Effect of cardiac resynchronization therapy in patients without left intraventricular dyssynchrony

Abstract

Aims: To evaluate the effects of cardiac resynchronization therapy (CRT) on long-term survival of patients without baseline left ventricular (LV) mechanical dyssynchrony.

Methods and results: 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 (≥60 ms) at baseline. In the group of patients without significant LV dyssynchrony, median LV dyssynchrony increased from 22 ms (inter-quartile range 16-34 ms) at baseline to 40 ms (24-56 ms) 48 h after CRT. The cumulative mortality rates at 1-, 2-, and 3-year follow-up of patients with LV dyssynchrony ≥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).

Conclusion: In patients without significant LV dyssynchrony, the induction of LV dyssynchrony after CRT may be related to a less favourable long-term outcome.

Figure 1

Assessment of LV dyssynchrony at baseline, 48 h after implantation, and at 6-month follow-up in patients without baseline LV dyssynchrony. At baseline, all patients showed LV dyssynchrony <60 ms [22 ms (inter-quartile range: 16–34 ms)]. At 48 h after cardiac resynchronization therapy implantation, LV dyssynchrony increased to 40 ms (inter-quartile range: 24–56 ms) and at 6-month follow-up remained unchanged [40 ms (inter-quartile range: 24–67 ms)] (P< 0.001).

Figure 2

The Kaplan–Meier estimates of time to all-cause mortality in patients without induced left ventricular dyssynchrony (n= 145) and induced left ventricular dyssynchrony (n= 145) and control group (baseline left ventricular dyssynchrony ≥60 ms, n= 290). LV, left ventricular. *Log-rank P < 0.001 vs. left ventricular dyssynchrony <40 ms.