REPRODUCIBILITY OF ONLINE VECTORCARDIOGRAPHY MEASUREMENTS IN PATIENTSWITH AND WITHOUT ACUTE ISCHEMIC-HEART-DISEASE

Objectives. The aim of the present study was to determine inter and in traobserver Variations of measurements with on-line vectorcardiography (VCG). Design. The VCG registrations were evaluated by two independen t observers. One observer also evaluated the VCG registrations on two separate occasions. Monitored VCG variables were: ST vector magnitude (ST-VM), ST vector lead X (ST-X), ST change vector magnitude (STC-VM) and QRS vector difference (QRS-VD). Subjects: On-line VCG was performe d for 24 hours in 60 patients (10 with low probability of ischaemic he art disease, 25 with unstable angina pectoris and 25 with acute myocar dial infarction). Results. A close correlation between the two observe rs and small coefficients of variation were found regarding the ST-VM initial value (r = 0.99, 4.7), the ST-X maximum depression (r = 0.99, 3.2) and the QRS-VD end value (r = 0.98, 5.6). A less close correlatio n and higher coefficients of variation were found regarding the number of QRS-VD episodes (r = 0.94, 41.5), ST-VM episodes (r = 0.89, 37.8) and STC-VM episodes (r = 0.87, 35.1). Correlation coefficients and coe fficients of variations for VCG measurements performed on two separate occasions by one observer ranged from 0.97 to 0.99 and from 18.1 to 1 .8 respectively. Three (12%) of 25 patients with acute myocardial infa rction did not meet the VCG infarction criterion (QRS-VD greater than or equal to 15 mu Vs) by both observers. In addition, five (20%) of th e 25 patients with unstable angina pectoris met the VCG infarction cri terion by both observers. Conclusion. The inter and intraobserver vari ation for VCG interpretations was low, but the number of QRS-VD, ST-VM and STC-VM episodes varied between the two observers. This finding su ggests that additional training may improve the results. Caution is al so recommended in using VCG to rule out or establish the diagnosis of acute myocardial infarction.