Significance of ST-segment elevation during ambulatory monitoring after acute myocardial infarction.

The significance of ST segment elevation during ambulatory monitoring after acute myocardial infarction was examined in 203 patients. Ambulatory monitoring was performed both early (mean 6.4 days [range 3 to 15]; N = 201) and late (38 days [range 22 to 93]; N = 177), and 174 patients underwent exercise treadmill testing (38 days [range 22 to 93]). Cardiac events (death, reinfarction, and coronary revascularization) were documented during a 1-year follow-up period. ST elevation (all silent) occurred in 25 of 201 patients (12%) on early monitoring but in only 4 of 177 (2%) on late monitoring (p < 0.001). Compared with patients (N = 148) without any ST deviation, those with early ST elevation had more pericarditis (8/25 [32%] vs 23/148 [16%]; p = 0.089) but no more angina or exercise ischemia. The mortality rate tended to be higher in patients with early ST elevation (4/25 [16%] vs 10/148 [7%]; p = 0.24), but ST elevation was too infrequent to be a valuable prognostic indicator. ST elevation is not uncommon during ambulatory monitoring early after myocardial infarction but is rare during later monitoring. Such ST elevation is almost always silent, does not usually reflect myocardial ischemia, and is not a useful prognostic indicator.