Aortocoronary Artery Graft During Early and Late Phases of Acute Myocardial Infarction

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1 Aortocoronary Artery Graft During Early and Late Phases of Acute Myocardial Infarction Chalit Cheanvechai, M.D., Donald B. Effler, M.D., Floyd D. Loop, M.D., Laurence K. Groves, M.D., William C. Sheldon, M.D., and F. Mason Sones, Jr., M.D. ABSTRACT From April, 1968, to August, 1972, 30 patients received one to three emergency saphenous vein grafts during acute myocardial infarction. In all but 1 patient, acute myocardial infarction occurred while the patients were in the hospital awaiting coronary angiography or myocardial revascularization. The patients were divided into two groups: those in the early and those in the late phases of acute myocardial infarction, depending on the time interval between the onset of chest pain and operation. Twenty-four patients (early phase) received grafts within 10 hours after the onset of infarction, and 18 of these 24 patients underwent operation within 4 hours after infarction. Two patients included in this group sustained myocardial infarctions in the operating room during elective myocardial revascularization procedures; another patient was brought to the operating room following cardiac arrest and was supported by internal cardiac massage throughout the opening of the chest and cardiac cannulation. Six patients (late phase) received grafts from three to fourteen days after acute infarction because of postinfarction angina. Only 1 patient was in cardiogenic shock prior to operation. Two patients, both from the early phase group, died in the postoperative period; and 1 patient died seven months postoperatively from a noncardiac cause. Twenty-five of 27 sufviving patients became asymptomatic, and 2 patients continue to have mild angina (Functional Class 11). Sixteen patients with 24 grafts were restudied in the postoperative period, and 22 of the grafts were found to be patent. This experience suggests that early operative intervention in acute myocardial infarction by the saphenous vein graft technique is beneficial to the patient. The rationale of revascularization in the early phase of acute myocardial infarction is to minimize the area of muscle necrosis by increasing perfusion to the ischemic myocardium around the infarct. M ore than 500,000 Americans die each year from acute myocardial infarction. The mortality among patients receiving medical treatment is still quite high, ranging from 17.5 to 32oj, [14, 171. When the infarction is associated with cardiogenic shock, the mortality From the Department of Thoracic and Cardiovascular Surgery, the Department of Cardiovascular Disease, and the Cardiac Laboratory, The Cleveland Clinic, Cleveland, Ohio. Presented at the Ninth Annual Meeting of The Society of Thoracic Su,rgeons, Houston, Tex., Jan , Address reprint requests to Dr. Cheanvechai, The Cleveland Clinic, 9500 Euclid Ave., Cleveland, Ohio VOL. 16, NO. 3, SEPTEMBER,

2 CHEANVECHAI ET AL. increases to 80 to 100yo [2, 6, 9, 13, 151. Many authors have reported encouraging results with aortocoronary artery grafts performed during acute myocardial infarction [3, 8, 11, 191. This is a report of the results of emergency saphenous vein bypass grafting performed at The Cleveland Clinic Hospital during the early and late phases of acute myocardial infarction. Clinical Material From April, 1968, to August, 1972, 27 men and 3 women ranging in age from 36 to 68 years (mean 53 years) received saphenous vein grafts as an emergency procedure during acute myocardial infarction. In all but 1 patient the infarction occurred in the hospital while the patient was awaiting coronary angiography or myocardial re iascularization. Acute myocardial infarction is defined as: (1) prolonged ch :st pain; (2) abnormal electrocardiographic findings-st segment elevation with reciprocal depression, abnormal Q wave, or absence of R wave; or (3) elevation of serum transaminase. The patients were divided into two groups, those in the early and those in the late phases of acute myocardial infarction, depending on the time interval between the onset of chest pain and operation. There were 24 patients in the early phase in whom operation was performed within 10 hours after the onset of infarction. There were 6 patients in the late phase of acute infarction who received grafts from three to fourteen days following the acute infarction. These patients underwent operation because of postinfarction angina. The types of operation are shown in Table 1. The early phase group included 2 patients who sustained acute myocardial infarction in the operating room during elective myocardial revascularization and 1 patient who was brought to the operating room without a heartbeat following cardiac arrest. This patient was supported by internal cardiac massage throughout the opening of the chest and cardiac cannulation. These 3 patients do not fulfill the above criteria of acute myocardial infarction because complete electrocardiograms and serum enzyme evaluations were not obtained before operation. Serum transaminase values were not obtained in another 2 patients preoperatively; however, their electrocardiographic findings were abnormal and were compatible with acute myocardial infarction. Preoperative serum transaminase values were obtained from 19 patients in the early phase group. None showed significant elevations. This is most likely due to the lack of sufficient time for the enzymes to rise, as the blood samples were all obtained at the onset of chest pain. Serial postoperative serum transaminase values were obtained, and they were all significantly elevated. 250 THE ANNALS OF THORACIC SURGERY

3 Coronary Bypass Graft During Myocardial Infarction TABLE 1. TYPE OF OPERATION PERFORMED IN 30 PATIENTS DURING ACUTE MYOCARDIAL INFARCTION, APRIL, 1968, TO AUGUST, 1972 No. of Phase of MI & Operation Patients Early phase SVG to LAD 2 LAD single implant" 1 LAD circumflex 6 LAD RCA circumflex 3 LAD + RCA + double implant" 1 RCA 5 RCA LAD 2 RCA diagonal 1 RCA + diagonal + LADb 1 Circumflex 2 Total 24 Late phase SVG to LAD LAD + RCA LAD + circumflex Total "Acute myocardial infarction occurred in the operating room. binternal mammary artery anastomosis. MI 1 myocardial infarction; SVG = saphenous vein graft; LAD = left anterior descending coronary artery; RCA = right coronary artery. CORONARY CINEANGIOGRAPHY During the period covered by this report, 16,814 patients underwent coronary angiography and left ventriculography. The decision to perform emergency saphenous vein grafting procedures was made in these 30 patients. In the 24 patients in the early phase of infarction, coronary angiography was performed on 3 patients within 3 hours after acute infarction. In 6 patients who were studied during crescendo angina, signs of infarction developed during the study. In the remaining 15 patients, acute myocardial infarction developed from 3 hours to seven days after angiography was carried out. Following angiography these 15 patients remained in the hospital awaiting urgent myocardial revascularization. Of 6 patients in the late phase of infarction, 5 underwent coronary angiography within three to fourteen days after the acute infarction. One patient had had coronary angiography three and one-half months preoperatively; three days prior to operation he had sustained an acute anteroseptal infarction and was treated conservatively. He continued to have angina, and bypass grafting to his anterior descending and circumflex coronary arteries was performed because of recurrent angina. All patients had lesions that were narrowed more than 80%. The number of vessels involved is shown in Table 2. Seven patients had normal VOL. 16, NO. 3, SEPTEMBER,

4 CHEANVECHAI ET AL. TABLE 2. CORONARY VESSELS INVOLVED IN 30 PATIENTS UNDERGOING BYPASS GRAFTING DURING MYOCARDIAL INFARCTION Vessel No. of Patients Single 13 Double 5 Triple 11 Left main trunk 1 Total 30 preoperative ventriculograms, and 23 patients had abnormal preoperative ven triculograms. TIME INTERVAL Of the 24 patients in the early phase of myocardial infarction, 18 were operated on within 4 hours after the onset of pain, 4 at 6 hours, 1 at 8 hours, and 1 at 10 hours. In the 6 patients in the late phase, the grafts were performed from three to fourteen days after the onset of the infarction (Fig. 1). ELECTROCARDIOGRAMS All patients had electrocardiograms, and 14 of them had electrocardiographic evidence of remote myocardial infarction. In the early phase group, 10 patients had acute anteroseptal infarctions, 9 had inferior infarctions, 4 had lateral infarctions, and 1 had cardiac arrest. Four patients in the late phase group had acute anteroseptal infarctions, and 2 patients had intramural infarctions. In all but the patient who had cardiac arrest, electrocardiographic findings were correlated with the angiographic findings. For example, acute inferior wall infarction was found in patients with lesions of the dominant right coronary artery or dominant circumflex artery; anteroseptal infarction was present in patients with anterior descending coronary artery lesions; and lateral infarction was found in patients with circumflex coronary artery lesions. wl I- f I- 2 z EARLY PHASE wl c g 21 if 0 LATE PHASE FIG TIME IN HOURS TIME IN DAYS Time interval from onset of infarction to completion of bypass grafting. 252 THE ANNALS OF THORACIC SURGERY

5 Coronary Bypass Graft During Myocardial Infarction OPERATIVE FINDINGS Common findings at operation were impaired contraction and cyanosis of the involved myocardium. Venouslike blood and minimal flows were observed at the site of the arteriotomy in most cases. Two patients in the early phase of acute myocardial infarction had fresh thrombi at the site of the arteriotomy. OPERATIVE TECHNIQUE The operative technique is the same as that previously described by Favaloro [7]; however, for the emergency saphenous vein bypass grafting procedures we have a new policy. (1) The operation should be performed immediately after diagnosis; (2) heparin, 100 mg., is given intravenously immediately after the onset of infarction to prevent clot formation in the distal artery; (3) all operations are performed with the aid of total cardiopulmonary bypass with complete decompression of the left ventricle using the left ventricular vent; (4) in multiple-graft procedures, grafting to the infarcted area (primary grafting) is performed first to perfuse this area while the secondary grafting is being done; (5) to avoid further anoxia to the myocardium, the operation must be performed without cross-clamping of the aorta; (6) bleeding at the arteriotomy site is controlled by looping 2-0 silk around the artery; and (7) temporary epicardial pacemaker wires and a left atrial pressure catheter are inserted for postoperative management. None of these patients had circulatory assistance before or after operation. One patient (see Fig. 5) who had triple-vessel disease experienced cardiogenic shock before the operation and was treated with vasopressors, and double-bypass grafts were completed about 3 hours after the onset of infarction. The patient came off the heart-lung bypass without difficulty, and he required no vasopressors in the postoperative course. POSTOPERATIVE COMPLICATIONS AND MORTALITY Twelve patients had postoperative complications (Table 3). None of the surviving patients had ventricular fibrillation or heart failure postoperatively. TABLE 3. POSTOPERATIVE COMPLICATIONS AMONG 30 PATIENTS UNDERGOING BYPASS GRAFTING DURING MYOCARDIAL INFARCTION Complication No. of Patients Atrial fibrillation 3 Hepatitis (mild) 2 Pneumonia 2 Mild cerebrovascular accident 1 Postcardiotomy syndrome 1 Thrombophlebitis of distal saphenous vein 1 Pulmonary embolus 1 Postoperative bleeding 1 VOL. 16, NO. 3, SEPTEMBER,

6 CHEANVECHAI ET AL. Two patients, both in the early phase group, died in the postoperative period. The first received a graft to his right coronary artery on April 4, He died immediately after the operation from massive inferior wall myocardial infarction. The second patient received triple grafts on July 13, He died on the third postoperative day from malfunction of the tracheostomy tube. There were no deaths in the most recent 15 patients, whose operations were performed without anoxic arrest. Results Twenty-eight patients have been followed from three months to two and one-half years. One patient died from a noncardiac cause seven months after operation. Postmortem examination revealed patent grafts. Twenty-five of 27 surviving patients became asymptomatic, and 2 patients continue to have FIG. 2. A 55-year-old man was admitted to the Cleveland Clinic Hospital because of an acute anteroseptal infarction. Coronary angiography was performed on November 9, 1971, 2 hours after the onset of chest pain and demonstrated (A) total obstruction of the left anterior descending coronary artery and (B) severe impairment of contraction of the anterior wall of the left ventricle. An emergency bypass graft to the anterior descending coronary artery was completed about 5 hours after the infarction. A repeat coronary angiogram six weeks later (C) demonstrated good function of the graft, and a left ventriculogram (D) demonstrated much improvement of ventricular contraction. 254 THE ANNALS OF THORACIC SURGERY

7 Coronary Byfiass Graft During Myocardial Infarction, FIG. 3. A cineangiogram of a 56-year-old man performed on February 10, 1972, demonstrated (A) 90% narrowing of the main trunk of the dominant circumflex coronary artery and (B) a normal ventriculogram. A bypass graft was performed on February 14, 1972,2 hours after the onset of acute infarction, while he was awaiting elective myocardial revascularization. Nine months later a repeat angiogram showed (C) a widely patent graft and (0) impairment of left ventricular contraction. mild angina (New York Heart Association Functional Class 11). Sixteen patients with 24 grafts were restudied from one month to two years after operation. Sixteen of the grafts were to the infarcted area (primary grafts); all were patent. Two of 8 secondary grafts (grafts to other areas) were occluded. Thus, overall, 22 of the 24 grafts remained patent. Preoperative and postoperative ventriculograms were compared in 16 of the patients. Three patients had improved ventricular function. Five patients had impaired ventricular function, and 2 of these patients had had normal preoperative ventriculograms. In 8 patients the ventriculograms demonstrated no change; 3 of these 8 patients had had normal preoperative ventriculograms. Comment The amount of myocardial ischemia and necrosis after coronary occlusion will increase in direct proportion with time as shown by the VOL. 16, NO. 3, SEPTEMBER,

8 CHEANVECHAI ET AL. FZG. 4. Cineangiogram obtained from a 50-year-old man fourteen days after an acute nontransmural infarction demonstrated (A) subtotal obstruction of the proximal anterior descending coronary artery and (B) a normal uentriculogram. Emergency bypass grafting was performed on June 30, Three and one-half months later a repeat angiogram showed (C) a patent graft and (D) a normal uentriculogram. experiments of Cox and associates [5]. Lie and his co-workers [16] also observed this ischemic myocardium in the human heart three to twelve days after acute infarction. The ultimate fate of the ischemic myocardium depends on the collateral circulation and its oxygen consumption. If the collateral circulation is adequate, there may be little or no muscle necrosis. Emergency bypass grafts provide immediate blood supply to the ischemic myocardium; and when the operation is performed in the early phase of infarction, most of the ischemic myocardium will return to normal and the area of muscle necrosis will be minimal, as shown in Figure 2. Although most of our patients sustained infarction in the hospital, the history of the patient shown in Figure 2 suggests that immediate bypass grafting is feasible for the patient who is admitted to the hospital a few hours after infarction. The muscle that is already necrotic cannot be salvaged, as shown in Figure 3. From this experience, we believe grafting should be done 256 THE ANNALS OF THORACIC SURGERY

9 Coronary Bypass Graft During Myocardial Znfarction FIG. 5. A cineangiogram of a 60-year-old woman performed on June 14, 1972, demonstrated (A) 90% narrowing of the anterior descending coronary artery, 80% narrowing of the right coronary artery (arrows), and total occlusion of the circumflex artery, along with (B) generalized impairment of the left ventricle. Left ventricular end-diastolic pessure was 30 mm. Hg. Bypass grafts to the right and anterior descending coronary arteries were performed while the patient was in cardiogenic shock on June 15, Three and onehalf months later a repeat angiogram demonstrated (C) patent grafts and (0) more impairment of left ventricular function. Left ventricular end-diastolic pressure was 35 mm. Hg. This patient is presently able to perform her usual housework without angina pectoris or dyspnea. as soon as possible in acute myocardial infarction; the optimal time is within 6 hours after the onset of infarction. Anoxic arrest should not be used in this type of operation. The rationale of acute revascularization is to prevent extension of the infarction by increasing perfusion to the ischemic myocardium around the area of the infarct. We believe this approach is beneficial, especially in patients with multiple-vessel disease. All patients in the late phase of infarction had postinfarction angina, which indicates the presence of viable myocardium (Fig. 4). We believe this type of patient should undergo emergency cineangiography, which can be performed with minimal risk [l]. All 6 patients in this group had critical proximal obstructions with good distal runoff. Ventriculograms showed only minimal impairment. All patients survived operation and are presently doing well.

10 CHEANVECHAI ET AL. The death rate among patients in cardiogenic shock is still high, regardless of the type of treatment used [Z, 6, 9, 13, 151. We believe that in acute myocardial infarction early intervention by the saphenous vein graft technique may prevent the extension of infarction and may be a lifesaving procedure, especially in patients with triple-vessel disease (Fig. 5). References 1. Begg, F. R., Kooros, M. A., Magovern, G. J., Kent, E. M., Baent, L. B., and Cushing, W. 3. The hemodynamics and coronary arteriography patterns during acute myocardial infarction. J. Thorac. Cardiovasc. Surg. 58:647, Buckley, M. J., Leinbach, R. C., Kastor, J. A., Laird, J. D., Kantrowitz, A. R., Madras, P. N., Sanders, C. A., and Austen, W. G. Hemodynamic evaluation of intra-aortic balloon pumping in man. Circulation 4 1 (Suppl. 11): 130, Cohn, L. H., Gorlin, R., Herman, M. V., and Collins, J. J., Jr. Aortocoronary bypass for acute coronary occlusion. J. Thorac. Cardiovasc. Surg. 64:503, Corday, E., Meerbaum, S., and Lang, T. Treatment of cardiogenic shock with mechanical circulatory assist-fact or fiction? Am. 1. Cardiol. 30:575, Cox, J. L., McLaughlin, V. W., Flowers, N. C., and Horan, L. G. The ischemic zone surrounding acute myocardial infarction: Its morphology as detected by dehydrogenase staining. Am. Heart J. 76:650, Cronin, R. F. P., Moore S., and Marpole, D. G. Shock following myocardial infarction: A clinical survey of 140 cases. Can. Med. Assoc. J. 93:57, Favaloro, R. G. Surgical Treatment of Coronary Arteriosclerosis. Baltimore: Williams & Wilkins, Favaloro, R. G., Effler, D. B., Cheanvechai, C., Quint, R. A., and Sones, F. M., Jr. Acute coronary insufficiency (impending myocardial infarction and myocardial infarction): Surgical treatment by the saphenous vein graft technique. Am. J. Cardiol. 28:598, Friedberg, C. K. Cardiogenic shock in acute myocardial infarction. Circulation 23:325, Goetz, R. H., Bregman, D., Esrig, B., and Laniado, S. Unidirectional intraaortic balloon pumping in cardiogenic shock and intractable left ventricular failure. Am. J. Cardiol. 29:213, Hill, J. D., Kerth, W. J., Kelly, J. J., Selzer, A., Armstrong, W., Popper, R. W., Langston, M. F., and Cohn, K. E. Emergency aortocoronary bypass for impending or extending myocardial infarction. Circulation 43 (Suppl. I): 105, Kantrowitz, A., Krakauer, J. S., Rosenbaum, A., Butner, A. N., Freed, P. S., and Jaron, D. Phase-shift balloon pumping in medically refractory cardiogenic shock: Results in 27 patients. Arch. Surg. 99:739, Killip, T., 111, and Kimball, J. T. Treatment of myocardial infarction in a coronary care unit: A two year experience with 250 patients. Am. J. Cnrdiol. 20:457, Killip, T., and Kimball, J. T. A survey of the coronary care unit: Concept and results. Progr. Cardiovasc. Dis. 11:45, Lawrie, D. M., Greenwood, T. W., and Goddard, M. A coronary-care unit in the routine management of acute myocardial infarction. Lancct 2: 109, Lie, J. T., Holley, K. E., Kampa, W. R., and Titus, 1. L. New histochemical method for morphologic diagnosis of early stages of myocardial ischemia. Mayo Clzn. Proc. 46:319, THE ANNALS OF THORACIC SURGERY

11 Corona y Byfmss Graft During Myocardial Znfarction 17. MacMillan, R. L., Brown, K. W. G., Peckman, G. B., Kahn, O., Hutchison, D. B., and Paton, M. Changing perspectives in coronary care: A five year study. Am. J. Cardiol. 20:451, Mundth, E. D., Buckley, M. J., Leinbach, R. C., DeSanctis, R. W., Sanders, C. A., Kantrowitz, A., and Austen, W. G. Myocardial revascularization for the treatment of cardiogenic shock complicating acute myocardial infarction. Surgery 70:78, Pifarre, R., Spinazzola, A., Nemickas, R., Scanlon, P. J., and Tobin, J. R. Emergency aortocoronary bypass for acute myocardial infarction. Arch. Surg. 103:525, Discussion DR. EARLE B. KAY (Cleveland, Ohio): I recall your stating specifically that you had 2 deaths, and I wonder whether these were in the early group or the later FOUP. DR. TOHN J. COLLINS, JR. (Boston, Mass.): Our own experience with revascularization in patients with impending or apparently evolving myocardial infarction includes 11 persons ranging in age from 32 to 64 years, of whom 3 were women and 8 were men. All had had prior myocardial infarction. Most had multiple-vein grafts performed, and there was 1 death in the group. Only 5 of these patients actually had a myocardial infarction evolve in the postoperative phase. There had been no late deaths up to two years after operation. We have been reluctant to describe these operations as intervention in the course of myocardial infarction unless the electrocardiogram showed significant Q waves or loss of the R-wave voltage across the precordium or unless there was a significant rise in the serum glutamic oxaloacetic transaminase level. I believe the criteria outlined by Dr. Cheanvechai fail to establish the presence of infarction in their group, and for that reason I think the title of the presentation tends to be a little misleading. There are, for example, several causes for elevation of ST segments which do not portend myocardial infarction. These include true posterior ischemia, any pain syndrome associated with a previous aneurysm, so-called Prinzmetal s variant angina that is occasionally seen, and the early repolarization seen in apparently normal persons. It is difficult in most patients to make an unassailable diagnosis of myocardial infarction in less than 4 hours, since, as the authors very properly point out, ischemia may be severe in these instances but the infarction may be minimal or even absent for up to 4 or 6 hours. These excellent results have been obtained in patients not in cardiogenic shock in the usual refractory sense, and I am sure Dr. Cheanvechai and his associates do not mean to infer that immediate revascularization will totally obviate the usefulness of balloon counterpulsation or other means of circulatory support either before or after such emergency operation. DR. ROBERT W. KENDALL (Spokane, Wash.): I would like to present our results with emergency operation in 27 patients with acute myocardial infarction. In Spokane, Washington, our cardiologists have studied about 2,000 patients, and we have done bypass procedures in 491 with a total of 863 grafts. We have had a 3y0 overall mortality, which was reduced in 1972 to 1.6y0. During this time we have operated upon 27 patients with acute myocardial infarction as evidenced by electrocardiographic changes and as proved by the emergent coronary arteriography. As soon as the diagnosis of acute coronary occlusion is made, the patient is operated upon. The elapsed time from diagnosis to operation has varied from 2 to 11 hours. At operation a small Fogarty catheter is passed into the occluded artery, and many times a small fibrin clot can be removed. A bypass graft is then done to this vessel, and other grafts are added if they are indicated. VOL. 16, NO. 3, SEPTEMBER,

12 CHEANVECHAI ET AL. The postoperative course has generally been uncomplicated. The average hospital stay is 11 days for these patients as compared with 9 days for the elective bypass operation. There has been 1 death in this group of 27 patients. Twenty-one patients have now been restudied, and three-quarters of the grafts have been patent. The left ventriculogram has been a primary concern, and it has returned to normal in 4 of the 21 patients. Ten patients have been classified as improved, 4 are the same, and 2 have become somewhat worse. All 26 surviving patients are alive and clinically doing well. In conclusion, we believe that people with acute myocardial infarction can be studied with a very low risk. They can be offered a vein bypass operation with an acceptably low risk also. It may be that a vein bypass procedure for acute myocardial infarction is the treatment of choice in certain selected patients if they can be operated on soon enough. DR. MORTIMER J. BUCKLEY (Boston, Mass.): I would like to emphasize the point of early intervention in acute myocardial infarction. Generally we have reserved our interventions for those patients with some evident complication of their infarction. Acute surgical intervention has been carried out in 8 patients subsequent to cardiac catheterization, and the histories have been similar to those of some of the patients presented by the authors. Three of our patients had to be taken to the operating room during external cardiac assist because of persistent ventricular fibrillation. One of the 3 is a long-term survivor, and the other 5 patients are long-term survivors. They were operated upon 8 to 24 hours after their catheterization, during which they developed evident infarction associated later with hypotension and definite electrocardiographic changes. I think it is important to emphasize the degree of infarction that we are treating surgically. The authors, however, may be emphasizing the direction that we should be going; that is, early evaluation and possible operation for those patients with a large, proved myocardial infarction even if there are no clinically evident complications. DR. CHEANVECHAI: In answer to Dr. Kay s question regarding mortality, both patients who died were in the early phase of myocardial infarction, and the first patient died in the operating room from massive myocardial infarction. The second patient received a triple-vein graft and died the third postoperative day from malfunction of a tracheostomy tube. I would like to thank Dr. Collins for his remarks. Regarding the electrocardiograms, I think it is difficult to distinguish evolving infarction from true infarction; that is the reason we grouped these patients in the early phase. In our group the patients already have had a previous electrocardiogram, and it is very easy for us to compare it with later tracings when chest pain begins. In a postmortem examination performed on 1 of these patients there was no hemorrhagic infarction. I would like to emphasize that in doing the emergency bypass grafting procedures during acute myocardial infarction, we accomplish nothing for the infarcted area; however, we are increasing perfusion to the ischemic area around the infarction and hope that this will limit the size of the infarcted area. The time factor is also important, as shown in 2 patients who had identical lesions of the dominant right coronary artery with normal ventriculograms. Both patients sustained acute inferior wall myocardial infarction. The first patient received a graft to the right coronary artery which was completed about 2y2 hours after the onset of chest pain. Postoperative recatheterization showed a patent graft with a normal ventricle. The second patient received a graft to the right coronary artery which was completed 5 hours after the onset of chest pain. The graft remained open; however, there was impairment of the diaphragmatic wall of the left ventricle. 260 THE ANNALS OF THORACIC SURGERY