Absence of Fibrosis Influences Prognosis of Cardiac Resynchronization in Nonischemic Cardiomyopathy

BACKGROUND: In patients with nonischemic cardiomyopathy (NICM) undergoing cardiac resynchronization therapy (CRT), there are no clear recommendations on selecting CRT with defibrillator (CRT-D) vs pacemaker (CRT-P). Patients with high probability of response to CRT and low arrhythmic risk may be ideal candidates to CRT-P. OBJECTIVES: The objectives of the study was to evaluate if the absence of late gadolinium enhancement (LGE) is associated with CRT response and ventricular arrhythmia (VA) in NICM treated with CRT. METHODS: A systematic review and meta-analysis was conducted. Search of PubMed, Web of Science, and Scopus identified observational studies of NICM patients who underwent cardiac magnetic resonance before CRT implantation. Studies assessing echocardiographic response to CRT or VA stratified by LGE status were included. The VA endpoint comprised sustained ventricular tachycardia, appropriate implantable cardioverter-defibrillator therapy, resuscitated cardiac arrest, and sudden death. RESULTS: Ten studies were included: 9 (n = 831) for CRT response and 6 (745 patients) for arrhythmic risk. CRT response was significantly higher in patients without LGE than in patients with LGE (78.7% vs 50.7%; P < 0.001). The cumulative incidence of VA was extremely low in LGE cases, significantly lower than that of LGE+ ones (0.8% vs 21.1%, P < 0.001). The absence of LGE was strongly associated with higher CRT response (OR: 3.52; 95% CI: 2.54-4.88; P < 0.001) and much lower arrhythmic risk (OR: 0.06; 95% CI: 0.02-0.15; P < 0.001). CONCLUSIONS: In NICM patients undergoing CRT, the absence of LGE is strongly associated with greater echocardiographic response and very low arrhythmic risk. In this subgroup the incremental benefit of CRT with defibrillator over CRT-P may be limited.