QRS width variation as a marker of prognosis after CRT implantation: getting slimmer is getting better

Abstract Introduction Cardiac resynchronization therapy (CRT) is a major therapeutic tool in the management of patients with systolic heart failure. However, controversy remains regarding who will most benefit from this device. The aim of the present study was to evaluate the impact of QRS duration on echocardiographic response and clinical outcomes. Methods We conducted a retrospective, observational, single-center study of patients submitted to CRT implantation. Only patients with electro and echocardiographic data on baseline and follow-up were included. CRT response was defined as an improvement of LVEF >10% or LVESV>5%. CRT superresponse was defined as an improvement of LVEF above the population 4th quartile (18%). Impact of QRS variables on CRT response was evaluated with ROC curve analysis. Clinical outcomes were defined as hospitalizations due to heart failure and all-cause mortality. Impact of QRS on clinical endpoints, response and superresponse was evaluated with survival analysis. Results From a total of 654 pts a total of 245 fulfilled the inclusion criteria. (57,3%% female, mean age). Most of the pts had a non-ischemic etiology (61,5%) and atrial fibrillation was present in 29.4%. The QRS characteristics were the following, baseline: 162+21ms, follow-up 159+28ms, mean QRS variation: 3+29ms. CRT response occurred in 69% of the pts and superresponse in 26%. QRS variation is the best predictor of CRT response (AUC =0,66, 95%CI 0,58-0,74, p<0,001). Interestingly, a QRS reduction above 8ms presented the best accuracy (S:70%;E:57%) for response to CRT. On multivariate analysis, after adjustment for gender, atrial fibrillation and cardiopathy etiology, only a QRS reduction above 8ms (p 0.028, HR 1.974 CI (1.075-3.623) and lower baseline LVEF (p = 0.02, 95% CI 0.943 (0.909-0.979) were significant independent predictors of CRT superresponse. Additionally, a QRS reduction higher than 8ms was a protective factor for long-term clinical outcomes during follow-up (p<0.001 HR (2,445) 1,553 a 3,849) – fig.1. Conclusion In pts with implanted CRT a reduction in QRS width, as small as 8ms, its a marker of improved LV function and a better clinical prognosis.