Whom should I refer in 2014 for cardiac resynchronization?

Heart failure continues to be a significant source of morbidity and mortality amongst Canadians. Many patients remain symptomatic despite guideline-directed medical therapy. For drug-refractory patients with dyssynchronous systolic heart failure, cardiac resynchronization therapy (CRT) has reliably reduced heart failure hospitalizations and related deaths. Unfortunately, despite significant advancements in technology and our understanding of its clinical effect, the CRT nonresponder rate remains approximately 30%. Great efforts have been invested into identifying clinical predictors of CRT response. Left bundle branch block conduction delay and wider QRS (> 150 ms) have consistently been associated with clinical response to CRT, earning them the strongest recommendations in the revised guidelines in Canada and across the world. Due in large part to the benefit observed in the Resynchronization-Defibrillation for Ambulatory Heart Failure Trial (RAFT) trial, patients with mild heart failure symptoms (New York Heart Association class II) are now also candidates for resynchronization therapy. Patients with atrial fibrillation, non-left bundle branch block conduction patterns, and chronic right ventricular pacing have historically been associated with poor response. However, these populations remain grossly underrepresented in the large trials. In the absence of more data, these patients continue to receive weaker recommendations for CRT in the guidelines.