Po-02-015 the impact of gender and lv size on cardiac resynchronization therapy response

Multiple studies have reported that female gender is predictive of positive response to cardiac resynchronization therapy (CRT). However, the mechanisms underlying this association remain unclear. We aimed to examine the association between gender and echocardiographic CRT response (reduction in LV end systolic volume (LVESV) >15% at 6 months), in patients recruited to the MORE-CRT MPP study. MORE-CRT MPP is a prospective, randomized, multicenter study. All patients initially receive conventional biventricular (BiV) CRT for 6 months. At this stage, echocardiographic non-responders are randomized to either continued conventional BiV pacing, or MultiPoint pacing. This post-hoc analysis examined predictors of initial response to 6 months of BiV pacing only. We performed univariable models using baseline variables. Multivariable models were conducted using stepwise model selections (n = 2,866). The criteria for baseline variables entering and staying into model was α=0.25 and α=0.05, respectively. Age and gender were forced into the model. Of 3739 patients in the analysis, 28% were female. The cardiac size in females was significantly smaller compared to males (175.8±60.3ml vs. 228.3±76.9ml, p<0.0001). Males had a significantly broader QRSd than females (157.7±26.1ms vs. 152.3±22.1ms, p<0.0001). The logistic regression model showed that: no history of AF, non-ischemic aetiology, left bundle branch block (LBBB), smaller heart (↓LVEDV), wide QRSd, no history of renal disease, and female gender are significant independent predictors for CRT response (see table). In a separate model, QRSd/LVEDV ratio was a significant response predictor in a univariable analysis, but not in multivariable analysis with gender included in the model (OR 1.21 95% CI 0.89-1.63, p=0.22). Female gender is a significant predictor of superior CRT response. This association is independent from variables including: AF, aetiology, LBBB and QRSd. However, QRSd/LVEDV, a ratio measuring dyssynchrony relative to heart size, was not independently predictive of response when gender is included in the multivariable analysis. This suggests that the female superiority of CRT response may be related to a higher degree of relative dyssynchrony (higher QRSd/LVEDV ratio). Female patients may benefit from a lower QRSd cut-off when considering their suitability for CRT, based on a smaller heart size, and thus a higher degree of relative dyssynchrony at a given QRSd.