On-line vectorcardiography in ischemic heart disease

The clinical usefulness of continuous on-line vector cardiography (VCG) was assessed in 435 patients, admitted to the coronary care unit. The ability of 24-hour VCG monitoring to differentiate patients with or without ischemic heart disease (IHD), to provide long-term prognostic information and to predict results from a predischarge exercise test in patients with unstable angina pectoris or acute myocardial infarction (MI) was evaluated.

Findings from dobutamine stress echocardiography during simultaneous VCG monitoring and the inter- and intra-observer variations of 24-hour VCG measurements were also evaluated. Patients with low probability of IHD (n=15) had significantly lower QRS-VD end values and fewer transient VCG changes (QRS-VD, ST-VM and STC-VM episodes) than patients with IHD. Patients with unstable angina pectoris (n=15) had a higher number of transient VCG changes but lower QRS-VD end values than patients with acute MI (n=31). In 100 patients with unstable angina pectoris, followed for 343±77 days, 7 died from cardiac causes and 8 suffered a non-fatal MI. Univariate predictors of cardiac death or non-fatal MI included higher age, rest pain during hospitalization, diabetes mellitus and high incidence of transient VCG changes.

Multivariate analysis showed that high incidence of STC-VM episodes (p<0.01) provided additional prognostic information beyond that of other clinical data. In 203 patients with acute MI, followed for 538±220 days, 36 died from cardiac causes and 30 suffered a non-fatal reinfarction. Univariate predictors of cardiac death included higher age, redistribution on chest X-ray, in-hospital ventricular fibrillation, diabetes mellitus, high QRS-VDend value, high incidence of transient VCG changes and VCG trend curves suggestive of failed coronaly reperfusion. Multivariate analysis showed that these VCG findings provided additional prognostic information beyond that of other clinical data. A total of 169 patients with acute MI and 73 patients with unstable angina pectoris performed a predischarge exercise test 3 to 13 days after admission.

During follow-up (487±135 days), 19 patients died from cardiac causes and 31 suffered a non-fatal MI. Maximum ST depression at the exercise test was related to the maximum ST depression in vector lead X and to the number of transient VCG changes. In multivariate analysis, high incidence of STC-VM episodes provided additional prognostic information for cardiac death beyond that of exercise test data. VCG monitoring during dobutamine stress echocardiography was performed in 55 patients with unstable angina pectoris and 16 patients with non-Q-wave MI 5 to 8 days after admission. A positive stress test, defined as new or worsening wall motion abnormality, was seen in 37 patients. Patients with a positive stress test showed higher maximum values of QRS-VD, ST-VMand STC-VM than patients with a negative test.

The maximum VCG values were also related to the number of segments showing new or worsening wall motion abnormality. Evaluation of inter- and intra-observer variation of VCG measurements was performed in 60 patients (10 with low probability of IHD, 25 with unstable angina pectoris and 25 with acute Ml). Inter- and intra-observer variations were small, but interpretations of the number of QRS-VD, ST-VM and STC-VM episodes varied between observers. It is concluded that on-line VCG changes may predict ischemia at a predischarge exercise test, are associated with ischemia as assessed by dobutamine stress echocardiography and can be interpreted with low inter- and intra-observer variations. In patients with unstable angina pectoris and acute MI, on-line VCG provides independent prognostic information.