Effects of cardiac resynchronization therapy in patients unselected for mechanical dyssynchrony

BackgroundObservational echocardiographic studies have suggested that pre-implant dyssynchrony is required for a response to cardiac resynchronization therapy. Some clinical guidelines on CRT have adopted dyssynchrony as a requirement prior to CRT.AimsTo assess the effects of CRT in patients with heart failure who are unselected for mechanical dyssynchrony.Methods248 consecutive patients with heart failure (sinus rhythm, NYHA class III [n = 171, 89%]) or IV (n = 77, 31%; LVEF ≤ 35%, QRS ≥ 120 ms) underwent a clinical assessment, including NYHA class, 6-min walking distance and quality of life (Minnesota Living with Heart Failure questionnaire) before and after CRT. Clinical event variables included mortality and hospitalizations for major cardiovascular events and for heart failure.ResultsAt follow-up, NYHA class was reduced from 3.25 ± 0.56 to 2.06 ± 0.84 (mean ± SD, p < 0.0001). There were also improvements in 6-min walking distance (232.2 ± 113.8 to 302.9 ± 119.5 m) and quality of life scores (56.1 ± 20.4 to 32.5 ± 23.4) (both p < 0.0001). Responder rate, defined as improvement by ≥ 1 NYHA classes or ≥ 25% in 6-min walking distance, was 81% (202/248 patients). Over a follow-up period of up to 7.4 years (median 720 days), the annualized total and cardiovascular mortality rates were 11.7% and 9.89%, respectively.ConclusionsIn patients undergoing CRT, the improvements in functional capacity and quality of life as well as the event rates expected from landmark trials are achievable by selecting patients on the basis of NYHA class, LVEF and QRS duration alone. The added value of echocardiographic measures of dyssynchrony remains questionable.