Prognostic value of exercise stress testing versus ambulatory electrocardiography after acute myocardial infarction: a 3 year follow-up study

Abstract

Background: The aim of this study was to evaluate the prognostic significance of myocardial ischemia detected by ambulatory ECG monitoring (AEM) and exercise stress testing (ExT) following acute myocardial infarction.

Methods: The prognostic value of AEM versus ExT was studied prospectively in 74 patients with a recent acute myocardial infarction. Myocardial ischemia was diagnosed by the presence of ST-segment depression occurring during AEM or ExT 4 +/- 2 and 7 +/- 4 days after hospital admission respectively. ST-segment depression during AEM was defined as a horizontal/downsloping depression of > or = 0.1 mV from the reference baseline, measured 80 ms after the J point, elapsing > or = 1 min. ST-segment depression at ExT was determined as > or = 1mm horizontal or downsloping ST-segment depression in at least two consecutive ECG leads.

Results: Twenty-two patients (30%) showed ST-segment depression during AEM and 34 (49%) on ExT. During a mean follow-up period of 3 years (36 +/- 15 months), 10 patients (45%) with ST-segment depression on AEM died compared with eight (15%) without; 12 patients (35%) with ST-segment depression on ExT died versus three (8%) without. Death or reinfarction occurred in 13 patients (59%) with ST-segment depression on AEM versus nine (17%) without, and in 13 patients (38%) with ST-segment depression on ExT compared with six (17%) without. Revascularization procedures were similar in patients with or without ST-segment depression during AEM and ExT. Cardiac events defined as death, nonfatal reinfarction or revascularization, occurred in 18 patients (82%) with ST-segment depression on AEM versus 20 (38%) without, and in 23 patients (68%) with ST-segment depression on ExT versus 11 (31%) without. Survival analysis using Kaplan-Meier curves showed that patients showing no ST-segment depression with either technique had longer survival times than did patients showing ST-segment depression on either AEM or ExT, or showing ST-segment depression with both techniques. This was also true when analyzing the cumulative survival rate until the occurrence of any endpoint. With multivariate regression analysis, ST-segment depression on AEM was the variable most strongly predictive of mortality, followed by ST-segment depression on ExT, hypertension, and diabetes.

Conclusions: These findings illustrate the ability AEM and Ext independently to predict long-term cardiac mortality and morbidity rates in patients recovering from acute myocardial infarction. The combined use of these techniques is useful for detecting patients at high risk after acute myocardial infarction.