ISCHEMIA MONITORING WITH ONLINE VECTORCARDIOGRAPHY DURING DOBUTAMINE STRESS ECHOCARDIOGRAPHY IN PATIENTS AFTER AN EPISODE OF UNSTABLE CORONARY-ARTERY DISEASE

Objectives. This study investigated the ability of online vectorcardio graphy (VCG) to detect myocardial ischaemia as assessed by dobutamine stress echocardiography after an episode of unstable coronary artery d isease. Design. Dobutamine stress test (incrementally infused doses of 5, 10, 20, 30 and 40 mu g kg(-1) per minute) was performed during sim ultaneous VCG monitoring. QRS vector difference (QRS-VD), ST vector ma gnitude (ST-VM), ST change vector magnitude (STC-VM) and T change vect or magnitude (TC-VM) were monitored. A new wall motion abnormality or worsening of abnormal wall motion was regarded as indicating a positiv e dobutamine stress test. Subjects. Fifty-five patients with unstable angina pectoris and 16 patients with an acute non-Q-wave myocardial in farction were studied 5-8 days after admission. Results. A positive do butamine stress test was observed in 37 patients (52%). The sensitivit y, specificity and total accuracy of identifying patients with a posit ive dobutamine stress test by VCG were: 38%, 91% and 63% for QRS-VD; 5 9%, 88% and 73% for ST-VM; 84%, 79% and 82% for STC-VM; and 86%, 23% a nd 56% for TC-VM. Patients with a positive dobutamine stress test show ed higher maximum VCG values than patients with a negative dobutamine stress test (SRS-VD, P < 0.01; ST-VM, P < 0.001; STC-VM, P < 0.001). T he maximum VCG values were related to the number of segments showing n ew or worsening wall motion abnormality (QRS-VD: r = 0.41, P < 0.001; ST-VM: r = 0.44, P < 0.001; STC-VM: r = 0.57, P <0.001). Conclusion. S TC-VM and ST-VM seem to be the best VCG variables for detection of myo cardial ischaemia as assessed by dobutamine stress echocardiography.