Shall CRT-D be downgraded to CRT-P in super-responders of cardiac resynchronization therapy?

Despite the established role of cardiac resynchronization therapy (CRT) in patients with heart failure (HF), researchers remain active in understanding the benefit of this therapy and exploring new indications. One important issue is the highly variable response rate to CRT and the identification of effective responders. Response to CRT also has a wide range of terminology, including mid-term left ventricular (LV) reverse remodeling, symptomatic improvement, reduction of HF events/mortality, or a combination of these parameters. Depending on the definition of response, nonresponse to CRT occurs in 30% to 45% of patients. On the other hand, dramatic favorable response occurs in a subset of patients, characterized by significant improvement of LV ejection fraction (LVEF) with reverse remodeling leading to normal or near normal recovery of cardiac function, a condition now referred as ‘‘superresponders’’ to CRT. As super-responders are characterized by significant improvement of LVEF, to near normalization, a new question arises on whether these patients continue to require CRT with defibrillator (CRT-D) upon device replacement, i.e., whether a CRT with pacemaker (CRT-P) downgrade will be sufficient. As LVEF is the single most important predictor of sudden cardiac death, a postCRT value well above 40% or even close to 50% may imply that the subsequent risk of sudden cardiac death will be low. For patients who received a defibrillator for primary prevention, theoretically a downgrade from CRT-D to CRT-P will render the therapy more cost-effective, especially in the elderly population. Understanding the relationship between the degree of CRT response and the reduction of risk of ventricular arrhythmias will shed light on this important clinical issue. In an article published in Revista Española de Cardiologı́a, Garcı́aLunar et al reported the results of a retrospective analysis of