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Unexpected Death Following Aortocoronary Bypass
Unexpected Death Following Aortocoronary Bypass William S. Stoney, M.D., Joseph L. Mulherin, Jr., M.D., William C. Alford, Jr., M.D., George R. Burrus, M.D., Robert A. Frist, M.D., and Clarence S . Thomas, Jr., M.D. ABSTRACT Since 1968,1,800 aortocoronary bypass number of grafts, have been found to be of less procedures have been performed with 37 operative significance to the immediate survival of the or early postoperative deaths (2.1%). Twenty-one patient [12]. deaths (57%) occurred in patients with one or more of It is probable that the operative mortality for the following predetermined risk factors: ventricular this procedure will continue to decrease. It is aneurysm, decreased left ventricular contractility, also likely that the greatest improvement in left main coronary artery stenosis, valve replacement, mortality rate can be achieved in those patients recent infarction, or cardiogenic shock. The remain- who do not have the disorders identified as ing 16 deaths (43%)were unexpected and occurred in major risk factors. patients with none of these risk factors. This report is a review of the 37 postoperative The most prominent single technical problem in deaths that have occurred in the first 1,800 paboth groups was related to the ascending aorta. Acute tients undergoing coronary artery bypass operaaortic dissection or rupture of the vein-aortic anas- tions at St. Thomas Hospital, Nashville. In each tomosis resulted in 6 deaths. patient the events leading to death were examAlthough the majority of the patients ultimately ined, with particular emphasis on unexpected died of cardiac or respiratory failure or a combination events and complications. of the two, a specific preceding catastrophe could be identified in 22 (590/0)patients. Materials and Methods
The postoperative mortality rate following aortocoronary bypass grafting has gradually declined from approximately 8% to as low as 1 to 2% during the past six years [8]. With increasing use of this procedure, it became obvious that patients with impaired left ventricular function were at higher risk than those with normal ventricular activity [7, 111. Subsequently, an increase in the postoperative mortality rate has been identified in patients with left main coronary artery stenosis [l],recent acute myocardial infarction [3], or aortic or mitral valve disease [6, 101. Patients with acute myocardial infarction and shock have an almost prohibitive operative mortality unless cardiac output can be modified by the surgical procedure and by assisted circulation [9]. Other risk factors, including age, sex, previous infarction, severity of angina, and From the Cardiac Surgical Service, St. Thomas Hospital, and the Department of Thoracic Surgery, Vanderbilt University Medical School, Nashville, TN. Presented at the Twenty-second Annual Meeting of the Southern Thoracic Surgical Association, Nov 64,1975, New Orleans, LA. Address reprint requests to Dr. Stoney, St. Thomas Medical Building, Suite501,4230 Harding Rd, Nashville, TN 37205. 528
Between February, 1967, and May, 1975, 1,800 patients had placement of one or more aortocoronary bypass grafts for ischemic heart disease. The 37 patients (2.1%) who died during the operative procedure or within the first 40 days included 28 men and 9 women with an average age of 56 years; the youngest was 33 years and the oldest, 73. Preoperative evaluation for each patient included coronary cinearteriography, ventriculography, calculation of ejection fraction, and ventricular pressure measurements. Right heart catheterization was performed when aortic or mitral valve disease or a large left ventricular aneurysm was present. The operative procedures were done utilizing cardiopulmonary bypass, moderate hypothermia, and intermittent aortic cross-clamping during performance of each distal anastomosis. The distal saphenous vein and left internal mammary artery were the preferred conduits, though a small number of grafts utilized cephalic vein, radial artery, or both mammary arteries. Eighty grafts were used, an average of 2.2 grafts per patient. Six patients had ventricular aneurysmectomy and 2 underwent concomitant valve replacement. Ten patients had an enddiastolic pressure above 18 mm Hg. Eleven pa-
529 Stoney et al: Unexpected Death Following Aortocoronary Bypass
tients had an abnormal ejection fraction ranging from 17 to 40%. Nine had left main coronary artery stenosis. Six patients had experienced an acute infarction within 10 days prior to the operative procedure, and 3 of these were in shock at the time of operation. A review of the record of each patient who died in the operating room or within 40 days of the procedure was conducted. Patients were classified as having been at increased risk if one or more of the following conditions were present prior to operation: ventricular aneurysm, decreased left ventricular function, left main coronary artery stenosis, cardiogenic shock, aortic or mitral valve disease, or recent acute myocardial infarction. Patients with none of these factors were classified as low-risk patients.
Results Seven patients died immediately in the operating room or shortly after arriving in the recovery room. The remaining 30 patients lived 1 to 40 days with an average of 12.6 days’ survival following the operation. Twenty-one patients (57%)were considered to have been at increased risk based on the presence of one or more of the factors described above; the remaining 16 patients (43%) had angina and coronary artery disease without these risk factors.
Patients at High Risk Among the 21 patients with one or more risk factors, 9 deaths were not directly related to the preoperative cardiac status. Three patients died of persistent arrhythmias, 2 because of stroke, and 1each from aortic dissection, rupture of the vein-aortic anastomosis, mesenteric embolus, and following cardiac tamponade. In the remaining 12 patients death was related to low cardiac output immediately following the operation. The low output was attributed to depressed ventricular contractility prior to operation with high preoperative left ventricular end-diastolic pressure in 7 patients, preoperative acute infarction and shock in 3, and myocardial infarction occurring during the operation in 2 patients. Thus, in more than 50% of the patients in this high-risk group, the cause of death was directly related to a known preexisting problem.
Patients at Low Risk In contrast to the patients with preoperative risk problems, deaths among the low-risk patients were not primarily related to poor cardiac output or depressed ventricular function. The most common problem, occurring in 4 patients, was aortic dissection at the site of cross-clamping or disruption of the vein-aortic anastomosis. Stroke during or after the operative period caused 4 deaths. Air or cholesterol embolization was suspected to have caused 2 of these, and 1 was an embolus from the left ventricle. Two patients had progressive respiratory distress syndrome and died after prolonged respirator support. Postoperative bleeding with tamponade and emergency reoperation in 2 patients began a series of events that ultimately led to death from tracheoesophageal fistula in 1 and uncontrolled ventricular arrhythmia in the second. One death each resulted from mediastinal sepsis, arrest during anesthesia induction, intraoperative myocardial infarction, and accidental laceration of the right ventricle. Catastrophic Events The mode of death was quite similar in most of these patients and involved combined failure of the pulmonary, renal, and cardiac systems. This complex interaction of events was preceded by a single specific catastrophic problem in 22 of the 37 patients. Some of these catastrophic events resulted in immediate death; the majority, however, began a series of problems from which there was no recovery. A catastrophic event was identified in 13 of the 16 low-risk patients and in only 9 of the 21 patients with one or more risk factors. These events are listed in the Table.
Aortic Dissection or Anastornotic Rupture Six patients died of complications related to the management and handling of the ascending aorta. Two suffered extensive aortic dissection in the operating room originating at the site of aortic cannulation or aortic cross-clamping, and 4 patients died after sudden rupture of the veinaortic anastomosis. (Two additional patients with ascending aortic dissection originating during aortic clamping were successfully managed by replacement of the ascending aorta with a woven graft, and survived.)
530 The Annals of Thoracic Surgery Vol 21 No 6 June 1976
When the opened aorta is found to be extenUnexpected Events Which Led to Death in 37 sively involved with atheromatous disease, it is Pa tien ts preferable to close the aortotomy and select a Event No. of Patients new site. Occasionally other procedures may be indicated such as total proximal aortic clamping Aortic dissection or anastomotic rupture 6 for the aortic anastomosis or insertion of a vein Stroke 6 or Dacron patch on the aorta prior to anasInfarction during operation 3 tomosis of the vein graft. Since late vein-aortic Tamponade 3 anastomotic rupture may produce sudden masMediastinal sepsis 1 sive blood loss, with little chance of secondary Arrest during anesthesia repair, any tenuous or imperfect anastomosis induction 1 should be closed or redone. Two patients have Mesenteric infarction 1 recently been reported by Kimbiris and colLaceration of right ventricle 1 leagues [5] in whom aortic dissection occurred at Total 22 the site of application of partially occluding If the ascending aorta is noted on preoperative clamps with unsuccessful repair. roentgenograms or by palpation to have circumferential calcification, several alternative Stroke techniques are available. Remote inflow cannu- Six patients died following a stroke. In 4 of these lation using the femoral, iliac, or subclavian ar- patients the neurological damage occurred durtery should be considered if the ascending aorta ing the operative procedure. One patient had an is found to be diseased. The use of both mam- embolus originating in the left ventricle. The mary arteries for grafts to the left coronary artery other 3 had diffuse neurological injury suggesthas been demonstrated to be practical. Also, ing either air or cholesterol embolization. It is splenic artery grafts have been used for the distal possible for air to enter the aortic root through right coronary artery [4]. Although we have an opened coronary artery when negative innever used the subclavian artery as the inflow tracardiac pressure is exerted by a ventricular anastomosis for a vein graft to a coronary artery, vent. Careful aspiration of the aortic root after this site has been used for other complex prob- each anastomosis should be a routine part of the lems and should be considered under unusual procedure. Recently some centers have omitted circumstances [2]. A very brittle, calcified aorta using a ventricular vent if aortic clamping is to can be occluded by introducing a large Foley be brief, thereby avoiding the chance of air emcatheter into the ascending aorta through a small bolism. arteriotomy in the innominate artery. We reTwo strokes occurred late. In 1 patient a cently performed this successfully with very lit- thrombosed graft was found at postmortem extle tension on the aortic wall and no aortic injury. amination, and fresh thrombus at the aortic Rupture of the vein-aortic anastomosis oc- anastomotic site was suspected as being the oricurred in4 patients. One ruptured at 10 days in a gin of the embolus. The other stroke occurred at patient with mediastinal sepsis. Three occurred 10 days, and the cause was not determined. suddenly within 4 days of the operative procedure. Several techniques have subsequently New Infarcts been adopted to lessen this possibility. When Three patients died of a new massive myocardial partial aortic occlusion is to be used, the trauma infarction. Two of these occurred during the opof clamping can be minimized by briefly reduc- eration and were associated with technical difing the aortic pressure to as low a level as possi- ficulties involving exposure and friability of the ble, either by turning the pump off for a short coronary artery. The artery and graft were both period while the clamp is applied or by transient ligated to control bleeding in 1 patient, and the inflow occlusion. Tangential or transverse aortic second infarction occurred after prolonged carclamping appears to exert more stress and tor- diac rotation and traction to expose the cirsion on the aorta than longitudinal clamping, cumflex coronary artery. The third patient died of an acute infarction after 3 days. A Y-graft to and it should be avoided.
531 Stoney et al: Unexpected Death Following Aortocoronary Bypass
the circumflex and anterior descending coronary arteries was found to be completely thrombosed, with subsequent extensive infarction of the left ventricle. In our early experience, Y-grafts were commonly used. In 7 patients examined postmortem, 5 Y-grafts were found to be thrombosed and only 2 were patent. The disadvantage of this configuration has been reported by both Walker [141 and Urschel [131 and their associates and is confirmed by these results.
Other Problems Early postoperative cardiac tamponade occurred in 3 patients, with secondary cardiac arrest, renal failure, or pulmonary edema. Although in each instance the tamponade was corrected by reoperation, the secondary events ultimately led to death. Since tamponade may have fatal consequences, we have adopted a policy of meticulous control of all bleeding before the patient is moved from the operating room. Arrest during anesthesia induction occurred twice. Both patients were resuscitated by rapid institution of femorofemoral bypass, and the planned operative procedure was completed. One of these patients died after 4 days of low cardiac output. The second had no major risk factors, and the arrest was preceded by intravenous induction of morphine anesthesia with subsequent generalized neurological damage. Single deaths occurred following postoperative mesenteric infarction, mediastinal sepsis, and accidental laceration of the right ventricle. Comment The major preoperative risk factors in aortocoronary bypass have become apparent and have been well documented. In this group of 37 patients who died after undergoing coronary artery bypass, a significant number expired following an unexpected event that was not directly related to the preoperative cardiac status or risk factors. Since this procedure is complex and involves a large number of both personnel and devices, it was suspected that human error might play a major role in these unexpected events and accidents. Fortunately, the only obvious error in this group was the accidental laceration of the right ventricle, which occurred while the sternum was being divided. Patients with unalterable structural cardiac
problems will continue to have a definite risk of death following coronary artery bypass. The greatest reduction in postoperative mortality is possible in the groups of patients with angina alone as the major problem. Identification of the unexpected problems that have occurred in the past may allow further reduction of the operative death rate. The two areas of greatest importance are cerebrovascular embolization and the techniques of manipulating the ascending aorta.
References 1. Alford WC Jr, Shaker IJ, Thomas CS Jr, et al: Aortocoronary bypass in treatment of left main coronary stenosis. Ann Thorac Surg 17:247,1974 2. Aquam AS, Ray JF, Sanoudos GM, et al: Subclavian coronary artery bypass in man. J Thorac Cardiovasc Surg 65:869, 1973 3. Dawson JT, Hall RJ, Hallman GL, et al: Mortality in patients undergoing coronary artery bypass surgery after myocardial infarction. Am J Cardiol 33:483, 1974 4. Edwards WS, Lewis CE, Blakeley WR, et al: Coronary artery bypass with internal mammary and splenic artery grafts. Ann Thorac Surg 15:35,1973 5. Kimbiris D, Dreifus LS, Adam A, et al: Dissection and rupture of the ascending aorta. Chest 68:313, 1975 6. Loop FD, Favaloro RG, Shirey EK, et al: Surgery for combined valvular and coronary heart disease. JAMA 220:372, 1972 7. Mitchel BF, Alivizatos PA, Adam M, et al: Myocardial revascularization in patients with poor ventricular function. J Thorac Cardiovasc Surg 69:52, 1975 8. Mundth ED, Austen WG: Surgical measures for coronary heart disease. NEngl JMed293:13,1975 9. Mundth ED, Buckley MJ, Leinbach RC, et al: Surgical intervention for the complications of acute myocardial ischemia. Ann Surg 178:379, 1973 10. Okies JE, Phillips SJ, Chaitman BR, et al: Technical consideration in multiple valve and coronary artery surgery. J Thorac Cardiovasc Surg 67:762, 1974 11. Spencer FC, Green GE, Tice DA, et al: Coronary artery bypass grafts for congestive failure. J Thorac Cardiovasc Surg 62:529, 1971 12. Thomas CS Jr, Alford WC Jr, Burrus GR, et al: The decreasing risk of aortocoronary bypass. J Tenn Med Assoc 662315, 1973 13. Urschel HC, Razzuk MA, Wood RE, et al: Factors influencing patency of aortocoronary artery saphenous vein grafts. Surgery 72:1048, 1972 14. Walker JA, Friedberg HD, Flemma RH, et al: Determinants of angiographic patency of aortocoronary vein bypass grafts. Circulation 45,46:Suppl 1236, 1972.
The postoperative mortality rate following aortocoronary bypass grafting has gradually declined from approximately 8% to as low as 1 to 2% during the past six years [8]. With increasing use of this procedure, it became obvious that patients with impaired left ventricular function were at higher risk than those with normal ventricular activity [7, 111. Subsequently, an increase in the postoperative mortality rate has been identified in patients with left main coronary artery stenosis [l],recent acute myocardial infarction [3], or aortic or mitral valve disease [6, 101. Patients with acute myocardial infarction and shock have an almost prohibitive operative mortality unless cardiac output can be modified by the surgical procedure and by assisted circulation [9]. Other risk factors, including age, sex, previous infarction, severity of angina, and From the Cardiac Surgical Service, St. Thomas Hospital, and the Department of Thoracic Surgery, Vanderbilt University Medical School, Nashville, TN. Presented at the Twenty-second Annual Meeting of the Southern Thoracic Surgical Association, Nov 64,1975, New Orleans, LA. Address reprint requests to Dr. Stoney, St. Thomas Medical Building, Suite501,4230 Harding Rd, Nashville, TN 37205. 528
Between February, 1967, and May, 1975, 1,800 patients had placement of one or more aortocoronary bypass grafts for ischemic heart disease. The 37 patients (2.1%) who died during the operative procedure or within the first 40 days included 28 men and 9 women with an average age of 56 years; the youngest was 33 years and the oldest, 73. Preoperative evaluation for each patient included coronary cinearteriography, ventriculography, calculation of ejection fraction, and ventricular pressure measurements. Right heart catheterization was performed when aortic or mitral valve disease or a large left ventricular aneurysm was present. The operative procedures were done utilizing cardiopulmonary bypass, moderate hypothermia, and intermittent aortic cross-clamping during performance of each distal anastomosis. The distal saphenous vein and left internal mammary artery were the preferred conduits, though a small number of grafts utilized cephalic vein, radial artery, or both mammary arteries. Eighty grafts were used, an average of 2.2 grafts per patient. Six patients had ventricular aneurysmectomy and 2 underwent concomitant valve replacement. Ten patients had an enddiastolic pressure above 18 mm Hg. Eleven pa-
529 Stoney et al: Unexpected Death Following Aortocoronary Bypass
tients had an abnormal ejection fraction ranging from 17 to 40%. Nine had left main coronary artery stenosis. Six patients had experienced an acute infarction within 10 days prior to the operative procedure, and 3 of these were in shock at the time of operation. A review of the record of each patient who died in the operating room or within 40 days of the procedure was conducted. Patients were classified as having been at increased risk if one or more of the following conditions were present prior to operation: ventricular aneurysm, decreased left ventricular function, left main coronary artery stenosis, cardiogenic shock, aortic or mitral valve disease, or recent acute myocardial infarction. Patients with none of these factors were classified as low-risk patients.
Results Seven patients died immediately in the operating room or shortly after arriving in the recovery room. The remaining 30 patients lived 1 to 40 days with an average of 12.6 days’ survival following the operation. Twenty-one patients (57%)were considered to have been at increased risk based on the presence of one or more of the factors described above; the remaining 16 patients (43%) had angina and coronary artery disease without these risk factors.
Patients at High Risk Among the 21 patients with one or more risk factors, 9 deaths were not directly related to the preoperative cardiac status. Three patients died of persistent arrhythmias, 2 because of stroke, and 1each from aortic dissection, rupture of the vein-aortic anastomosis, mesenteric embolus, and following cardiac tamponade. In the remaining 12 patients death was related to low cardiac output immediately following the operation. The low output was attributed to depressed ventricular contractility prior to operation with high preoperative left ventricular end-diastolic pressure in 7 patients, preoperative acute infarction and shock in 3, and myocardial infarction occurring during the operation in 2 patients. Thus, in more than 50% of the patients in this high-risk group, the cause of death was directly related to a known preexisting problem.
Patients at Low Risk In contrast to the patients with preoperative risk problems, deaths among the low-risk patients were not primarily related to poor cardiac output or depressed ventricular function. The most common problem, occurring in 4 patients, was aortic dissection at the site of cross-clamping or disruption of the vein-aortic anastomosis. Stroke during or after the operative period caused 4 deaths. Air or cholesterol embolization was suspected to have caused 2 of these, and 1 was an embolus from the left ventricle. Two patients had progressive respiratory distress syndrome and died after prolonged respirator support. Postoperative bleeding with tamponade and emergency reoperation in 2 patients began a series of events that ultimately led to death from tracheoesophageal fistula in 1 and uncontrolled ventricular arrhythmia in the second. One death each resulted from mediastinal sepsis, arrest during anesthesia induction, intraoperative myocardial infarction, and accidental laceration of the right ventricle. Catastrophic Events The mode of death was quite similar in most of these patients and involved combined failure of the pulmonary, renal, and cardiac systems. This complex interaction of events was preceded by a single specific catastrophic problem in 22 of the 37 patients. Some of these catastrophic events resulted in immediate death; the majority, however, began a series of problems from which there was no recovery. A catastrophic event was identified in 13 of the 16 low-risk patients and in only 9 of the 21 patients with one or more risk factors. These events are listed in the Table.
Aortic Dissection or Anastornotic Rupture Six patients died of complications related to the management and handling of the ascending aorta. Two suffered extensive aortic dissection in the operating room originating at the site of aortic cannulation or aortic cross-clamping, and 4 patients died after sudden rupture of the veinaortic anastomosis. (Two additional patients with ascending aortic dissection originating during aortic clamping were successfully managed by replacement of the ascending aorta with a woven graft, and survived.)
530 The Annals of Thoracic Surgery Vol 21 No 6 June 1976
When the opened aorta is found to be extenUnexpected Events Which Led to Death in 37 sively involved with atheromatous disease, it is Pa tien ts preferable to close the aortotomy and select a Event No. of Patients new site. Occasionally other procedures may be indicated such as total proximal aortic clamping Aortic dissection or anastomotic rupture 6 for the aortic anastomosis or insertion of a vein Stroke 6 or Dacron patch on the aorta prior to anasInfarction during operation 3 tomosis of the vein graft. Since late vein-aortic Tamponade 3 anastomotic rupture may produce sudden masMediastinal sepsis 1 sive blood loss, with little chance of secondary Arrest during anesthesia repair, any tenuous or imperfect anastomosis induction 1 should be closed or redone. Two patients have Mesenteric infarction 1 recently been reported by Kimbiris and colLaceration of right ventricle 1 leagues [5] in whom aortic dissection occurred at Total 22 the site of application of partially occluding If the ascending aorta is noted on preoperative clamps with unsuccessful repair. roentgenograms or by palpation to have circumferential calcification, several alternative Stroke techniques are available. Remote inflow cannu- Six patients died following a stroke. In 4 of these lation using the femoral, iliac, or subclavian ar- patients the neurological damage occurred durtery should be considered if the ascending aorta ing the operative procedure. One patient had an is found to be diseased. The use of both mam- embolus originating in the left ventricle. The mary arteries for grafts to the left coronary artery other 3 had diffuse neurological injury suggesthas been demonstrated to be practical. Also, ing either air or cholesterol embolization. It is splenic artery grafts have been used for the distal possible for air to enter the aortic root through right coronary artery [4]. Although we have an opened coronary artery when negative innever used the subclavian artery as the inflow tracardiac pressure is exerted by a ventricular anastomosis for a vein graft to a coronary artery, vent. Careful aspiration of the aortic root after this site has been used for other complex prob- each anastomosis should be a routine part of the lems and should be considered under unusual procedure. Recently some centers have omitted circumstances [2]. A very brittle, calcified aorta using a ventricular vent if aortic clamping is to can be occluded by introducing a large Foley be brief, thereby avoiding the chance of air emcatheter into the ascending aorta through a small bolism. arteriotomy in the innominate artery. We reTwo strokes occurred late. In 1 patient a cently performed this successfully with very lit- thrombosed graft was found at postmortem extle tension on the aortic wall and no aortic injury. amination, and fresh thrombus at the aortic Rupture of the vein-aortic anastomosis oc- anastomotic site was suspected as being the oricurred in4 patients. One ruptured at 10 days in a gin of the embolus. The other stroke occurred at patient with mediastinal sepsis. Three occurred 10 days, and the cause was not determined. suddenly within 4 days of the operative procedure. Several techniques have subsequently New Infarcts been adopted to lessen this possibility. When Three patients died of a new massive myocardial partial aortic occlusion is to be used, the trauma infarction. Two of these occurred during the opof clamping can be minimized by briefly reduc- eration and were associated with technical difing the aortic pressure to as low a level as possi- ficulties involving exposure and friability of the ble, either by turning the pump off for a short coronary artery. The artery and graft were both period while the clamp is applied or by transient ligated to control bleeding in 1 patient, and the inflow occlusion. Tangential or transverse aortic second infarction occurred after prolonged carclamping appears to exert more stress and tor- diac rotation and traction to expose the cirsion on the aorta than longitudinal clamping, cumflex coronary artery. The third patient died of an acute infarction after 3 days. A Y-graft to and it should be avoided.
531 Stoney et al: Unexpected Death Following Aortocoronary Bypass
the circumflex and anterior descending coronary arteries was found to be completely thrombosed, with subsequent extensive infarction of the left ventricle. In our early experience, Y-grafts were commonly used. In 7 patients examined postmortem, 5 Y-grafts were found to be thrombosed and only 2 were patent. The disadvantage of this configuration has been reported by both Walker [141 and Urschel [131 and their associates and is confirmed by these results.
Other Problems Early postoperative cardiac tamponade occurred in 3 patients, with secondary cardiac arrest, renal failure, or pulmonary edema. Although in each instance the tamponade was corrected by reoperation, the secondary events ultimately led to death. Since tamponade may have fatal consequences, we have adopted a policy of meticulous control of all bleeding before the patient is moved from the operating room. Arrest during anesthesia induction occurred twice. Both patients were resuscitated by rapid institution of femorofemoral bypass, and the planned operative procedure was completed. One of these patients died after 4 days of low cardiac output. The second had no major risk factors, and the arrest was preceded by intravenous induction of morphine anesthesia with subsequent generalized neurological damage. Single deaths occurred following postoperative mesenteric infarction, mediastinal sepsis, and accidental laceration of the right ventricle. Comment The major preoperative risk factors in aortocoronary bypass have become apparent and have been well documented. In this group of 37 patients who died after undergoing coronary artery bypass, a significant number expired following an unexpected event that was not directly related to the preoperative cardiac status or risk factors. Since this procedure is complex and involves a large number of both personnel and devices, it was suspected that human error might play a major role in these unexpected events and accidents. Fortunately, the only obvious error in this group was the accidental laceration of the right ventricle, which occurred while the sternum was being divided. Patients with unalterable structural cardiac
problems will continue to have a definite risk of death following coronary artery bypass. The greatest reduction in postoperative mortality is possible in the groups of patients with angina alone as the major problem. Identification of the unexpected problems that have occurred in the past may allow further reduction of the operative death rate. The two areas of greatest importance are cerebrovascular embolization and the techniques of manipulating the ascending aorta.
References 1. Alford WC Jr, Shaker IJ, Thomas CS Jr, et al: Aortocoronary bypass in treatment of left main coronary stenosis. Ann Thorac Surg 17:247,1974 2. Aquam AS, Ray JF, Sanoudos GM, et al: Subclavian coronary artery bypass in man. J Thorac Cardiovasc Surg 65:869, 1973 3. Dawson JT, Hall RJ, Hallman GL, et al: Mortality in patients undergoing coronary artery bypass surgery after myocardial infarction. Am J Cardiol 33:483, 1974 4. Edwards WS, Lewis CE, Blakeley WR, et al: Coronary artery bypass with internal mammary and splenic artery grafts. Ann Thorac Surg 15:35,1973 5. Kimbiris D, Dreifus LS, Adam A, et al: Dissection and rupture of the ascending aorta. Chest 68:313, 1975 6. Loop FD, Favaloro RG, Shirey EK, et al: Surgery for combined valvular and coronary heart disease. JAMA 220:372, 1972 7. Mitchel BF, Alivizatos PA, Adam M, et al: Myocardial revascularization in patients with poor ventricular function. J Thorac Cardiovasc Surg 69:52, 1975 8. Mundth ED, Austen WG: Surgical measures for coronary heart disease. NEngl JMed293:13,1975 9. Mundth ED, Buckley MJ, Leinbach RC, et al: Surgical intervention for the complications of acute myocardial ischemia. Ann Surg 178:379, 1973 10. Okies JE, Phillips SJ, Chaitman BR, et al: Technical consideration in multiple valve and coronary artery surgery. J Thorac Cardiovasc Surg 67:762, 1974 11. Spencer FC, Green GE, Tice DA, et al: Coronary artery bypass grafts for congestive failure. J Thorac Cardiovasc Surg 62:529, 1971 12. Thomas CS Jr, Alford WC Jr, Burrus GR, et al: The decreasing risk of aortocoronary bypass. J Tenn Med Assoc 662315, 1973 13. Urschel HC, Razzuk MA, Wood RE, et al: Factors influencing patency of aortocoronary artery saphenous vein grafts. Surgery 72:1048, 1972 14. Walker JA, Friedberg HD, Flemma RH, et al: Determinants of angiographic patency of aortocoronary vein bypass grafts. Circulation 45,46:Suppl 1236, 1972.