Cardiac resynchronization therapy (CRT) non-responders in the contemporary era. a state-of-the-art review

: Since 2000s CRT became a revolutionary therapy for heart failure with reduced left ventricular ejection fraction (HFrEF) and wide QRS. However, about one third of CRT recipients do not show a favorable response. This review of current literature aims to better define the concept of CRT response/non-response. The diagnosis of CRT non-responder should be viewed as a continuum, and it cannot rely solely on a single parameter. Moreover, several patients' baseline features might predict an unfavorable response. A strong collaboration between HF specialists and electrophysiologists is key to overcoming this challenge with multiple strategies. In the contemporary era, new pacing modalities, such as His bundle pacing (HBP) and left bundle branch area pacing (LBBAP) represent a promising alternative to CRT. Observational studies demonstrated their potential; however, several limitations should be addressed. Large randomized controlled trials are needed to prove their efficacy in HFrEF with electromechanical dyssynchrony.