The effect of CRT in non-LBBB
In contemporary practice, the use of CRT in non-LBBB patients remains controversial, mainly due to high rates of non-response among such patients. In previous studies, PR prolongation was identified as a strong predictor for CRT response in non-LBBB patients. Interestingly, in our study PR prolongation did not predict the occurrence of VTA, or VTA and death. However the mechanism in which CRT reduces heart failure hospitalization is entirely distinctive than the mechanism in which CRT may be proarrhythmic. In our study, with the utilization of simple RF, we were able to identify a large group of patients without RF, in whom CRT is potentially beneficial and may be associated with an antiarrhythmogenic effect. This group of non-LBBB patients may therefore derive benefit from treatment with cardiac resynchronization therapy. In contrast, in non-LBBB patients with ≥ 1 RF, implantation of CRT-D was associated with increased risk of VTA, VTA or death, and appropriate defibrillator shocks, suggesting a possible proarrhytmic effect. Thus, this group of non-LBBB patients may experience improved outcomes with ICD therapy alone rather than combined with cardiac resynchronization therapy.