Non-classical Indications for Cardiac Resynchronization Therapy
Keywords:Cardiac resynchronization therapy, biventricular pacing, left bundle branch
Based on randomized controlled studies, cardiac resynchronization therapy (CRT) is currently indicated in patients with systolic heart failure of New York Heart Association (NYHA) functional class III and IV, left ventricular ejection fraction?< 35% and wide QRS (>120 ms). Most of the enrolled patients were in sinus rhythm, were not previously paced and had mainly LBBB. Thus, there are uncertainties regarding several other populations, not included or underrepresented in the main studies.These populations include patients with atrial fibrillation (AF), previous pacemakers considered for upgrade to CRT, RBBB, narrow QRS < 120 ms, NYHA functional class? < III, or right heart failure. These non-classical indications are herein reviewed.Although CRT seems to benefit patients with AF and patients with preexisting pacemakers, in patients with NYHA functional class II-III, or with narrow QRS, or with RBBB, or in those with predominant right heart failure, the role of CRT is not established yet and further relevant clinical trials are needed.
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