The Prognostic Value of DeltaST/HR Index and Rate-Recovery Loop during Predischarge Exercise Test in Acute Myocardial Infarction

ABSTRACT

BACKGROUND: The heart rate adjusted ST segment criteria(Delta ST/HR index and rate-recovery loop or R-R loop) compared to standard ST segment criteria may improve the ability of the exercise electrocardiogram for the prediction of severe coronary artery disease and future cardiac events in patients with chronic angina pectoris, but the predictive value of these criteria for predicting these issues has not been studied in patients with acute myocardial infarction. METHODS: 64 patients with first uncomplicated myocardial infarction were studied. All patients performed predischarge(mean 8+/-4 days) symptom-limited exercise test and coronary angiography(mean 11+/-15 days). During the follow-up period(mean 449+/-273 days), the occurrence of the major cardiac events(death, reinfarction, coronary artery bypass surgery) and minor cardiac event(angina, heart failure) were recorded, and then univariate and multivariate analysis of several clinical and exercise variables known to be as prognostic markers were performed. RESULTS: The results are as follows 1) The sensitivities of Delta ST/HR index and R-R loop(92%, 83% respectively) for predicting multivessel disease showed no significant difference compared to that of standard ST segment criteria(83%). 2) Major cardiac events occurred in 12(20%) of 64 patients and only single independent predictive factor for its prediction was multivessel coronary artery disease(p=0.0001), whereas total cardiac event occurred in 32(50%), multivessel disease(p=0.003), and maximal workload <5mets(p=0.038). 3) For the prediction of total cardiac event, DeltaST/HR index and R-R loop(all 97%) were significantly more sensitive(p<0.05) than standard ST segment criteria(78%), and there was a tendency to increase in specificity in R-R loop(84%) compared to DeltaST/HR index(59%) or standard ST segment criteria(66%). 4) The negative predictive value of all negative test of three ST segment criteria for predicting total cardiac event was 100%. CONCLUSION: Although the heart rate-adjusted ST segment criteria have no advantage over standand ST segment criteria for the prediction of severe coronary artery disease, they can be more useful prognostic markers by enhancing the accuracy of the predischarge exercise electrocardiogram for the prediction of subsequent cardiac events after a first acute myocardial infarction.