Value of exercise vectorcardiography and exercise radionuclide ventriculography in identification of coronary arterial disease in patients with left bundle branch block

Abstract

Twelve patients (8 male and 4 female, age ranged 39 – 60 years) with suspected coronary arterial disease with left bundle branch block were evaluated for ischemia by simultaneous exercise vectorcardiography and radionuclide-ventriculography. Selective coronary angiography revealed normal coronary arteries in 5 and significant coronary arterial disease in 7 patients. Radionuclide ventriculography revealed no significant difference in resting left ventricular ejection fraction in patients with normal coronary arteries (44.0 ± 13.9%) and coronary arterial disease (45.7 ± 11.9%). Exercise radionuclide ventriculography showed positive response suggestive of ischemia in 11 patients ( 11 12 ), including all 5 with normal coronary arteries and 6 7 with coronary arterial disease. The magnitude of spatial ‘R’ maximum cardiac vector in both groups at rest (normal coronary arteries: 1.61 ± 0.22 mV, coronary arterial disease: 1.63 ± 0.35 mV) did not show any significant difference. On exercise, the magnitude of spatial ‘R’ maximum cardiac vector uniformly increased in patients with normal coronary arteries (1.61 ± 0.22 to 1.75 ± 0.25 mV, P < 0.01) and decreased in 6 and remained unchanged in 1 patient with coronary arterial disease (1.63 ± 0.35 to 1.34 ± 0.46 mV, P < 0.01). There was no change in rotational characteristics of QRS and T loops at end exercise in either group. Our preliminary observations indicate that exercise induced alteration of the magnitude of the maximal spatial ‘R’ cardiac vector appears to be an useful parameter to diagnose underlying coronary arterial disease in patients with left bundle branch block. Having a high false positive response, exercise radionuclide ventriculography appears to be of limited value in these patients.