Ischemia monitoring with on line vectorcardiography compared with results from a predischarge exercise test in patients with acute ischemic heart disease.

Information from 24 hour monitoring with on line vectorcardiography, starting immediately after admission, was compared with results from a predischarge exercise test 3 13 days after admission. A total of 169 patients with acute myocardial infarction and 73 patients with unstable angina pectoris were investigated. Patients were followed for 487 +/  135 days. During the follow up period, 19 patients (8%) died from cardiac causes and 34 (14%) were hospitalized for a myocardial infarction. The QRS vector difference (QRS VD), ST change vector magnitude (STC VM), ST vector magnitude (ST VM), and ST vector leads X, Y, Z were monitored. Patients with ST depression on the exercise test showed higher occurrence of transient, supposedly ischemic, episodes of QRS VD, STC VM, and ST VM than patients without ST depression. The sensitivity and specificity of identifying patients with ST depression at the exercise test were respectively, 71 and 47% for QRS VD episodes, 58 and 56% for ST VM episodes, and 55 and 65% for STC VM episodes. The maximum ST depression at the exercise test was related to the maximum ST depression in vector lead X (r = .44, P < .001) and the number of STC VM (r = .40, P < .001), ST VM (r = .37, P < .001), and QRS VD (r = .33, P < .001) episodes on the VCG. In multivariate analysis, maximum ST depression in vector lead X and STC VM episodes were the best determinants for ST depression at the exercise test. In a Cox regression model, the optimal combination of exercise test data in patients who died from cardiac causes exhibited a global chi square value of 20.0. The combination of these data and the number of STC VM episodes increased the global chi square value to 30.6. This study indicates that in patients with acute ischemic heart disease, early continuous vectorcardiographic monitoring may predict the results from a predischarge exercise test and also contributes independent prognostic information beyond that of exercise test data.