Cardiac resynchronization therapy in heart failure based on Strauss criteria for left bundle branch block

The left bundle branch block (LBBB) is a strong predictor of response to cardiac resynchronization therapy (CRT). However, a significant number of patients do not respond to the treatment. The study sought to evaluate the impact of the stricter Strauss criteria for left bundle branch block (St-LBBB) on CRT response, hospitalizations, ventricular arrhythmia (VA) events and mortality.

This study is a retrospective analysis of prospectively collected data on heart failure (HF) patients with LBBB admitted for CRT implantation. Patients were divided into two groups according to the fulfilment or not of St-LBBB criteria.

The study included 82 patients with ischaemic (ICM) and non-ischaemic (NICM) cardiomyopathy [46 (56%) with St-LBBB and 36 (44%) with non-St-LBBB]. Patients with St-LBBB showed higher CRT response rates compared with those with non-St-LBBB (P < 0.01), while the group with NICM exhibited the greatest benefit (P < 0.01). St-LBBB CRT responders displayed significantly lower rates of HF hospitalization (P < 0.0001) compared with the non-St-LBBB group. According to Kaplan-Meier time curves, this was primarily evident in patients with NICM (P < 0.0001). CRT responders displayed significantly fewer VA events (P < 0.001) and lower mortality rates (P < 0.0001) than non-responders. Kaplan-Meier estimates demonstrated a significantly lower incidence of VAs in NICM patients with St-LBBB (P = 0.049) compared with ICM patients with St-LBBB (P = 0.25). Lower mortality rates were observed in CRT responders than non-responders (P < 0.0001), with the group of NICM with St-LBBB criteria exhibiting the greatest benefit (P = 0.0238).

Patients with NICM and St-LBBB present the greatest benefit concerning CRT response, HF hospitalizations, VA events and mortality. Although St-LBBB criteria seem to improve patient selection for CRT, more data are needed to elucidate the role of St-LBBB criteria in this setting.