EDITORIAL
Asymptomatic CoronaryArtery Disease and Coronary BypassSurgery ARTHUR SELZER, MD, FACC KEITH COHN, MD, FACC
San Francisco, California
Aortocoronary bypass now is the most frequently performed open heart operation. It is currently being recommended for two purposes: as a remedial procedure, aimed at the relief of disabling symptoms, and as prophylactic therapy, designed to prevent myocardial infarction and death. The successes of the operation and the reduction in operative mortality to a low level have gradually shifted the emphasis in some centers from remedial to prophylactic surgery. Some of the enthusiastic surgeons take it for granted that the operation is as effective when employed prophylactically as it is for the relief of symptoms and use superb salesmanship to disseminate their view. The principal point often made is that only the anatomic changes in the coronary artery matter; whether or not the patient is symptomatic is irrelevant. As a consequence, coronary arteriography is being performed in many centers not as a well considered procedure in response to specific indications but as a broad means of case finding. Thus, arteriographic studies are being performed in anyone with a twinge of pain above the umbilicus and even in totally asymptomatic patients because they have some electrocardiographic abnormality, show S-T segment changes of one variety or another on a stress test, have coronary risk factors or a bad family history or had an uncomplicated myocardial infarction in the past. When obstructive lesions are found, many asymptomatic patients undergo aortocoronary bypass surgery. Evaluation of any type of therapy, medical or surgical, requires an assessment of both sides of the therapeutic "ledger," its debits and credits; and this assessment in turn requires a reasonable knowledge of the natural history of a given disease. Thus, it is of considerable importance to review the present knowledge concerning the natural history of ischemic heart disease, with special reference to the asymptomatic patient. Natural History of Coronary Artery Disease
Various methods have been used to evaluate the prognosis and natural history of ischemic heart disease. Some studies dealt with life expectancy of patients who at a given time showed clinical evidence of coronary From the Division of Cardiology,PresbyterianHospital of Pacific Medical Center, San Francisco, California. Address for reprints: Arthur Seizer, MD, Division of Cardiology, Pacific Medical Center, P. O. Box 7999, San Francisco, California 94120.
614
disease, usually the onset of angina pectoris or myocardial infarction. Using as a yardstick 5 year survival rates, collected series 1-5 showed findings ranging from 10 to 65 percent or, to translate this range into annual mortality rates, from 2 to 13 percent. More recent studies dealt mostly with survival of patients according to the extent of coronary arterial involvement as determined by coronary arteriography. Reeves et al. 6 collected data in 1973 indicating an annual mortality rate of 2.2 percent for patients with one vessel coronary artery disease, 6.8 percent for those with two vessel disease and 11.4 percent for those with three vessel disease. Three additional studies 7-9 have been reported yielding an annual mortality rate in the combined series of 2.6 percent for patients with one vessel disease, 7.1 percent for those with two vessel disease and 10.4 percent for those with three vessel disease. The clinically collected studies show great variability, whereas those derived from coronary angiography show a remarkable consistency. It is apparent that in many series cases consist of a combination of various subsets with widely diverging prognoses. It is therefore probably no coincidence that the two clinically designed series with the most favorable mortality data dealt with large population sets {that of Frank et al., 5 showing an annual mortality rate of 1.6 percent for the "low risk group" studied at the Health Insurance Plan of New York City, and that of Zuckel et al. ~ showing a 2 percent annual mortality rate in the U.S. Army) whereas other series collected from clinical and hospital populations involved considerably greater preselection. Similarly, one can assume that the arteriographic series just discussed represented a highly selected population. Regardless of the mode of collection of the population studied, it is evident that each series contains at one end of the spectrum patients with anginal pain as the only detectable abnormality and at the other end those with heart failure, cardiomegaly, extensive myocardial damage or grossly abnormal electrocardiograms who also suffer from anginal pain; patients with various intermediate forms are found between these extremes. The composition of the mixture, then, determines the prognosis. It is also obvious that one patient population is unrepresented in all of the series, the asymptomatic patient. In clinical studies symptoms were the basis for inclusion; the arteriographic studies dealing with the actuarial curves of survival were all collected before
April 1977 The American Journal of CARDIOLOGY Volume 39
EDITORIAL
1970. Because asymptomatic patients have been included among those undergoing coronary arteriography for only 3 or 4 years, one can reasonably assume that none or a very small minority of the patients without cardiac symptoms were represented in the arteriographic series. One can develop a thesis that arteriographic studies were weighted toward the unfavorable case and probably do not represent the average mortality for the entire population of symptomatic patients. The two clinical series presenting a more favorable annual survival rate may well present data closer to the average yearly mortality data for the symptomatic patient. No information at all is available regarding the prognosis of the asymptomatic patient who has arteriographicaUy demonstrable coronary artery disease.
Are Symptoms Unimportant? In evaluating the natural history of coronary artery disease it is important to examine the view expressed in some quarters that symptoms do not matter and that only anatomic changes in the coronary arteries are important. To address this problem it is necessary to review what is really known about serious life-threatening coronary artery disease without cardiac symptoms. We know that sudden death occurs in subjects who are apparently in good health and are presumed to be asymptomatic. We know that acute myocardial infarction may be painless, and it is presumed that in such subjects the warning angina may be missing. And we know that stress testing may uncover electrocardiographic evidence of ischemia in asymptomatic patients. In trying to explain the discrepancy between serious indexes of coronary artery disease and the lack of symptoms one can suggest three possibilities: (1) myocardial ischemia in some subjects fails to invoke the warning pain; (2) pain is present but is ignored or misinterpreted by the patient or physician; and (3) the myocardium in these patients is not ischemic. There is little doubt that each of these three possibilities applies to some patients, but perhaps the most important point to be made is that for a variety of reasons severe coronary artery disease demonstrated on arteriography may be present without producing myocardial ischemia. First, arteriographic estimates of the severity of coronary obstructive lesions are very crude--gross errors in either direction are common; furthermore, the length, eccentricity, irregularity and number of coronary lesions, in series or parallel, are of immeasurable and highly unpredictable import. Second, collateral vessels often supply a totally occluded or severely stenotic coronary artery, meeting most myocardial demands. Third, electrocardiographic evidence of ischemia has many limitations (for example, S-T segment changes during stress testing may represent a false positive response or may be misinterpreted). Thus, although the absence of symptoms in patients with coronary disease is not a guarantee of benign prognosis, an asymptomatic clinical state may reflect a myocardium that seldom if ever becomes ischemic.
Risk Versus Benefit of Coronary Bypass Operations Risks: If one expresses this therapeutic ratio in terms of a ledger, the totality of risks belong on its debit side. First, the operative mortality rate is usually quoted at I to 2 percent. However, this figure is not realistic if one considers that the published data from one of the best known large volume surgical units 1° indicate a 6.9 percent mortality rate; furthermore, this rate is probably still higher in community hospitals across the country with small case loads, and a large proportion of coronary bypass operations are being performed in these small hospitals. Certainly, case series are seldom reported unless favorable, so that the les~ successful operative results go unreported. Second, the risk includes a 10 to 15 percent probability of sustaining an intraoperative transmural myocardial infarction (which the operation is expected to prevent) with an additional 5 to 15 percent incidence rate of electrocardiographic appearance of intraventricular conduction defects. Third, there is a 10 to 15 percent probability of graft closure, further nullifying the "protection" the operation is expected to offer. Fourth, it is known that obstructive lesions in bypassed vessels progress at an accelerated rate. All of these risks are based on independent observations involving several institutions. Benefits: On the credit side of the ledger is symptomatic improvement of patients with disabling angina. This is the principal yield and the only definitively established benefit of aortocoronary bypass s u r g e r y . Preliminary reports of the randomized studies of medical versus surgical therapy for symptomatic patients provide no evidence that mortality from coronary disease is reduced by the operation except in the small group of patients with severe lesions of the main left coronary trunk. Claims that mortality curves of surgically treated patients are much better than those from nonsimultaneously collected medically treated groups with comparable coronary lesions have little validity because, as explained, the patient populations differ in several ways. Thus, the'accounting" shows a small but well defined debit (risk) on one side of the ledger against a credit (benefit) for the disabled patient but no proved benefit for the prophylactic aspects of the operation.
Fallacies Concerning the Progression of Coronary Disease Reliance upon the arteriographic demonstration of obstructive lesions in the coronary arteries encourages the impression of the inevitability of progressive coronary changes. It is assumed that a 60 percent obstructive lesion will with time become an 80 percent obstructive lesion and then will occlude the artery producing myocardial infarction. This assumption serves as the basis for prophylactic coronary surgery in asymptomatic patients. The simplistic approach of a steady-rate anatomic progression of coronary lesions overlooks many modifiers of the course of coronary artery disease. First, the role of collateral circulation has been unjustly downplayed, as aptly argued by McGregor. 11 In some
April 1977
The American Journal of CARDIOLOGY
Volume 39
615
EDITORIAL
patients a long-term "balance" may be established between obstruction and collateralization. This is best illustrated by complete occlusion of a major branch, which may or may not have led to myocardial infarction but which is consistent not only with absence of symptoms but also with absence of any indexes of ischemia. Kattus 12 has called these lesions "non-precarious." Second, most studies dealing with serial coronary arteriograms show a slow rate of progression of disease. Third, pathologists have recognized for a long time what they consider to be "burned out" atherosclerotic plaques, and these must be distinguished from the more lipid-rich, "active" plaques, 13 a point that cannot be perceived from a single arteriographic study. Thus, certain arteriographicaUy demonstrated lesions are altogether nonprogressive. On the other hand, myocardial infarction and sudden death, the two disasters against which prophylactic operations are aimed, are not necessarily caused by progression of a critical lesion. Other mechanisms include thrombosis, in situ or embolic, rupture of an atherosclerotic plaque and subintimal hemorrhage-each mechanism not limited to severely obstructed coronary arteries but occurring at sites of lesser lesions as well. Thus, myocardial infarction or death (or both) occurs in a highly unpredictable fashion.
Role of Coronary Arteriography Coronary arteriography is an essential step in the chain of events leading to bypass operations. Its risk is small but not neligible. The average mortality rate is 0.45 percent 14 with higher figures quoted in laboratories with low case loads. Complications such as stroke and myocardial infarction represent additional hazards. Yet, as stated, coronary arteriography is widely used in some centers as a case-finding procedure for asymptomatic patients. The benefit of the study--demonstration of anatomic lesions in the coronary arteries--is a mixed blessing, indeed. The reassurance of the failure to find a significant lesion in the coronary arteries is indubi-
tably valuable. However, the demonstration of obstructive coronary artery disease in asymptomatic patients may present the cardiologist with a difficult problem: The emotional impact of the "silent" coronary lesion leads to a great temptation to recommend bypass surgery regardless of the current scientific evidence yet failing to support its wisdom. This may be especially true when his medical or surgical colleagues subscribe to the simplistic view that obstructing lesions automatically call for bypass, regardless of the circumstances. The staggering cost to our society of overuse of diagnostic and surgical cardiac facilities must also not be overlooked. 15
Summary and Conclusions The actuarial survival curves of "medically treated" patients whose arteriographic studies demonstrated coronary arterial lesions of various degrees--now used widely as a reference point for the natural history of coronary artery disease--are not applicable to the asymptomatic patient. No information is available regarding the course or prognosis of the asymptomatic patient with demonstrated lesions in the coronary arteries. For the reasons explained one can propose a hypothesis that the overall prognosis of this type of patient is better than average, probably better than that shown in the best data collected on symptomatic patients. The prophylactic value of aortocoronary bypass operations in preventing myocardial infarction and death has not been established. One can therefore question the justification for the wide case-finding effort of subjecting asymptomatic persons to coronary arteriography, even in light of the low risk of this procedure, unless unusual findings suggest an especially poor prognosis (one example might be past myocardial infarction in a very young patient). Although there are exceptional instances when prophylactic surgery is indicated for asymptomatic patients, further investigation of this subject is needed before the procedure becomes generally accepted.
References 1. Bloch WJ Jr, Crumpacker EL, Dry TJ, et al: Prognosis of angina pectoris. Observations in 6,883 cases. JAMA 150:259-264, 1952 2. Richards DW, Bland EF, White PD: A completed 25-year follow-up study of 456 patients with angina pectoris. J Chron Dis 4:423-433, 1956 3. Zuckel WJ, Cohen BM, fdatUngly TW, et ah Survival following the first diagnosis of coronary heart disease. Am Heart J 78:159-170, 1969 4. Kannel WB, Feinleib M: Natural history of angina pectoris in the Framingham study. Prognosis and survival. Am J Cardiol 29: 154-163, 1972 5. Frank CW, Weinblatt E, Shapiro S: Angina pectoris in men: prognostic significance of selected medical factors. Circulation 47:509-517, 1973 6. Reeves TJ, Oberman A, Jones WB, et ah Natural history of angina pectoris. Am J Cardiol 33:423-430, 1974 7. Bruschke AVG, Proudfit WL, Sones FM Jr: Prognostic study of 590 consecutive nonsurgical cases of coronary disease followed 5-9 years. Arteriographic correlations. Circulation 47:1147-1163, 1973
616
April 1977
The American Journal of CARDIOLOGY
8. Webster JS, Moberg V, Rincon G: Natural history of severe proximal coronary artery disease as documented by coronary arteriography. Am J Cardiol 33:195-200, 1974 9. Burggraf GW, Parker JO: Prognosis in coronary artery disease: angiographic, hemodynarnic and clinical factors. Circulation 51: 146-156, 1975 10. Dawson JT, Hall RJ, Ha,man GL, et ah Mortality in patients undergoing coronary artery bypass surgery after myocardial infarction. AmJ Cardiol 33:483-486, 1974 11. McGregor M: The coronary collateral circulation. A significant compensatory mechanism or a functionless quirk of nature. Circulation 52:529-530, 1975 12. Kattus AS; Prognosis of coronary arterial lesions classified according to precariousness (abstr). Clin Res 21:186, 1973 13. Vlodaver Z, Edwards JE: Pathology of coronary atherosclerosis. Prog Cardiovasc Dis 14:256-274, 1971 14. Adams DF, Fraser DB, Abrams HL: The complications of coronary arteriography. Circulation 48:609-618, 1973 15. Ross RS: The problem of ischemic heart disease: current approach and implications for curriculum design. Johns Hopkins Med J 138:217-228, 1976
Volume 39
Asymptomatic CoronaryArtery Disease and Coronary BypassSurgery ARTHUR SELZER, MD, FACC KEITH COHN, MD, FACC
San Francisco, California
Aortocoronary bypass now is the most frequently performed open heart operation. It is currently being recommended for two purposes: as a remedial procedure, aimed at the relief of disabling symptoms, and as prophylactic therapy, designed to prevent myocardial infarction and death. The successes of the operation and the reduction in operative mortality to a low level have gradually shifted the emphasis in some centers from remedial to prophylactic surgery. Some of the enthusiastic surgeons take it for granted that the operation is as effective when employed prophylactically as it is for the relief of symptoms and use superb salesmanship to disseminate their view. The principal point often made is that only the anatomic changes in the coronary artery matter; whether or not the patient is symptomatic is irrelevant. As a consequence, coronary arteriography is being performed in many centers not as a well considered procedure in response to specific indications but as a broad means of case finding. Thus, arteriographic studies are being performed in anyone with a twinge of pain above the umbilicus and even in totally asymptomatic patients because they have some electrocardiographic abnormality, show S-T segment changes of one variety or another on a stress test, have coronary risk factors or a bad family history or had an uncomplicated myocardial infarction in the past. When obstructive lesions are found, many asymptomatic patients undergo aortocoronary bypass surgery. Evaluation of any type of therapy, medical or surgical, requires an assessment of both sides of the therapeutic "ledger," its debits and credits; and this assessment in turn requires a reasonable knowledge of the natural history of a given disease. Thus, it is of considerable importance to review the present knowledge concerning the natural history of ischemic heart disease, with special reference to the asymptomatic patient. Natural History of Coronary Artery Disease
Various methods have been used to evaluate the prognosis and natural history of ischemic heart disease. Some studies dealt with life expectancy of patients who at a given time showed clinical evidence of coronary From the Division of Cardiology,PresbyterianHospital of Pacific Medical Center, San Francisco, California. Address for reprints: Arthur Seizer, MD, Division of Cardiology, Pacific Medical Center, P. O. Box 7999, San Francisco, California 94120.
614
disease, usually the onset of angina pectoris or myocardial infarction. Using as a yardstick 5 year survival rates, collected series 1-5 showed findings ranging from 10 to 65 percent or, to translate this range into annual mortality rates, from 2 to 13 percent. More recent studies dealt mostly with survival of patients according to the extent of coronary arterial involvement as determined by coronary arteriography. Reeves et al. 6 collected data in 1973 indicating an annual mortality rate of 2.2 percent for patients with one vessel coronary artery disease, 6.8 percent for those with two vessel disease and 11.4 percent for those with three vessel disease. Three additional studies 7-9 have been reported yielding an annual mortality rate in the combined series of 2.6 percent for patients with one vessel disease, 7.1 percent for those with two vessel disease and 10.4 percent for those with three vessel disease. The clinically collected studies show great variability, whereas those derived from coronary angiography show a remarkable consistency. It is apparent that in many series cases consist of a combination of various subsets with widely diverging prognoses. It is therefore probably no coincidence that the two clinically designed series with the most favorable mortality data dealt with large population sets {that of Frank et al., 5 showing an annual mortality rate of 1.6 percent for the "low risk group" studied at the Health Insurance Plan of New York City, and that of Zuckel et al. ~ showing a 2 percent annual mortality rate in the U.S. Army) whereas other series collected from clinical and hospital populations involved considerably greater preselection. Similarly, one can assume that the arteriographic series just discussed represented a highly selected population. Regardless of the mode of collection of the population studied, it is evident that each series contains at one end of the spectrum patients with anginal pain as the only detectable abnormality and at the other end those with heart failure, cardiomegaly, extensive myocardial damage or grossly abnormal electrocardiograms who also suffer from anginal pain; patients with various intermediate forms are found between these extremes. The composition of the mixture, then, determines the prognosis. It is also obvious that one patient population is unrepresented in all of the series, the asymptomatic patient. In clinical studies symptoms were the basis for inclusion; the arteriographic studies dealing with the actuarial curves of survival were all collected before
April 1977 The American Journal of CARDIOLOGY Volume 39
EDITORIAL
1970. Because asymptomatic patients have been included among those undergoing coronary arteriography for only 3 or 4 years, one can reasonably assume that none or a very small minority of the patients without cardiac symptoms were represented in the arteriographic series. One can develop a thesis that arteriographic studies were weighted toward the unfavorable case and probably do not represent the average mortality for the entire population of symptomatic patients. The two clinical series presenting a more favorable annual survival rate may well present data closer to the average yearly mortality data for the symptomatic patient. No information at all is available regarding the prognosis of the asymptomatic patient who has arteriographicaUy demonstrable coronary artery disease.
Are Symptoms Unimportant? In evaluating the natural history of coronary artery disease it is important to examine the view expressed in some quarters that symptoms do not matter and that only anatomic changes in the coronary arteries are important. To address this problem it is necessary to review what is really known about serious life-threatening coronary artery disease without cardiac symptoms. We know that sudden death occurs in subjects who are apparently in good health and are presumed to be asymptomatic. We know that acute myocardial infarction may be painless, and it is presumed that in such subjects the warning angina may be missing. And we know that stress testing may uncover electrocardiographic evidence of ischemia in asymptomatic patients. In trying to explain the discrepancy between serious indexes of coronary artery disease and the lack of symptoms one can suggest three possibilities: (1) myocardial ischemia in some subjects fails to invoke the warning pain; (2) pain is present but is ignored or misinterpreted by the patient or physician; and (3) the myocardium in these patients is not ischemic. There is little doubt that each of these three possibilities applies to some patients, but perhaps the most important point to be made is that for a variety of reasons severe coronary artery disease demonstrated on arteriography may be present without producing myocardial ischemia. First, arteriographic estimates of the severity of coronary obstructive lesions are very crude--gross errors in either direction are common; furthermore, the length, eccentricity, irregularity and number of coronary lesions, in series or parallel, are of immeasurable and highly unpredictable import. Second, collateral vessels often supply a totally occluded or severely stenotic coronary artery, meeting most myocardial demands. Third, electrocardiographic evidence of ischemia has many limitations (for example, S-T segment changes during stress testing may represent a false positive response or may be misinterpreted). Thus, although the absence of symptoms in patients with coronary disease is not a guarantee of benign prognosis, an asymptomatic clinical state may reflect a myocardium that seldom if ever becomes ischemic.
Risk Versus Benefit of Coronary Bypass Operations Risks: If one expresses this therapeutic ratio in terms of a ledger, the totality of risks belong on its debit side. First, the operative mortality rate is usually quoted at I to 2 percent. However, this figure is not realistic if one considers that the published data from one of the best known large volume surgical units 1° indicate a 6.9 percent mortality rate; furthermore, this rate is probably still higher in community hospitals across the country with small case loads, and a large proportion of coronary bypass operations are being performed in these small hospitals. Certainly, case series are seldom reported unless favorable, so that the les~ successful operative results go unreported. Second, the risk includes a 10 to 15 percent probability of sustaining an intraoperative transmural myocardial infarction (which the operation is expected to prevent) with an additional 5 to 15 percent incidence rate of electrocardiographic appearance of intraventricular conduction defects. Third, there is a 10 to 15 percent probability of graft closure, further nullifying the "protection" the operation is expected to offer. Fourth, it is known that obstructive lesions in bypassed vessels progress at an accelerated rate. All of these risks are based on independent observations involving several institutions. Benefits: On the credit side of the ledger is symptomatic improvement of patients with disabling angina. This is the principal yield and the only definitively established benefit of aortocoronary bypass s u r g e r y . Preliminary reports of the randomized studies of medical versus surgical therapy for symptomatic patients provide no evidence that mortality from coronary disease is reduced by the operation except in the small group of patients with severe lesions of the main left coronary trunk. Claims that mortality curves of surgically treated patients are much better than those from nonsimultaneously collected medically treated groups with comparable coronary lesions have little validity because, as explained, the patient populations differ in several ways. Thus, the'accounting" shows a small but well defined debit (risk) on one side of the ledger against a credit (benefit) for the disabled patient but no proved benefit for the prophylactic aspects of the operation.
Fallacies Concerning the Progression of Coronary Disease Reliance upon the arteriographic demonstration of obstructive lesions in the coronary arteries encourages the impression of the inevitability of progressive coronary changes. It is assumed that a 60 percent obstructive lesion will with time become an 80 percent obstructive lesion and then will occlude the artery producing myocardial infarction. This assumption serves as the basis for prophylactic coronary surgery in asymptomatic patients. The simplistic approach of a steady-rate anatomic progression of coronary lesions overlooks many modifiers of the course of coronary artery disease. First, the role of collateral circulation has been unjustly downplayed, as aptly argued by McGregor. 11 In some
April 1977
The American Journal of CARDIOLOGY
Volume 39
615
EDITORIAL
patients a long-term "balance" may be established between obstruction and collateralization. This is best illustrated by complete occlusion of a major branch, which may or may not have led to myocardial infarction but which is consistent not only with absence of symptoms but also with absence of any indexes of ischemia. Kattus 12 has called these lesions "non-precarious." Second, most studies dealing with serial coronary arteriograms show a slow rate of progression of disease. Third, pathologists have recognized for a long time what they consider to be "burned out" atherosclerotic plaques, and these must be distinguished from the more lipid-rich, "active" plaques, 13 a point that cannot be perceived from a single arteriographic study. Thus, certain arteriographicaUy demonstrated lesions are altogether nonprogressive. On the other hand, myocardial infarction and sudden death, the two disasters against which prophylactic operations are aimed, are not necessarily caused by progression of a critical lesion. Other mechanisms include thrombosis, in situ or embolic, rupture of an atherosclerotic plaque and subintimal hemorrhage-each mechanism not limited to severely obstructed coronary arteries but occurring at sites of lesser lesions as well. Thus, myocardial infarction or death (or both) occurs in a highly unpredictable fashion.
Role of Coronary Arteriography Coronary arteriography is an essential step in the chain of events leading to bypass operations. Its risk is small but not neligible. The average mortality rate is 0.45 percent 14 with higher figures quoted in laboratories with low case loads. Complications such as stroke and myocardial infarction represent additional hazards. Yet, as stated, coronary arteriography is widely used in some centers as a case-finding procedure for asymptomatic patients. The benefit of the study--demonstration of anatomic lesions in the coronary arteries--is a mixed blessing, indeed. The reassurance of the failure to find a significant lesion in the coronary arteries is indubi-
tably valuable. However, the demonstration of obstructive coronary artery disease in asymptomatic patients may present the cardiologist with a difficult problem: The emotional impact of the "silent" coronary lesion leads to a great temptation to recommend bypass surgery regardless of the current scientific evidence yet failing to support its wisdom. This may be especially true when his medical or surgical colleagues subscribe to the simplistic view that obstructing lesions automatically call for bypass, regardless of the circumstances. The staggering cost to our society of overuse of diagnostic and surgical cardiac facilities must also not be overlooked. 15
Summary and Conclusions The actuarial survival curves of "medically treated" patients whose arteriographic studies demonstrated coronary arterial lesions of various degrees--now used widely as a reference point for the natural history of coronary artery disease--are not applicable to the asymptomatic patient. No information is available regarding the course or prognosis of the asymptomatic patient with demonstrated lesions in the coronary arteries. For the reasons explained one can propose a hypothesis that the overall prognosis of this type of patient is better than average, probably better than that shown in the best data collected on symptomatic patients. The prophylactic value of aortocoronary bypass operations in preventing myocardial infarction and death has not been established. One can therefore question the justification for the wide case-finding effort of subjecting asymptomatic persons to coronary arteriography, even in light of the low risk of this procedure, unless unusual findings suggest an especially poor prognosis (one example might be past myocardial infarction in a very young patient). Although there are exceptional instances when prophylactic surgery is indicated for asymptomatic patients, further investigation of this subject is needed before the procedure becomes generally accepted.
References 1. Bloch WJ Jr, Crumpacker EL, Dry TJ, et al: Prognosis of angina pectoris. Observations in 6,883 cases. JAMA 150:259-264, 1952 2. Richards DW, Bland EF, White PD: A completed 25-year follow-up study of 456 patients with angina pectoris. J Chron Dis 4:423-433, 1956 3. Zuckel WJ, Cohen BM, fdatUngly TW, et ah Survival following the first diagnosis of coronary heart disease. Am Heart J 78:159-170, 1969 4. Kannel WB, Feinleib M: Natural history of angina pectoris in the Framingham study. Prognosis and survival. Am J Cardiol 29: 154-163, 1972 5. Frank CW, Weinblatt E, Shapiro S: Angina pectoris in men: prognostic significance of selected medical factors. Circulation 47:509-517, 1973 6. Reeves TJ, Oberman A, Jones WB, et ah Natural history of angina pectoris. Am J Cardiol 33:423-430, 1974 7. Bruschke AVG, Proudfit WL, Sones FM Jr: Prognostic study of 590 consecutive nonsurgical cases of coronary disease followed 5-9 years. Arteriographic correlations. Circulation 47:1147-1163, 1973
616
April 1977
The American Journal of CARDIOLOGY
8. Webster JS, Moberg V, Rincon G: Natural history of severe proximal coronary artery disease as documented by coronary arteriography. Am J Cardiol 33:195-200, 1974 9. Burggraf GW, Parker JO: Prognosis in coronary artery disease: angiographic, hemodynarnic and clinical factors. Circulation 51: 146-156, 1975 10. Dawson JT, Hall RJ, Ha,man GL, et ah Mortality in patients undergoing coronary artery bypass surgery after myocardial infarction. AmJ Cardiol 33:483-486, 1974 11. McGregor M: The coronary collateral circulation. A significant compensatory mechanism or a functionless quirk of nature. Circulation 52:529-530, 1975 12. Kattus AS; Prognosis of coronary arterial lesions classified according to precariousness (abstr). Clin Res 21:186, 1973 13. Vlodaver Z, Edwards JE: Pathology of coronary atherosclerosis. Prog Cardiovasc Dis 14:256-274, 1971 14. Adams DF, Fraser DB, Abrams HL: The complications of coronary arteriography. Circulation 48:609-618, 1973 15. Ross RS: The problem of ischemic heart disease: current approach and implications for curriculum design. Johns Hopkins Med J 138:217-228, 1976
Volume 39
