---------+----------+---------+----------+-----+
| 40333     | 16     | 90      | 14       | 105     | 15       | 97  |
+-----------+--------+---------+----------+---------+----------+-----+

> **MRI Safe**: The Wallstent Venous Endoprosthesis has shown no
> deflection or torque in the area of maximum spatial gradient (450
> gauss centimeter) of a 1.5 tesla MRI system under conditions that
> produced a Specific Absorption Rate (SAR) of 1.3 W/kg. Imaging
> artifacts affect the region of interest at the location of the device
> (artifact ratio 1.2 to 6.7), while areas away from the device appear
> unaffected by their presence.

# 4. Contraindications

The Wallstent Venous Endoprosthesis is contraindicated for use in:

Patients with bleeding disorders unresponsive to vitamin K or blood
product therapy.

# 5. Warnings and Precautions

See WARNINGS AND PRECAUTIONS in the final labeling (Information for Use)

# Adverse Events

**6.1 Observed Adverse Events**

> A total of 42 patients were enrolled in the multi-center study of
> Wallstent Venous Endoprosthesis for central lesions. This study was
> conducted at 12 investigational sites.
>
> Patients from the Wallstent Venous Endoprosthesis study form the
> basis of the observed events described in Table 2.
>
> Five (5) patients enrolled in the Wallstent Venous Study died during
> the trial. None of these deaths occurred in the first 6 months
> following the Wallstent procedure and none were considered device
> related. The cause of death was reported as follows: (1) hyperkalemia
> 475 days post procedure; (2 and 3) cardiac arrest at 343 and 631 days
> post procedure; (4) septicemia with peripheral vascular disease and
> gangrene 902 days post procedure; (5) stomach cancer 276 days post
> procedure.

+-----------------------+-----------------------+-----------------------+
| Table 2               |                       |                       |
|                       |                       |                       |
| Safety Results,       |                       |                       |
| Wallstent Venous      |                       |                       |
| Central Patients      |                       |                       |
| (N=42)                |                       |                       |
+-----------------------+-----------------------+-----------------------+
| Adverse Event         | Result                | 95% C.I.              |
+-----------------------+-----------------------+-----------------------+
| # General Events      | 11.9% (5/42)          | \[4.0%, 25.6%\]       |
|                       |                       |                       |
| > Death               | 4.8% (2/42)           | \[0.6%, 16.2%\]       |
| >                     |                       |                       |
| > Surgical Revision   | 40.5% (17/42)         | \[25.6%, 56.7%\]      |
| >                     |                       |                       |
| > Access abandoned    | 21.4% (9/42)          | \[10.3%, 36.8%\]      |
| > from central lesion |                       |                       |
| >                     |                       |                       |
| > Access abandoned    |                       |                       |
| > from peripheral     |                       |                       |
| > graft               |                       |                       |
+-----------------------+-----------------------+-----------------------+
| # Non                 | 45.2% (19/42)         | \[29.8%, 61.3%\]      |
| -Stent-Related Events |                       |                       |
|                       | 16.7% (7/42)          | \[7.0%, 31.4%\]       |
| > Graft               |                       |                       |
| >                     | 14.3% (6/42)          | \[5.4%, 28.5%\]       |
|  Occlusion/Restenosis |                       |                       |
| >                     | 4.8% (2/42)           | \[0.6%, 16.2%\]       |
| > Pseudoanuerysm      |                       |                       |
| >                     |                       |                       |
| > Infection           |                       |                       |
| >                     |                       |                       |
| > Hematoma            |                       |                       |
+-----------------------+-----------------------+-----------------------+
| #                     | 76.2% (32/42)         | \[60.5%, 87.9%\]      |
|  Stent-Related Events |                       |                       |
|                       | 50.0% (21/42)         | \[34.2%, 65.8%\]      |
| > Stent Restenosis    |                       |                       |
| >                     | 2.4% (1/42)           | \[0.1%, 12.6%\]       |
| > Stent Thrombosis    |                       |                       |
| >                     | 40.5% (17/42)         | \[25.6%, 56.7%\]      |
| > Migration           |                       |                       |
| >                     |                       |                       |
| > Edema               |                       |                       |
+-----------------------+-----------------------+-----------------------+

Results are percent (count/sample size) of all patients experiencing the
event, and reflect each patient's entire study experience regardless of
length of follow-up.

Mean [+]{.underline} SD (sample size) (min, max) length of follow-up in
days; 350.5[+]{.underline}299.4 (42) (4.0.1434). Confidence intervals
are based on exact limits.

**Note:** Surgical revision refers to those events where the graft was
revised, but not abandoned. Patients reporting edema are a subset of
patients with stent restenosis/thrombosis.

Additional clinical safety data was retrospectively obtained on 12
patients enrolled in a physician's registry study of the Wallstent
Venous Endoprosthesis for the treatment of stenotic or occluded
subclavian veins of patients undergoing hemodialysis. Four deaths were
reported among these 12 patients. The reported cause and time of
occurrence for these deaths is: sepsis at 16 days post-procedure,
aspiration pneumonia at 32 days post-procedure, myocardial
infarction/subdural hematoma at 81 days post-procedure, and hypotension
at 240 days post procedure.

Adverse events related to either the stent or the stent implant
procedure included stent thrombosis (5), stent restenosis (8), stent
migration (3), and an allergic reaction to contrast media (1). The three
stent migrations in this physician single-center study and the one stent
migration in the multi-center Wallstent Venous central lesion study were
attributed to incorrect sizing of the stent and/or dislodgment with the
guide catheter. All of the stent migration cases were treated with a
percutaneous procedure and none resulted in abandonment of the access
site.

#### 6.2 Potential Adverse Events

Potential adverse events associated with use of the WALLSTENT Venous
Endoprosthesis may include the usual adverse events reported for
conventional percutaneous transluminal angioplasty such as: hemorrhage,
infection, contrast media reactions, dissection, distal emboli, graft
rupture, graft/vein thrombosis or occlusion, perforation of the vein,
suture disruption of the anastomosis, thromboembolism or transient
spasm.

Potential adverse events associated with the WALLSTENT Venous
Endoprosthesis are stent misplacement, stent migration, or vein
perforation.

#### 6.3 Observed Device Malfunctions

Two incidents of stent malfunction were reported in the central venous
lesion study. In one incident, the delivery system failed to deploy. In
the second incident, the stent did not fully expand.

# 

# 7. Alternative Practices or Procedures

> Alternative procedures include percutaneous transluminal angioplasty
> (PTA).

# 8. Marketing History

Boston Scientific Scimed has not marketed the Wallstent Venous
Endoprosthesis for the central vein indication.

# Summary of Preclinical Studies

## Biocompatibility

> The biocompatibility of the WALLSTENT Venous Endoprosthesis and the
> Unistep Plus delivery catheter was evaluated in accordance with the
> FDA-modified matrix of International Standard ISO-10993, "Biological
> Evaluation of Medical Devices Part 1: Evaluation and Testing." All
> materials were found to be biocompatible.

## 9.2 Bench Testing

> *Stent Material Composition Conformance*

The chemical composition of the biomedical superalloy wire conforms to
the ASTM F1058 standard and the composition of the tantalum core
material conforms to the ASTM F560-68 standard.

> *Stent Wire Mechanical Properties Conformance*

The mechanical properties (tensile strength and elongation) of the stent
wire were documented through tensile testing.

*Corrosion Resistance*

Samples of the stent wire were tested for resistance to corrosion
resistance. There was no evidence of galvanic corrosion among the test
samples.

*Stent Percent Free Area*

The percent free area, i.e., the area not in contact with the vessel
wall, was calculated for all stent diameters. The results found that the
stent percent free area was approximately 80 percent from fully open to
nearly 50 percent constrained.

*Stent Uniformity*

To determine the uniformity of the stent dimensions, the outer diameter
and length (constrained and unconstrained) of all stent diameters were
measured. The measurements documented the uniformity of the outer
diameters and the stent lengths.

> *Radial Force*
>
> The force exerted by the self-expanding stent as a function of its
> diameter was measured to determine the exerted radial tension from one
> stent to another over a constrained diameter range. The test results
> show consistent radial force between the stents.
>
> *Fatigue*

Finite element stress analysis was performed on all stent sizes. The
analysis included fabrication stresses and the calculation of stress as
a function of diameter, ranging from fully constrained (loaded on the
catheter) to unconstrained (fully deployed). The stress analysis
indicated a satisfactory safety factor was present and fatigue failure
of the stent was unlikely.

*Stent Deformation*

To determine the ability of the stent to withstand deformation from an
external force, all stent diameters underwent compression testing. The
stent were exposed to a uniform external force and a focal external
force. All of the stents, except one, survived the compression testing
without a fracture of the stent wire.

> *Magnetic Resonance Imaging (MRI) CompatibilityTesting*
>
> MRI compatibility testing determined the location of the maximum
> spatial gradient within the scanner and measured the average
> deflection for each stent from the displacement force and from the
> displacement torque. The change in temperature of the stent was
> measured during a pulse sequence that produced a whole body averaged
> specific absorption rate of 1.3W/kg. Geometric distortion was
> calculated under a gradient pulse echo sequence and a conventional
> spin echo pulse sequence. The results found that the stent was MRI
> safe with artifact affecting imaging at the location of the stent.
>
> *Delivery Catheter Trackability*

To determine the amount of force necessary to pass a delivery catheter
with mounted stent over a guidewire, six to seven of the smallest and
largest stent sizes were tested in a simulated clinical model. The
results found that the tracking forces were acceptable.

> *Delivery Catheter Stent Deployment Force*
>
> To determine the force required to deploy and reconstrain the stent,
> six to seven of the smallest and largest stent sizes were tested in a
> simulated clinical model. All of the samples were within the test
> specifications.
>
> *Delivery Catheter Bond Strength*
>
> To demonstrate the strength of the bonded joints and their ability to
> resist failure, bond strength testing was performed on 26-78 units per
> 10 different bond sites. The results of each of the bond strength
> tests exceeded the test specification.
>
> 9.3 **Sterility and Packaging Testing**
>
> *Sterility*
>
> The Wallstent Venous Endoprosthesis is sterilized by a validated
> ethylene oxide sterilization process. The validated protocol was based
> on the ANSI/AAMI/ISO 1135-1994 "Medical Devices-Validation and Routine
> Control of Ethylene Oxide Sterilization". The validation results
> demonstrated that the sterilization process can achieve a sterility
> assurance level of 10^-6^.
>
> *Shipping and Shelf Life Tests*
>
> Sterilized, packaged devices were subjected to accelerated aging and
> simulated transportation testing. Results of a visual examination,
> peel and burst strength testing, burst strength testing, and
> performance testing support a claim for a 2-year shelf life.

# 10. Summary of Clinical Studies

A total of 42 patients at 12 investigational sites within the United
States were enrolled in a prospective, multi-center, non-randomized
study with a historical percutaneous transluminal angioplasty (PTA)
control cohort to investigate the safety and efficacy of the Wallstent
Venous Endoprosthesis for improving central venous luminal diamter
following unsuccessful angioplasty in patients on chronic hemodialysis.

**Primary Endpoint**: The primary endpoint for the Wallstent Venous
trial was *circuit secondary patency* at 6 months. Circuit Secondary
Patency is defined as the proportion of patients, over time, that have
an occluded vessel that is successfully opened. Failure of
[circuit]{.underline} secondary patency occurs at the time the dialysis
site is abandoned due to the inability to treat the stenosis, or
occlusion of either the central lesion under consideration or any other
peripheral or *de novo* central lesion.

Other endpoints evaluated include:

**Stent Primary Patency,** defined as the proportion of patients, over
time, that have had uninterrupted (intervention-free) patency since the
initial procedure. Primary patency ends at the first occurrence of one
of the following: initial re-intervention for the purpose of treating
patency of the central lesion; anatomical failure (50% or greater
stenosis) of the central lesion; or when the dialysis site is abandoned
due to the inability to treat the original central lesion. If percent
stenosis of the central lesion is undetermined, the occurrence of
arm/face edema indicates the end of primary patency.

**Stent Secondary Patency,** defined as the time to failure of the
access site due to stenosis or occlusion of the stented central lesion.
Anatomical failure (\>50% stenosis) of the central lesion which is not
successfully reopened is also considered failure of stent secondary
patency. Patients failing circuit secondary patency due to other
peripheral lesions, problems at the access site (e.g. pseudoaneurysm,
infection), or a *de novo* central lesion that does not involve the
stent margin, do not fail stent secondary patency. These patients are
censored from analysis at the date of the last follow-up documenting
patency of the stent.

Patency rates were estimated by means of Kaplan-Meier Survival Analysis.

**Patient Elgibility:** Patients were eligible for the study if they
were on chronic hemodialysis and had a central venous stenosis which was
treatable with PTA. If the PTA failed to reduce the stenosis to less
than 50% in patients with a vein \>10 mm in diameter, or 30% in a vein
[\<]{.underline}10mm in diameter, the patient received a WALLSTENT^®^
Venous Endoprosthesis. If the PTA was successful, but the stenosis
recurred within 4 months, the patient received a WALLSTENT^®^ Venous
Endoprosthesis.

**Study Methods:** Clinical follow-up was obtained at 1 week, 2 months,
6 months, and every 6 months thereafter until study conclusion, or the
graft site was abandoned. Baseline quantitative angiography was
performed pre-procedure, following balloon angioplasty, following device
deployment, and at the 2-month and 6-month visit. The stent primary
patency, stent secondary patency, and circuit secondary patency were
analyzed.

**Results:** Among the 42 patients enrolled in the study, lesions
involved the innominate vein in 14, subclavian vein in 23, and both
subclavian and innominate veins in 5 patients. The mean lesion length
was 25.8mm (±18.8, range = 2.0-81.6mm). Multiple stents were implanted
in 5 patients (11.9%). A total of 28.6% of the patients (12/42) had
occluded (100% stenoses) veins at the time of the study enrollment.

Initial intraoperative success, as measured by the reduction in stenosis
to [\<]{.underline}30%, or angiographic demonstration of an increase in
venous outflow, was achieved in 100% of patients. Analysis of the
clinical data demonstrated a 74.3% circuit secondary patency rate at six
months for the WALLSTENT^®^ study group, compared to a 50% secondary
patency rate for the historical control of percutaneous transluminal
angioplasty (PTA), resulting in a highly significant statistical
difference (p\<0.0003). The WALLSTENT^®^ Venous Endoprosthesis was found
to provide superior efficacy in the central venous patient cohort when
compared to the historical control (PTA).

Baseline demographic and lesion characteristics were individually
regressed on time to loss of circuit secondary patency to assess
possible predictors of clinical outcome (univariate analysis). Presence
of an occluded lesion pre-procedure was significantly associated with
circuit secondary patency (p=0.022). The same variables were analyzed
using stepwise selection to identify a multivariate predictor model.
Presence of a totally occluded lesion pre-procedure was the only
variable associated with time to loss of circuit secondary patency
(p=0.0072). Implantation of multiple stents approached significance in
the multivariate model (p=0.062).

Principal Efficacy and Safety results are summarized in Table 3.

Table 3. Principal Efficacy and Safety Results, BSC Patients (N=42)

  ----------------------------- -------------------- ---------------------
  **Efficacy Measures**         **Result**           **95% C.I.**

  Device Success                100.0% (42/42)       \[91.6%,100.0%\]

  Initial Intraoperative                             
  Success:                                           

  Criterion 1: ≤30% Residual    64.3% (27/42)        \[48.0%,78.4%\]
  Stenosis                                           

  Criterion 2: Increased Venous 90.5% (38/42)        \[77.4%,97.3%\]
  Flow                                               

  Met Either Criterion          100.0% (42/42)       \[91.6%,100.0%\]

  Acute Procedure Success       64.3% (27/42)        \[48.0%,78.4%\]

  Initial Clinical Success      95.8% (23/24)        \[78.9%,99.9%\]

  Pre-PTA RVD (mm)              12.6±3.7 (42)\       \[11.5,13.7\]
                                (3.0,20.1)           

  Post-Stent MLD (mm)           8.8±2.8 (39)\        \[7.9,9.7\]
                                (3.7,20.2)           

  Post-Stent %DS                24.1±18.4 (42)\      \[18.5,29.6\]
                                (0.0,63.0)           

  6-Month RVD (mm)              10.4±3.3 (25)\       \[9.1,11.7\]
                                (4.0,18.3)           

  6-Month MLD (mm)              3.0±2.7 (26)\        \[1.9,4.0\]
                                (0.0,11.0)           

  6-Month %DS                   67.9±29.1 (26)\      \[56.7,79.1\]
                                (9.0,100.0)          

  Patency                                            

  6-Month Stent Primary Patency 24.4%                \[9.8%,39.0%\]
  (K-M)                                              

  6-Month Stent Secondary       82.5%                \[69.7%,95.2%\]
  Patency (K-M)                                      

  6-Month Circuit Secondary     74.3%                \[60.6%,88.1%\]
  Patency (K-M)                                      

  Stent Restenosis              76.2% (32/42)        \[60.5%,87.9%\]

  Arm-Face Edema                40.5% (17/42)        \[25.6%,56.7%\]

  **Safety Measures**           **Result**           **95% C.I.**

  Major In-Hospital Event       0.0% (0/42)          \[0.0%,8.4%\]

  Out-of-Hospital                                    
  (Stent-Related) Event                              

  Stent Thrombosis              50.0% (21/42)        \[34.2%,65.8%\]

  Migration                     2.4% (1/42)          \[0.1%,12.6%\]

  Death                         11.9% (5/42)         \[4.0%,25.6%\]
  ----------------------------- -------------------- ---------------------

Results are mean ± SD (sample size) (min, max) for continuous variables,
and percent (count/sample size) for binary variables.

Confidence intervals for binomial proportions are based on exact limits.

Patency rates are Kaplan-Meier estimates at 180 days; confidence
intervals based on Greenwood standard errors.

RVD = Reference Vessel Diameter

MLD = Minimum Lumen Diameter

%DS = percent diameter stenosis which refers to \"within lesion\"
measurement technique

Device Success = Stent(s) deployed completely.

Initial Intraoperative Success, Criterion 2 = angiographic demonstration
of an increase in venous outflow (visualization of less collateral flow,
more rapid rate of contrast media clearing or less reflux flow
post-procedure).

Acute Procedure Success = ≤30% residual stenosis and absence of major
in-hospital event.

Initial Clinical Success = \<20% recirculation fraction one week
post-procedure. (Note: incomplete number of assessments (N=24) reflects
a change in clinical practice during the course of the study in which
many institutions stopped using recirculation fractions to monitor
patients.)

Stent Restenosis = within stent %DS of 50% or greater, or in the absence
of angiography presence of arm-face edema.

Stent Thrombosis = total thrombotic stent occlusion documented by
angiography. (Note: Stent Thrombosis is a subset of stent restenosis).

Additional clinical efficacy data was also retrospectively obtained on
12 patients enrolled in physician's registry study of the Wallstent
Venous Endoprosthesis for the treatment of stenotic or occluded
subclavian veins of patients undergoing hemodialysis. The enrollment
criteria for this study were similar to the multicenter Wallstent Venous
central lesion study. A Kaplan-Meier Survival analysis estimated the
six-month circuit secondary patency, stent primary patency, and stent
secondary patency rates at 68.6%, 33.8%, and 75%, respectively, for this
patient cohort.

**11. Conclusions Drawn from Studies**

The preclinical studies indicate that the Wallstent Venous
Endoprosthesis with Unistep Plus Delivery Catheter meets or exceeds
safety, reliability and performance specifications. The results of the
clinical study indicate that the data show that the Wallstent Venous
Endoprosthesis with Unistep Plus Delivery System is reasonably safe and
effective for the treatment of patients on chronic hemodialysis
following unsuccessful angioplasty of the innominate and subclavian
veins, when used in accordance with the directions for use.

**12. Panel Recommendations**

In accordance with the provisions of section 515©(2) of the Federal
Food, Drug and Cosmetic Act as amended by the Safe Medical Devices Act
of 1990, this PMA was not referred to the Circulatory System Devices
Panel, an FDA advisory committee, for review and recommendation because
the information in the PMA substantially duplicates information
previously reviewed by this panel.

13. **FDA Decision**

The FDA issued an approval order on November 16, 2001. .

A condition of the sale of the device was further characterization of
long-term safety and effectiveness of the Wallstent Venous
Endoprosthesis through clinical follow-up of the study patients out to
one-year post-procedure.

14. **Approval Specifications**

> Directions for Use: See the labeling.
>
> Hazards to Health from User of the Device: See INDICATIONS,
> CONTRAINDICATIONS,WARNINGS AND PRECAUTIONS, AND ADVERSE EVENTS in the
> final draft labeling (Information for Use).
>
> Post-approval Requirements and Restrictions: See Approval Order