The incidence and outcomes of delayed response to cardiac resynchronization therapy.

Background: The incidence and clinical outcomes of delayed response to cardiac resynchronization therapy (CRT) have not been well clarified. We aimed to observe the incidence and prognosis of delayed response and to identify its possible mechanisms.

Methods: A total of 115 CRT patients were retrospectively analyzed in our study. Patients who met the enrollment criteria were divided into two groups: group A, conventional responders who showed response at 1-year follow-up, and group B, delayed responders who showed response after 1-year follow-up. CRT response was defined as an absolute increase of ≥10% in left ventricular ejection fraction.

Results: Fifty-two patients (61 ± 12 years, 37 male) experienced conventional response to CRT and 17 patients (63 ± 11 years, 10 male) experienced delayed response. The mean follow-up time was 5.2 ± 2.4 years. The incidence of delayed response was 14.8% (17/115). All-cause mortality and hospitalization rates for heart failure were similar for delayed and conventional responders. Multivariate logistic regression analysis revealed that scar burden > 35% was an independent predictor of CRT delayed response (odds ratio 8.794, P  =  0.038).

Conclusions: A significant proportion of patients demonstrated delayed response to CRT. The delayed responders had a good prognosis that was similar to that of conventional responders. More scar burden might be related to the incidence of delayed response.