Pathophysiology and Natural History Coronary Artery Disease

Patients registered by the 1971 Perth Coronary Register as having suffered a myocardial infarction were followed up for 9 years. The Register was a community-based study that used standard methods and criteria as part of a World Health Organization collaborative investigation. Of the 1078 patients studied, 77% survived the first 24 hr and 62% the first 28 days; 0.3% were lost to follow-up. For the 666 patients alive at 28 days, the crude 1, 5, and 9 year survival rates were 88%, 67%, and 52%, respectively. The relationship between 54 variables and the survival of patients alive 28 days after myocardial infarction was examined by life-table methods and the log rank test, and then by fitting a proportional hazards model to the data. The important prognostic factors were age, sex, past history of myocardial infarction, stroke, diabetes and hypertension, tachycardia at presentation, hypotension at presentation, and the occurrence of arrhythmias as short-term complications. The most appropriate mathematical description of the joint effects of the prognostic factors was a multiplicative model with no interaction. Circulation 68, No. 5, 961-969, 1983. ASSESSMENT of factors that affect the prognosis of individual patients after myocardial infarction (MI) is potentially useful in patient management, design of clinical trials of therapy after MI, elucidation of the mechanisms of death after MI, and stratification to permit valid comparison of cohorts of post-MI patients. 1-' However, lack of agreement among previous studies on these prognostic factors has raised doubts that have limited their usefulness. The most important potential sources of disagreement are various kinds of bias, poor statistical power, and variations in factor definition or measurement. Current knowledge of survival after MI is largely based on results from patients treated in the hospital,'3 patients selected for clinical trials of therapy after MI,14, 15 or patients identified in health insurance studies.3 These groups have been particularly liable to From the Department of Medicine, University of Western Australia, and the Department of Cardiovascular Medicine, Sir Charles Gairdner Hospital, Nedlands, Western Australia. Supported by the Raine Centre for the Study of the Epidemiology, Aetiology, and Community Control of Hypertensive and Atherosclerotic Vascular Disease and the National Heart Foundation of Australia. Address for correspondence: Dr. A. K. Armstrong, NH & MRC Research Unit in Epidemiology and Preventive Medicine, Department of Medicine, University of Western Australia, Nedlands, 6009, Western Australia. Received Nov. 17, 1982; revision accepted July 7, 1983. Vol. 68, No. 5, November 1983 selection bias and poor standardization of diagnostic criteria. This article reports the 9 year survival of 666 patients registered in the 1971 Perth Coronary Register (PCR) who survived the acute phase of MI. The PCR was a community-based study that used standard methods and diagnostic criteria as part of a World Health Organization (WHO) collaborative investigation. '161 Evidence from several sources suggested a fairly complete ascertainment of cases of MI. 16 Furthermore, the stability of Perth's population due to its relatively isolated location provided an opportunity for near-total follow-up of patients registered.