Discontinuous contraction in the left ventricle assessed by 2-D speckle tracking echocardiography benefits from CRT.

Abstract

Cardiac resynchronization therapy (CRT) improves the morbidity and mortality rate in patients with left bundle-branch block (LBBB); however, some LBBB patients are non-responders for CRT. Previous studies have shown that a transmural functional line block alters the left ventricular (LV) activation sequence, and that the presence of a line block is predictive for responders. We investigated whether responders could be predicted in patients with LBBB by 2-dimensional (2-D) speckle tracking strain imaging. We enrolled 54 patients with LBBB, who underwent echocardiography before and 6 months after CRT implantation. A responder was defined by a decrease in the LV end-systolic volume>15% at the 6-month follow-up. We calculated a difference in the time from QRS onset to maximum strain between adjacent segments and defined the Tmax-diff as the maximum difference among six intersegments. We compared the Tmax-diff between responders and non-responders. Among 54 patients, 37 patients were identified as responders. The Tmax-diff of the responders was significantly longer than that of the non-responders (309.6 ± 168.6ms vs 181.5 ± 138.4ms, P=.009). Furthermore, Tmax-diff ≥ 195ms was higher in the septal and the anterior area. And patients with a Tmax-diff ≥ 195ms tended to be responders (P=.02). The present study showed that discontinuous contraction of the LV could be detected in CRT responders by 2-D speckle tracking strain imaging, which may be a useful tool to identify the contraction pattern of patients with LBBB and predict CRT responders.