Prognostic significance of transient myocardial ischemia on ambulatory monitoring after acute myocardial infarction.

The prognostic value of ambulatory ST-segment monitoring after myocardial infarction was prospectively assessed in 203 patients both early (mean 6 days, n = 201) and late (38 days, n = 177). During at least 1 year of follow-up there were 21 cardiac deaths and 44 cardiac events (death, reinfarction or coronary revascularization). ST depression was seen less often during early than late monitoring (29 of 201 [14%] vs 56 of 177 [32%]). Early ST depression was significantly associated with increased mortality (7 of 29 [24%] vs 14 of 172 [8%]) (< 0.05) and increased cardiac events (13 of 29 [45%] vs 30 of 172 [17%]) (p < 0.001) and had independent value after allowing for clinical factors and coronary prognostic indexes (adjusted relative risks 3.40 and 2.70, respectively). ST depression on late monitoring was only associated with increased cardiac events when it was: (1) frequent (e.g., > or = 3 episodes/day [10 of 31 patients, 32% vs 18 of 146, 12%]) (p < 0.01); (2) prolonged (e.g., > or = 20 minutes/day [8 of 25, 32% vs 20 of 152, 13%]) (p < 0.05); or (3) severe (e.g., maximum of > or = 1.5 mm [8 of 28, 29% vs 20 of 149, 13%]) (p < 0.05). Thus, ST depression occurs less frequently during ambulatory monitoring before discharge than during late monitoring, but is a more specific prognostic indicator; however, it is more benign during late monitoring. Ambulatory ST-segment monitoring can be used to predict prognosis in the first year after myocardial infarction, although its relative value as a screening test compared with exercise testing remains to be established.