Comparison of coronary hemodynamics in patients with internal mammary artery and saphenous vein coronary artery bypass grafts: a noninvasive approach using combined two-dimensional and Doppler echocardiography

Blood flow in bypass grafts and recipient left anterior descending coronary arteries was evaluated with combined two-dimensional and Doppler echocardiography in 15 patients with an internal mammary artery graft and in 24 patients with a saphenous vein graft. Comparative studies of coronary hemodynamics were also performed regarding these two different grafting techniques. The graft vessel was detected in 11 (79%) of 14 patients with an internal mammary artery graft and in 20 (87%) of 23 with a saphenous vein graft. The recipient left anterior descending coronary artery was detected in 10 (67%) of the former group and 17 (71%) of the latter. The blood flow patterns obtained were generally biphasic, consisting of systolic and diastolic phases with higher velocity during diastole. The maximal diastolic flow velocity in internal mammary artery grafts was much higher than that in saphenous vein grafts. In patients with an internal mammary artery graft, the flow pattern characteristics within the recipient coronary artery were quite similar to those within the arterial graft, and flow velocities within the recipient coronary artery and the arterial graft were quantitatively almost identical. This outcome may contribute to the long-term patency seen in internal mammary artery grafts. On the other hand, the flow velocity in saphenous vein grafts was fairly low throughout the cardiac cycle. Flow velocity in the recipient coronary artery in patients with a saphenous vein graft was accelerated only in early diastole. As a result, the recipient coronary artery flow pattern and velocity differed substantially from those in the saphenous vein graft.(ABSTRACT TRUNCATED AT 250 WORDS)     

Sequential internal mammary artery bypass for multiple coronary stenoses

Long-term studies (10 years) show a 50 per cent patency rate of saphenous vein autograft and 95 per cent patency rate of internal mammary artery coronary bypass grafts. In some situations (after saphenous vein stripping, varicose and fibrotic veins) it is not possible to use venous grafts and the internal mammary artery has to be used. However, the internal mammary artery is usually only used for revascularisation of the left anterior descending artery. Sequential internal mammary artery bypass is a technique which can be used for revascularizing the left anterior descending artery. Seven men aged 44 to 68 years (average 55 years) were operated between November 1983 and February 1985. These patients had clinically stable (4 cases) or instable (3 cases) angina. Two patients had previously undergone bilateral saphenous vein stripping and one patient a terminal anastomosis on the left anterior descending and a latero-lateral anastomosis on the diagonal artery. Three patients had an associated venous bypass graft and one patient also underwent aortic valve replacement. There were no cases of postoperative myocardial infarction. Five control angiographies were carried out during the first postoperative month. In 4 patients the internal mammary graft ant the latero-lateral and termino-lateral anastomoses were patent. In the other case, the latero-lateral anastomosis and the diagonal artery was occluded but the internal mammary graft and the termino-lateral anastomosis on the left anterior descending artery were patent. The average follow-up period is now 18 months: there have been no recurrences of chest pain or any ECG changes. These results show that internal mammary artery bypass grafting is a delicate procedure.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of flow reserve in internal mammary artery in situ bypass

The internal mammary artery, when used as a conduit for coronary artery bypass, offers a better long-term patency and survival rate than the saphenous vein. However, concern exists that the flow through the internal mammary artery may be inadequate during periods of peak myocardial demand. This flow was investigated in 18 consecutive patients who were selected for coronary bypass of the left anterior descending artery using the internal mammary artery. All patients were evaluated post-operatively within 12 months by means of graded maximal stress test, cardiac catheterization and exercise thallium-201 scintigraphy. Significant improvement in work capacity, maximal rate-pressure product, effort angina and ECG abnormalities during exercise stress testing were observed following internal mammary artery myocardial revascularization. The patency rate for internal mammary artery grafts was 100% (vs 85% for vein grafts); during the followup period, occlusion of a saphenous vein bypass or development of a new stenosis in a native coronary artery was noted in five patients, and two patients were classified as having partial revascularization. Ischemia, demonstrated by perfusion deficits at peak stress which disappeared in the 3-hour delayed film, was documented in 7.4% (4/54) of the areas supplied by internal mammary artery grafts, compared to 31% (13/42) of the regions revascularized using saphenous vein conduits. Although this result was not statistically significant, a definite trend is suggested. We conclude that ischemia demonstrated by stress thallium scintigraphy in the post-operative period is uncommon when an internal mammary artery graft has been used. This suggests that adequate coronary flow exists at peak myocardial demand during exercise.     

10-year results of anastomoses of the left internal mammary artery to the anterior interventricular artery. Angiographic and radionuclide controls

The long term patency of left internal mammary artery graft is better than that of saphenous vein graft. The aim of this study was to determined if this high patency rate was accompanied by a satisfactory myocardial perfusion. Among 143 patients treated with an internal mammary artery graft on the left anterior descending artery between 1972 and 1976, 42 patients underwent coronary angiogram and exercise tomoscintigraphy (thallium 201) over 10 years after surgery. The left internal mammary artery was patent in 92% without any atheromatous lesions. The myocardial perfusion in the area supplied by the left anterior descending artery was normal in 74%. A slight ischemia appeared during exercise in 19% without any clinical symptoms. This long term study shows excellent anatomical results correlated with a good myocardial perfusion during exercise in most cases.     

Internal mammary artery versus saphenous vein graft. Comparative performance in patients with combined revascularisation.

Thirty three patients with coronary artery disease undergoing combined myocardial revascularisation with internal mammary artery and saphenous vein grafts underwent angiographic studies up to 10 years after operation. Each patient had one internal mammary artery graft and one or more saphenous vein grafts. Eleven symptom-free patients, studies one month to five years (mean 1.9 years) after operation, had intact internal mammary artery and saphenous vein grafts in a good state of preservation. Of the six patients developing symptoms within the first year after surgery, three had evidence of poor flow in the internal mammary artery graft because of large side branches and the other three had stenosis or occlusion of the saphenous vein grafts. Sixteen patients developed symptoms after several years free of symptoms and were studied three to 10 years (mean six years) after operation. Of the 23 saphenous vein grafts in this group, 17 (74%) were either occluded or severely stenosed and six (26%) were in good condition. One internal mammary artery graft was occluded and the remaining 15 were in good condition. Saphenous vein graft failure was the predominant cause of late development of symptoms in patients with combined revascularisation. Long term performance of the internal mammary artery grafts is far superior to the saphenous vein grafts.     

Internal mammary artery bypass graft in reoperative myocardioal revascularization.

Thirty-two consecutive patients who earlier received indirect or direct myocardial revascularization underwent reoperation with one or more internal mammary artery grafts either alone or in combination with saphenous vein grafts. The main indication for reoperation was graft closure or progression of coronary atherosclerosis in nongrafted vessels, or both. Graft construction was performed under normothermic perfusion and anoxic arrest with interrupted suture technique. No intraoperative infarctions or hospital deaths occurred. All patients are alive after an average follow-up period of 20 months, and two thirds are asymptomatic. Arteriography after reoperation in nine patients revealed patency of eight of nine internal mammary artery and five of five secondary vein grafts. When angiographic and symptomatic indications for reoperation exist, the internal mammary artery bypass graft has become a valuable alternative, particularly for patients with small coronary vessels or previous vein graft failure.     

Internal mammary artery versus saphenous vein graft. Comparative performance in patients with combined revascularisation

Thirty three patients with coronary artery disease undergoing combined myocardial revascularisation with internal mammary artery and saphenous vein grafts underwent angiographic studies up to 10 years after operation. Each patient had one internal mammary artery graft and one or more saphenous vein grafts. Eleven symptom-free patients, studies one month to five years (mean 1.9 years) after operation, had intact internal mammary artery and saphenous vein grafts in a good state of preservation. Of the six patients developing symptoms within the first year after surgery, three had evidence of poor flow in the internal mammary artery graft because of large side branches and the other three had stenosis or occlusion of the saphenous vein grafts. Sixteen patients developed symptoms after several years free of symptoms and were studied three to 10 years (mean six years) after operation. Of the 23 saphenous vein grafts in this group, 17 (74%) were either occluded or severely stenosed and six (26%) were in good condition. One internal mammary artery graft was occluded and the remaining 15 were in good condition. Saphenous vein graft failure was the predominant cause of late development of symptoms in patients with combined revascularisation. Long term performance of the internal mammary artery grafts is far superior to the saphenous vein grafts.     

Intraarterial digital subtraction angiography for evaluation of internal mammary artery graft in coronary bypass surgery

Digital subtraction angiography (DSA) was performed to evaluate graft patency in 60 patients who had undergone coronary artery bypass grafting with the internal mammary artery (IMA). Sixty IMA grafts with 62 distal anastomoses, and 84 saphenous vein grafts with 85 distal anastomoses were evaluated by intraarterial DSA with an image frequency of 4 frames/sec. A No. 4 Fr. angiography catheter was introduced percutaneously into the left brachial artery and contrast medium was injected both into the subclavian artery for opacification of the IMA grafts and into the ascending aorta for opacification of aortocoronary saphenous vein grafts. Bypass grafts were defined as patent when grafts were opacified through their entire course, including anastomotic sites. Fifty-nine IMA grafts with 61 distal anastomoses (98%) and 76 saphenous vein grafts with 77 distal anastomoses (91%) were patent. The overall patency rate for total grafts was 94%. In 4 patients, DSA showed a "string sign" in the IMA graft which was patent but narrowed at its distal segment. In 5 patients, large first intercostal branches were opacified. Intraarterial DSA with the retrograde brachial approach is not difficult, and is an excellent low risk method of evaluating the patency of IMA and saphenous vein grafts. DSA provided information about functional patency as well as anatomical patency of the IMA graft.     

A comparison of morphologic and angiographic findings in long-term internal mammary artery and saphenous vein bypass grafts

Internal mammary artery grafts are currently considered the conduits of choice for myocardial revascularization. Comparisons of long-term morphologic changes in internal mammary artery grafts and saphenous vein grafts and correlation with premortem angiography have not been reported. Eighteen internal mammary artery and 15 saphenous vein grafts that had been in place for 12 to 118 months (mean 56) in 18 patients were removed either surgically or at necropsy and examined histologically. Premortem angiograms were performed within 1 month of histologic study in 15 of these patients. Fibrointimal proliferation was more frequent in internal mammary artery than in saphenous vein grafts 8 [( 44%] of 18 versus 4 [27%] of 15; p = NS). In contrast, atherosclerosis was common in saphenous vein grafts but was extremely rare in internal mammary artery grafts (10 of 15 versus 1 of 18; p = 0.01). A good correlation was noted between the degree of narrowing estimated by angiographic and histologic measurements in both internal mammary artery grafts (d = 0.90) and saphenous vein grafts (d = 0.71). Accelerated atherosclerosis did not occur in internal mammary artery grafts, but was common in saphenous vein grafts. Fibrointimal proliferation was commonly associated with graft narrowing in internal mammary artery grafts and may be an important factor in late graft closure. This study also confirms that internal mammary artery grafts have greater longevity compared with saphenous vein grafts.     

Starting aspirin therapy after operation. Effects on early graft patency. Department of Veterans Affairs Cooperative Study Group.

BACKGROUND. Although aspirin therapy started before operation improves vein graft patency after coronary artery bypass grafting, it also causes bleeding. The objective of this prospective, centrally directed, randomized, double-blind, placebo-controlled trial was to compare the effects of aspirin therapy started before operation with aspirin started 6 hours after operation on early (7-10-day) graft patency. METHODS AND RESULTS. Patients were randomized to receive either aspirin 325 mg or placebo the night before surgery; after operation, all patients received aspirin 325 mg daily, with the first dose administered through the nasogastric tube 6 hours after operation. Angiography was performed in 72% of the analyzed patients an average of 8 days after operation, and the primary end point was saphenous vein graft patency in 351 patients. Internal mammary artery graft patency was also assessed in 246 patients because many individuals received both internal mammary artery and vein grafts. In the patients given preoperative aspirin, the vein graft occlusion rate was 7.4 +/- 1.3% compared with 7.8 +/- 1.5% in those who received preoperative placebo (p = 0.871). In the subgroup of patients receiving Y grafts, 0.0% of the grafts were occluded in the preoperative aspirin group compared with 7.0 +/- 3.6% in the preoperative placebo group (p = 0.066). The internal mammary artery occlusion rate was 0.0% (0 of 131) in the aspirin group compared with 2.4 +/- 1.4% (three of 125) in the placebo group (p = 0.081). Patients in the aspirin group received more transfusions than those in the placebo group (median, 900 versus 725 ml, p = 0.006). The reoperation rate for bleeding in the aspirin group was 6.3% compared with 2.4% in the placebo group (p = 0.036). Median chest tube drainage within the first 6 hours after operation was 500 ml in the aspirin group compared with 448 ml in the placebo group (p = 0.011). CONCLUSIONS. Thus, preoperative aspirin is associated with increased bleeding complications and offers no additional benefit in early vein graft patency compared with starting aspirin therapy 6 hours after operation. There was a trend, although not significant, toward improved early patency for Y grafts and internal mammary artery grafts with preoperative aspirin.     

Saphenous vein grafts: to use or not to use?

The choice of the graft conduit is crucial to the success of coronary artery bypass grafting (CABG) because the patency of a coronary conduit is closely associated with an uneventful postoperative course and better long-term patient survival. From the beginning of coronary bypass surgery venous conduits particularly the great saphenous vein (GSV) has been the most frequently used coronary conduit. However, over the last decade or so, coronary bypass graft surgery with arterial revascularization of all diseased coronaries has shown to be efficient because arterial grafts have better long-term patency, especially left internal mammary artery (LIMA), compared with venous grafts. Early vein graft failure coupled with occlusion is the most important limitation of saphenous vein grafts. Nevertheless, vein grafting is still an integral part of cardiac surgical practice. This review provides a summary of the patency rates, technical features and certain characteristics of the venous conduits. It also examines the current understanding and knowledge of venous histology, vein graft pathology and the associated endothelial and smooth muscle cell physiology and pharmacology. In addition, the existing and the emerging strategies to combat and control vein graft intimal hyperplasia and accelerated atherosclerosis are reviewed in detail.     

The radial artery as a conduit for coronary artery bypass grafting: review of current knowledge.

The effect of coronary artery bypass grafting (CABG) lasts as long as the grafts are patent. The internal mammary artery has been considered the "golden" graft due to the superb long-term patency, exceeding 90% at 10 years. The saphenous vein grafts, unfortunately, tend to occlude with a rate of 10-15% within a year after surgery, and eventually, at 10 years after the operation, as much as 60-70% of these vein grafts are either occluded or have angiographic evidence of atherosclerosis. The search for another "arterial conduit", the radial artery, has intensified through the last 15 years in hope to provide a better graft than the saphenous vein for CABG. This article reviews the current knowledge for the radial artery as a conduit in CABG.     

Saphenous vein grafts: to use or not to use?

The choice of the graft conduit is crucial to the success of coronary artery bypass grafting (CABG) because the patency of a coronary conduit is closely associated with an uneventful postoperative course and better long-term patient survival. From the beginning of coronary bypass surgery venous conduits particularly the great saphenous veins (GSV) have been the most frequently used coronary conduit from the beginning of the coronary bypass surgery. However, over the last decade or so, coronary bypass graft surgery with arterial revascularization of all diseased coronaries has shown to be efficient because arterial grafts have better long-term patency, especially left internal mammary artery (LIMA), compared with venous grafts. Early vein graft failure coupled with occlusion is the most important limitation of saphenous vein grafts. Nevertheless, vein grafting is still an integral part of cardiac surgical practice. This review provides a summary of the patency rates, technical features and certain characteristics of the venous conduits. It also examines the current understanding and knowledge of venous histology, vein graft pathology and the associated endothelial and smooth muscle cell physiology and pharmacology. In addition, the existing and the emerging strategies to combat and control vein graft intimal hyperplasia and accelerated atherosclerosis are reviewed in detail.     

Early postoperative occlusion of a left internal mammary artery bypass graft with subsequent restoration of patency.

Total occlusion of a left internal mammary artery (LIMA) bypass graft is a rare complication, and reversal of a documented occlusion has not been reported. This is a case of an early postoperative occlusion of a LIMA graft that was found to be patent 4 months later. A patient with three vessel disease (including a moderate lesion in the proximal left anterior descending artery and a severe lesion in its mid-portion) underwent coronary artery bypass grafting with a LIMA to the mid-left anterior descending artery (LAD) and saphenous vein grafts to the right coronary and left circumflex arteries. Coronary angiography 3 months after surgery revealed a totally occluded internal mammary artery and saphenous vein grafts. The patient then underwent a successful angioplasty of the more distal lesion in the LAD. She subsequently returned with recurrent angina. Repeat coronary angiography revealed rapid progression of the disease in the proximal LAD with the more distal angioplasty site being widely patent. Selective arteriography of the internal mammary artery at that time revealed a patent vessel. Thus, the internal mammary graft is a physiologically active conduit that is dependent on flow dynamics. Competitive flow through the nonobstructive native LAD in combination with impedance of flow through the internal mammary artery due to a severe lesion in the LAD distal to the anastomosis led to a functionally occluded LIMA. When the obstruction in the proximal LAD progressed and the distal obstruction was successfully angioplastied, the flow dynamics in the internal mammary improved, allowing for its dilatation and restoration of patency.(ABSTRACT TRUNCATED AT 250 WORDS)     

Vascular biology of coronary bypass grafts. Literature review

Myocardial revascularisation by coronary bypass surgery is the treatment of choice for patients with multivessel disease. The most commonly used grafts are the internal mammary artery and the saphenous vein. Although the use of internal mammery artery grafts gives excellent results, venous grafts, with time, are subject to atheroma which affects their patency. Improved physiopathological understanding of the natural history of grafts, especially the saphenous vein grafts, has opened the field for different operative strategies to try and reduce the incidence of coronary graft disease. This paper reviews the literature concerning the biology of coronary grafts used for myocardial revascularisation and the current and future therapeutic implications of this data.     

Early postoperative occlusion of a left internal mammary artery bypass graft with subsequent restoration of patency

Total occlusion of a left internal mammary artery (LIMA) bypass graft is a rare complication, and reversal of a documented occlusion has not been reported. This is a case of an early postoperative occlusion of a LIMA graft that was found to be patent 4 months later. A patient with three vessel disease (including a moderate lesion in the proximal left anterior descending artery and a severe lesion in its mid-portion) underwent coronary artery bypass grafting with a LIMA to the mid-left anterior descending artery (LAD) and saphenous vein grafts to the right coronary and left circumflex arteries. Coronary angiography 3 months after surgery revealed a totally occluded internal mammary artery and saphenous vein grafts. The patient then underwent a successful angioplasty of the more distal lesion in the LAD. She subsequently returned with recurrent angina. Repeat coronary angiography revealed rapid progression of the disease in the proximal LAD with the more distal angioplasty site being widely patent. Selective arteriography of the internal mammary artery at that time revealed a patent vessel. Thus, the internal mammary graft is a physiologically active conduit that is dependent on flow dynamics. Competitive flow through the nonobstructive native LAD in combination with impedance of flow through the internal mammary artery due to a severe lesion in the LAD distal to the anastomosis led to a functionally occluded LIMA. When the obstruction in the proximal LAD progressed and the distal obstruction was successfully angioplastied, the flow dynamics in the internal mammary improved, allowing for its dilatation and restoration of patency. Therefore, an angiographically occluded internal mammary graft may be only functionally occluded and reversible even when the occlusion is demonstrated several days apart.     

Saphenous vein graft vs. radial artery graft searching for the best second coronary artery bypass graft

Coronary artery bypass grafting (CABG) was first used in the late 1960s. This revolutionary procedure created hope among ischemic heart disease patients. Multiple conduits are used and the golden standard is the left internal mammary artery to the left anterior descending artery. Although all approaches were advocated by doctors, the use of saphenous vein grafts became the leading approach used by the majority of cardiac surgeons in the 1970s. The radial artery graft was introduced at the same time but was not as prevalent due to complications. It was reintroduced into clinical practice in 1989. The procedure was not well received initially but it has since shown superiority in patency as well as long-term survival after CABG. This review provides a summary of characteristics, technical features and patency rates of the radial artery graft in comparison with venous conduits. Current studies and research into radial artery grafts and saphenous vein grafts for CABG are explored. However, more studies are required to verify the various findings of the positive effects of coronary artery bypass grafting with the help of radial arteries on mortality and long-lasting patency.     

Arterial conduits update

Arterial grafting for coronary artery disease has been practiced routinely at the Epworth Hospital for 20 years. Bilateral versus single internal thoracic artery grafts is associated with improved survival, which progressively increased over the 20 years of post-surgery. The average increase in survival was 15% at 20 years. The question of whether to use the radial artery or the saphenous vein graft as supplementary grafts remains unanswered. Current patency data suggest that there is a marginal advantage of radial artery over saphenous graft patency, particularly between 5 and 10 years after surgery. However, there appears to be improved patency of the saphenous vein when used as a coronary artery bypass with the advent of aspirin, lipid-lowering and anti-hypertensive therapy.     

Assessment of coronary bypass graft patency by electron-beam computed tomography

Twenty-one patients undergoing coronary artery bypass grafting were prospectively evaluated by conventional selective coronary angiography and electron-beam computed tomography. Eighty bypass grafts (60 saphenous vein and 20 left or right internal mammary artery) were evaluated for patency. The sensitivity and specificity of electron-beam computed tomography were 72% and 100%, respectively; positive and negative predictive values were 100% and 92.5%, respectively. Sensitivity and specificity according to coronary region were: left anterior descending artery, 33% and 100%; diagonal artery, 67% and 100%; circumflex artery, 75% and 100%; right coronary artery, 100% and 100%. Electron-beam computed tomography is relatively accurate and a promising tool for noninvasive evaluation of graft patency after coronary artery bypass graft surgery.     

Coronary flow reserve provided by sequential internal mammary artery grafts

Although internal mammary artery bypass grafts have a high patency rate, the adequacy of blood flow through such conduits, particularly if used sequentially, has been questioned. To evaluate this issue, coronary flow reserve was studied in 20 patients after coronary bypass surgery. Nine patients had sequential internal mammary grafts to the diagonal and left anterior descending coronary arteries; five had a single internal mammary graft to the left anterior descending artery and six had sequential saphenous vein grafts. Fifteen additional single vein grafts were also placed in these patients. Coronary flow reserve was measured after contrast-induced hyperemia by a digital subtraction angiographic technique an average of 25 days after surgery. There was no difference in coronary flow reserve between the proximal and distal anastomotic regions in either the sequential internal mammary graft group (2.14 +/- 0.50 versus 2.29 +/- 0.68, n = 8, p = NS) or the sequential vein group (1.77 +/- 0.49 versus 2.08 +/- 0.78, n = 6, p = NS). In addition, the flow reserve provided to either vascular bed of the sequential internal mammary graft was not different from that provided by a single internal mammary graft (1.64 +/- 0.39, n = 5), a single vein graft (1.95 +/- 0.95, n = 15) or nonstenotic native coronary arteries (2.04 +/- 0.87, n = 34). No cases of intracoronary steal were observed. Although some patients had unequal flow reserves between the proximal and distal anastomotic zones, these occurred in the setting of residual coronary stenoses distal to the site of graft insertion or prior myocardial infarction in the grafted distribution.(ABSTRACT TRUNCATED AT 250 WORDS)