Revisiting diastolic filling time as mechanistic insight for response to cardiac resynchronization therapy

Abstract

Intraventricular dyssynchrony and commonly associated prolonged atrioventricular conduction both reduce diastolic filling time (DFT), which can be improved by cardiac resynchronization therapy (CRT). Our aim was to investigate whether change in DFT corrected for RR interval (DFTC) after CRT might serve to assess the mechanistic response to CRT. Echocardiography data of consecutive patients in sinus rhythm (n = 91) were studied before and 6 months after implantation. Mortality and heart failure hospitalization data were collected. Patients with vs. without DFTC increase after 6 months were compared. The programmed atrioventricular delay, percentage of biventricular pacing, and change in PR interval were similar in both groups. DFTC increase after 6 months reflected favourable reverse left ventricular remodelling and was significantly associated with freedom from death or heart failure admission (P = 0.008). In multivariate analysis including guideline criteria for CRT (i.e. QRS width, presence of left bundle branch block, and ejection fraction), interventricular mechanical delay, and Tei index, baseline DFTC was the strongest predictor of adverse outcome. Notably, while patients with impaired relaxation had a large and highly significant reduction in all-cause mortality and heart failure admissions when DFTC increased [hazard ratio (HR), 95% confidence interval (CI) = 0.24, 0.08-0.73; P = 0.012], this benefit was less pronounced and did not reach statistical significance in patients with pseudonormal or restrictive filling (HR, 95% CI = 0.64, 0.23-1.77; P = 0.388). DFTC increase after CRT reflects favourable reverse remodelling and is associated with better clinical outcome.