Surgical Therapy for Prinzmetal's Variant Angina

Transcription

1 Surgical Therapy for Prinzmetal's Variant Angina Edgar C. Schick, Jr., M.D., Zev Davis, M.D., Robert M. Lavery, M.D., John R. McCormick, M.D., Martha Fay, M.A., and Robert L. Berger, M.D. ABSTRACT Fifty-two patients underwent coronary artery bypass grafting between 1973 and 1979 for variant angina, defined as pain, usually at rest, associated with S-T segment elevation. Only patients with fixed occlusive coronary artery disease, defined as greater than 70% narrowing in diameter, were included. When fixed coronary artery stenosis is present, variant angina-whether presenting as stable, unstable, or postinfarction angina, and regardless of the number of vessels diseased-is effectively treated by myocardial revascularization. Preoperative intraaortic balloon pumping is a useful therapeutic adjunct in the unstable subset refractory to medical therapy. The results of revascularization in patients with Prinzmetal's variant angina and fixed coronary disease were no different from those in patients with classic angina pectoris of comparable clinical categories. The indications for myocardial revascularization in variant angina remain controversial. Several reports contain a pessimistic appraisal of the surgical approach because of excessive operative morbidity and mortality [l-71. Other series present a more favorable outlook [8-101, but the improved results may apply to a subgroup of the population with variant angina still to be defined [ll]. In an attempt to clarify this issue, we reviewed our surgical experience with variant angina in association with fixed coronary obstructive disease to evaluate the response to myocardial revascularization and to compare the results with those for classic angina pectoris of similar clinical presentation. From the Department of Cardiothoracic Surgery and the Section of Cardiology, Evans Memorial Department of Clinical Research and Department of Medicine, University Hospital, Boston University Medical Center, Boston, MA. Accepted for publication June 26, Address reprint requests to Dr. Schick, Department of Cardiology, University Hospital, 75 E Newton St, Boston, MA Material and Methods Fifty-two patients underwent coronary artery bypass grafting at Boston University Hospital between January 1, 1973, and June 1, 1979, for variant angina with significant fixed coronary artery disease. The surgical group comprised 76% of the total of 68 patients diagnosed as having variant angina during this period. In all patients, an electrocardiogram during chest pain demonstrated S-T segment elevation of at least 1 mm, corresponding to the distribution of a diseased vessel, with return to baseline between attacks. Ergonovine testing was not used routinely at the time of these studies, spontaneous spasm was not encountered during angiography, and in no instance was the degree of a fixed narrowing substantially altered by nitroglycerin. Three subgroups were defined by their pattern of symptoms according to accepted criteria [12-141: stable angina, unstable angina, and postinfarction angina. Clinical characteristics of these groups are outlined in Table 1, and angiographic data are summarized in Table 2. Assignments for number of diseased vessels were based on 70% reduction in luminal diameter (50% for left main coronary artery disease). Functional classification followed the recommendations of the Canadian Cardiovascular Society [15]. Stable patients underwent operation for Class 3 or 4 angina or left main coronary artery disease. In 11 patients in the unstable group and 10 in the postinfarction group, ischemic chest pain persisted despite intensive medical therapy, and intraaortic balloon pumping was instituted prior to catheterization. Perioperative infarction was diagnosed when new pathological Q waves appeared on postoperative electrocardiograms. Results Surgical and Follow-up Data Surgical and follow-up data on the three subgroups are summarized in Table by The Society of Thoracic Surgeons

2 360 The Annals of Thoracic Surgery Vol 33 No 4 April 1982 Table 1. Clinical Characteristics Angina Variable Stable Unstable Postinfarction No. of patients Age (yr) Mean f SD Range Sex (M/F) Prior MI Baseline ECG Normal Q waves S-T segment and T wave abnormalities S-T elevation Anteriorlinferior 9 48 f / f /4 Preoperative treatment Propranolol Nitrates IABP f SD = standard deviation; MI = myocardial infarction; ECG = electrocardiogram; IABP = intraaortic balloon pump Table 2. Angiographic Data Angina Variable Stable Unstable Pos tinfarction No. of patients No. of vessels involved One Two Three Left main coronary artery Ejection fraction (%) < Segmental motion abnormality Table 3. Surgical and Follow-up Data Arteries Bypassed Mortality Infarction Follow-up Classa Angina No. of Subgroup Patients Early Late Early Late Ob Stable angina Unstable angina Postinfarction Tanadian Heart Association. basymptomatic.

3 361 Schick et al: Prinzmetal s Variant Angina STABLE ANGINA GROUP. All 9 patients with stable angina were followed for 1 to 69 months (mean, 32 months). One patient sustained a perioperative anteroseptal infarction following left anterior descending coronary artery bypass. No operative deaths or late deaths occurred. Six patients are asymptomatic, and 3 have Class 1 angina. The 3 patients with residual symptoms include both patients in whom electrocardiographic changes occurred with exercise [HI. One patient with single-vessel disease involving the circumflex coronary artery and Class 3 angina, predominantly at rest, displayed lateral S-T segment elevation during exercise testing prior to operation [16]. Following bypass grafting, he experienced chest discomfort on exertion less than once per month, but a stress test one year postoperatively was negative. A second patient with left main coronary artery disease displayed S-T elevation and hypotension during recovery from exercise preoperatively. After operation, atypical chest pain developed but several stress tests were negative. Recatheterization at three years demonstrated patency of all grafts. The third symptomatic patient experienced infrequent exertional discomfort but displayed angiographic evidence of mitral valve prolapse with mild mitral regurgitation. The basis for his symptoms remains uncertain. UNSTABLE ANGINA GROUP. Follow-up in the 31 patients with unstable angina ranged from 1 to 75 months (mean, 29 months) and was 92% complete. No patient died. Six perioperative infarctions occurred, three in patients having a single bypass to the right coronary artery. Angina recurred in 7 patients. Four of them had multivessel disease with return of exertional symptoms 3 months to five years postoperatively; 1 sustained a late infarction six years after operation. Another patient with single-vessel disease experienced a single episode of rest pain and S-T segment elevation in the early postoperative period, but is currently asymptomatic without medication. Two others with single-vessel disease noted recurrence of angina 12 and 15 months after operation with late infarction in 1. S-T segment elevation with pain was not documented in either patient. POSTINFARCTION ANGINA GROUP. Follow-up in the 12 patients with postinfarction angina ex- tended from 1 to 24 months (mean, 11 months) and was 93% complete. There were 3 operative deaths: 1 patient with severe preoperative left ventricular dysfunction died, and 2 died following perioperative infarction. All 3 of these patients underwent operation within two weeks of acute infarction because of persistent anginal attacks despite intensive medical therapy and intraaortic balloon counterpulsation. No late deaths occurred. Seven patients are asymptomatic, and 2 are in Class 1. One patient who required mitral valve replacement has no angina, but suffers from congestive heart failure. He is in New York Heart Association Functional Class 111. Angiographic Features Because it has been suggested that patients with variant angina and high-grade fixed obstruction fare better surgically than those with less severe obstruction [lo], results in patients with obstruction of less than 90% were compared with results in those with stenoses of 90% and greater. Overall, 29 of 37 patients in the former group and 8 of 12 patients in the latter group were asymptomatic after operation (xz = 0.19, p = not significant). No significant differences were noted in any of the surgical groups when compared similarly (Fisher s exact test) for anginal status and perioperative infarction. Five patients received bypass grafts to totally occluded vessels supplying an area corresponding to S-T segment elevation on the electrocardiogram. Three of these patients had significant lesions in vessels supplying collaterals to the occluded vessels, and none of these 3 were symptomatic at follow-up. Two patients, both with isolated complete occlusion of the right coronary artery, have Class 1 atypical angina: one had mitral prolapse and the other, mitral valve replacement. S-T segment elevation has not been noted in either patient. Comment To our knowledge, this series constitutes the largest surgical experience with variant angina reported to date. In an attempt to provide a more precise basis for comparison of results of revascularization between Prinzmetal s and conventional angina, we subdivided our pop-

4 362 The Annals of Thoracic Surgery Vol 33 No 4 April 1982 ulation into stable, unstable, and unstable postinfarction groups. This classification, commonly used in analyzing results with classic angina, has not been emphasized in previous reports of surgical results with variant angina. The impetus for bypass operations in patients with variant angina stems from early reports suggesting a relatively poor response to medical therapy. Although the length of follow-up is not specified in the original paper of Prinzmetal and co-workers [17], 11 of their 35 patients (31%) eventually sustained a myocardial infarction, with 3 apparently related deaths. Selzer and colleagues [18] suggested that the prognosis might be favorable in variant angina due to spasm alone, but found that patients with fixed lesions (a group also characterized by an accelerated course) who were treated medically did very poorly. In a small group of 7 such patients, 4 infarctions occurred with 3 deaths within two weeks of presentation. While there was general agreement in the earlier literature that surgical intervention was indicated in some patients with variant angina, uncertainty remained about which subgroup might benefit from the operation. Gaasch and associates [3] expressed concern over increased risk and limited benefit obtained by the surgical approach in 24 patients with variant angina. They cited a 12% operative mortality, infarction or graft occlusion in 20% of patients, and continued chest pain in 30%. Conti and Curry [19] summarized the results of eighteen reports published prior to 1977, totaling 89 surgical patients. Perioperative infarction occurred in 17%, operative mortality was 13%, and angina recurred during follow-up of 12 months in 32%. They concluded that surgical treatment was most successful and could be recommended enthusiastically only for individuals with three-vessel disease. No definite recommendation regarding management of patients with one- and two-vessel disease was made. These results do not match contemporary expectations with classic angina, but it is not always possible to decipher the clinical presentation. The experience with conventional angina pectoris suggests that the risk with urgent operation in patients with unstable angina is greater than that for elective bypass in pa- tients with stable angina [ While it seems logical that this should apply equally to patients demonstrating variant angina, previous series do not present the information necessary for such a comparison. Possible explanations for the poor surgical outcome in patients with variant angina reported in early series include inexperience with the bypass technique, diffuse vasospasm involving the graft insertion site or the coronary artery distal to the anastomosis, and inclusion of patients without fixed lesions. Experience has demonstrated repeatedly that bypass grafting in the absence of fixed coronary artery disease is associated with high morbidity, mortality, and recurrence of angina. These patients are not candidates for bypass operation, even if they have severe disabling symptoms [3, 7, 251, and data from early surgical series, which often included such patients, should be interpreted with this in mind. Early concern over diffuse coronary vasospasm as a cause for a high failure rate with coronary bypass [25] has not been borne out in recent series dealing with high-grade fixed disease [8-101 or in our experience. The recurrent angina in the 2 patients with single-vessel disease in the unstable angina group could potentially have represented vasospasm, but S-T segment elevation has not been observed. Favorable surgical outcomes reported by Johnson [9], Shubrooks [8]; and their colleagues apply almost exclusively to patients with at least one fixed lesion greater than 70%. The majority of patients in the series of Shubrooks and co-workers had 90% or greater lesions. In 1979, Pasternak and associates [lo] described persistent postoperative angina in 8 of 26 patients (31%) with at least one narrowing greater than 90 /0, in contrast to persistent postoperative angina in 7 of 9 patients (78%) with lesions between 50% and 90%. Critical stenosis that was greater than 90% of the luminal diameter of the vessel supplying the area of elevation of the S-T segment occurred in a large percentage of our patient population: 6 of 9 patients with stable angina (67%), 25 of 31 patients with unstable angina (81%), and 7 of 12 patients with postinfarction angina (58%). The high prevalence of severely narrowed coronary

5 363 Schick et al: Prinzmetal's Variant Angina arteries may account for the favorable results in terms of the low rates of postoperative anginal recurrence and perioperative infarction, but no statistically significant difference in outcome was seen when patients with stenoses greater than 90% were compared with those with 70% to 90% narrowing. The small number of patients must be considered in interpretation of these results. Our patients with chronic stable angina tolerated operation well. No operative deaths, and only one perioperative myocardial infarction occurred, results comparable to large series of patients with classic chronic stable angina [ To date, there have been no late myocardial infarctions. A point of interest is the high percentage of single-vessel disease encountered in this group. S-T segment elevation with recurrent postoperative angina has not been documented in any of these patients. The largest subgroup in this series (31 patients) was seen with unstable angina. Our results are comparable to those obtained with surgical management of unstable angina not of the Prinzmetal variety [ and those from the subset of patients with unstable angina and S-T segment elevation in the National Cooperative Study [30]. Perioperative infarctions occurred in 20% of patients, and there were no operative deaths. At late follow-up, SO% of patients remained free from angina, only 2 patients had Class 3 angina, and 2 additional patients sustained late infarctions. That these results compare favorably with series dealing with treatment of unstable angina is not surprising in view of the evidence that coronary vasospasm plays a prominent role in the unstable syndromes [ It should be noted that one-third of the patients in this subgroup could not be stabilized with medical management and underwent urgent operation, a circumstance probably reflected in the relatively high incidence of perioperative infarction [34]. The subgroup with postinfarction unstable angina was managed surgically with some success. An effort was made to stabilize these patients with medical treatment, and operation was deferred three to four weeks from the time of acute infarction whenever possible. All deaths occurred in patients operated on be- cause of severe refractory episodes of angina early after infarction. Late results show substantial benefit when compared with those reported by Stenson and colleagues [14] in a similar postinfarction group of 9 patients. Eight of their patients did not undergo bypass. Three of them had another infarction, and 3 patients died, 2 after another infarction. Class I1 or I11 angina persisted in 3 patients. Only 2 patients became asymptomatic, 1 following another infarction. An additional point of interest is the successful use of the intraaortic balloon pump in some of the patients with unstable or postinfarction angina. Counterpulsation was instituted in 21 patients and resulted in control of symptoms in 11, while 10 patients continued to experience angina with S-T segment elevation. Although the balloon is less effective in patients with Prinzmetal's angina than in the unstable non-prinzmetal population, our results confirm previous reports that the aortic balloon is helpful in some patients with unstable angina and S-T segment elevation refractory to medical management [lo, 351. The mechanism for this is uncertain, but counterpulsation may alter cardiovascular reflex tone, thereby alleviating factors that foster coronary vasospasm. No late deaths occurred in the present series during a follow-up period of up to six years, a survival of 94%. The probability of sustaining a new myocardial infarction was less than 4%. We conclude that the results of coronary bypass grafting in patients with variant angina, when subdivided into standard clinical categories, are comparable to those reported in patients with conventional angina undergoing operation for similar indications. References 1. Silverman ME, Flamm MD: Variant angina pectoris: anatomical findings and prognostic implications. Ann Intern Med 74:339, MacAlpin RN, Kattus AA, Alvaro AB: Angina pectoris at rest with preservation of exercise capacity: Prinzmetal's variant angina. Circulation 47:946, Gaasch WH, Lufschanowski R, Leachman RD, et al: Surgical management of Prinzmetal's variant angina. Chest 66:614, Endo M, Kanda I, Hosada S, et al: Prinzmetal's

6 364 The Annals of Thoracic Surgery Vol 33 No 4 April 1982 variant form of angina pectoris: re-evaluation of mechanisms. Circulation 52:33, Betriu A, Solignac A, Bourassa MG: The variant form of angina: diagnostic and therapeutic implications. Am Heart J 87:272, Wiener L, Kasparian HK, Duca PR, et al: Spectrum of coronary arterial spasm: clinical angiographic and myocardial metabolic experience with 29 cases. Am J Cardiol 38:945, Clark DA, Quint RA, Mitchell RL, et al: Coronary artery spasm: medical management, surgical denervation and autotransplantation. J Thorac Cardiovasc Surg 73:332, Shubrooks SJ, Bete JM, Hutter AM, et al: Variant angina pectoris: clinical and anatomic spectrum and results of coronary bypass surgery. Am J Cardiol 36:142, Johnson AD, Stroud HA, Vieweg WVR, et al: Variant angina pectoris: clinical presentations, coronary angiographic patterns, and the results of medical and surgical management in 42 consecutive patients. Chest 73:786, Pasternak RC, Hutter AM, DeSanctis RW, et al: Variant angina: clinical spectrum and results of medical and surgical therapy. J Thorac Cardiovasc Surg 78:614, Gaasch WB: Exercise testing in variant angina. Chest 74:612, Mathur VS, Guinn GA, Anastassiades LC, et al: Surgical treatment for stable angina pectoris: prospective randomized study. N Engl J Med 292:709, Hultgren HN, Pfeifer JF, Angel1 WW, et al: Unstable angina: comparison of medical and surgical management. Am J Cardiol39:734, Stenson RE, Flamm MD, Zaret BL, et al: Transient ST-segment elevation with postmyocardial infarction angina: prognostic significance. Am Heart J 89:449, Campeau L: Grading of angina pectoris. Circulation 54:522, Weiner DA, Schick EC, Hood WB, et al: STsegment elevation during recovery from exercise: a new manifestation of Prinzmetal s variant angina. Chest 74:133, Prinzmetal M, Ekmekci A, Kennamer R, et al: Variant form of angina pectoris: previously undelineated syndrome. JAMA 174:1794, Selzer R, Langston M, Ruggeroli C, et al: Clinical syndrome of variant angina with normal coronary arteriogram. N Engl J Med 295:1343, Conti CR, Curry RC Jr: Therapy of unstable angina pectoris. In Cohn PF (ed): Diagnosis and Therapy of Coronary Artery Disease. Boston, Little, Brown, 1979, pp Selden R, Neil1 WA, Ritzman LW, et al: Medical versus surgical therapy for acute coronary insufficiency. N Engl J Med 293:1329, Bertolasi CA, Tronge JE, Riccitelli MA, et al: Natural history of unstable angina with medical or surgical therapy. Chest 70:596, National Cooperative Study Group: Unstable angina pectoris-national Cooperative Study Group to compare surgical and medical therapy: 11. In-hospital experience and initial follow-up results in patients with one, two and three vessel disease. Am J Cardiol43939, Pugh B, Platt MR, Mills LJ, et al: Unstable angina pectoris: a randomized study of patients treated medically and surgically. Am J Cardiol 41:1291, Golding LAR, Loop FD, Sheldon WC, et al: Emergency revascularization for unstable angina. Circulation 58:1163, MacAlpin RN: Who will benefit from coronary artery surgery? Chest 66:610, Mathur VS, Guinn GA: Prospective randomized study of surgical therapy for stable angina. Cardiovasc Clin 8:131, Kloster FE, Kremkau EL, Rahimtoola SH, et al: Prospective randomized study of coronary bypass surgery for chronic stable angina. Cardiovasc Clin 8:145, Murphy ML, Hultgren HN, Detre K, et al: Treatment of chronic stable angina. N Engl J Med 297:621, Sheldon WC, Loop FD: Direct myocardial revascularization-1976 progress report on the Cleveland Clinic experience. Cleve Clin Q 43:97, Schroeder JS, Russell RO, Resnekov L, et al: Un- stable angina pectoris-national randomized study of surgical vs medical therapy: results in Prinzmetal type angina (abstract). Am J Cardiol 41:397, Maseri A, Seven S, DeNes M, et al: Variant angina: one aspect of a continuous spectrum of vasospastic myocardial ischemia. Am J Cardiol 42:1019, Maseri A, L Abbate A, Baroldi G, et al: Coronary vasospasm as a possible cause of myocardial infarction: a conclusion derived from the study of preinfarction angina. N Engl J Med 299:1271, Madias JE: The syndrome of variant angina culminating in myocardial infarction. Circulation 49:297, Langou R, Geha AS, Hammond GL: Surgical approach for patients with unstable angina pectoris: role of the response to initial medical therapy and intraaortic balloon pumping in perioperative complications after aortocoronary bypass grafting. Am J Cardiol 42:629, Levine FH, Gold HK, Leinbach RC: Management of acute myocardial ischemia with intra-aortic balloon pumping and coronary bypass surgery (abstract). Circulation 57:Suppl3:60, 1977