Stepwise risk stratification soon after acute myocardial infarction

Abstract

A stepwise rise stratification procedure sequentially combining historical and clinical characteristics and treadmill exercise test results was applied to 702 consecutive men aged less than or equal to 70 years who were alive 21 days after acute myocardial infarction (MI). Historical characteristics alone (prior MI and prior angina or recurrence of pain in the coronary care unit) identified 10% of patients with the highest rate of reinfarction and death within 6 months (18%). Clinical contraindications to exercise testing identified another 40% of patients with an intermediate rate of cardiac events (6.4%). In the 50% of patients who underwent treadmill testing 3 weeks after MI, the rate of cardiac events within 6 months was 4.4%: 3.9% in patients with a negative test and 9.7% in patients with a positive test (ischemic ST-segment depression greater than or equal to 0.2 mV and a peak heart rate less than or equal to 135 beats/min). Patients with negative treadmill tests, who comprised 46% of patients less than or equal to 70 years and 53% of patients less than or equal to 60 years, had a cardiac death rate of less than 2% in the 6 months after MI. The stepwise classification procedure correctly classified 72% of patients with hard medical events within 6 months. Thus, most patients who experience subsequent cardiac events are correctly classified on the basis of historical and clinical risk characteristics. In patients without these risk characteristics, early treadmill testing is useful for further discriminating high-risk from very low risk patients.