Should We Be Trying to Define Responders to Cardiac Resynchronization Therapy?

CARDIAC RESYNCHRONIZATION THERAPY (CRT) MAY PROVIDE A DRAMATIC IMPROVEMENT of symptom status and outcome in many patients with heart failure. Unfortunately, the use of current selection criteria is associated with a failure to respond on symptomatic or functional grounds of approximately 30%. Does the falling implant rate reflect a lack of enthusiasm for a treatment whose efficacy is not guaranteed-despite the certainty of risk and cost-or does it reflect the inappropriate application of other criteria of mechanical synchrony? The accompanying positions encapsulate the arguments of skeptics and supporters of the role of mechanical dyssynchrony.