Age, prognostic impact of QRS prolongation and left bundle branch block, and utilization of cardiac resynchronization therapy: findings from 14,713 patients in the Swedish Heart Failure Registry

Age is not a contraindication to cardiac resynchronization therapy (CRT), but the prevalence and prognostic impact of QRS prolongation with intraventricular conduction delay (IVCD) and left bundle branch block (LBBB), as well as CRT utilization, may differ with age. We tested the hypotheses that in the elderly: (i) IVCD and LBBB are more prevalent, (ii) IVCD and LBBB are more harmful, and (iii) CRT is underutilized.We studied 14 713 patients with ejection fraction ≤39% in the Swedish Heart Failure Registry and divided into age groups ≤65 years, 66-80 years and80 years. Among 13 782 patients without CRT, IVCD was present in the three age groups in 11% vs. 15% vs. 19% and LBBB was present in 20% vs. 27% vs. 28%, respectively, (P 0.001). The multivariable hazard ratio (HR) for all-cause mortality over a median (interquartile range) follow-up of 29 (12-53) months for IVCD vs. narrow QRS was 1.31 (1.06-1.63, P = 0.013) in the ≤65 year group, 1.32 (1.17-1.47, P 0.001) in the 66-80 year group, and 1.26 (1.21-1.41, p 0.001) in the80 year group. For LBBB vs. narrow QRS it was 1.29 (1.07-1.56, P = 0.009), 1.17 (1.06-1.30, P = 0.002), and 1.10 (0.99-1.22, P = 0.091), respectively. The adjusted P for interaction between age and QRS morphology was 0.664. In the three age groups, CRT was present in 6% vs. 8% vs. 4% and absent but with indication in 23% vs. 32% vs. 37%, respectively (P 0.001).Both IVCD and LBBB were more common with increasing age and were similarly strong independent predictors of mortality and in all ages. The underutilization of CRT was worse with increasing age.