J Cardiol 2006 Dec; 48（6）: 305 – 314

Noninvasive Quantitative Evaluation of the Patency of Internal
Mammary Artery Grafts to the Left
Anterior Descending Coronary
Artery by Transthoracic Doppler
Echocardiography
Naoko MIZUKAMI, RCS
Shinichi MINAGOE, MD, FJCC＊1
YutakaOTSUJI, MD, FJCC＊2

Yoji NEISHI, MD＊3
Takashi

AKASAKA, MD, FJCC＊4

Shuichi HAMASAKI, MD, FJCC＊2
Toshinori YUASA, MD＊2
Masaaki MIYATA, MD＊2
Seiro

MARUYAMA, MD＊5

Kiyoshi

YOSHIDA, MD, FJCC＊3

Ryuzo

SAKATA, MD＊6

Chuwa

TEI, MD, FJCC＊2

Abstract ─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
Objectives. Evaluation of left anterior descending coronary artery（LAD）flow by transthoracic Doppler
echocardiography（TTDE）may allow assessment of anastomosis of the internal mammary artery（IMA）
grafted to the LAD. This study tested the feasibility of TTDE to evaluate anastomotic stenosis of the IMA
grafted to the LAD.
Methods. TTDE was performed in 66 patients（48 men and 18 women, mean age 67 ± 10 years）withleft or right IMA grafts to the LAD. The distal IMA flow at the anastomosis was visualized and the percentage stenosis was evaluated by the continuity equation using the anastomotic and pre-anastomotic flow
velocity measured by TTDE as well as by angiography. If the anastomotic flow was not visualized by
TTDE, the absence of augmented diastolic flow of the proximal IMA, by using the supraclavicularapproach, with diastolic to systolic mean velocity ratio ＜ 0.25 was considered as anastomotic occlusion.
Results. Anastomotic flow was visualized and the percentage stenosis was obtained by the continuity
equation in 50 patients. In 4 of the remaining 16 patients, the proximal IMA flow by TTDE showed theocclusion pattern. In these 54（82%）
patients, the percentage stenosis by TTDE showed a significant correlation with that by angiography（r 2 ＝ 0.86, p ＜ 0.0001）. In all the remaining 12 patients with the patentproximal IMA pattern but without visualized anastomotic flow, the patency was confirmed by angiogra──────────────────────────────────────────────
鹿児島大学病院 検査部 : 〒 890−8520 鹿児島県鹿児島市桜ヶ丘 8−35−1 ; ＊ 1 国立病院機構鹿児島医療センター 循環器科，
鹿児島 ; ＊ 2 鹿児島大学大学院医歯学総合研究科 循環器・呼吸器・代謝内科学，＊ 5 血管代謝病態学，＊ 6 循環器・呼吸器制御学，鹿児島 ; ＊ 3 川崎医科大学 循環器内科，岡山 ; ＊ 4 和歌山県立医科大学 循環器内科，和歌山
Department of Clinical Laboratory, Kagoshima University Hospital, Kagoshima, ＊ 1Department of Cardiology, National Hospital
Organization Kagoshima Medical Center, Kagoshima, ＊ 2Department of Cardiovascular, Respiratory and Metabolic Medicine,＊5
Department of Laboratory and Vascular Medicine, ＊ 6Department of Thoracic and Cardiovascular Surgery, Graduate School of
Medicine, Kagoshima University, Kagoshima, ＊ 3Department of Cardiovascular Medicine, Kawasaki Medical School, Okayama ;＊4
Department of Cardiovascular Medicine, Wakayama Medical University, Wakayama
Address for correspondence : MIZUKAMI N, RCS, Division of Clinical Laboratory, Kagoshima University Hospital, Sakuragaoka 8−35−1, Kagoshima, Kagoshima 890−8520 ; E-mail : mizukami@m.kufm.kagoshima-u.ac.jp
Manuscript received July 26, 2006 ; revised September 11, 2006 ; accepted October 16, 2006
RCS ＝ registered cardiac sonographer

305

306

Mizukami, Minagoe, Otsuji et alphy.
Conclusions. TTDE enables direct visualization and quantitative evaluation of the anastomotic patency
in patients with IMA graft to the LAD.
─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────J Cardiol 2006 Dec ; 48
（6）
: 305−314

Key Words
Echocardiography, transthoracic
Cardiac surgery bypass, anastomosis

INTRODUCTION
The internal mammary arteries（IMA）are widelyused for vessel grafts to the left anterior descending
coronary artery（LAD）in patients with ischemic
heart disease.1）Evaluation of the patency of thecoronary artery bypass grafting（CABG）, with rela2）
tion to patient outcome, usually requires invasive
angiography.3）Transthoracic Doppler echocardiography（ TTDE）can evaluate proximal to middle
IMA flow, and is the only currently available noninvasive method to evaluate the patency of thegraft.4−8）However, noninvasive methods are indirect and with potential limitations.
Evaluation of the visualization of LAD flow by
TTDE has suggested the potential utility of thismethod to enable both visualization and evaluationof the flow in the distal IMA and the anastomosis
directly connected to the LAD.9,10）By applying acontinuity equation using flow velocities atprestenotic and stenotic regions, Doppler echocardiography can provide quantitative evaluation ofvessel stenosis in native coronary arteries. 11,12）
However, the feasibility of TTDE for direct visualization and quantitative evaluation of the anastomotic patency between the IMA and the LAD has
not been fully investigated.
We hypothesized that TTDE enables noninvasive
and direct visualization of the flow through theanastomosis between the grafted IMA and the LAD
in patients with CABG, which allows quantitativeevaluation of the anastomotic stenosis by continuity
equation with measurements of the flow velocities
at the pre-anastomotic and anastomotic regions. A
major problem with this hypothesis is that TTDE is
not expected to be feasible if the graft is occluded
and flow through the anastomosis is absent.
However, even in this situation, proximal IMA flow
velocities near the subclavian artery by TTDE canstill offer reliable information as to whether thegraft is occluded.6,7）Thus, TTDE could be expected
to be useful in evaluating graft patency, especiallyCoronary artery disease
Doppler ultrasoundin patients with an IMA grafted to the LAD.
Therefore, the present study tested our hypothesis
in patients with CABG with an IMA grafted to the
LAD.
SUBJECTS AND METHODS
Study patients
The subjects consisted of 66 consecutive patients（48 men and 18 women, mean age 67 ± 10 years）
with recent or previous history of IMA grafted to
the LAD, who underwent both TTDE and coronary
angiography. Patients with sequential anastomosesof the IMA to the LAD were excluded due to thepotential limitation to evaluate the patency using
proximal IMA flow. The clinical characteristics ofthe patients are summarized in Table 1. Written
informed consent was obtained from all patients.
Visualization of LAD and anastomotic flow by
TTDEStandard two-dimensional and Doppler echocarTable 1

Clinical characteristics of study patients

Number of patients66

Male/female

48/18

Age（yr）

46−84〔68±10〕Symptomatic angina

28/66

Congestive heart failure

12/66

Previous myocardial infarction

21/66

Months after CABG

0.5−140〔22±58〕

Number of grafts

1−5〔2.6±0.9〕

Grafted vessel to the LAD
Left IMA to segment 7

13

Left IMA to segment 8

46

Right IMA to segment 8

7

Native LAD diameter stenosis（%）

59−100〔91±14〕

Incidence of retrograde flowfrom LAD to IMA（%）

0（0/50）〔 〕: mean±SD.
CABG＝coronary artery bypass grafting ; LAD＝left anterior
descending coronary artery ; IMA＝internal mammary artery.

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Noninvasive Evaluation of Graft Anastomosis

TTDE

307

Angiography

Percentage stenosis by TTDE ＝（1 − mean Vpre-anast./mean Vanasto.）
× 100 ＝ 8%

Percentage stenosis by QCA ＝ 13%

Fig. 1 Visualization and evaluation of the anastomotic flow between the internal mammary artery
graft and left anterior descending artery by transthoracic Doppler echocardiography（middle2 panels）
The anastomosis between the grafted IMA and the LAD was visualized at the fourth or fifth intercostal
space（left panel）. Using the continuity equation with pre-anastomotic and anastomotic flow velocity measured by pulsed transthoracic Dopper echocardiography, anastomotic stenosis was evaluated as trace tomild, which was confirmed by quantitative coronary angiography（right panel）in this patient. Color flow
image was rotated to unify image direction to angiography.
TTDE ＝ transthoracic Dopper echocardiography ; Vpre-anast.＝ pre-anastomotic flow velocity ;Vanasto.＝ anastomotic flow velocity ; QCA ＝ quantitative coronary angiography. Other abbreviations as
in Table 1.

diography were performed with a digital ultrasoundsystem（HDI-5000, ATL Ultrasound, Bothell ;Acuson Sequoia, Siemens, Mountain View）using a
2 to 4 MHz transducer, then middle to distal LAD
flow was evaluated with a 4 to 7 MHz transducer.
By placing the transducer at the fourth or fifth intercostal space between the cardiac apex and theparasternal area, the anterior interventriculargroove was visualized in the short axis view andcolor flow mapping was applied to visualize thedistal LAD flow in the groove. Then, the transducer
was rotated counterclockwise to visualize the longaxis of the distal LAD flow. By shifting the transducer toward the left ventricular base, the distal to
middle LAD flow was visualized, and the anastomotic flow entering the LAD could be identified（Fig. 1）. The Nyquist limit was set in the range of
15 to 25 cm/sec to visualize relatively slow LAD
and IMA flow. After visualization of the anastomotic flow, flow velocities at the anastomosis andpre-anastomosis at the distal IMA, which is approximately 0.5 cm proximal from the anastomosis,
were measured by pulsed Doppler echocardiography with a sample volume size of 1 mm
（Fig. 1）. In
the presence of color aliasing at the anastomosis,
J Cardiol 2006 Dec; 48（6）: 305 – 314

indicating stenosis, a higher Nyquist limit wasapplied to identify lesions with the fastest velocity.
If these velocities were too high, high pulse repetition frequency or continuous wave Doppler
echocardiography was used. Transducer positionand direction were adjusted to minimize the angle
between the Doppler beam and the IMA flow direction by color flow mapping as much as possible,
and an angle correction was performed when necessary.
Evaluation of anastomotic stenosis by Doppler
echocardiography
Two methods were used to evaluate anastomotic
stenosis by TTDE.
Method 1 : If the anastomotic flow was visualized by color flow mapping, a continuity equation
was applied to obtain the stenosis（［pre-anastomotic vessel area］×［pre-anastomotic mean flow
velocity］＝［anastomotic vessel area］×［anastomotic mean flow velocity］）. Therefore, the percentage area stenosis at the anastomosis was calculated as［1−（pre-anastomotic mean velocity/anastomotic mean velocity）］× 100（%）（Fig. 1）
.11,12）
Method 2 : If the anastomotic flow was not visu-

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Mizukami, Minagoe, Otsuji et al

Fig. 2 Relationship between proximal internal mammary artery flow velocity profile and the patency of the internal mammary artery graft
Color flow mapping was applied to visualize the proximal IMA flow near the subclavian artery（middle
panel）by using the supraclavicular approach（left panel）. Augmented diastolic flow with diastolic to systolic mean velocity ratio（D/S）＞ 0.25 suggested patent internal mammary artery graft（right-upper panel）,
whereas absence of the augmentation suggests total occlusion of the graft（right-lower panel）.
SCA ＝ subclavian artery. Other abbreviation as in Table 1.

Fig. 3 Flow chart of the quantitative or qualitativeevaluation of the anastomotic stenosis bytransthoracic Doppler echocardiography
D/S ＝ diastolic to systolic mean velocity ratio. Other
abbreviations as in Table 1, Fig. 1.

alized, it was difficult to judge whether this wasdue to total occlusion with absent flow or suboptimal imaging despite the presence of the flow. A
previous study has demonstrated that absence ofaugmented diastolic flow in the proximal IMA witha diastolic to systolic mean velocity ratio（D/S）＜0.25 represents total or advanced occlusion and the
D/S ＞ 0.25 represents patent anastomosis in the
majority of patients.6）In patients without visualized
anastomotic flow, the proximal IMA D/S ＜ 0.25

was considered to represent total occlusion of theanastomosis and its presence was considered to represent patent anastomosis（Fig. 2）.
Therefore, the steps for the quantitative evaluation of the anastomotic stenosis by TTDE included :evaluation of the presence or absence of anastomotic flow by color flow mapping ; application of acontinuity equation to calculate the percentage
stenosis in the presence of visual anastomotic flow ;and in the absence of visual anastomotic flow, qualitative evaluation of the graft occlusion by examining the proximal IMA flow pattern near the subclavian artery（Fig. 3）.
In vitro validation of the continuity equation
applied to the junctional lesion
Although the continuity equation has alreadybeen validated to quantify lumen stenosis,13,14）it has
not been validated for junctional lesions such as
anastomosis between the IMA and the LAD.
Therefore, we performed an in vitro validation
study in a junctional lesion created using latex rubber tubing with internal diameters between 4−
2 mm（Fig. 4）. The diameter of the latex rubber
tube which represented the native LAD was 4 mm.
The diameter of the tube to represent the proximal
IMA was 3 or 4 mm and the distal diameter of thistube to represent the distal IMA at the anastomosis
J Cardiol 2006 Dec; 48（6）: 305 – 314

Noninvasive Evaluation of Graft Anastomosis309

the scan lines perpendicular to the center lines of
the graft. The image was calibrated on the basis of
the known size of the catheter, and the vessel diameters were displayed for the length of the segment
analyzed. The minimum lumen diameter and thepercentage diameter stenosis were automaticallycalculated.15）The native LAD stenosis was also
quantitatively measured by the same method.

Fig. 4 In vitro flow model of the native left anterior
descending artery and the internal mammary
artery flow
Abbreviations as in Table 1.

was 2 or 3 mm. Combination of these tubes could
create 0%, 44%, 56%, and 75% anastomotic stenosis. Doppler Test Fluid Model 707, which is a dispersion of plastic particles in a glycerin water mixture, was used for ultrasound scattering within the
tubes. The flow in the tube was pulsated by a roller
pump（Masteflex Model No.7523-10, Yamamoto
Scientific Co.）, and the flow volumes of the tubes
were set for 10, 20, or 40 ml/min to create a wide
spectrum of the flow volume through the tubes representing native LAD and IMA graft flow. A commercially available ultrasound system（Acuson
Sequoia, Siemens, Mountain View）and 7 MHztransducer were utilized to evaluate the flow velocity at the anastomosis and the pre-anastomotic site.
Percentage area stenosis was calculated by the continuity equation using the anastomotic and preanastomotic flow velocity by pulsed Doppler
echocardiography.
Angiographic evaluation of the IMA to LAD
anastomotic stenosis
All patients underwent coronary angiography
within 1 month after the TTDE study, using thefemoral approach and standard techniques. A doseof 0.3 mg nitroglycerin was injected selectively into
each bypass graft. For the anastomotic site between
the IMA and the LAD, the percentage stenosis wasevaluated quantitatively using a computer-assisted
method（Cardiovascular Measurement System version 2.0, Medical Imaging System）. A selected cinematic frame was digitized, and an automatic edgedetection program determined the graft and coronary artery contours by assessing brightness along
J Cardiol 2006 Dec; 48（6）: 305 – 314

Reproducibility of measurements
Two independent observers repeated 10 measurements of the percentage stenosis of the anastomosis
by TTDE. The differences between the two
observers were examined to estimate inter-observer
variability. Similarly, intra-observer variability wascalculated by the difference derived from the repetition of 10 measurements by the same observer.
Statistics
All data are expressed as the mean value ± SD.
Relationships between continuous variables were
examined by linear regression analysis. A pvalue ＜ 0.05 was considered statistically significant.
RESULTS
Incidence of quantitative evaluation of anastomotic stenosis by TTDE
（Fig. 3）
Anastomotic flow was visualized with TTDE in
50 of the 66 patients（76%）. Failure to visualize
anastomotic flow in the remaining 16 patients wasdue to total occlusion or technical difficulty in flow
visualization, as evaluation of proximal IMA flownear the subclavian artery showed the total occlusion pattern with D/S ＜ 0.25 in 4 patients and thepatent pattern in the remaining 12 patients. In addition to the 50 patients with visual anastomotic flow
leading to the continuity equation, quantitativeevaluation was also considered possible in the 4patients without visual anastomotic flow but withthe total occlusion pattern in the proximal IMA.
Therefore, quantitative evaluation by TTDE waspossible in 54 of 66（82%）
patients, and only qualitative evaluation was possible in the remaining 12（18%）
patients.
Relationship between TTDE stenosis and angiographic stenosis
In the 54 patients with quantitative evaluation by
TTDE, the percentage stenosis by TTDE correlated
significantly with that directly obtained by angiog-

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Mizukami, Minagoe, Otsuji et al

raphy（Fig. 5）. Figs. 1, 6, and 7 show representative patients with no stenosis, severe stenosis, or
total occlusion both by TTDE and angiography. In
all the remaining 12 patients with the qualitatively
patent pattern of proximal IMA flow by TTDE, thepatency was confirmed by angiography with a percentage anastomotic stenosis of 8 to 58%（15 ±14%）.

In vitro validation of the continuity equation in
the junctional lesion
Percentage stenosis by the continuity equation
with Doppler echocardiography showed a significant and good correlation with the actual stenosis
without major influences from the variability in theflow volume of tubes representing the LAD and theIMA（r 2 ＝ 0.99, p ＜ 0.0001 ; Fig. 8）.
Reproducibility
The inter-and intra-observer variabilities for themeasurement of percentage stenosis by TTDE were
3.5 ± 1.7% and 2.1 ± 1.7%, respectively.
DISCUSSION

Fig. 5 Scatter graph demonstrating the significant correlation between the anastomotic stenosis evaluated by transthoracic Doppler echocardiography and that by quantitative coronary angiography
Abbreviations as in Table 1, Fig. 1.

The present study demonstrated that quantitativeevaluation of the anastomotic stenosis of IMA
grafts to the LAD is feasible by TTDE in mostpatients using a continuity equation with visual
anastomotic flow or by the demonstration of a total
occlusion pattern in the proximal IMA. In theremaining patients, a qualitative but still reliableevaluation of the patency by TTDE was feasible.
Reliability of continuity equation in the junctional lesion
The significant correlation between the lumen

TTDE

Stenosis by TTDE ＝ 96％

Angiography

Stenosis by QCA ＝ 94％

Fig. 6 Representative patient with severe anastomotic stenosis
Anastomotic stenosis was evaluated as severe by transthoracic Doppler echocardiography（left panel）using
the continuity equation with pre-anastomotic and anastomotic flow velocity（middle panel）and also by
quantitative coronary angiography（right panel）. Color flow image（left panel）was rotated to unify image
direction to angiography（right panel）.
Abbreviations as in Table 1, Fig. 1.

J Cardiol 2006 Dec; 48（6）: 305 – 314

Noninvasive Evaluation of Graft Anastomosis

TTDE

D/S ratio ＝ 0.11
Total occlusion pattern

311

Angiography

Total occlusion of the IMA

Fig. 7 Representative patient with total occlusion of the internal mammary artery graft
The anastomosis was evaluated as total occlusion with diastolic to systolic mean velocity ratio（D/S）＜ 0.25
（middle panel）at the proximal internal mammary artery flow
（left panel）by transthoracic Doppler echocardiography and also by angiography（right panel）.
Abbreviations as in Table 1, Fig. 1.

Fig. 8 Scatter graph showing a significiant correlation
between percentage stenosis by the continuity
equation with Doppler echocardiography
applied to the junctional lesion and the actual
stenosis
Abbreviations as in Table 1.

stenosis by echocardiographic continuity equation
and actual stenosis in the vitro flow model, which
created similar hemodynamics to the anastomosis
between the IMA and the LAD, confirmed the reliability of the continuity equation in the in vivo
lesion. LAD stenosis without significant pressure
J Cardiol 2006 Dec; 48（6）: 305 – 314

fall allows occasional development of retrograde
flow from LAD to IMA.16）In a previous study, theincidence of the retrograde flow was frequent（5/13
or 38%）only with LAD stenosis ＜ 50% and wasvery rare in patients with significant LAD stenosis
with percentage diameter stenosis ＞ 50% or only
3%（3 of 87 patients）.17）In the present study, allpatients had significant stenosis or occlusion of
middle to proximal LAD［percentage diameter
stenosis of 59 to 100（91 ± 14）%］by angiography（Table 1）. In addition, all patients presented continuous antegrade flow at the anastomosis from
IMA to LAD throughout systole and diastole byDoppler echocardiography（Table 1）. Therefore,
application of the continuity equation to the evaluation of anastomotic stenosis in the present patientswith significant LAD stenosis or occlusion andcontinuous antegrade flow throughout systole anddiastole by Doppler echocardiography seems to bereasonable.
The percentage stenosis by TTDE with the continuity equation indicates area stenosis, whereas
stenosis by angiography indicates diameter stenosis. Therefore, the stenosis obtained by TTDE
could be greater than that by angiography. On theother hand, the spatial flow velocity profile in the
cross sectional plane of the vessel is not uniform312

Mizukami, Minagoe, Otsuji et alwith the greatest velocity in the center if the stenosis is absent or only mild, as is typically present in
the pre-anastomotic region, whereas the spatial
velocity profile is more uniform if the stenosis issignificant,18）as is typically observed at the anastomotic site. In this case, the mean pre-anastomotic
flow velocity is overestimated by TTDE and thecontinuity equation can underestimate the stenosis.
These two opposing effects resulted in a relatively
linear and equal relationship between the degree of
stenosis by TTDE and that by angiography in thepresent study.
Therefore, the present study demonstrated thefeasibility of TTDE for the noninvasive evaluationof the anastomotic stenosis or patency of the IMA
graft to the LAD.
Relationships to previous studies
Since the initial recording of the coronary flow
velocity using TTDE, 9）TTDE has been used toevaluate multiple aspects of coronary pathophysiology, such as the noninvasive evaluation of epicardial coronary artery stenosis,10）coronary vasodilator response,19−21）coronary obstruction with collateral flow,22）intramyocardial small coronary arteryflow dynamics,23,24）the nature of coronary reperfusion in acute myocardial infarction,25）and others.
In relation to this study, the feasibility of using amodified continuity equation to evaluate epicardialcoronary artery stenosis,12）visualization and qualitative evaluation of the anastomotic patency of the
IMA grafted to the LAD,26）and the feasibility ofdetermining the proximal left IMA flow pattern by
TTDE for the evaluation of the anastomotic patency of the left IMA graft have all been demonstrated.6）The present study confirmed the feasibility of
TTDE to evaluate coronary and IMA pathophysiology and further demonstrated its utility in the direct
visualization and quantitative evaluation of theanastomotic patency in patients with IMA graft to
the LAD.
Intra-operative Doppler echocardiographic studies have demonstrated the feasibility of the Doppler
technique to detect anastomotic stenosis.27−29）This
intra-operative technique enables early detection ofanastomotic stenosis, and potentially allows regrafting to be undertaken during the same surgery,which can prevent or minimize the need for a second surgical procedure at a later date. The present
study confirmed the feasibility of the Doppler technique to evaluate the degree of anastomotic steno-sis, and further demonstrated the utility of postoperative noninvasive Doppler examination to allow
serial evaluation even in the chronic phase.
Limitations
In the present study, patients were limited tothose with IMA graft to the LAD. Patients withvenous or other artery grafts to the LAD were notincluded. In addition, the feasibility of TTDE toevaluate bypass grafts to the right coronary or theleft circumflex artery was not tested, because
TTDE is especially suited to evaluate the LAD
flow. Although the present study demonstrated thefeasibility of using TTDE for the quantitative evaluation of anastomotic patency or stenosis in mostpatients with IMA graft to the LAD, the quantitative evaluation was not feasible in 12 of 66 patients
due to technical difficulties in visualizing the anastomotic flow despite the presence of the flow byangiography. Further advances in imaging technology with or without the addition of contrast agentsare required to overcome these limitations.30）The
continuity equation to evaluate the anastomotic
stenosis cannot be applied to patients with back andforth flow through the anastomosis, which frequently develops in patients with native LAD stenosis＜ 50%. 15,16）Therefore, the method used in thisstudy may not be suitable for patients with IMA
grafted to LAD with only modest stenosis. The
angle between the Doppler beam and flow direction
can be different between the anastomosis and the
pre-anastomotic site. We tried to visualize the flow
direction at both anastomosis and pre-anastomosis
sites by color Doppler echocardiography andapplied different angle correction when the angle
difference was clear. However, the whole flow
stream from pre-anastomotic site to anastomosis isoccasionally difficult to visualize. In the present
study, the pre-anastomotic flow velocity was evaluated at the distal or proximal IMA approximately
0.5 cm proximal to the anastomosis. Therefore,
long lesions causing anastomotic stenosis or a middle IMA lesion may not be accurately evaluated by
the present method, although such lesions are relatively rare. Notwithstanding these limitations, thepresent study demonstrated the feasibility of using
TTDE for the direct visualization and quantitativeevaluation of anastomotic flow and stenosis in mostpatients with IMA graft to the LAD.

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Noninvasive Evaluation of Graft Anastomosis

要

313

約

経胸壁ドップラー心エコー図法による内胸動脈−左前下行枝バイパスグラフト
吻合部狭窄の非侵襲的定量評価
水上

尚子

皆越

眞一

尾 辻

豊

根石

陽二

赤阪

隆史

濱崎

秀一

湯浅

敏典

宮田

昌明

丸山

征郎

吉 田

清

坂田

隆造

鄭

忠 和

目

的 : 近年，経胸壁ドップラー心エコー図法により，左冠動脈前下行枝の血流を評価することが可能となった．しかし，冠動脈バイパス術後におけるグラフト吻合部狭窄の評価については十分な検討がなされていない．今回我々は，経胸壁ドップラー心エコー図法により内胸動脈−左前下行
枝吻合部狭窄の評価が可能か否か検討した．
方

法 : 右もしくは左内胸動脈−左前下行枝の冠動脈バイパス術を施行した連続 66 例
（男性 48 例，

女性 18 例，平均年齢 67 ± 10 歳）を対象とした．左前胸壁より内胸動脈−左前下行枝吻合部の描出を試み，吻合部および吻合前のグラフト内平均血流速より連続の式により狭窄率を算出した．吻合部血流が検出されなかった症例では，胸骨上窩より内胸動脈起始部近位の血流速を記録し，バイパ
ス術後の拡張期血流の増大が欠如し，拡張期・収縮期平均血流速比＜ 0.25 の症例を吻合部閉塞と判断した．また，冠動脈造影を施行し，定量的冠動脈造影により吻合部の狭窄率を算出し，経胸壁
ドップラー心エコー図法による狭窄率と比較した．
結

果 : 経胸壁ドップラー心エコー図法により 66 例中 50 例で内胸動脈−左前下行枝吻合部の血流を検出し，検出不能の 16 例中 4 例は内胸動脈起始部の血流速比より吻合部閉塞と診断され，計54 例（82%）で経胸壁ドップラー心エコー図法による内胸動脈−左前下行枝吻合部狭窄の定量評価が可能であった．経胸壁ドップラー心エコー図法により算出した内胸動脈−左前下行枝吻合部狭窄率と定量的冠動脈造影による狭窄率は良好な相関を示した（r 2 ＝ 0.86，p ＜ 0.0001）．経胸壁ドップ
ラー心エコー図法により定量的評価が不能であった 12 例（18%）では，内胸動脈起始部の血流速比により吻合部開存の定性的評価は可能であり，全例冠動脈造影により吻合部開存が確認された．
結論 : 経胸壁ドップラー心エコー図法では内胸動脈−左前下行枝吻合部の非侵襲的定量評価が可能である．

J Cardiol 2006 Dec; 48（6）: 305−314

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