Changing circadian variation of transient myocardial ischemia during the first year after a first acute myocardial infarction.

Abstract In a consecutive series of 123 men (aged 55 ± 8 years) with a recent first acute myocardial infarction (AMI), 24-hour ambulatory ST-segment monitoring was performed early after discharge (day 11 ± 5), 6 months (day 185 ± 6) and 1 year (day 368 ± 8) after AMI. No difference in the prevalence of transient myocardial ischemia was found between the 3 recordings (17, 17 and 20%), and most ischemic episodes were silent (98,100 and 97%). In the early postinfarction period, a peak of ischemic activity was demonstrated between 6 P.M. and midnight (40 of 93 episodes [43%]). Over time, the maximal occurrence of ischemia gradually advanced toward the morning hours with a peak activity between 6 A.M. and noon at 1-year follow-up (32 of 73 episodes [44%]). Significantly more patients (16 of 21 [76%]) had ischemia from 6 P.M. to midnight at discharge compared with the findings 1 year later (9 of 23 patients [39%]) (p