195 Mechanical dyssyncrony and response to cardiac resynchronization therapy in patients with narrow QRS complex

Abstract

To assess whether LV mechanical dyssynchrony may be used to predict response to CRT in patients with narrow QRS complex (<120 ms). CRT was performed in 183 symptomatic heart failure patients (64 ± 12 years, EF = 25 ± 8%) with narrow (n = 41) and wide QRS complex (n = 142). Mechanical dyssynchrony before CRT implantation was quantified by the 12 segment standard deviation of peak longitudinal strain by speckle tracking (12SD) and the strain delay index (SDI) defined as the sum of difference between end systolic and peak strain across the 16 segments. Before CRT, wide and narrow QRS patients had similar 12SD (100 ± 32 ms vs. 105 ± 35 ms) and SDI (36 ± 14% vs. 38 ± 15%). However, in wide QRS patients, QRS duration decreased after CRT (143 ± 35 ms vs. 120 ± 34 ms, p < 0.0001) and ESV reduction (mean = −21%, ESVR>15% in 66%, 92/139) correlated with SDI (r = 0.41, p < 0.0001) and 12SD (r = 0. 21, p = 0.01) before CRT. In contrast, in narrow QRS population, QRS duration increased after CRT (96 ± 16 ms vs. 108 ± 28 ms, p = 0.006) and ESV reduction (Mean = −11%, ESVR>15% in 39% (25/41) failed to correlate with mechanical dyssynchrony before CRT. Importantly, increase in QRS duration after CRT in narrow QRS population was associated with adverse remodeling (r = 0.43, p = 0.01) and tended to correlate with an increase in SDI after CRT (r = 0.32, p = 0.08). Response to CRT does not correlate to the importance of mechanical dyssynchrony in narrow QRS population. The benefice of CRT despite a significant LV dyssynchrony appears counterbalanced by a significant QRS enlargement after CRT implantation in narrow QRS population.