Potential role of biventricular pacing beyond advanced systolic heart failure.

Cardiac resynchronization therapy (CRT) is an effective therapy for advanced heart failure (HF) patients. The indications are well defined in recent guidelines and broadly indicate that CRT is suitable for chronic HF patients with left ventricular ejection fraction (EF) ≤35% and in NYHA class III or IV (Class I), and those with prolonged QRS duration ≥120 ms with left bundle branch block (LBBB) QRS morphology, or QRS duration ≥150 ms irrespective of QRS morphology (Class IIa). For patients with NYHA class II symptoms, CRT is recommended for patients with EF ≤30% and QRS duration ≥130 ms with LBBB QRS morphology (Class I, level of evidence: A), or QRS duration ≥150 ms irrespective of QRS morphology (Class IIa, level of evidence: A). However, CRT may benefit additional patients outside these criteria. In this review, we summarize the role of CRT in some subgroups, including patients with mild and moderate HF, upgrading to CRT from right ventricular (RV) pacing, bradycardia patients with routine pacing indications, congenital heart disease and specific cardiomyopathies. It is possible that CRT can give symptomatic and mortality benefits in some of these subgroups in the future and further clinical trials are warranted.