The Surgical Treatment of Unstable Angina Pectoris CHARLES R. HATCHER, JR., M.D., ELLIS L. JONES, M.D., SPENCER B. KING, BILL T. GRAY, B.S., P.A., THOMAS N. NALLEY, B.S., P.A.
Since the advent of saphenous vein bypass grafting as successful means of myocardial revascularization, a variety of coronary artery disease syndromes have come under surgical attack. The proper role of surgery in many of these coronary syndromes remains il-defined. However, clear indications for surgical revascularization exist in patients with unstable angina pectoris, i.e., progressive angina and onset of rest pain and noctural angina in spite of adequate medical therapy. An analysis has been made of 100 consecutive patients with unstable angina pectoris who underwent myocardial revascularization over the past 2 years at the Woodruff Medical Center of Emory University. Included in this group are the following subgroups: 1) Emergency cases with preinfarction angina (including Printzmetal angina); 2) Cases of combined valvular heart disease and coronary artery disease; and 3) Advanced coronary artery disease with certain complications of previous myocardial infarction. A discussion of the relative merits of saphenous vein grafts and internal mammary artery anastomoses is presented and indicates that the technique selected should be determined by the quality of the distal native coronary circulation. Surgical mortality and morbidity figures, patency rates of saphenous vein grafts and internal mammary artery anastomoses visualized postoperatively, and the number of patients with dramatic relief of angina pectoris in this series support current enthusiasm for available surgical techniques for myocardial revascularization.
III,
M.D.,
From the Department of Surgery, Emory University School of
Medicine, Atlanta, Georgia
were: 1) initial onset angina (within 30 days) plus rest pain; 2) changing anginal pattern (pain with less exertion) without rest pain; 3) rest pain plus mild exertional angina; 4) rest pain plus disabling exertional angina; 5) prolonged pain (more than 30 minutes) without evidence of acute myocardial infarction in patients who have previously experienced brief pain; and 6) prolonged pain without acute myocardial infarction but with prior objective evidence of atherosclerotic heart disease. (Table 1). One hundred consecutive surgical patients whose clinical profiles were defined by these subsets were analyzed using a computer assisted data pool consisting of all patients undergoing coronary angiography at Emory University Hospital.
Clinical Material In a 14-month period from July, 1973 to October, 1974, 100 consecutive patients with unstable angina pectoris as S INCE the advent of saphenous vein bypass grafting as a previously defined underwent myocardial revascularizaat Emory University Hospital. There were 81 men successful means of myocardial revascularization a tidn and 19 women in this group. Age range was 33 to 73 years spectrum of coronary artery disease syndromes have (mean 54.2 years). come under surgical attack. 1,5,10 The proper role of surgery Sixty of these 100 patients had electrocardiographic in many of these coronary syndromes remains ill de- evidence 'Q' waves) of previous myocardial fined.6'8 However, strong indications for surgical revas- infarction.(significant revealed significant Coronary cularization exist in patients with unstable angina (75% occlusion) singlearteriography vessel disease in 23 patients, doupectons.3'10 ble vessel disease in 32 triple vessel disease in 43 Unstable angina pectoris has been difficult to define in and left main disease inpatients, 10 Eight of the patients precise terms yet it is imperative that such a definition be with left main disease had patients. involvement. other vessel made if the diagnostic and therapeutic efforts of different Preoperative ejection fractions could be accurately calcenters are to be properly compared and correlated. culated in 86 patients. These ejection fractions were near In this report unstable angina pectoris has been defined normal in approximately one half of the patients but were by using a list of clinical subsets. The six subsets selected significantly decreased in others (Table 2). Left ventricular endiastolic pressure (LVEDP) at rest Presented at the Annual Meeting ofthe Southern Surgical Association, December 9-11, 1975, Boca Raton, Florida. and two minutes post-angiogram are listed in Table 3. The
754
UNSTABLE ANGINA PECTORIS
Vol. 181 * NO. 5
TABLE 3. Left Ventricular End Diastolic Pressure (LVEDP)
TABLE 1. Definition of Unstable Angina Pectoris
6 9 14 53
Post-injection
At rest
Number
Initial onset anginia + rest pain Changing anginal pattern (less exertion) without rest pain Rest pain + mild exertional angina Rest pain + disabling exertional angina Prolonged pain (more than 30 min) without evidence of AMI in patients who have had brief pain Prolonged pain (more than 30 min) without AMI but with prior objective evidence ASHD Total
755
1 12 12-20 t 20 not calculated
71 21 7 1
45 35 19 1
Total
100
100
8 10 100
normal LVEDP in 71 patients at rest and 45 patients postangio demonstrated that severe left ventricular dysfunction was not a typical finding in these patients presenting with unstable angina pectoris. Methods and Results Myocardial revascularization was classified as emergency, urgent, or elective. Eleven patients underwent emergency coronary bypass immediately following coronary arteriography. These were patients experiencing prolonged pain (more than 30 minutes) without evidence of myocardial infarction (Printzmetal angina). Twentytwo patients were classified as urgent. Included in this group were patients with left main obstruction and severe effort angina plus rest pain. Sixty-seven patients were added to the elective operative schedule following cardiac catheterization and completion of preoperative evaluation. Surgical Technique. A median sternotomy incision was employed in all cases. Mid and distal saphenous veins were harvested through multiple small incisions in the lower extremities. Cardiopulmonary bypass and moderate systemic hypothermia (28-32 C) were employed using a disposable bubble oxygenator. In some patients saphenoaortic anastomoses were performed using partial occlusion clamps applied prior to the institution of cardiopulmonary bypass and in others these anastomoses TABLE 2. Preoperative Ejection Fractions
Patients
T .6 .5-.6 .4-.5 .3-.4 .2-.3 not calculated
41 18 17 8 2 14
Total
100
were performed during the phase of rewarming. Electrical fibrillation, induced if not occurring spontaneously, was used to facilitate the minimum dissection necessary for coronary artery exposure. The LV was sump drained in all cases. During the sapheno-coronary anastomoses tne aorta was cross clamped for period of 20 minutes or less. At least 5 mlnutes ofcoronary flow was permitted between distal anastomoses when multipie bypasses were performed. Sapheno-aortic anastomoses were performed under normal vision or magnification (3.5 power) with 5-0 prolene in a running suture technique. Segments of saphenous vein were beveled to the desired degree and the resulting flaps were not trimmed but were employed to give a cobra head takeoff. A small button of aortic wall was removed at some but not all of the anastomotic sites. The sapheno-coronary and internal mammary arterycoronary artery anastomoses were performed with multiple interrupted sutures of 6-0 or 7-0 prolene placed under magnification (3.5 power). Technique for Takedown ofthe Internal Mammary Artery. After the median sternotomy incision was completed, a small retractor was placed at the lower portion of the sternum and the left sternal border elevated as the retractor was opened. This maneuver elevated the entire left sternum without undue strain on the first assistant while the IMA was taken down. External counter pressure on the anterior chest wall invaginated the perforating branches of the internal mammary artery for better visibility. The internal mammary artery was dissected out with scissors and ligated at its distal portion (level of the sixth intercostal space). A pedicle of vein and artery approximately three-quarters of an inch in width was taken down entirely with the electrocautery. The internal mammary artery was dissected proximally to the level of the first rib. Once the pedicle had been brought down, inspection of the artery for proper diameter was made. Mammary arteries of less than 2 mm in diameter was deemed unacceptable for use. Three to four cc's of papaverine diluted one to six in normal saline was injected into the distal end of the mammary artery with a 21 angiocath needle. The suture was tied down, the angiocath removed, and the distended internal mammary artery laid aside for later use. The left anterior descending coronary artery was then dissected. The IMA usually will not reach below the mid-portion of
Ann. Surg. * May 1975
HATCHER ET AL.
756 TABLE 4. Number and Type of Bypass Grafts
Saphenous Veins Single Double Triple Quadruple Internal Mammary Artery Isolated IMA IMA + Single Vein IMA + Double Vein
20 43 10 I
8 14 4
but they must be accepted as a definite complication of revascularization surgery. Surgical Mortality. Five patients (5%) died during hospitalization (Table 5). In two patients cardiopulmonary bypass could not be discontinued and these patients ultimately expired in the operating room. One patient died on the second postoperative day of complications of low cardiac output. Another patient expired on the eighth postoperative day from an acute aortic dissection apparently arising at the site of application of a partial occlusion clamp to the ascending aorta. The final patient expired on the tenth postoperative day of acute renal failure and other complications. All 5 patients had severe triple vessel disease. Four exhibited generalized ventricular hypokinesia and decreased ejection fractions. Two patients had a history of documented congestive heart failure. Two patients had experienced multiple myocardial infarction in their past. Two of the patients had triple bypass grafts; three patients had double bypass grafts. Followup Studies. Fifty-nine of the 100 patients have returned for repeat coronary arteriography and ventriculography. Seventeen patients were studied one month postoperatively, as part of a study to establish our early patency rate. Failures (graft occlusions) during this interval are related primarily to technical failures and improper vessel selection. All asymptomatic patients were encouraged to return for later followup studies between one month and one year; to date 42 patients have had these later follow up studies. All patients who developed recurrence of symptoms were restudied. Therefore, the followup group presently includes routine early studies, surgical failures, and a group of co-operative volunteers for later studies. Subjective Data. The effectiveness of bypass surgery in the relief of angina pectoris has been clearly demonstrated.2'5 Relief of angina pectoris in our patients compares favorably with reported experience. Seventy-three per cent of patients received complete relief of angina and an additional 19% were significantly improved. In 5% of the patients symptoms were unchanged and in 3% symptoms
the LAD. Once the aorta was cross clamped and the left anterior descending coronary opened, calipers were used to make the arteriotomy incision in the LAD 4 mm in length. An oblique cut in the internal mammary artery was made 4.5 to 5 mm in length. A single 7-0 prolene suture is then used to construct the anastomosis and just prior to tying this suture, the bulldog clamp was removed from the IMA and the aortic cross clamp released. This distended the anastomotic site as the suture was then tied. Flow rates were recorded using an electromagnetic flow meter. Artificial ventilation was maintained for a period of 12 to 24 hours. Anticoagulants were not employed on a routine basis. However, anticoagulation therapy was begun immediately if evidence of phlebitis was observed in the lower extremities. The number and type of bypass grafts employed in this series are listed in Table 4. Twenty-eight patients received either a single vein graft or an isolated IMA graft. Thus, in 23 patients with single vessel disease complete revascularization was accomplished but only a single bypass was possible in 5 patients with double or triple vessel disease. Fifty-seven patients received double bypass grafts (32 patients with double vessel disease and 25 patients with triple vessel disease), triple bypass was achieved in 15 or 43 patients having triple disease. Our policy is to perform complete revascularization whenever possible, especially in critically ill patients. However this was not always possible in some patients with severe triple vessel disease due to total obstruction and obliteration or TABLE 5. inadequate distal vessels. A significant element of surgical morbidity was opera- Patients tive myocardial infarction. These infarctions were diag- Deaths Operative 2 (%) nosed by the appearance of new 'Q' waves in the post3 (%) Hospital This occurred complication operative electrocardiogram. Infarctions Operative in 16% of the patients. There was no apparent relationship between such infarctions and hospital course or survival. Patient, Day Six patients experiencing operative infarctions have been H.P., 10 re-catheterized and demonstrated areas of decreased conH.S., 8 tractility in the postoperative ventriculorgram not present H.W., 2 in earlier studies. The instance of peri-operative myocarJ.N., 0 dial infarction has been reported to range from 5 to 20%o.4'9 M.T., 0 The true clinical significance of these infarctions is unclear
Surgical Mortality and Morbidity 100 5 (%)
16 (%)
Mortality Cause Acute renal failure Aortic dissection Low output syndrome Unable to come off bypass Unable to come off bypass
Vol. 181 * NO. 5
UNSTABLE ANGINA PECTORIS
TABLE 8. Preoperative Ejection LVDEP
TABLE 6. Graft Patency
Number of Grafts Total grafts patent One graft patent Two grafts patent Three grafts patent 0 grafts patent
105 84 (80%o) 24) 24 . (88%) 4) 7 (12%)
were worse. In summary, 54 of 59 patients restudied up to a year following surgery were subjectively improved
(92%). Objective Data. The overall graft patency (Table 6) was 80%o or 84 patent grafts out of 105 total grafts performed. Fifty-two patients (88%) had one or more functioning grafts at followup and 7 (12%) had no grafts patent. IMA grafts have demonstrated a high patency rate.7 Twenty of our IMA grafts have been studied and 19 or 95% were patent. The single occlusion (5%) occurred in a woman with a mammary artery of questionable adequacy. It has been our policy to employ internal mammary artery grafts primarily for obstructive disease of the anterior descending coronary artery. If the distal LAD is of small caliber and the runoff poor, it is most desirable to use an IMA graft. If the distal vessel and vascular bed are ofgood size and quality, saphenous vein bypass may be selected, accepting the slightly lower patency rate in this anatomical situation in order to achieve the maximum increase in coronary blood flow. There is no doubt that flow rates with saphenous vein grafts are superior to flow rates with IMA grafts. Occasionally patients with patent IMA grafts continue to experience angina; angina with patent vein grafts is most unusual. Postoperative ejection fractions (Table 7) were quite similar to the preoperative studies. If 26 patients having ejection fractions greater than .6 before and after surgery are excluded, an analysis of 33 abnormal postoperative ejection fractions showed that 9 were unchanged, 6 were improved, 11 were worse and 7 were not calculated. The left ventricular endiastolic pressure was determined postoperatively in the resting and post injection states (Table 8). In the resting stares, there were 42 normal values and 17 abnormal values. Ofthe 17 abnormal LVEDP's, one was unchanged, 6 were improved, and 10 TABLE 7. Postoperative Ejection Fractions Normal (> .6) Abnormal
Unchanged Improved Worse Not calculated
Total
757
26 33 9 6 11 7
59
Post-injection
Resting
Normal ( 1 12 mm) Abnormal Unchanged Improved Worse
42 17 1 6 10
Normal Abnormal Unchanged Improved Worse
19 40 5 20
15
were worse compared to preoperative values. In the post injection state, only 19 LVEDP's were below 12 mm Hg and 40 were abnormal compared to preoperative post injection values. Five were unchanged, 20 were improved and 15 were worse. This data suggests that a ventricle under stress may demonstrate evidence of improvement secondary to revascularization which is not apparent in resting studies. Discussion In an attempt to clarify the definition of unstable angina pectoris, clinical subsets were defined prior to study. Patients so classified ranged from those with moderate exertional pain and episodes of rest or decubitus pain to prolonged episodes of pain with transient EKG changes which did not progress to extensive myocardial infarction. Indentification of and separation into clinical and anatomical subsets should allow a clearer delineation of those patients who will benefit most from myocardial revascularization. Single vessel disease is unusual in patients with unstable angina and even more unusual when rest pain is present. Therefore adequate revascularization for unstable angina usually involves double and triple bypass grafts. There are advantages and disadvantages to both saphenous vein and IMA grafts. The IMA grafts offer the higher patency rate (95% vs overall rate of 80%). The IMA grafts are limited in this experience to the management of proximal lesions of the LAD. Flow rates achieved with IMA grafts are generally lower than flow rates with saphenous vein grafts and may be inadequate for the total relief of angina in patients with a severely ischemic left ventricle. Saphenous veins offer the advantages of multiple grafts to distal sites of all major coronary arteries. In general, saphenous vein grafts are indicated for lesions of the distal right and circumflex coronary arteries and for LAD lesions if the distal vessel and vascular bed will permit the high flow rate necessary for vein graft patency. IMA grafts are preferable only for proximal LAD and diagonal lesions with small distal vessels and poor runoff. Saphenous vein grafts properly employed demonstrate a patency rate which is only slightly inferior to IMA patency rates and provide maximum increase in coronary blood flow.
758
Ann. Surg. * May 1975
HATCHER ET AL.
Myocardial revascularization is effective in the relief of angina pectoris (73% of patients with complete and 9%o with partial relief of angina). This dramatic relief of pain permits a return to normal activities in over 3/4 of patients favoring coronary bypass surgery. Relief of pain correlates well with graft patency rates. Surgical results show little impact of myocardial revascularization over ventricular function except in those cases where acute ischemia was present at the time of the preoperative ventriculogram (improved) or when operative infarction occurred (worse). Data suggest that stress testing may demonstrate an improvement in ventricular function secondary to myocardial revascularization not apparent in the resting state. Undoubtedly, the greatest impact of myocardial revascularization on patient survival will be demonstrated on those patients with double, triple, and left main disease.
Conclusions Unstable angina pectoris must be separated into clinical subsets to permit future definition of patients who will benefit from myocardial revascularization. Patients with unstable angina pectoris, even in emergency circumstances, undergo myocardial revascularization at acceptable low operative risk (5%).
DISCUSSION
DR. WALTER JANKE (Fort Lauderdale, Florida): (Slide) Our total experience, prior to coming down to Florida, encompasses 543 consecutive patients, with a mortality of six patients, or 1. 1%. On 27 ofthese patients, preinfarction was a prime indication for surgery. Six of these patients went ahead and developed acute infarction a few hours before or during induction of the anesthetic. Two of those patients required external and internal cardiac massage during cannulation. An additional patient had an acute infarction, went into cardiac shock, had to have a cardiac catheterization while in cardiogenic shock. Subsequently, we took him to surgery within three hours, and he survived the procedure. As we see, 16 patients had valvular replacement. We lost two of those patients. (Slide) Of the patients with valve replacement, three had mitral valvular replacement, 11 had an aortic valvular replacement, and one was a triple bypass. One patient had an open mitral commissurotomy. (Slide) We feel that probably the most important factor in the selection of patients for coronary artery surgery is the run-off, distal to the area of obstruction. We don't consider that congestive heart failure or elevated end diastolic pressure are a contraindicationfor surgery, if they do have a good run-off distal to the area of obstruction. I would like to know Dr. Hatcher's opinion in this respect. DR. CARLOS M. CHAVEZ (Jackson, Mississippi): I think we are now in need of a redefinition of what is called "unstable angina", and to limit the term of unstable angina to those cases where there is solid evidence of a pre-infarction state. In our experience, we have been unable to document a case of unstable angina with single vessel disease except for left main artery disease. Most of our cases have been of double, triple, vessel involvement, in the presence of dyskinesia, severe arrhythmias, and so forth. I was a little surprised that Dr. Hatcher's series did not include any case
Myocardial revascularization is quite effective in relieving anginal pain, but has little demonstrable effect on ventricular function in resting states. References 1. Alford, W. C. Jr., Shaker, I. J., Thomas, C. S. Jr., et al.: Aortocornary Bypass in Treatment of Left Main Coronary Artery Stenosis. Ann. Thorac. Surg., 17:247, March 1974.
2. Anderson, R. P., Shahbudin, H., Rahimtoola, M. C., et al.: The Prognosis of Patients with Coronary Artery Disease after Coronary Bypass Operations. Time-Related Progress of 532 Patients with Disabling Angina Pectoris. Circulation, 50:274, August 1974. 3. Bertolasi, C. A., Tronge, J. E., Carreno, C. A., et al.: Unstable Angina-Prospective and Randomized Study of its Evolution, With and Without Surgery. Am. J. Cardiovasc., 33:201, 1974. 4. Brewer, D. L., Bilbro, R. H., Bartel, A. G., Kouchoukos, N. T.: Myocardial Infarction as a Complication of Coronary Bypass Surgery. Circulation, 47:58, 1973. 5. Cooley, D. A., Dawson, J. T., Hailman, G. L., et al.: Aortocoronary Saphenous Vein Bypass. Results in 1492 Patients with Particular Reference to Patients with Complicating Features. Ann. Thorac. Surg., 16:380, 1973. 6. Favalora, R.: Direct and Indirect Coronary Surgery, Circulation, 46:1197, 1972. 7. Green, G. E. and Kemp, H. G.: Evaluation of Internal Mammary Artery Implantation. Am. J. Cardiovasc., 31:304, 1972. 8. Kaltman, A. J.: Indications for Aortocoronary Artery Bypass Surgery. Am. Heart J., 86:420, 1973. 9. Kouchoukos, N. T., Kirklin, J. W. and Oberman, A.: George C. Griffith Lecture. An Appraisal of Coronary Bypass Grafting. Circulation, 50:11, 1974. 10. Vermeulen, F., Huysmans, H., Van Riempst, A. S., et al.: J. Cardiovasc., Surg., 15:221, 1974.
of ventncular aneurysms, which are very commonly associated with multiple vessej involvement, which is also the case for patients with unstable angina. I would like to ask him whether he has in his series, any of these cases which required the management of ventricular aneurysm as well as the bypass grafts.
DR. GEORGE C. MORRIS, JR. (Houston, Texas): My comments are related primarily to patency rates. My own series exceeds 2000 in the last seven years, and in analyzing followup arteriograms in over 200 patients, most of whom had problems, the patency rate is 93%, excluding small secondary branches, such as the diagonal and distal branches ofthe right. I believe we should all be able to achieve a patency rate of this category with the saphenous vein; and this is comparable to the experience with the internal mammary. In the case of the internal mammary, one is usually working with the ideal recipient artery, the left anterior descending, which, as we all know, has the highest flow rates. DR. H. NEWLAND OLDHAM, JR. (Durham, North Carolina): We have been interested in the meaning of perioperative myocardial infarction. I noticed an incidence of 1 1% in this series of patients. We consistently have found that approximately 20% of our patients have EKG evidence of myocardial infarction, and a significantly larger number have CPK-M Bisoenzymes present during the perioperative period, indicating degrees of myocardial damage. We have evaluated recently 65 of these patients, one year following their surgery, with complete cardiac catheterization, selective angiography, and evaluation of ventricular function. We specifically were interested in those patients with EKG changes and those with CPK-MB evidence of myocardial damage at the time of operation. We were unable to demonstrate any statistical differences in functional classification, the results of treadmill exercise testing, graft patency rates or changes in ventricular function between patients with or without evidence of perioperative myocardial damage.
Since the advent of saphenous vein bypass grafting as successful means of myocardial revascularization, a variety of coronary artery disease syndromes have come under surgical attack. The proper role of surgery in many of these coronary syndromes remains il-defined. However, clear indications for surgical revascularization exist in patients with unstable angina pectoris, i.e., progressive angina and onset of rest pain and noctural angina in spite of adequate medical therapy. An analysis has been made of 100 consecutive patients with unstable angina pectoris who underwent myocardial revascularization over the past 2 years at the Woodruff Medical Center of Emory University. Included in this group are the following subgroups: 1) Emergency cases with preinfarction angina (including Printzmetal angina); 2) Cases of combined valvular heart disease and coronary artery disease; and 3) Advanced coronary artery disease with certain complications of previous myocardial infarction. A discussion of the relative merits of saphenous vein grafts and internal mammary artery anastomoses is presented and indicates that the technique selected should be determined by the quality of the distal native coronary circulation. Surgical mortality and morbidity figures, patency rates of saphenous vein grafts and internal mammary artery anastomoses visualized postoperatively, and the number of patients with dramatic relief of angina pectoris in this series support current enthusiasm for available surgical techniques for myocardial revascularization.
III,
M.D.,
From the Department of Surgery, Emory University School of
Medicine, Atlanta, Georgia
were: 1) initial onset angina (within 30 days) plus rest pain; 2) changing anginal pattern (pain with less exertion) without rest pain; 3) rest pain plus mild exertional angina; 4) rest pain plus disabling exertional angina; 5) prolonged pain (more than 30 minutes) without evidence of acute myocardial infarction in patients who have previously experienced brief pain; and 6) prolonged pain without acute myocardial infarction but with prior objective evidence of atherosclerotic heart disease. (Table 1). One hundred consecutive surgical patients whose clinical profiles were defined by these subsets were analyzed using a computer assisted data pool consisting of all patients undergoing coronary angiography at Emory University Hospital.
Clinical Material In a 14-month period from July, 1973 to October, 1974, 100 consecutive patients with unstable angina pectoris as S INCE the advent of saphenous vein bypass grafting as a previously defined underwent myocardial revascularizaat Emory University Hospital. There were 81 men successful means of myocardial revascularization a tidn and 19 women in this group. Age range was 33 to 73 years spectrum of coronary artery disease syndromes have (mean 54.2 years). come under surgical attack. 1,5,10 The proper role of surgery Sixty of these 100 patients had electrocardiographic in many of these coronary syndromes remains ill de- evidence 'Q' waves) of previous myocardial fined.6'8 However, strong indications for surgical revas- infarction.(significant revealed significant Coronary cularization exist in patients with unstable angina (75% occlusion) singlearteriography vessel disease in 23 patients, doupectons.3'10 ble vessel disease in 32 triple vessel disease in 43 Unstable angina pectoris has been difficult to define in and left main disease inpatients, 10 Eight of the patients precise terms yet it is imperative that such a definition be with left main disease had patients. involvement. other vessel made if the diagnostic and therapeutic efforts of different Preoperative ejection fractions could be accurately calcenters are to be properly compared and correlated. culated in 86 patients. These ejection fractions were near In this report unstable angina pectoris has been defined normal in approximately one half of the patients but were by using a list of clinical subsets. The six subsets selected significantly decreased in others (Table 2). Left ventricular endiastolic pressure (LVEDP) at rest Presented at the Annual Meeting ofthe Southern Surgical Association, December 9-11, 1975, Boca Raton, Florida. and two minutes post-angiogram are listed in Table 3. The
754
UNSTABLE ANGINA PECTORIS
Vol. 181 * NO. 5
TABLE 3. Left Ventricular End Diastolic Pressure (LVEDP)
TABLE 1. Definition of Unstable Angina Pectoris
6 9 14 53
Post-injection
At rest
Number
Initial onset anginia + rest pain Changing anginal pattern (less exertion) without rest pain Rest pain + mild exertional angina Rest pain + disabling exertional angina Prolonged pain (more than 30 min) without evidence of AMI in patients who have had brief pain Prolonged pain (more than 30 min) without AMI but with prior objective evidence ASHD Total
755
1 12 12-20 t 20 not calculated
71 21 7 1
45 35 19 1
Total
100
100
8 10 100
normal LVEDP in 71 patients at rest and 45 patients postangio demonstrated that severe left ventricular dysfunction was not a typical finding in these patients presenting with unstable angina pectoris. Methods and Results Myocardial revascularization was classified as emergency, urgent, or elective. Eleven patients underwent emergency coronary bypass immediately following coronary arteriography. These were patients experiencing prolonged pain (more than 30 minutes) without evidence of myocardial infarction (Printzmetal angina). Twentytwo patients were classified as urgent. Included in this group were patients with left main obstruction and severe effort angina plus rest pain. Sixty-seven patients were added to the elective operative schedule following cardiac catheterization and completion of preoperative evaluation. Surgical Technique. A median sternotomy incision was employed in all cases. Mid and distal saphenous veins were harvested through multiple small incisions in the lower extremities. Cardiopulmonary bypass and moderate systemic hypothermia (28-32 C) were employed using a disposable bubble oxygenator. In some patients saphenoaortic anastomoses were performed using partial occlusion clamps applied prior to the institution of cardiopulmonary bypass and in others these anastomoses TABLE 2. Preoperative Ejection Fractions
Patients
T .6 .5-.6 .4-.5 .3-.4 .2-.3 not calculated
41 18 17 8 2 14
Total
100
were performed during the phase of rewarming. Electrical fibrillation, induced if not occurring spontaneously, was used to facilitate the minimum dissection necessary for coronary artery exposure. The LV was sump drained in all cases. During the sapheno-coronary anastomoses tne aorta was cross clamped for period of 20 minutes or less. At least 5 mlnutes ofcoronary flow was permitted between distal anastomoses when multipie bypasses were performed. Sapheno-aortic anastomoses were performed under normal vision or magnification (3.5 power) with 5-0 prolene in a running suture technique. Segments of saphenous vein were beveled to the desired degree and the resulting flaps were not trimmed but were employed to give a cobra head takeoff. A small button of aortic wall was removed at some but not all of the anastomotic sites. The sapheno-coronary and internal mammary arterycoronary artery anastomoses were performed with multiple interrupted sutures of 6-0 or 7-0 prolene placed under magnification (3.5 power). Technique for Takedown ofthe Internal Mammary Artery. After the median sternotomy incision was completed, a small retractor was placed at the lower portion of the sternum and the left sternal border elevated as the retractor was opened. This maneuver elevated the entire left sternum without undue strain on the first assistant while the IMA was taken down. External counter pressure on the anterior chest wall invaginated the perforating branches of the internal mammary artery for better visibility. The internal mammary artery was dissected out with scissors and ligated at its distal portion (level of the sixth intercostal space). A pedicle of vein and artery approximately three-quarters of an inch in width was taken down entirely with the electrocautery. The internal mammary artery was dissected proximally to the level of the first rib. Once the pedicle had been brought down, inspection of the artery for proper diameter was made. Mammary arteries of less than 2 mm in diameter was deemed unacceptable for use. Three to four cc's of papaverine diluted one to six in normal saline was injected into the distal end of the mammary artery with a 21 angiocath needle. The suture was tied down, the angiocath removed, and the distended internal mammary artery laid aside for later use. The left anterior descending coronary artery was then dissected. The IMA usually will not reach below the mid-portion of
Ann. Surg. * May 1975
HATCHER ET AL.
756 TABLE 4. Number and Type of Bypass Grafts
Saphenous Veins Single Double Triple Quadruple Internal Mammary Artery Isolated IMA IMA + Single Vein IMA + Double Vein
20 43 10 I
8 14 4
but they must be accepted as a definite complication of revascularization surgery. Surgical Mortality. Five patients (5%) died during hospitalization (Table 5). In two patients cardiopulmonary bypass could not be discontinued and these patients ultimately expired in the operating room. One patient died on the second postoperative day of complications of low cardiac output. Another patient expired on the eighth postoperative day from an acute aortic dissection apparently arising at the site of application of a partial occlusion clamp to the ascending aorta. The final patient expired on the tenth postoperative day of acute renal failure and other complications. All 5 patients had severe triple vessel disease. Four exhibited generalized ventricular hypokinesia and decreased ejection fractions. Two patients had a history of documented congestive heart failure. Two patients had experienced multiple myocardial infarction in their past. Two of the patients had triple bypass grafts; three patients had double bypass grafts. Followup Studies. Fifty-nine of the 100 patients have returned for repeat coronary arteriography and ventriculography. Seventeen patients were studied one month postoperatively, as part of a study to establish our early patency rate. Failures (graft occlusions) during this interval are related primarily to technical failures and improper vessel selection. All asymptomatic patients were encouraged to return for later followup studies between one month and one year; to date 42 patients have had these later follow up studies. All patients who developed recurrence of symptoms were restudied. Therefore, the followup group presently includes routine early studies, surgical failures, and a group of co-operative volunteers for later studies. Subjective Data. The effectiveness of bypass surgery in the relief of angina pectoris has been clearly demonstrated.2'5 Relief of angina pectoris in our patients compares favorably with reported experience. Seventy-three per cent of patients received complete relief of angina and an additional 19% were significantly improved. In 5% of the patients symptoms were unchanged and in 3% symptoms
the LAD. Once the aorta was cross clamped and the left anterior descending coronary opened, calipers were used to make the arteriotomy incision in the LAD 4 mm in length. An oblique cut in the internal mammary artery was made 4.5 to 5 mm in length. A single 7-0 prolene suture is then used to construct the anastomosis and just prior to tying this suture, the bulldog clamp was removed from the IMA and the aortic cross clamp released. This distended the anastomotic site as the suture was then tied. Flow rates were recorded using an electromagnetic flow meter. Artificial ventilation was maintained for a period of 12 to 24 hours. Anticoagulants were not employed on a routine basis. However, anticoagulation therapy was begun immediately if evidence of phlebitis was observed in the lower extremities. The number and type of bypass grafts employed in this series are listed in Table 4. Twenty-eight patients received either a single vein graft or an isolated IMA graft. Thus, in 23 patients with single vessel disease complete revascularization was accomplished but only a single bypass was possible in 5 patients with double or triple vessel disease. Fifty-seven patients received double bypass grafts (32 patients with double vessel disease and 25 patients with triple vessel disease), triple bypass was achieved in 15 or 43 patients having triple disease. Our policy is to perform complete revascularization whenever possible, especially in critically ill patients. However this was not always possible in some patients with severe triple vessel disease due to total obstruction and obliteration or TABLE 5. inadequate distal vessels. A significant element of surgical morbidity was opera- Patients tive myocardial infarction. These infarctions were diag- Deaths Operative 2 (%) nosed by the appearance of new 'Q' waves in the post3 (%) Hospital This occurred complication operative electrocardiogram. Infarctions Operative in 16% of the patients. There was no apparent relationship between such infarctions and hospital course or survival. Patient, Day Six patients experiencing operative infarctions have been H.P., 10 re-catheterized and demonstrated areas of decreased conH.S., 8 tractility in the postoperative ventriculorgram not present H.W., 2 in earlier studies. The instance of peri-operative myocarJ.N., 0 dial infarction has been reported to range from 5 to 20%o.4'9 M.T., 0 The true clinical significance of these infarctions is unclear
Surgical Mortality and Morbidity 100 5 (%)
16 (%)
Mortality Cause Acute renal failure Aortic dissection Low output syndrome Unable to come off bypass Unable to come off bypass
Vol. 181 * NO. 5
UNSTABLE ANGINA PECTORIS
TABLE 8. Preoperative Ejection LVDEP
TABLE 6. Graft Patency
Number of Grafts Total grafts patent One graft patent Two grafts patent Three grafts patent 0 grafts patent
105 84 (80%o) 24) 24 . (88%) 4) 7 (12%)
were worse. In summary, 54 of 59 patients restudied up to a year following surgery were subjectively improved
(92%). Objective Data. The overall graft patency (Table 6) was 80%o or 84 patent grafts out of 105 total grafts performed. Fifty-two patients (88%) had one or more functioning grafts at followup and 7 (12%) had no grafts patent. IMA grafts have demonstrated a high patency rate.7 Twenty of our IMA grafts have been studied and 19 or 95% were patent. The single occlusion (5%) occurred in a woman with a mammary artery of questionable adequacy. It has been our policy to employ internal mammary artery grafts primarily for obstructive disease of the anterior descending coronary artery. If the distal LAD is of small caliber and the runoff poor, it is most desirable to use an IMA graft. If the distal vessel and vascular bed are ofgood size and quality, saphenous vein bypass may be selected, accepting the slightly lower patency rate in this anatomical situation in order to achieve the maximum increase in coronary blood flow. There is no doubt that flow rates with saphenous vein grafts are superior to flow rates with IMA grafts. Occasionally patients with patent IMA grafts continue to experience angina; angina with patent vein grafts is most unusual. Postoperative ejection fractions (Table 7) were quite similar to the preoperative studies. If 26 patients having ejection fractions greater than .6 before and after surgery are excluded, an analysis of 33 abnormal postoperative ejection fractions showed that 9 were unchanged, 6 were improved, 11 were worse and 7 were not calculated. The left ventricular endiastolic pressure was determined postoperatively in the resting and post injection states (Table 8). In the resting stares, there were 42 normal values and 17 abnormal values. Ofthe 17 abnormal LVEDP's, one was unchanged, 6 were improved, and 10 TABLE 7. Postoperative Ejection Fractions Normal (> .6) Abnormal
Unchanged Improved Worse Not calculated
Total
757
26 33 9 6 11 7
59
Post-injection
Resting
Normal ( 1 12 mm) Abnormal Unchanged Improved Worse
42 17 1 6 10
Normal Abnormal Unchanged Improved Worse
19 40 5 20
15
were worse compared to preoperative values. In the post injection state, only 19 LVEDP's were below 12 mm Hg and 40 were abnormal compared to preoperative post injection values. Five were unchanged, 20 were improved and 15 were worse. This data suggests that a ventricle under stress may demonstrate evidence of improvement secondary to revascularization which is not apparent in resting studies. Discussion In an attempt to clarify the definition of unstable angina pectoris, clinical subsets were defined prior to study. Patients so classified ranged from those with moderate exertional pain and episodes of rest or decubitus pain to prolonged episodes of pain with transient EKG changes which did not progress to extensive myocardial infarction. Indentification of and separation into clinical and anatomical subsets should allow a clearer delineation of those patients who will benefit most from myocardial revascularization. Single vessel disease is unusual in patients with unstable angina and even more unusual when rest pain is present. Therefore adequate revascularization for unstable angina usually involves double and triple bypass grafts. There are advantages and disadvantages to both saphenous vein and IMA grafts. The IMA grafts offer the higher patency rate (95% vs overall rate of 80%). The IMA grafts are limited in this experience to the management of proximal lesions of the LAD. Flow rates achieved with IMA grafts are generally lower than flow rates with saphenous vein grafts and may be inadequate for the total relief of angina in patients with a severely ischemic left ventricle. Saphenous veins offer the advantages of multiple grafts to distal sites of all major coronary arteries. In general, saphenous vein grafts are indicated for lesions of the distal right and circumflex coronary arteries and for LAD lesions if the distal vessel and vascular bed will permit the high flow rate necessary for vein graft patency. IMA grafts are preferable only for proximal LAD and diagonal lesions with small distal vessels and poor runoff. Saphenous vein grafts properly employed demonstrate a patency rate which is only slightly inferior to IMA patency rates and provide maximum increase in coronary blood flow.
758
Ann. Surg. * May 1975
HATCHER ET AL.
Myocardial revascularization is effective in the relief of angina pectoris (73% of patients with complete and 9%o with partial relief of angina). This dramatic relief of pain permits a return to normal activities in over 3/4 of patients favoring coronary bypass surgery. Relief of pain correlates well with graft patency rates. Surgical results show little impact of myocardial revascularization over ventricular function except in those cases where acute ischemia was present at the time of the preoperative ventriculogram (improved) or when operative infarction occurred (worse). Data suggest that stress testing may demonstrate an improvement in ventricular function secondary to myocardial revascularization not apparent in the resting state. Undoubtedly, the greatest impact of myocardial revascularization on patient survival will be demonstrated on those patients with double, triple, and left main disease.
Conclusions Unstable angina pectoris must be separated into clinical subsets to permit future definition of patients who will benefit from myocardial revascularization. Patients with unstable angina pectoris, even in emergency circumstances, undergo myocardial revascularization at acceptable low operative risk (5%).
DISCUSSION
DR. WALTER JANKE (Fort Lauderdale, Florida): (Slide) Our total experience, prior to coming down to Florida, encompasses 543 consecutive patients, with a mortality of six patients, or 1. 1%. On 27 ofthese patients, preinfarction was a prime indication for surgery. Six of these patients went ahead and developed acute infarction a few hours before or during induction of the anesthetic. Two of those patients required external and internal cardiac massage during cannulation. An additional patient had an acute infarction, went into cardiac shock, had to have a cardiac catheterization while in cardiogenic shock. Subsequently, we took him to surgery within three hours, and he survived the procedure. As we see, 16 patients had valvular replacement. We lost two of those patients. (Slide) Of the patients with valve replacement, three had mitral valvular replacement, 11 had an aortic valvular replacement, and one was a triple bypass. One patient had an open mitral commissurotomy. (Slide) We feel that probably the most important factor in the selection of patients for coronary artery surgery is the run-off, distal to the area of obstruction. We don't consider that congestive heart failure or elevated end diastolic pressure are a contraindicationfor surgery, if they do have a good run-off distal to the area of obstruction. I would like to know Dr. Hatcher's opinion in this respect. DR. CARLOS M. CHAVEZ (Jackson, Mississippi): I think we are now in need of a redefinition of what is called "unstable angina", and to limit the term of unstable angina to those cases where there is solid evidence of a pre-infarction state. In our experience, we have been unable to document a case of unstable angina with single vessel disease except for left main artery disease. Most of our cases have been of double, triple, vessel involvement, in the presence of dyskinesia, severe arrhythmias, and so forth. I was a little surprised that Dr. Hatcher's series did not include any case
Myocardial revascularization is quite effective in relieving anginal pain, but has little demonstrable effect on ventricular function in resting states. References 1. Alford, W. C. Jr., Shaker, I. J., Thomas, C. S. Jr., et al.: Aortocornary Bypass in Treatment of Left Main Coronary Artery Stenosis. Ann. Thorac. Surg., 17:247, March 1974.
2. Anderson, R. P., Shahbudin, H., Rahimtoola, M. C., et al.: The Prognosis of Patients with Coronary Artery Disease after Coronary Bypass Operations. Time-Related Progress of 532 Patients with Disabling Angina Pectoris. Circulation, 50:274, August 1974. 3. Bertolasi, C. A., Tronge, J. E., Carreno, C. A., et al.: Unstable Angina-Prospective and Randomized Study of its Evolution, With and Without Surgery. Am. J. Cardiovasc., 33:201, 1974. 4. Brewer, D. L., Bilbro, R. H., Bartel, A. G., Kouchoukos, N. T.: Myocardial Infarction as a Complication of Coronary Bypass Surgery. Circulation, 47:58, 1973. 5. Cooley, D. A., Dawson, J. T., Hailman, G. L., et al.: Aortocoronary Saphenous Vein Bypass. Results in 1492 Patients with Particular Reference to Patients with Complicating Features. Ann. Thorac. Surg., 16:380, 1973. 6. Favalora, R.: Direct and Indirect Coronary Surgery, Circulation, 46:1197, 1972. 7. Green, G. E. and Kemp, H. G.: Evaluation of Internal Mammary Artery Implantation. Am. J. Cardiovasc., 31:304, 1972. 8. Kaltman, A. J.: Indications for Aortocoronary Artery Bypass Surgery. Am. Heart J., 86:420, 1973. 9. Kouchoukos, N. T., Kirklin, J. W. and Oberman, A.: George C. Griffith Lecture. An Appraisal of Coronary Bypass Grafting. Circulation, 50:11, 1974. 10. Vermeulen, F., Huysmans, H., Van Riempst, A. S., et al.: J. Cardiovasc., Surg., 15:221, 1974.
of ventncular aneurysms, which are very commonly associated with multiple vessej involvement, which is also the case for patients with unstable angina. I would like to ask him whether he has in his series, any of these cases which required the management of ventricular aneurysm as well as the bypass grafts.
DR. GEORGE C. MORRIS, JR. (Houston, Texas): My comments are related primarily to patency rates. My own series exceeds 2000 in the last seven years, and in analyzing followup arteriograms in over 200 patients, most of whom had problems, the patency rate is 93%, excluding small secondary branches, such as the diagonal and distal branches ofthe right. I believe we should all be able to achieve a patency rate of this category with the saphenous vein; and this is comparable to the experience with the internal mammary. In the case of the internal mammary, one is usually working with the ideal recipient artery, the left anterior descending, which, as we all know, has the highest flow rates. DR. H. NEWLAND OLDHAM, JR. (Durham, North Carolina): We have been interested in the meaning of perioperative myocardial infarction. I noticed an incidence of 1 1% in this series of patients. We consistently have found that approximately 20% of our patients have EKG evidence of myocardial infarction, and a significantly larger number have CPK-M Bisoenzymes present during the perioperative period, indicating degrees of myocardial damage. We have evaluated recently 65 of these patients, one year following their surgery, with complete cardiac catheterization, selective angiography, and evaluation of ventricular function. We specifically were interested in those patients with EKG changes and those with CPK-MB evidence of myocardial damage at the time of operation. We were unable to demonstrate any statistical differences in functional classification, the results of treadmill exercise testing, graft patency rates or changes in ventricular function between patients with or without evidence of perioperative myocardial damage.
