Clinical outcomes and predictors of delayed echocardiographic response to cardiac resynchronization therapy

IntroductionThe clinical outcomes and mechanisms of delayed responses to cardiac resynchronization therapy (CRT) remain unclear. We aimed to investigate the differences in outcomes and gain insight into the mechanisms of early and delayed responses to CRT.MethodsThis retrospective study included 110 patients who underwent CRT implantation. Positive response to CRT was defined as >= 15% reduction of left ventricular (LV) end-systolic volume on echocardiography at 1 year (early phase) and 3 years (delayed phase) after implantation. The latest mechanical activation site (LMAS) of the LV was identified using two-dimensional speckle-tracking radial strain analysis.ResultsSeventy-eight (71%) patients exhibited an early response 1 year after CRT implantation. Of 32 non-responders in the early phase, 12 (38%) demonstrated a delayed response, and 20 (62%) were classified as non-responders after 3 years. During the follow-up time of 10.3 +/- 0.5 years, the delayed and early responders had a similar prognosis of mortality and heart failure (HF) hospitalization. In contrast, non-responders had a worse prognosis. Multivariate analysis revealed that a longer duration (months) between initial HF hospitalization and CRT (odds ratio [OR]: 1.126; 95% confidence interval [CI]: 1.036-1.222; p = .005), non-exact concordance of LV lead location with LMAS (OR: 32.744; 95% CI: 1.101-973.518; p = .044), and pre-QRS duration (OR: 0.901; 95% CI: 0.827-0.981; p = .016) were independent predictors of delayed response to CRT compared with early response.ConclusionThe prognoses were similar regardless of the response time after CRT. A longer history of HF, suboptimal LV lead position, and shorter pre-QRS duration were related to delayed response than early response. A total of 38% of patients who did not exhibit an echocardiographic response 1 year after CRT implantation experienced a positive response after 3 years. Delayed responders had a similar prognosis of all-cause death and HF hospitalization rates as early responders. Predictors of delayed response compared with early response were a longer duration from initial HF hospitalization to CRT, the non-exact concordant LV lead location to the latest mechanical activation site, and shorter pre-QRS duration.image