The noninvasive diagnosis of coronary artery disease in patients with left bundle-branch block.

The prognosis in patients with left bundle-branch block (LBBB) is related primarily to the presence or absence of underlying cardiac disease. Because coronary artery disease (CAD) is the most common underlying disease found in these patients, it would be desirable, in the presence of LBBB, to have a noninvasive method of differentiating between patients with and without CAD. We reviewed our experience in patients with LBBB who had undergone coronary arteriography with regard to electrocardiographic (ECG) stress testing, exercise radionuclide ventriculography (RNV), and exercise thallium scintigraphy; we also reviewed their clinical histories. A clinical history of typical angina pectoris was specific for CAD, a false-positive history being present in only one of 12 patients without CAD. The frequency of a positive ECG ST response to exercise was equal in patients with and without CAD. False-positive ejection fraction and wall-motion responses to exercise were frequent by RNV. A modification of the usual RNV criteria for positivity improved specificity but resulted in poor sensitivity for CAD. False-positive thallium study results also were. frequent in these patients. The perfusion defects usually involved the ventricular septum; the inferior and posterior walls were involved only in patients with CAD. We conclude that the usual noninvasive diagnostic tests for CAD are of limited value in patients with LBBB.