On-line vectorcardiography in ischemic heart disease

Sammanfattning: ON-LINE VECTORCARDIOGRAPHY IN ISCHEMIC HEART DISEASEPeter Lundin, KAROLINSKA INSTITUTET, DANDERYD HOSPITAL, Division of IntemalMedicine, S-182 88, Danderyd, Sweden The clinical usefulness of continuous on-line vectorcardiography (VCG) was assessed in 435patients, admitted to the coronary care unit. The ability of 24-hour VCG monitoring todifferentiate patients with or without ischemic heart disease (IHD), to provide long-temmprognostic information and to predict results from a predischarge exercise test in patients withunstable angina pectoris or acute myocardial infarction (MI) was evaluated. Findings fromdobutamine stress echocardiography during simultaneous VCG monitoring and the inter- andintra-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 andfewer transient VCG changes (QRS-VD, ST-VM and STC-VM episodes) than patients withIHD. Patients with unstable angina pectoris (n=15) had a higher number of transient VCGchanges 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 cardiaccauses and 8 suffered a non-fatal MI. Univariate predictors of cardiac death or non-fatal MIincluded higher age, rest pain during hospitalization, diabetes mellitus and high incidence oftransient 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 and30 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 failedcoronaly reperfusion. Multivariate analysis showed that these VCG findings provided additionalprognostic information beyond that of other clinical data. A total of 169 patients with acute MI and 73 patients with unstable angina pectoris perfommeda predischarge exercise test 3 to 13 days after admission. During follow-up (487±135 days), 19patients died from cardiac causes and 31 suffered a non-fatal MI. Maximum ST depression atthe exercise test was related to the maximum ST depression in vector lead X and to the numberof transient VCG changes. In multivariate analysis, high incidence of STC-VM episodesprovided additional prognostic information for cardiac death beyond that of exercise test data. VCG monitoring during dobutamine stress echocardiography was perfommed in 55 patientswith 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 abnommality, was seen in 37patients. 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 relatedto the number of segments showing new or worsening wall motion abnommality. Evaluation of inter- and intra-observer variation of VCG measurements was performed in 60patients (10 with low probability of IHD, 25 with unstable angina pectoris and 25 with acuteMl). 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 beinterpreted with low inter- and intra-observer variations. In patients with unstable angina pectorisand acute MI, on-line VCG provides independent prognostic information.Key words: Vectorcardiography, ischemia monitoring, coronary artery disease, exercise test,echocardiography, dobutamine, unstable angina pectoris, myocardial infarction, prognosis.ISBN 91-628-1764-7