New York Heart Association functional class, QRS duration, and survival in heart failure with reduced ejection fraction: implications for cardiac resychronization therapy

Abstract

Aims: Symptom severity assessed by NYHA functional class and QRS duration are essential criteria for selection of heart failure (HF) patients for CRT. This study assessed the relationship between NYHA class, QRS duration, and survival in a nationwide HF registry.

Methods and results: We studied 13 423 patients with HF in NYHA class II-IV and LVEF <40% in the Swedish Heart Failure Registry. Survival was followed via the Swedish Population Registry. Of 12 534 patients without CRT (age 71 ± 12 years, 29% women), 51% and 49% were in NYHA class II and III-IV, respectively. Patients in NYHA class II compared with class III-IV were younger (69 vs. 73 years), and had a better systolic function (49% vs. 58% with LVEF <30%), P <0.001 for all, and a favourable co-morbidity profile. QRS duration was 116 ± 29 ms in NYHA class II and 119 ± 29 ms in NYHA class III-IV with QRS ≥120 ms found in 37% vs. 44%, and an LBBB in 23% vs. 28% (P < 0.001 for all). Upon multivariable Cox regression adjusting for 40 clinically relevant variables, mortality risk was higher in NYHA class III-IV vs. class II, with a hazard ratio (HR) of 1.31, 95% confidence interval (CI) 1.23-1.40. Mortality was also higher with QRS prolongation ≥120 ms vs. narrow QRS. The HR in NYHA class II patients with non-LBBB was 1.19 (95% CI 1.05 - 1.36) and in those with LBBB it was 1.16 (95% CI 1.03-1.41). The corresponding HRs in NYHA class III-IV were 1.33 (95% CI 1.21-1.47) and 1.12 (95% CI 1.02-1.22). There was no significant interaction between the effects of NYHA class and QRS duration or morphology on mortality. Applying different scenarios to estimate guideline adherence, fewer patients with NYHA class II (range 14.4-42.6%) compared with NYHA class III-IV (18.0-45.4%) had received a CRT device when indicated.

Conclusions: In HF with reduced LVEF, QRS prolongation is common and independently linked to worse survival. The increase in mortality risk associated with QRS prolongation of both LBBB and non-LBBB morphology is similar in NYHA class II and III-IV.

Keywords: Cardiac resynchronization therapy; Epidemiology; Heart failure; Left bundle branch block; NYHA functional class; QRS width.