Effect of cardiac resynchronization therapy in patients without left intraventricular dyssynchrony

To evaluate the effects of cardiac resynchronization therapy (CRT) on long-term survival of patients without baseline left ventricular (LV) mechanical dyssynchrony. A total of 290 heart failure patients (age 67 10 years, 77 males) without significant baseline LV dyssynchrony (60 ms as assessed with tissue Doppler imaging) were treated with CRT. Patients were divided according to the median LV dyssynchrony measured after 48 h of CRT into two groups. All-cause mortality was compared between the subgroups. In addition, the all-cause mortality rates of these subgroups were compared with the all-cause mortality of 290 heart failure patients treated with CRT who showed significant LV dyssynchrony (epsilon 60 ms) at baseline. In the group of patients without significant LV dyssynchrony, median LV dyssynchrony increased from 22 ms (inter-quartile range 1634 ms) at baseline to 40 ms (2456 ms) 48 h after CRT. The cumulative mortality rates at 1-, 2-, and 3-year follow-up of patients with LV dyssynchrony epsilon 40 ms 48 h after CRT implantation were significantly higher when compared with patients with LV dyssynchrony 40 ms (10, 17, and 23 vs. 3, 8, and 10, respectively; log-rank P 0.001). Finally, the cumulative mortality rates at 1-, 2-, and 3-year follow-up of patients with baseline LV dyssynchrony were 3, 8, and 11, respectively (log-rank P 0.375 vs. patients with LV dyssynchrony 40 ms). Induction of LV dyssynchrony after CRT was an independent predictor of mortality (hazard ratio: 1.247; P 0.009). In patients without significant LV dyssynchrony, the induction of LV dyssynchrony after CRT may be related to a less favourable long-term outcome.