Ischaemia monitoring with on‐line vectorcardiography during dobutamine stress echocardiography in patients after an episode of unstable coronary artery disease

Abstract

Abstract. Lundin P, Eriksson SV, Andrén B, Lindahl B, Tornvall P, Melcher A (Danderyd Hospital, Danderyd, University Hospital, Uppsala, Karolinska Hospital, Stockholm, Sweden). Ischaemia monitoring with on‐line vectorcardiography during dobutamine stress echocardiography in patients after an episode of unstable coronary artery disease. J Intern Med 1998; 244: 61–70.ObjectivesThis study investigated the ability of on‐line vectorcardiography (VCG) to detect myocardial ischaemia as assessed by dobutamine stress echocardiography after an episode of unstable coronary artery disease.DesignDobutamine stress test (incrementally infused doses of 5, 10, 20, 30 and 40 μg kg−1 per minute) was performed during simultaneous VCG monitoring. QRS vector difference (QRS‐VD), ST vector magnitude (ST‐VM), ST change vector magnitude (STC‐VM) and T change vector magnitude (TC‐VM) were monitored. A new wall motion abnormality or worsening of abnormal wall motion was regarded as indicating a positive dobutamine stress test.SubjectsFifty‐five patients with unstable angina pectoris and 16 patients with an acute non‐Q‐wave myocardial infarction were studied 5–8 days after admission.ResultsA positive dobutamine stress test was observed in 37 patients (52%). The sensitivity, specificity and total accuracy of identifying patients with a positive dobutamine stress test by VCG were: 38%, 91% and 63% for QRS‐VD; 59%, 88% and 73% for ST‐VM; 84%, 79% and 82% for STC‐VM; and 86%, 23% and 56% for TC‐VM. Patients with a positive dobutamine stress test showed higher maximum VCG values than patients with a negative dobutamine stress test (QRS‐VD, P < 0.01; ST‐VM, P < 0.001; STC‐VM, P < 0.001). The maximum VCG values were related to the number of segments showing new 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).ConclusionSTC‐VM and ST‐VM seem to be the best VCG variables for detection of myocardial ischaemia as assessed by dobutamine stress echocardiography.