Frequency and importance of silent myocardial ischemia identified with ambulatory electrocardiographic monitoring in the early in-hospital period after acute myocardial infarction.

The incidence and clinical significance of silent myocardial ischemia occurring in the early period after acute myocardial infarction (AMI) was studied in 59 patients who had an uncomplicated early course after admission for AMI. Calibrated 2-lead ambulatory electrocardiographic monitoring performed for 39 +/- 2 hours starting 4 +/- 1 days after AMI identified silent myocardial ischemia, defined as greater than or equal to 1 mm ST-segment change lasting greater than or equal to 2 minutes, in 27 patients. These patients had 5 +/- 1 episodes lasting a median of 11 minutes/episode (range 2 to 36 minutes/episode). Patients with and without silent ischemia had comparable baseline demographics, were receiving similar anti-ischemic medications and had similar severity of coronary disease by angiography. No reinfarctions occurred during the in-hospital period. Fourteen of 27 patients (52%) with silent ischemia had greater than or equal to 1 in-hospital clinical ischemic event (pulmonary edema, n = 5, cardiac death, n = 1, and postinfarction angina, n = 11). In contrast, only 7 of 32 patients without silent ischemia (22%) had greater than or equal to 1 in-hospital event (pulmonary edema, n = 1, cardiac death, n = 1, and postinfarction angina, n = 6). The frequency of ischemic events was significantly greater in patients with silent ischemia compared to those without silent ischemia, p less than 0.02. Silent ischemia occurs frequently very early after AMI and identifies a group of patients who are at increased risk for adverse in-hospital clinical outcomes.