Myocardial perfusion scintigraphy in left bundle branch block: a perspective on the issue from image analysis in a...

Among selected study populations, myocardial perfusion scintigraphy (MPS) in patients with left bundle branch block (LBBB) has been reported to show a low specificity for the diagnosis of coronary disease. However, the stress electrocardiogram (ECG) is nondiagnostic in this setting. To place this method in its appropriate clinical context, we evaluated MPS in all 69 consecutive patients with LBBB studied with scintigraphy for clinical reasons during a 4-year period. Among 32 patients who underwent coronary angiography for clinical indications, per patient sensitivity, 96%; per vessel sensitivity, 84%, 50%, and 100% for left anterior descending (LAD), left circumflex (LCX), and right coronary artery (RCA) involvement, respectively; and per vessel specificity, 95% and 68% for LCX and RCA disease, respectively, were not significantly different from those previously published for the method in patients without LBBB. Although per patient specificity, 38%, and specificity, 39%, for LAD disease were low, the predictive value of a positive test remained relatively high (83%) owing to the small number of patients selected for angiography, in part based on scintigraphic findings, with normal coronary anatomy. In addition to a possible specific pathophysiologic cause related to LBBB, apparent perfusion abnormalities in the LAD distribution may relate to generic conditions that can make scintigraphic interpretation ambiguous, often in the anterior distribution, regardless of the clinical setting. Additionally, the apparent lack of scintigraphic specificity in the LAD distribution could relate in part to a selection bias toward catheterization of patients with induced scintigraphic abnormalities, especially in the LAD distribution.(ABSTRACT TRUNCATED AT 250 WORDS)