Abstract
Background
Cardiac resynchronization therapy (CRT) improves survival in patients with heart failure, reduced ejection fraction (HFrEF) and left bundle branch block (LBBB). However, little is known about the incidence of LBBB in HFrEF and the risk factors for developing this. We addressed these questions in the PARADIGM-HF and ATMOSPHERE trials.
Methods
We identified 7703 patients with a non-paced rhythm on their baseline ECG, a QRS<130 ms, and at least one follow-up ECG (done at annual visits and end of study). Patients were stratified by baseline QRS duration (≤100 ms - reference; 101–115 ms and 116–129 ms) and followed until development of QRS duration ≥130 ms with a LBBB configuration or latest available ECG. The crude LBBB incidence rate per 100 person-years (py) was identified in the three QRS duration subgroups. Additionally, we examined risk of the primary composite outcome of cardiovascular death or HF hospitalization, and all-cause mortality, in patients with incident LBBB vs. no incident LBBB.
Results
Overall, 313 of 7703 patients (4%) developed LBBB during a mean follow-up of 2.7 years, yielding an incidence rate of 1.5 per 100 py. The rate ranged from 0.9 in those with QRS ≤100 ms to 4.0 per 100 py in patients with QRS 116–129 ms. Other predictors of incident LBBB included male sex, age, lower LVEF, HF duration and absence of AF. The risk of the primary composite endpoint was higher among those who developed incident LBBB vs no incident LBBB; event rates 13.5 vs 10.0 per 100 py, yielding an adjusted HR of 1.43 (1.05–1.96). For all-cause mortality the corresponding rates were 12.6 vs 7.3 per 100 py; HR 1.55 (1.16–2.07) (Table 1).
Table 1. Risk of outcomes according to incident LBBB during follow-up No. events Crude rate per 100py Adjusted* HR (95% CI) HF hospitalization or CV death No incident LBBB 2145 10.0 (9.6–10.4) 1.00 (ref.) Incident LBBB 43 13.5 (10.0–18.2) 1.43 (1.05–1.96) All-cause mortality No incident LBBB 1662 7.3 (6.9–7.6) 1.00 (ref.) Incident LBBB 48 12.6 (9.5–16.7) 1.55 (1.16–2.07)
Conclusion
Among patients with HFrEF, the annual incidence of new-onset LBBB (and a potential indication for CRT), was around 1.5%, ranging from 1% in those with QRS duration below 100 ms to 4% in those with QRS 116–129 ms. Incident LBBB was associated with a much higher risk of adverse outcomes, highlighting the importance of repeat ECG monitoring in patients with HFrEF.
Acknowledgement/Funding
Novartis
Three dimensional echocardiography documents haemodynamic improvement by biventricular pacing in patients with severe heart failure