Expectations of myocardial revascularization

Surgical treatment of coronary artery disease has been under development for more than 35 years, during which time it has been met with considerable enthusiasm. As the surgical risk decreases, indications for coronary bypass procedures are being liberalized somewhat and increasing numbers of patients are being referred for surgical treatment. The most immediate benefit of such treatment is prompt relief from angina and improvement in the quality of life. Other benefits for various patient subgroups are improvement in left ventricular function and prolonged life. Further experience and controlled studies gradually will elucidate further indications for coronary artery bypass surgery and will result in improved evaluation of this treatment.

Coronary artery surgery in South Australia 1970-1976

The South Australian population of approximately 1,245,000 is 9.2% of the total Australian population. The Cardio-Thoracic Surgical Unit of the Royal Adelaide Hospital is the only one such unit in the State which is equipped for open heart surgery, and coronary artery grafting was first undertaken there in December, 1970. From that time until the end of December, 1976, 701 patients underwent coronary artery grafting with an overall hospital mortality of 3.0%, and a late mortality of 3.2%. The principal indication for operation was incapacitating angina, and of the 628 patients who have been followed-up after operation for a minimum period of six months, 78.6% were judged by their cardiologist to be completely relieved of this symptom. A further 8.9% of patients were considered to be significantly improved. Coronary artery surgery has rapidly assumed a dominant role in our Unit so that, in 1976, of the 435 open heart operations which were performed, 267 (61%) were procedures which necessitated coronary artery grafting. The rate of increase has slowed considerably over the past 18 months, and it is expected that, with current operative indications, the proportion of coronary artery cases will not rise much above 60% of the open heart work load of the Unit.

Coronary artery surgery

This paper assesses the results in 543 patients undergoing coronary artery surgery between 1969 and March, 1976. Indications included angina, acute infarction and ventricular arrhythmia, and there were some angina-free patients. Surgical techniques were constantly reviewed and frequently changed. The mortality in all groups was 4.2%. The mortality in chronic stable angina (424 cases) was 3%, but as from January, 1975, it has been 2%. The perioperative infarction rate in all groups was 10.7%, and this condition was the most significant cause of perioperative mortality. Modern principles of myocardial protection during surgery have helped to lower mortality and morbidity rates.

Reoperations for myocardial revascularization

Reoperations solely for myocardial revascularization were performed in 219 consecutive patients (1967 to 1975). Indications were (1) graft failure, 46 (21 per cent); (2) progressive atherosclerosis, 42 (19 per cent); (3) incomplete revascularization, 39 (18 per cent); and (4) combinations, 92 (42 per cent). Primary operations included bypass grafts in 100 patients; mammary artery implants, 87; and combinations of direct and indirect procedures, 32. Reoperations performed were single bypass, 141 patients; double, 61; and triple or other coronary artery operations, 17. Eight patients died within 30 days of operation (3.7 per cent). Major postoperative complications included hepatitis, 24 (11 per cent); myocardial infarction, 19 (9 per cent); bleeding, 21 (10 per cent); and respiratory insufficiency, 12 (5 per cent). Follow-up for 202 long-term survivors was complete (mean 29 months). In patients who originally underwent direct revascularization, Class I or II (N.Y.H.A.) was attained in 35 of 43 (81 per cent) of those reoperated upon for primary graft failure, in 14 of 15 (93 per cent) of those with progressive atherosclerosis, and in 27 of 33 (82 per cent) of patients with combined indications. Arteriography was performed after the reoperation in 55 patients (mean interval 17 months), and 65 of 77 (84 per cent) grafts were patent. Nineteen of 22 grafts performed for primary graft failure were patent. We have made the following conclusions: (1) Reoperation for direct myocardial revascularization can be accomplished with low mortality rates although morbidity is high; (2) complete relief of symptoms was achieved in 65 per cent of survivors; (3) results in patients reoperated upon for graft failure alone were similar to results in those operated upon for progressive atherosclerosis or combined indications; and (4) high graft patency was found in secondary grafts constructed to arteries involved with primary graft failure.

Aortic valve replacement combined with myocardial revascularization. Late clinical results and survival of surgically-treated aortic valve patients with and without coronary artery disease

From 1967 through 1973, 80 consecutive patients underwent simultaneous aortic valve replacement (AVR) and coronary bypass grafting. Fourteen (18%) experienced no angina pectoris and had no history or electrocardiographic evidence of coronary atherosclerosis. Seven of these 14 had severe multiple vessel disease. All operations were performed under normothermic conditions without coronary perfusion. Seven patients (9%) died during operation. Intra-operative myocardial infarction was documented in eight (10%). After a mean follow-up of 35 months, overall mortality was highest in aortic regurgitation patients [seven of 13 (54%)] compared to aortic stenosis [17 of 54 (31%)] (P less than 0.07), and mixed pathology [1 of 13 (8%)]. Thirty-one of 34 (91%) grafts in 25 patients were patent an average of 12 months postoperatively. After 42 months a 65% actuarial survival was found in the combined AVR and graft(s) series versus a 76% survival in 300 AVR patients proven by angiography not to have severe coronary atherosclerosis.

The VA cooperative randomized study of surgery for coronary arterial occlusive disease II. Subgroup with significant left main lesions

From a large cooperative prospective randomized study, data relating to a subgroup of 113 patients with angina pectoris and a significant lesion of the left main coronary artery were analyzed. Of these patients, 53 had been randomly allocated to a medical treatment group and 60 to a surgical treatment group. The former group received conventional medical treatment, while the surgical treatment group received one or more aortocoronary saphenous vein bypass grafts. Important risk factors were approximately uniformly distributed between the two groups. Both are being followed up to 60 months (average follow-up, 30 months). To date, 12 of 60 surgical patients (20%) and 19 of 53 medical patients (36%) died (P less than 0.06). The operative (30-day) mortality declined from a rate of 25% for the first 2 years of the study to 7% for the last 3 years. Of patients randomized in the latter 3 years of the study, 12 of 41 medical patients (29%) and three of 42 surgical patients (7%) died (P less than 0.01). The average follow-up period in this group was 24 months. The proportion surviving 24 months was clearly larger in the surgically treated group (P less than 0.02). The difference in the proportion of patients surviving after surgery as compared with medical treatment was greatest in patients with additional significant disease involving the right coronary artery, with or without left ventricular dysfunction. Relief of angina as assessed by an "anginal score" was also better in surgical patients to a significant degree. Graft-patency rates correlated well with relief of angina, but objective studies including treadmill testing are not yet available.

Experience with fifty repeat procedures for myocardial revascularization

Fifty coronary reoperations were performed in 49 patients. The reasons for the operations were occluded or stenotic grafts in 23 patients, an inadequate first operation in 13, progression of coronary atherosclerosis in 3, and combinations of these reasons in 11. Mediastinal adhesions made the operations difficult and produced hazards. Six patients died from the operation. Seven surgical mishaps occurred, including damage to five functioning grafts from the previous operation and laceration of two ventricles. Nine patients had less than complete operations because angiographically demonstrated targets could not be found. Repeat angiography was performed on 9 of the surviving patients. Ten of the 14 new or revised grafts were found to be functioning. Although a repeat operation is more difficult technically and carries additional risks as compared with a first operation, the indications are thought to be the same for both first and secondary revascularization procedures. The increased risks of the repeat operations are compelling arguments to strive for complete revascularization at an initial operation in order to avoid the necessity of the second one.

Medical versus surgical treatment of stable angina pectoris: progress report of a large scale study

A large scale, prospective, randomized study of surgical v. medical management of disabling angina pectoris is being conducted as a cooperative study among thirteen Veterans Administration hospitals in the U.S.A. A total of 1015 patients have been entered into the study and follow-up data are currently being evaluated. Patient entry into the study was concluded in December 1974. Patient compliance has been acceptable with only 7% of patients not adhering to their randomization category. Thirty-day operative mortality (1972-1974) in 309 patients was 5-3%. The patient population exhibited a severe degree of coronary disease. There was ECG evidence of prior myocardial infarction in 40%. There were significant obstructive lesions in three major coronary arteries in 51% and significant lesions of the left main coronary artery in 11%. Medical and surgical treatment groups demonstrated no significant differences in objective descriptive characteristics. Mortality in the medical group at 1 year was 8%. Mortality was influenced by several factors including the number of vessels involved, left ventricular function and the presence of left main coronary artery disease. The lowest mortality occurred in patients with single vessel disease and normal LV function who had a 1-year mortality of 3%. Patients with 3-vessel disease and abnormal LV function exhibited a 14% 1-year mortality. Patients with disease of the left main coronary artery and poor LV function had a 1-year mortality of 37%. Analyses of the results of treatment modalities in sub-groups is currently being performed and will be reported in future publications.

Does coronary surgery prolong life in comparison with medical management?

This analysis attempts to utilize natural history controls to answer the question as to whether coronary surgery prolongs life in comparison to medical management. Selected natural history studies are compared and contrasted in an effort to obtain an average survival curve for patients with coronary artery disease comparable to those presently being operated. The Duke University Medical Center series of concurrent operated and non-operated patients is reviewed to demonstrate the difference of prognosis of patients with coronary artery disease and the complexities involved in answering the question. It is concluded that, on average, coronary surgery does not prolong life in comparison to medical management over the span of 2-5 years. There may be certain higher risk patients whose lives may be prolonged by aortocoronary bypass surgery but more patients and more prolonged follow-up are needed fully to answer the question.

Propranolol therapy in patients undergoing myocardial revascularization

The records of 185 consecutive patients having myocardial revascularization were reviewed with regard to preoperative administration of propranolol and intraoperative or postoperative complications. Tachycardia and hypertension before cardiopulmonary bypass were slightly more common in patients never taking propranolol or those who had discontinued it for more than 48 hours before operation. There was no statistically significant difference in the incidence of postbypass hypotension among patients who took propranolol within 24 hours of operation, those who discontinued it more than 24 hours before operation, and those who never took the drug. Operative mortality was not significantly different among patients who received propranolol within 48 hours of operation (3%), those who never took it and those who discontinued it more than 48 hours before operation (4%). Early in the series, five patients had an acute myocardial infarction within 48 hours after routine preoperative withdrawal of propranolol. Because complete withdrawal of propranolol in patients with unstable angina pectoris may lead to acute myocardial infarction, we recommend gradual withdrawal of the drug during 48 hours before operation. If this is not possible because anginal pain recurs or intensifies, then reduced doses may be given safely up to 10 hours before revascularization, provided that the patient is a satisfactory candidate for bypass and that adequate myocardial revascularization can be accomplished.

Long-term results of mammary artery implants

Eighty out of eighty-six patients (93%) with mammary artery implants were followed postoperatively for an average of three and a half years. The immediate mortality rate was 7% (6 cases), and the late mortality was 6% (5 cases). All had angina preoperatively. Twenty-four had a history of myocardial infarction and thirty-one were on limited physical activity, because of the pain. After surgery, thirty-three (45%) became asymptomatic. The angina improved significantly in thirty-five (47%) and remained unchanged in six (8%). Improvement in ventricular repolarization on ECG was observed in 69% of the patients. Postoperative cineangiography was performed in twenty-three patients; thirteen with single and ten with double implants. Out of the total of thirty-three implants, four (12%) were obstructed and twenty-seven patent (82%); twenty were in two cases of double implant, only one implant could be satisfactorily studied effectively functioning (61%). No obstructions were seen in the single implants. Non functioning implants were found in five (38%) of the thirteen single implants and in two of the twenty double ones (10%). The highest incidence of obstruction or non-functioning implants occurred in the group that did not show improvement (43%). This rate fell to 40% in the group that had some improvement and to 29% in those that were completely asymptomatic. Twelve of the eighteen patent mammary implants (67%) on the anterior wall of the left ventricle and eight of nine (89%) on the lateroinferior wall, established collateral circulation to the coronaries. Indication for surgery was considered satisfactory for nineteen out of the twenty-three patients and poor in four. There were two cases of obstruction of the implant (7%) in the group where surgery was correctly indicated and three of the twenty-three (11%) patent implants were non-functioning. Clinical improvement of the angina occurred in 84% in the first group and 50% in the other. In conclusion, this technique of indirect revascularization of the myocardium is valid for patients with severe diffuse lesions of the coronaries with a collateral network and preserved myocardial contractility.

Operative risk in patients with previous coronary artery bypass

The records of 141 patients who had had coronary artery bypass and myocardial revascularization were reviewed. Fifteen percent (20) of the patients in this series required a surgical procedure from three months to five years following coronary artery bypass. Twelve percent (16) of these patients had elective operations, and 3% had emergency operations. In the elective group there were no deaths. One patient had a proved myocardial infarction, and three patients had transient arrhythmias with no changes in myocardial enzymes. In the emergency group there was one death, from sepsis following splenectomy for splenic abscess. Although the series is small, the data suggest that patients with coronary artery disease who have had myocardial revascularization are acceptable risks for elective and emergency operations. Whether the risk is lower in this group as compared to that in other patients with coronary disease who have not had bypass surgery has not been demonstrated.

Coronary artery surgery. Operative technique and patient education

Coronary artery surgery, the preferred technique for myocardial revascularization in patients with ischemic heart disease, promptly increases blood flow to areas of the myocardium distal to the coronary obstruction. CAS completely relieves angina in 90% of patients. The risk of 1 to 5% is decreasing as operative technique and patient selection improve. Patients having CAS need comprehensive preoperative and discharge teaching to restore them to normal, active, optimistic lives.

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.

Myocardial revascularization in high-risk coronary patients

It is recognized that postoperative mortality, infarction and the need for inotropic support are increased following myocardial revascularization in highrisk patients. Operations were carried out in 57 such patients in whom one or more of the following factors were present: ventricular dysfunction-ejection fraction less than 0.4 (17), unstable (8) or preinfarction angina (29), evolving infarction (8), recent infarction (less than two weeks before) (5) and refractory ventricular tachyarrhythmia (4). Combined risk factors were present in nine patients. The following principles were utilized to minimize ischemic injury: (1) avoidance of prebypass hypertension and hypotension, (2) avoidance of extreme hemodilution, (3) avoidance of ventricular fibrillation, (4) maintenance of beating empty heart, when possible, (5) the limiting of ischemic periods to less than 12 minutes (hypothermia 32 degrees C) and (6) repaying myocardial oxygen debt with total (vented) bypass, when necessary. The following results were obtained: inotropic support was required in five patients (9 percent), "new" postoperative infarction occurred in five patients (9 percent) and one patient died (2 percent). These results are comparable to those reported in good-risk patients, and indicate that optimal myocardial protection will allow safe revascularization in a high-risk patient.

Emergency coronary surgery: Evolving indications

Between December 1970 and October 1973, 74 patients underwent emergency myocardial revascularization for the relief of acute coronary insufficiency. Through our experience in this area, we have established three categories for which we perform emergency surgery. The first of these is cardiogenic shock complicating acute myocardial infarction for which 14 patients underwent emergency saphenous vein grafting. Seven of these patients expired during operation and one died three months after operation. The second category is acute unstable myocardial infarction for which 25 patients received surgery. There were no operative deaths in this group, but two patients died at six weeks and four months after operation. Thrity-five patients were classified as pre-infarctional angina, the third category for which we perform surgery on an emergency basis. There was one operative death and two late deaths at four and ten months in this group of patients. Our experience suggests that immediate coronary angiography and revascularization will improve survival in the three above-named categories.

Surgical treatment of postinfarction ventricular aneurysm

We have operated on 62 consecutive patients for postinfarction ventricular aneurysm since coronary bypass grafting became available. Analysis of hemodynamic and angiographic data reveals that the prognosis of operation is favorable if mean pulmonary artery pressure is less than 45 mm Hg and cardiac index is greater than 2.0 L/min/m2; such factors as the preoperative New York Heart Association Functional Class, number of coronary grafts, aneurysm size, left ventricular end-diastolic pressure, and coronary score were not closely related to the outcome of operation. Hospital mortality was 6.5% (4 patients) and late mortality, with a mean follow-up of two years, was 11% (7 patients). The prognosis among survivors was good: 82% (46) achieved NYHA Class I or II status, whereas 87% (54) had been in Class III or IV preoperatively. Concomitant vein grafting with aneurysmectomy did not significantly enhance operative or late survival, nor did it add appreciably to the risk of operation. Long-term benefits of revascularization in addition to aneurysmectomy are expected but not yet proved.