The clinical course, early prognosis and coronary anatomy of subendocardial infarction.

The following prospective study was undertaken to observe the clinical course, early prognosis and coronary anatomy of patients with subendocardial infarction. Subendocardial infarction was defined as typical chest apin (greater than 15 minutes), serum enzyme elevation and persistent (greater than 48 hours) new T wave inversion and/or S-T segment depression in the absence of new pathologic Q waves. Fifty consecutive patients were defined, followed in a prospective manner and subjected to early coronary arteriography. A prior history of unstable angina was found in 33 patients (66 per cent); 22 patients (44 per cent) had significant dysrhythmias during the acute hospital phase, and seven patients (14 per cent) had evidence of mild left ventricular failure. Coronary arteriography demonstrated significant lesions (greater than 75 per cent narrowing in at least one vessel) in all 50 patients, with 30 patients (60 per cent) having either double- or triple-vessel disease. Follow-up (mean 10.6 months) revealed that 15 patients (30 per cent) had stable angina, 23 patients (46 per cent) unstable angina and only 12 patients (24 per cent) remained free of angina. Of 28 patients in a medically treated group, acute transmural infarctions developed in six (21 per cent) and one died (3 per cent). We conclude that subendocardial infarction is symptomatically an unstable entity, is associated with severe coronary artery disease and, in a medically treated group, is followed by a significant incidence of early transmural myocardial infarction (21 per cent). Therefore, these patients require in-hospital monitoring, careful follow-up and consideration for early coronary arteriography.     

Clinical correlates of coronary cineangiography in young males with myocardial infarction.

Thirty-eight men who suffered acute transmural myocardial infarction before age 40, and after recovery were New York Heart Association functional Class I or II, were studied by noninvasive means and by coronary angiography in order to determine whether these nonivasive studies could predict the presence of significant coronary artery disease remote from that felt to be responsible for the previous myocardial infarction. Patients were divided into two groups on the basis of the absence (Group I) or presence (Group II) of obstructive disease in a major coronary artery supplying myocardium remote from the prior myocardial infarction. There were 21 patients in Group I and 17 patients in Group II. They did not differ with respect to age, abnormalities of lipid or glucose metabolism, family history, history of hypertension or cigarette use, presence of obesity, or infarct localization. Ten of 17 patients in Group II had angina pectoris; only 3/21 patients in Group I had angina pectoris (p less than 0.01). All 12 patients tested in Group II had a positive maximal exercise tolerance test; only 1/17 patients tested in Group I was similarly positive (p less than 0.001). The absence of angina pectoris and the presence of a negative maximal exercise tolerance test is strong evidence against the pressure of significant CAD remote from that responsible for the prior myocardial infarction.     

Pitfalls in the prediction of coronary artery disease from the electrocardiogram or vectorcardiogram

Seventy-eight patients with inferior, lateral and dorsal myocardial infarction patterns on electrocardiogram and vectorcardiogram had coronary cineangiographic studies. Of 41 cases with inferior infarction patterns 11 (27%) had entirely normal coronary arteries on cineangiography. Six of these had rheumatic heart disease, 2 had primary myocardial disease and 3 with angina pectoris had no demonstrable abnormality. Of 16 cases with lateral wall infarction patterns 4 (25%) had normal coronary arteries on cineangiography. Three of these had primary myocardial disease and one had idiopathic hypertrophic subaortic stenosis. With revised and stringent criteria for isolated dorsal wall infarction 21 cases were analyzed. Six of 21 (29%) were free of coronary artery disease. Five of these had angina pectoris but no demonstrable disease and 1 had rheumatic heart disease. When coronary artery disease was found in the overall group of 78 patients, double and triple vessel involvement occurred in 75% of the cases.Thus, patients with infarction patterns on electrocardiogram and vectorcardiogram frequently slow complete absence of coronary artery obstruction when studied by the technique of selective coronary arteriography. When such patients are found to have diseased coronary arteries, the disease, is frequently widespread and involves multiple vessels.     

Myocardial infarction before age 36: Risk factor and arteriographic analysis

One-hundred twenty consecutive patients who were 35 years of age or younger underwent coronary arteriography after clinical myocardial infarction. Ninety-two percent were men. Four distinct subgroups were identified: Ninety-four patients (78 percent) had significant coronary artery disease (greater than 50 percent diameter narrowing of at least one major coronary artery), 20 (17 percent) had normal coronary arteries, 5 (4 percent) had major coronary arterial anomalies and 1 patient had coronary arteritis. Of the patients with obstructive coronary disease, risk factors were smoking in 89 percent, positive family history of coronary artery disease in 48 percent, hypertension in 21 percent and a history of lipid abnormality in 20 percent. Risk factors were distinctly less frequent in the groups without coronary atherosclerosis. In the group with coronary artery disease, the prevalence rate of one, two and three vessel disease was 32, 26 and 42 percent, respectively. Coronary arterial anomalies included anomalous origin of the left coronary artery from the pulmonary artery (three patients) and single right and single left coronary artery (one patient each).It is concluded that myocardial infarction before age 36 is a disease of men who smoke and who often have a family history of premature coronary artery disease. Twenty-two percent of patients will have normal coronary arteries, coronary arterial anomalies or coronary vasculitis. Coronary arteriography should be considered for patients who sustain a myocardial infarction before age 36 for purposes of diagnosis, management and prognosis.     

The incidence and pattern of angina prior to acute myocardial infarction: A study of 577 cases

In order to determine the incidence and pattern of angina as a premonitory symptom of acute myocardial infarction, 577 consecutive patients with acute myocardial infarction were questioned shortly after hospital admission about the presence and pattern of chest pain prior to onset of infarction, with particular emphasis on the month prior to infarction. Two hundred and seventy-six patients (48 per cent) had no angina before infarction (Group I), whereas 301 (52 per cent) did. One hundred and seventy-nine patients (31 per cent) had a history of chronic angina, and of these, 75 had no change in the pattern of angina prior to infarction (Group II) while 104 noticed worsening of their symptoms in the month prior to infarction (Group III). One hundred and twenty-two patients (21 per cent) had new onset angina in the month prior to infarction (Group IV). The number of patients with unstable angina prior to infarction (Groups III and IV) was therefore 226 or 39 per cent of the total series. In patients with unstable angina, the increase in severity of symptoms or the development of new onset angina occurred within a period of 1 week or less in 69 per cent. Patients with a history of previous infarction or chronic angina had a higher incidence of unstable angina prior to infarction than patients without such a history (p < 0.05). Patients with prior angina (Groups II, III, and IV) had a higher incidence of subendocardial infarction than patients without angina (p < 0.05). The hospital mortality rate in the four groups did not differ significantly.     

Angina pectoris, myocardial infarction and sudden cardiac death with normal coronary arteries: a clinicopathologic study of 9 patients with progressive systemic sclerosis

The syndrome of angina pectoris or acute myocardial infarction without obstructive coronary artery disease has been the subject of much interest. We studied nine autopsied patients with progressive systemic sclerosis and evidence of ischemic heart disease but morphologically normal coronary arteries. Three patients had angina pectoris and three others chest pains of unknown etiology, six had ventricular arrhythmias, four had clinically suspected acute myocardial infarction, and eight had sudden cardiac death. At autopsy extensive focal myocardial necrosis was present in seven patients and myocardial scarring in all nine, but all patients had widely patent intramural and extramural coronary arteries. The finding of contraction band myocardial necrosis in seven of the eight patients who experienced sudden death suggests that the myocardial damage was a consequence of reperfusion of focally nonperfused myocardium, and thus due to a myocardial Raynaud's phenomenon. Patients with PSS may provide a model of spasm of intramyocardial vessels causing angina pectoris or myocardial infarction with morphologically normal coronary arteries.     

Hemorrhagic myocardial infarction associated with aortocoronary bypass revascularization.

Experimentally, hemorrhage and extension of myocardial infarction occur commonly when there is reperfusion after coronary artery occlusion. To investigate this hazard in a clinical setting, we compared the histopathologic picture of myocardial infarction in 44 patients who had undergone aortocoronary bypass: 14 (Group I) had myocardial infarction that predated aortocoronary bypass by 1 to 7 days; 13 (Group II) had infarction 1 to 14 days after the surgery; and 17 (Group III) had infarction 15 to 90 days postoperatively. All 44 patients had two or more coronary arteries with luminal narrowing of more than 75 per cent and patent vein grafts to arteries supplying areas of infarction. Hemorrhagic infarcts were present in 57 per cent of patients (eight of 14) in group I and 38 per cent of patients (five of 13) in Group II, contrasting with 6 per cent of patients (one of 17) in Group III (P < 0.005 and P < 0.05, respectively). In hemorrhagic infarcts, the extravasated blood formed irregular intramural dissecting tracts beyond the area of infarction, and foci of myocardial necrosis were present in the border zones. Infarcts affected more than 50 per cent of the left ventricular muscle in 64 per cent of cases of hemorrhagic infarction and in 13 per cent of cases of nonhemorrhagic infarction (P < 0.05). The prevalence of hemorrhagic infarction after revascularization may account for the high mortality of evolving and perioperative myocardial infarction associated with aortocoronary bypass, and this finding militates against wholesale immediate revascularization in patients who have uncomplicated myocardial infarction.     

Candidates for transluminal coronary angioplasty

An analysis was made of clinical and electrocardiographic prognostic determinants of multiple vessel disease in 100 men, aged under 45 years, who survived a myocardial infarction. All patients underwent selective coronary arteriography within 1 year after sustaining a myocardial infarction. Multivessel disease was present in 64 patients; 33 patients had single vessel disease and 3 had either normal coronary arteries or minimal lesions. Exercise stress testing, electrocardiographic location of the infarction, total serum cholesterol and clinical features including body build, arterial blood pressure, smoking habits, family history of coronary artery disease and the presence of angina pectoris either before or after the acute event proved to be poor predictors of multiple vessel disease. Only 74 percent of the patients were correctly classified by a discriminant function analysis. Thus, for prognostic reasons, coronary arteriography seems warranted in young patients after acute myocardial infarction, even in the absence of residual angina or multiple risk factors.     

Comparative results of coronary angioplasty performed at the time of coronarography and at a later time

Between January 1986 and December 1988, 558 patients underwent percutaneous transluminal coronary angioplasty (PTCA) of whom 40 per cent were dilated at the time of diagnostic coronary arteriography. In order to assess the value of this therapeutic strategy we compared the results of 221 patients dilated at the time of diagnostic coronary arteriography (Group 1) with those of 337 patients who underwent deferred PTCA. In Group 1, the incidence of stable angina was lower (26.7% vs 46.3%, p less than 10-5), that of thrombolysed myocardial infarction was higher (24% vs 2.7%, p less than 10-9) and a higher proportion of patients had previously undergone PTCA (29.4% vs 3.2%, p less than 10-9). The proportion of patients with single vessel disease was higher in Group 1 (84.6% vs 74.7%, p less than 0.01) as was that of angioplasty of a single lesion (97.7% vs 88.1%, p less than 10-4). There were fewer dilations of the left circumflex artery in Group 1 (17.2% vs 27.3%, p less than 0.05) which was compensated by a higher number involving the right coronary artery (26.1% vs 15.5%, p less than 0.01). The immediate results were comparable in the two groups with 87.8 per cent primary successes, 3.6 per cent of myocardial infarcts and 1.3 per cent of coronary bypass operations with no fatalities in Group 1. These favorable results encourage the development of PTCA at the time of diagnostic coronary arteriography in the following indications: unstable angina, thrombolysed myocardial infarction and restenosis irrespective of the patient's symptomatology.(ABSTRACT TRUNCATED AT 250 WORDS)     

Coronary arteriography in acute transmural myocardial infarction

Coronary arteriography was performed 16 ± 3 days (range 7 to 21 days) in 106 patients with acute transmural myocardial infarction (61 posterior infarct, 45 anterior infarct). Coronary arteriography was performed without serious complications. Only 44 per cent of patients with anterior infarct had total occlusion of the left anterior descending artery while a significant stenosis of the vessel was observed in the others ?27 per cent had a single vessel disease, 49 per cent had two lesions and 22 per cent had three lesions; one patient had angiographically normal coronary arteries. Among the patients with posterior infarction, 21 per cent had one vessel disease and double or triple lesions accounted for 39 per cent of each.Sixty per cent of patients with anterior infarction and 45 per cent with posterior infarction had no collateral vessels. In the others patients collateral circulation had a protective effect only in anterior infarction. Age has no effect on the distribution and number of lesions nor on the development of a collateral circulation. The location and severity of the lesions were not different in patients who presented with arrythmias and those who did not.     

Myocardial infarction in young Indian patients: risk factors and coronary arteriographic profile

One hundred four patients (101 men, three women), under 40 years of age, with myocardial infarction (MI), underwent coronary arteriography. Eighty patients had significant obstructive coronary artery disease (CAD) (group 1), 23 had normal coronary arteries (group 2), and one patient had coronary ostial stenosis as a result of nonspecific aortoarteritis (group 3). Coronary risk factors in group 1 included smoking (76.2%), hypercholesterolemia (36.3%), hypertension (32.5%), positive family history (28.7%), and diabetes mellitus (5%). Multiple risk factors were frequent (56.2%). Smoking was common (p less than 0.01) and diabetes mellitus less frequent (p less than 0.05) as compared to older (greater than 40 years) patients with MI and arteriographically proved CAD. The frequency of one-, two-, and three-vessel disease was 33.7%, 26.2%, and 40%, respectively, in group 1. Group 2 patients were almost devoid of coronary risk factors. The only group 3 patient had left coronary ostial stenosis with no risk factors. Similar to their counterparts in developed countries, young Indian patients with MI and obstructive CAD have a high frequency of coronary risk factors, especially smoking and severe multiple-vessel disease. Since normal coronary arteriograms are also frequent in this setting, a detailed evaluation is recommended for purposes of prognosis and management.     

Coronary artery disease in premenopausal Indian women: risk factors and angiographic profile.

Coronary angiographic and clinical profile of 47 premenopausal women presenting with myocardial infarction (MI) or angina is presented. Seventeen patients (36%) had significant obstructive coronary artery disease (CAD) (Group I), while 30 (64%) had normal coronaries (Group II). The latter group included 4 who had MI and 26 who presented with angina. Risk factors in Group I included hypertension (53%), diabetes mellitus (24%), hypercholesterolemia (29%), oral contraceptives and a positive family history (11.8%). Frequency of one, two and three vessel disease was 47%, 18% and 35% respectively. The left anterior descending artery was most commonly affected (82%). In Group II the risk factors included hypertension (17%) and diabetes (7%). No patient in either group was a smoker. This analysis shows that significant obstructive CAD in premenopausal Indian females is more commonly associated with hypertension, diabetes and hypercholesterolemia. Smoking was not encountered and ingestion of contraceptive pills is uncommon.     

Myocardial infarction without obstructive coronary artery disease

The present report describes five cases of transmural myocardial infarction occurring in patients without occlusive coronary artery disease or other discernible abnormalities. It is apparent from these cases and others described in the literature that such patients may present with or without angina and, in some, the clinical course will be complicated by recurrent infarction and/or significant residual myocardial dysfunction. At present the exact incidence and natural history of this syndrome is unclear. Undoubtedly the increasing application of coronary arteriography will identify many more such patients. Delineation of the genesis and the full clinical spectrum of myocardial infarction without coronary artery disease warrants further investigative attention.     

Surgical implications and results of combined aortic valve replacement and myocardial revascularization.

To better define the indications for and results of simultaneous aortic valve replacement and myocardial revascularization, a cohort of 271 patients with angiographically defined coronary anatomy who underwent xenograft bioprosthetic aortic valve replacement were analyzed. Two hundred and twelve patients had predominant aortic stenosis, and 55 had pure aortic regurgitation. Discordance between the clinical assessment of angina and the angiographic assessment of coronary artery disease was apparent in 39 percent of the patients with aortic stenosis and 45 percent of the patients with aortic regurgitation. Thirty-seven percent of patients in the aortic stenosis subgroup without angina and 41 percent of patients in the aortic regurgitation subgroup without angina had hemodynamically significant coronary artery disease. Concomitant coronary artery bypass grafting and aortic valve replacement were performed in 101 patients. The incidence of perioperative myocardial infarction and operative death was significantly greater (P < 0.05) in the subsets of patients with coronary disease than in those without coronary disease (9.9 percent versus 0.7 percent and 8.3 percent versus 2.2 percent, respectively). Late postoperative angina and myocardial infarction also correlated with the preoperative presence of coronary artery disease. Excluding operative mortality, the late actuarial survival rate (mean follow-up, 1.6 years; maximal follow-up, 4.9 years) was not statistically lower for the patients with coronary disease.It is concluded that angina pectoris in patients with aortic valve disease is not a reliable indicator of coronary artery disease and that patients with coronary disease who undergo aortic valve replacement have an increased risk. It is inferred from this study that preoperative coronary arteriography is advisable in most adults undergoing the evaluation of aortic valve disease and that simultaneous aortic valve replacement and myocardial revascularization may provide some protection against late attrition due to the combined effects of coexistent aortic valve and coronary artery disease.     

Profile of coronary artery disease in Indian women: correlation of clinical, non invasive and coronary angiographic findings

Clinical and risk factor profile of 101 consecutive female patients subjected to coronary angiography was analysed. Coronary angiography showed single vessel disease (SVD) in 15.8 per cent, double vessel disease (DVD) in 12.9 per cent, triple vessel disease (TVD) in 39.6 per cent and normal coronary arteries (NC) in 30.7 per cent. Risk factor profile in patients with angiographic coronary artery disease (group II) included hypertension (HT) in 52.9 per cent, diabetes mellitus (DM) in 44.3 per cent, post menopausal state in 84.3 per cent, positive family history in 51.4 per cent, obesity in 58.3 per cent, low density and high density lipoprotein ratio (LDL/HDL) more than 3.0 in 58 per cent and smoking in 4.3 per cent. Risk factors in 31 patients with NC (group I) included HT in 29 per cent, DM in 6.5 per cent, positive family history in 45.2 per cent, obesity in 45.2 per cent, post menopausal state in 48.4 per cent, LDL/HDL ratio more than 3.0 in 30 per cent and smoking in none. The clinical presentation in group II was unstable angina in 64.3 per cent, stable angina pectoris in 24.3 per cent, myocardial infarction in 4.3 per cent and atypical chest pain in 2.8 per cent. In group I half the patients presented with atypical chest pain. The other modes of presentation included unstable angina 25.8 per cent, stable angina pectoris in 16.2 per cent and myocardial infarction in 6.5 per cent. Predictive value of exercise electrocardiography (Ex ECG) or exercise radionuclide studies (Ex RNU) was 61.7 and 68.4 per cent respectively. DM, post-menopausal state and LDL/HDL ratio more than 3 were significant risk factors in women.(ABSTRACT TRUNCATED AT 250 WORDS)     

Collateral circulation to the diagonal artery from the infundibular coronary artery in obstructive coronary arterial disease

We report an unusual collateral pathway from the isolated infundibular (third coronary) artery to the diagonal artery in a young adult male with a history of recent anteroseptal myocardial infarction and apparently angiographically normal left and right coronary arteries. The isolated infundibular (conus) artery is an important source of collateral pathways in obstructive coronary arterial disease. Its selective arteriography is essential for complete angiographic evaluation of these patients.     

Coronary anatomy and arteriography in patients with unstable angina pectoris.

A prospective series of 188 patients with the syndrome of unstable angina pectoris undergoing coronary arteriography was reviewed to determine the spectrum of anatomic coronary artery disease, suitability for coronary revascularization and in-hospital morbidity and mortality. Thirty-two patients demonstrated normal to moderately diseased coronary arteries. None of these patients sustained myocardial infarction or died. Twenty patients (10.6 percent) had normal coronary arteriograms. Of the 156 patients having severe coronary artery disease (greater than 70 percent stenosis), 20 patients (13 percent) had left main coronary artery disease. One hundred forty-two patients (91 percent) were potential candidates for coronary surgery; 14 were not candidates because of distal vessel disease or poor left ventricular function. During cardiac angiography or in the subsequent hospital period 12 patients sustained a myocardial infarction and 7 of these died. Of these seven, six had left main coronary artery disease and one had three vessel disease. In three patients who died (1.9 percent of those with severe coronary artery disease) the death may have been related to cardiac catheterization because evidence of myocardial necrosis began within 24 hours of study. Thus, patients with the syndrome of unstable angina pectoris usually presented with severe coronary artery disease and were candidates for coronary revascularization. The anatomic severity of coronary artery disease appeared to be the most important factor contributing to myocardlal infarction or death after cardiac catheterization. Mortality after catheterization was primarily associated with left main coronary artery disease.     

Mental arithmetic stress testing in patients with coronary artery disease

A mental arithmetic stress test was performed by 122 consecutive patients undergoing diagnostic coronary arteriography. Twenty-two patients showed significant ST segment abnormalities during the test (group 1). Of these patients, 20 performed a bicycle exercise test, which was positive in all of them. Seventy patients had a negative mental stress but a positive exercise test (group 2), whereas in 30 patients both tests were negative (group 3). There were no patients with a positive mental stress test and a negative exercise test. Mental stress induced a significant increase in heart rate and systolic blood pressure in the three groups of patients. Group 1 patients, however, achieved higher values of double product during mental stress and had a shorter exercise duration than group 2 and group 3 patients. The extent of coronary artery disease (CAD) was similar in groups 1 and 2, while group 3 patients had a significantly lower prevalence of two or more vessel disease. To investigate the pathogenetic mechanism of mental stress-induced myocardial ischemia, great cardiac vein flow was measured by means of the thermodilution technique in four patients with isolated left anterior descending artery disease, who showed ST segment depression in anterior leads in response to mental stress. In three patients without vasospastic angina the calculated coronary resistance decreased during mental stress, as a result of a normal vasodilatory response to the increased myocardial oxygen consumption induced by the test. By contrast, in one patient with variant angina, coronary resistance increased suggesting coronary vasoconstriction. Our findings demonstrate that mental arithmetic stress testing may induce significant ST segment abnormalities in patients with CAD. Such patients respond to mental stress with a disproportionate increase in myocardial oxygen consumption and have decreased exercise capacity. Although coronary resistance generally decreases during mental stress-induced myocardial ischemia, coronary vasoconstriction may occur in patients with variant angina.     

Chest pain with angiographically insignificant coronary arterial obstruction: Clinical presentation and long-term follow-up

Among 3,242 coronary angiograms performed from November 1972 through October 1975 at the Massachusetts General Hospital, 175 patients had normal coronary arteries or luminal narrowings of less than 30 per cent. All patients were studied for chest pain, and none had experienced prior myocardial infarction. Subsequent information was available in 159 patients over a mean follow-up period of 42.7 months. There were no deaths, and only one myocardial infarction occurred during this period. However, among the patients followed, continued chest pain with episodes occurring at least once monthly was present in 54 per cent. In addition, 17 per cent of all patients required subsequent hospitalization and 44 per cent continued to receive antianginal medication. Nearly half of the group (46 per cent) suffered some limitation of activity, and 22 per cent stated that they had either changed jobs or stopped work because of chest pain. Continuing chest pain was significantly more common in women and in patients who had experienced chest pain for more than one year before angiography. However, typicality of chest pain for angina or the occurrence of electrocardiographic changes of ischemia prior to angiography did not predict continued chest pain during the follow-up period. Thus, although mortality and morbidity are low in this group of patients, the syndrome of chest pain with angiographically insignificant coronary artery obstruction has an important impact on the lives of a majority of those affected.     

Clinical and hemodynamic evaluation of coronary collateral vessels in coronary artery disease

To appraise the functional significance of coronary collateral vessels, 78 consecutive patients with angina pectoris and at least 75 per cent obstruction in a major coronary vessel were studied clinically, hemodynamically, and angiographically and by stress testing. Forty-eight of them (62 per cent) had coronary collateral vessels. When patients with collaterals were compared with those without, the severity of angina pectoris and the number of positive treadmill ECG's were not statistically different. The patients with collaterals had a greater incidence of past myocardial infarction, $\text{33}\text{48}$ (68 per cent) vs. $\text{8}\text{30}$ (27 per cent) (P = 0.001); more extensive obstructive disease angiographically, 8.0 ± 0.4 vs. 6.3 ± 0.5 (P = 0.05); more abnormal pacing ventricular function curves, $\text{22}\text{23}$ (96 per cent) vs. $\text{9}\text{15}$ (60 per cent) (P = 0.01); and a greater incidence of left ventricular contraction abnormalities, $\text{43}\text{48}$ (90 per cent) vs. $\text{16}\text{30}$ (53 per cent) (P = 0.025).Patients who have coronary artery disease and collateral vessels cannot be distinguished from their counterparts without collaterals on a clinical basis except for a greater incidence of myocardial infarction in the former. Present evidence implies that collateral vessels may protect the patient by delaying the onset of angina pectoris, but when angina occurs these patients have more extensive coronary artery disease and greater myocardial dysfunction. In addition, collaterals, although not preventing, may limit the extent of myocardial infarction and reduce immediate mortality. The prognosis from the onset of angina pectoris may be worse in those patients with collateral vessels, however, because of their more extensive disease.