Prediction of super-responders to cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) is usually offered to those with heart failure symptoms despite optimal medical therapy and having evidence of dyssynchrony in the form of wide QRS complex. But about one third of them do not respond well to CRT.  Identification of those with poor response initially has been challenging. On the contrary there is also a group who respond very well to CRT, often referred to as super-responders. Super-responders to cardiac resynchronization therapy are in the upper quartile of improvement in left ventricular ejection fraction (LVEF). Hsu JC and colleagues evaluated the predictors of super response in the MADIT-CRT study [J Am Coll Cardiol, 2012; 59:2366-2373. Predictors of Super-Response to Cardiac Resynchronization Therapy and Associated Improvement in Clinical Outcome. The MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial With Cardiac Resynchronization Therapy) Study]. They could identify 191 super responders with 14.5 percent or more improvement in the LVEF (left ventricular ejection fraction). The six predictors of super-response were female sex, absence of prior myocardial infarction, QRS duration of 150 milliseconds, left bundle branch block, body mass index less than 30 kilograms per square meter and smaller baseline left atrial volume index. The probability of all cause mortality was 4 percent in super-responders compared to 26 percent in hypo-responders and 11 percent in responders. The study group consisted of mildly symptomatic heart failure patients treated with CRT-D (cardiac resynchronization therapy with defibrillator).