From the Texas Heart Institute and the University of Texas Medical
School, Houston.
Correspondence to Denton A. Cooley, MD, Surgeon-in-Chief, Texas Heart Institute, PO Box 20345, Houston, TX 77225.
Now that
coronary artery bypass grafting has entered its fourth decade,
cardiac surgeons unanimously agree that arterial grafts
yield a more satisfactory long-term clinical outcome than do autologous
saphenous vein grafts. With time, venous grafts are vulnerable to
accelerated atherosclerosis, which may necessitate
high-risk repeat coronary bypass surgery. In contrast,
arterial grafts are highly resistant to
atherosclerosis. If patent immediately after surgery,
they tend to remain patent indefinitely; if angina recurs,
it is usually manageable with medical therapy, so repeat
coronary bypass may be avoided.
Why do arteries offer superior long-term patency? Apparently, the
elastic and smooth muscle elements in the arterial wall are
better able to withstand pulsatile flow. An important key appears to be
the integrity of the arterial endothelium,
which serves as a barrier between the blood and vascular smooth muscle.
After implantation as bypass conduits, arteries continue to have a
basically intact endothelium1; any
endothelial defects that do develop are essentially
nonthrombogenic. Moreover, the arterial
endothelium releases vasoactive mediators that confer
additional protection.2 These mediators include
prostacyclin and nitric oxide, vasodilators that prevent atherogenesis
and thrombogenesis by limiting platelet aggregation and cell
adhesion. Saphenous vein grafts also produce these vasodilators but not
to such a great extent.
The arterial conduit of choice is the internal thoracic
artery (ITA), also known as the internal mammary artery. Use of the ITA
as a bypass graft was pioneered by Green and
associates3 in 1968. Critics doubted its ability
to provide sufficient flow, and early experience yielded a high
complication rate, dampening enthusiasm for the use of this artery. In
1984, however, Grondin and coworkers4 showed that
at
An alternative arterial conduit is the right gastroepiploic
artery (GEA), which was first implanted as a direct bypass graft in
1974 by Edwards.8 The GEA is generally used as a
pedicled graft to avoid an aortic anastomosis. It is suitable for
bypassing the right coronary artery, the circumflex artery, or
the left anterior descending artery or its diagonal branch. Because the
media of the GEA contains smooth muscle cells, the artery is vulnerable
to spasm. Therefore, papaverine should be injected into the GEA
intraluminally during bypass, and patients should take calcium
antagonists on a life-long basis. Some GEA recipients also
require short-term vasopressor therapy for vasoplegia. Pedicled GEA
grafts offer satisfactory midterm patency: In a series of 400 patients,
376 of whom received pedicled GEA grafts, Suma and
associates9 documented a 94% patency rate
without any evidence of significant intimal hyperplasia at up to 5
years after surgery.
Other potential bypass conduits include the inferior
epigastric artery and the radial artery. Rather than being used as
primary bypass grafts, alternative arterial conduits
(including the GEA) are generally reserved for the following groups:
patients undergoing redo coronary bypass whose ITAs and
saphenous veins have already been used as grafts; those whose saphenous
veins have been surgically stripped or are of poor quality; those with
ascending aortic disease or severe vascular disease of the lower
extremity; and obese, diabetic patients at high risk for sternal wound
complications associated with bilateral use of the
ITA.10 Use of alternative arterial
conduits also may be indicated for young coronary bypass
patients with vein graft failure or hyperlipidemia.
To avoid using vein grafts at all, some experts recommend that
arterial grafts be used exclusively, even for multivessel
bypass. Among the foremost proponents of triple arterial
bypass are Bergsma and associates,11 whose
excellent results in 256 consecutive patients are reported in this
issue of Circulation. Having originally described these
patients in 1996,12 the authors are now
publishing their updated results. These data are compared with the
findings of other investigators, who used vein grafts and/or ITA grafts
in coronary bypass patients.7 13 14 15 16
After a maximal follow-up period of 7 years (mean, 51±15 months),
Bergsma and coworkers' patients had an actuarial survival rate of
91.1%, including 4 in-hospital deaths. Considering that all
of these patients had triple-vessel disease, this rate is extremely
satisfactory. The cumulative probability of freedom from myocardial
infarction (97.3%, including 5 in-hospital infarctions) surpassed that
of vein and/or ITA graft recipients (maximal freedom, 95%). Moreover,
the actuarial freedom from reintervention (95.4%) was comparable to
that of other series. In addition, Bergsma's group had 85.4% freedom
from angina pectoris at 7 years, which is considerably lower than that
of the control groups. No other investigator has published a longer
follow-up study regarding the combined use of GEA and bilateral ITA
grafts. Although the results favor the use of triple
arterial bypass, further studies are needed to draw
meaningful conclusions about this approach.
At the Texas Heart Institute, we use at least one arterial
graft for all coronary bypass patients, regardless of age, even
those with left main disease. We reserve triple arterial
grafts for patients less than 55 years of age or those who lack an
adequate saphenous vein. In weighing the advantages and disadvantages
of triple arterial grafts, the following points should be
borne in mind: (1) Most published series involving triple-artery grafts
do not include elderly patients, who are not optimal candidates for
this approach. (2) Because of the need for harvesting three arteries,
the operative time is prolonged. (3) The loss of both ITAs may result
in sternal complications, especially in diabetic and osteoporotic
women. Moreover, the operative mortality rate of female
coronary bypass patients is increased when the ITA is
used.17 18 (4) Harvesting of the GEA necessitates
an abdominal extension of the sternal incision, which may cause
additional postoperative pain and may be a potential site for
herniation and/or adhesion formation. Additional possible
complications include post-operative ileus, pancreatitis, and
intra-abdominal hemorrhage. Should abdominal surgery later
become necessary in a GEA graft recipient, optimal management would be
unclear. Use of the GEA is contraindicated in patients who have
undergone gastric resection. Relative contraindications include severe
obesity, abdominal aortic surgery, or a previous cholecystectomy.
Although triple arterial bypass may be ideal from a
theoretical standpoint, caution is necessary in using this approach.
Because of a steep learning curve, triple arterial bypass
should be attempted only by highly skilled surgeons. As with any other
operation, the surgeon must use sound judgment and must tailor the
procedure to fit each individual case.
Footnotes
The opinions expressed in this editorial are not necessarily those of the editors or of the American Heart Association.
References
© 1998 American Heart Association, Inc.
Editorials
Coronary Bypass Grafting With Bilateral Internal Thoracic Arteries and the Right Gastroepiploic Artery
Key Words: Editorials • bypass • grafting • arteries
12 years after surgery, ITA grafts had a 95% patency rate. In
contrast, the patency rate for saphenous vein grafts was only 
50%.
By the mid 1980s, thallium scintigraphy had confirmed that
the ITA could provide enough flow to perfuse the myocardium
adequately.5 Moreover, open heart techniques had
improved to the point where use of the ITA no longer entailed excessive
risk. Consequently, this artery became the conduit of choice for
coronary bypass, particularly of the left anterior descending
artery. Recently, Cameron and coauthors6 found
that an ITA graft lengthens the mean survival rate by 4.4 years
compared with the survival rate after venous grafting alone. These
authors documented the continued beneficial influence of an ITA graft
on the survival rate and clinical events at 20 years. Other
investigators have shown that, in patients undergoing multiple
bypasses, the addition of a second ITA graft confers a survival benefit
at 15 years among hospital survivors
(P=0.05).7 When bilateral ITAs are
used, the left one is typically used to bypass the left anterior
descending artery and the right one is extended as a free graft to the
next most important diseased artery.
This article has been cited by other articles:
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  O. Jegaden, L. Bontemps, G. de Gevigney, C. Chatel, R. Itti, and P. Mikaeloff Two-year assessment by exercise Thallium scintigraphy of myocardial revascularization using bilateral internal mammary and gastroepiploic arteries Eur. J. Cardiothorac. Surg., August 1, 1999; 16(2): 131 - 134. [Abstract] [Full Text] [PDF]
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 All Arterial Grafts Yield a Better Outcome Journal Watch Cardiology, July 24, 1998; 1998(724): 10 - 10. [Full Text]
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