Critical Appraisal of the Use of Cardiac Resynchronization Therapy Beyond Current Guidelines

Cardiac resynchronization therapy (CRT) is an effective treatment for patients with drug-refractory, chronic heart failure. Multiple single-center and multicenter studies have shown significant reductions in left ventricular (LV) volumes and an increase in LV systolic function. More importantly, CRT reduces mortality and morbidity during long-term follow-up. Current guidelines consider CRT as a Class I indication for heart failure patients in New York Heart Association (NYHA) functional class III to IV with depressed LV ejection fraction ≤35% and a wide QRS complex (≥120 ms). However, the benefits of this therapy could possibly be extended to selected subgroups of patients who do not fulfill these criteria. These subgroups include patients with mildly symptomatic heart failure and patients with a narrow QRS complex (