Abstract 4347: Comparison of Dyssynchrony in Heart Failure Patients with Narrow QRS to Those with Wide QRS: Implications for Resynchronization Therapy

Background Although cardiac resynchronization therapy (CRT) has been clearly shown to benefit patients with wide QRS, its use for patients with narrow QRS is currently unclear. Our objective was to test the hypothesis that there are significant differences in the prevalence and severity of dyssynchrony in heart failure patients with narrow QRS compared to wide QRS. Methods We studied 310 class III-IV heart failure (HF) patients with ejection fraction ≤35% referred for CRT and/or implantable cardioverter defibrillator; 168 had QRS ≥120 ms and 142 had QRS <120 ms. Overall, 59% had ischemic disease. Dyssynchrony was assessed by tissue Doppler longitudinal velocity opposing wall delay (OWD), speckle tracking radial strain, pulsed Doppler interventricular mechanical delay (IVMD) and pre-ejection delay (PED). Results Overall, the prevalence of interventricular dyssynchrony (IVMD> 40 ms) was significantly less (5%) in narrow QRS patients compared with 38% in wide QRS patients (p<0.001). Global dyssynchrony by IVMD and PED significantly correlated with QRS width (r=0.54 and r=0.58, p<0.001). The degree of radial dyssynchrony was also significantly less in the narrow QRS patients:118±93 versus 204±118 ms in the wide QRS patients (p<0.001). Interestingly, TDI opposing wall delay was not significantly different in narrow vs wide QRS groups. Conclusions Narrow QRS HF patients have significantly less prevalent and less severe interventricular and intraventricular radial dyssynchrony, compared with those with wide QRS. However, TDI measures were similar in both groups. These findings may impact future CRT considerations. ![][1] [1]: /embed/graphic-1.gif