Prognostic value of ambulatory ST segment monitoring compared with exercise testing at 1-3 months after acute myocardial infarction.

The relative value of ambulatory ST segment monitoring for assessing prognosis following acute myocardial infarction is currently uncertain. Ambulatory monitoring was performed in 177 patients at a mean of 38 days (range 22-93) post-myocardial infarction and its prognostic value was compared with exercise treadmill testing (n = 170). Cardiac events (myocardial infarction, cardiac death or coronary revascularisation) were noted during at least 1 year of follow-up. The presence or absence of ST depression on ambulatory monitoring did not predict increased fatal or non-fatal cardiac events although more severe ST depression had some predictive power: after adjusting for clinical variables and coronary prognostic indices, the duration/24 h (P = 0.03) and magnitude (P = 0.007) of ST depression had independent value. ST deviation on exercise testing was associated (P < 0.05) with increased events (19/90; 21% vs 7/80; 9%) and in patients with a positive exercise test ST depression on ambulatory monitoring did not identify any additional events (8/41; 20% vs 11/49; 22%). No factor available from ambulatory monitoring was predictive of outcome once variables from exercise testing were taken into account. Ambulatory ST segment monitoring performed in the late recovery phase (1-3 months) after acute myocardial infarction is inferior to exercise testing for predicting prognosis and does not increase the predictive power of an exercise test. Ambulatory monitoring may only be indicated in patients unable to perform an exercise test.