Transient myocardial ischemia after a first acute myocardial infarction and its relation to clinical characteristics, predischarge exercise testing and cardiac events at one-year follow-up

Abstract

The relation between early out-of-hospital ambulatory ST-segment monitoring, clinical characteristics, predischarge maximal exercise testing and cardiac events was determined in 123 consecutive men (age 55 ± 8 years) with a first acute myocardial infarction (AMI). During 36 hours of ambulatory recording 11 ± 5 days after AMI 23 patients (19%) had 123 ischemic episodes (group 1), whereas 100 patients demonstrated no ischemia (group 2). Exercise-induced ST-segment depression was more prevalent in group 1 (83%) than in group 2 (47%) (p < 0.005). Group 1 patients also had more severe ischemia as judged from a shorter exercise duration before significant ST-segment depression (5.5 ± 2.4 vs 7.7 ± 4.1 minutes; p < 0.03) and more pronounced ST-segment depression on exercise testing (4.1 ± 2.6 vs 2.6 ± 1.6 mm; p < 0.03). Furthermore, exercise test results revealed an impaired hemodynamic response in group 1 compared with group 2: systolic blood pressure at maximal work toad 160 ± 31 vs 176 ± 28 mm Hg (p < 0.025) and systolic Mood pressure increase during exercise 41 ± 24 vs 56 ± 22 mm Hg (p < 0.01). Within 368 ± 8 days of follow-up the frequency of cardiac events (cardiac death, nonfatal reinfarction, and severe angina including the need of revascularization) was 52% in group 1 compared with 22% in group 2 (p < 0.01). Exercise-induced ischemia did not predict an adverse outcome: event rate 30 vs 25% in patients without residual ischemia (p = NS). None of the 5 patients who died had residual ischemia on either ambulatory monitoring or exercise testing. Patients having cardiac death had a significantly lower left ventricular ejection fraction, 32 ± 16% than the 118 survivors, 49 ± 11% (p < 0.02).