Left bundle branch block with and without coronary artery disease: Which value for a tissue Doppler-derived post-systolic motion?

Background. An asynchronous contraction occurring during a prolonged relaxation period, defined as post-systolic motion (PSM), has been described as being a consequence of coronary occlusion but also in other conditions including isolated left bundle branch block (LBBB). The aim of this study was to characterize PSM of the interventricular septum at pulsed tissue Doppler in LBBB with or without stenosis of the left anterior descending coronary artery (LAD). Methods. Forty-two patients with chronic, complete LBBB and tissue Doppler-derived septal PSM were divided into two groups on the basis of their coronary angiography: 27 without LAD stenosis and 15 with LAD stenosis (≥ 50%). Standard Doppler echocardiography and tissue Doppler of both the middle posterior septum and lateral mitral annulus were performed in the apical 4-chamber view. Results. Standard Doppler diastolic indexes were comparable between the two groups. Septal tissue Doppler showed lower myocardial systolic (S_m) and atrial peak velocities (both p < 0.05), a higher PSM (p < 0.005), and a longer relaxation time (p < 0.02) and pre-contraction time (p < 0.05) in patients with LAD stenosis. A Sm/ PSM ratio < 1 was detected in 86% of patients with LAD stenosis and in 22% without LAD stenosis (sensitivity 73%, specificity 77%, positive predictive value 64%, negative predictive value 84%). Tissue Doppler of the mitral annulus showed a significantly longer relaxation time and pre-contraction time and a lower atrial velocity in the presence of LAD stenosis. In the overall population, PSM was positively associated with ejection fraction and negatively with age and septal thickness. In a multiple linear regression analysis, only LAD stenosis (ß = 0.42, p < 0.005) and ejection fraction (ß = 0.32, p = 0.03) were independent predictors of PSM (cumulative r² = 0.27, p < 0.002). Conclusions. Tissue Doppler may be useful to distinguish septal myocardial asynchrony in LBBB with and without LAD stenosis.