Detection of left anterior descending coronary artery stenosis in patients with left bundle branch block: Exercise, adenosine or dobutamine imaging?

Objectives. This study sought to assess the diagnostic value of myocardial perfusion imaging during exercise and pharmacologic stress in patients with left bundle branch block Background. Patients with left bundle branch block often have septal perfusion defects during exercise perfusion tomography that mimic defects caused by coronary artery disease. These defects appear to be less frequent during pharmacologic stress using adenosine or dipyridamole. Data are scanty on the value of dobutamine tomography in these patients. Methods. We studied 383 consecutive patients with left bundle branch block referred for perfusion scintigraphy over a 5-year span. Perfusion tomogmphy was performed in conjunction with exercise in 206 patients, adenosine in 127 and dobutamine in 50. Coronary angiography was performed within 1 month of the nuclear study in 77, 50 and 27 patients, respectively. Results. Exercise, adenosine and dobutamine tomography had similar sensitivity and specificity for the detection of > 50% stenosis in the left circumflex (74% and 96%; 50% and 1000%; 63% and 91%, respectively) and right coronary arteries (96% and 86%; 82% and 91%; 79% and 100%, respectively) and similar sensitivity for left anterior descending coronary artery stenosis (88%, 79% and 100%, respectively). However, the false-positive rate for septal defects was higher by exercise tomography (26 [46%] of 57) than by pharmacologic methods (5 [10%] of 48, p < 0.001), and there was no significant difference between adenosine (4 [11%] of 35) and dobutamine (1 [8%] of 13, p = 0.7). The specificity and predictive value of a positive test response for left anterior descending coronary artery stenosis were 36% and 51% for exercise compared with 81% and 85% for adenosine (p ≤ 0.001) and 80% and 90% for dobutamine (p < 0.05), respectively. Conclusions. In patients with left bundle branch block, pharmacologic stress is more specific than exercise tomography in the diagnosis of left anterior descending coronary artery stenosis. Dobutamine and adenosine tomography appear to be equally specific in these patients.