Are changes in the extent of left ventricular dyssynchrony as assessed by speckle tracking associated with response to cardiac resynchronization therapy?

Echocardiographic assessment of left ventricular (LV) dyssynchrony is used to predict response to cardiac resynchronization therapy (CRT). However, the association between reduction in the extent of speckle tracking based LV-dyssynchrony and echocardiographic response to CRT has not been explored yet. The aim of this study was to assess the changes in the extent of LV dyssynchrony as a result of CRT and its association with echocardiographic response to CRT in a large consecutive series of patients. We studied 138 patients with standard CRT indication. Time-based speckle tracking longitudinal strain (maximal delay between 6-segments in 4-chamber view) was performed to assess LV-dyssynchrony at baseline and after a mean follow-up of 22 ± 8 months. Echocardiographic CRT response was defined as a reduction in LV end-systolic volume ≥15 %. Mean age was 68 ± 8 years (30 % female). Mean LV ejection fraction (LVEF) was 26 ± 7 %. Ninety six patients (70 %) were classified as echocardiographic responders. In the total study group, LV-dyssynchrony decreased from 196 ± 89 ms at baseline to 180 ± 105 ms during follow-up, P = 0.01. Of note, in responders there was a pronounced reduction in LV dyssynchrony (198 ± 88 ms at baseline vs 154 ± 50 ms after CRT, P < 0.001), whereas in non-responders there was a significant increase (191 ± 92 ms at baseline vs 243 ± 160 ms after CRT, P = 0.04). After multivariate analysis, decreased in LV-dyssynchrony, wider QRS duration and non-ischemic etiology were independently and significantly associated with CRT response. Changes in the extent of LV dyssynchrony as measured by speckle tracking after CRT are independently associated with response to CRT.