Early fluctuations of the ST-segment elevation indicating intermittent opening and reocclusion of the infarct artery has been well documented by angiographic monitoring in individual acute myocardial infarction patients undergoing thrombolytic therapy. However, the frequency of such episodes has not been studied in a consecutive patient group. Furthermore, it is not known what impact this finding has on the reinfarction risk during hospitalization and on left ventricular healing. The present investigation included 79 patients with acute myocardial infarction (pain < or = 6 h). Continuous Holter monitoring of the infarct-related ST elevation was initiated before or directly after starting thrombolytic therapy. During the 24-h observation period, 34 patients (43%) showed episodes of recurrent ST elevation after an initial resolution (group 1). Among those without episodes, ST elevation resolved within 4 h in 34 (43%, group 2) and persisted > or = 4 h in 11 (14%, group 3). Episodes of re-elevation were more frequent during the first 4 h (0.25 episodes per hour) than in the late part of the observation period (0.04 episodes per hour). Most episodes were transient and short lasting; only nine patients showed persistent re-elevations longer than 60 min. During hospitalization, group 1 patients had a higher incidence of reinfarctions and severe ischemic events than those without episodes (group 1 12/34 (35%) vs. group 2 4/34 (12%) vs. group 3 1/11 (9%), p = 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)