PROGNOSTIC IMPORTANCE OF MYOCARDIAL-ISCHEMIA DETECTED BY AMBULATORY MONITORING EARLY AFTER ACUTE MYOCARDIAL-INFARCTION

Background, After an acute myocardial infarction, it is important to d etermine the risk of a subsequent coronary event, We studied the progn ostic value of myocardial ischemia detected by ambulatory electrocardi ographic (EGG) monitoring in patients who had recently had an acute my ocardial infarction. Methods. Five to seven days after acute myocardia l infarction, 406 patients underwent 48-hour ambulatory ECG monitoring , with submaximal exercise testing before discharge and measurement of the left ventricular ejection fraction within 28 days after infarctio n. Death, nonfatal myocardial infarction, and admission to the hospita l because of unstable angina were the principal end points recorded du ring the one-year follow-up period. Results. The overall incidence of myocardial ischemia detected by ambulatory ECG monitoring was 23.4 per cent, The mortality rates at one year were 11.6 percent among the pati ents with ischemia and 3.9 percent among those without ischemia (P=0.0 09); 3.9 percent among the patients with a positive exercise test, 3.0 percent among those with a negative exercise test, and 16.4 percent a mong those in whom an exercise test was not performed (P<0.001); and 3 .6 percent among the patients with an ejection fraction greater than 5 0 percent, 3.5 percent among those with an ejection fraction between 3 5 and 50 percent, and 18.2 percent among those with an ejection fracti on below 35 percent (P=0.001), Using multiple logistic regression, we found that no diagnostic test performed after myocardial infarction pr ovided additional prognostic information beyond that provided by the s tandard clinical variables used to predict the risk of death. When non fatal myocardial infarction and admission to the hospital because of u nstable angina were also included as outcome variables, ambulatory mon itoring for ischemia was the only test that contributed significantly to the model. For the patients with ischemia detected by ambulatory mo nitoring, as compared with those who did not have evidence of ischemia , the odds ratio was 2.3 (95 percent confidence interval, 1.2 to 4.5) for death or nonfatal myocardial infarction (P=0.009) and 2.8 (95 perc ent confidence interval, 1.6 to 4.8) for death, nonfatal myocardial in farction, or admission to the hospital because of unstable angina (P<0 .001). Conclusions. Myocardial ischemia detected by ambulatory ECG mon itoring is common early after acute myocardial infarction and provides prognostic information beyond that available from standard clinical i nformation.