Utility of Cardiac Magnetic Resonance in Assessing Arrhythmic Risk in Patients With Nonischemic Cardiomyopathy Undergoing Biventricular Pacing.

Abstract

Nonischemic cardiomyopathy (NICM) is responsible for approximately one-third of heart failure and is associated with significant morbidity and mortality. Recent data suggested the lack of mortality reduction from adding a defibrillator to cardiac resynchronization therapy (CRT) in all patients with NICM. Myocardial fibrosis detected by cardiac magnetic resonance late gadolinium enhancement (CMR-LGE) can help risk stratify patients who would benefit from adding a defibrillator to CRT in this patient population. We aim to assess the relationship between the presence of myocardial fibrosis detected by CMR-LGE and the rate of major arrhythmic events (MAE) that included sustained ventricular tachycardia (VT), appropriate cardiac resynchronization therapy-defibrillator (CRT-D) intervention, ventricular fibrillation (VF), and sudden cardiac death (SCD) in patients with NICM undergoing CRT and to compare all-cause mortality and heart failure improvement between patients receiving cardiac resynchronization therapy-pacing (CRT-P) versus those receiving CRT-D based on the presence of myocardial fibrosis. All consecutive patients with NICM satisfying a guideline-directed indication for CRT implantation were included in the study after excluding patients who refused to consent, patients with acute decompensated heart failure, and those contraindicated for a cardiac magnetic resonance (CMR). Patients were divided into two groups based on the presence of fibrosis in cardiac MRI: the LGE/CRT-D group and the No LGE/CRT-P group. They were then followed for 1 year. Sixty patients were enrolled. Sixteen patients (26.6%) developed MAE during the study duration, among those patients, seven had myocardial fibrosis (receiving CRT-D as per protocol), while nine had no myocardial fibrosis (receiving CRT-P as per protocol), (41.2%vs. 20.9%, p = 0.045). The presence of CMR-LGE, regardless of the extent and distribution, predicted MAE with an odds ratio of 2.6 (CI = 1.78-8.9, p = 0.04). The presence of ≥7.5% of myocardial fibrosis by CMR was associated with 54% sensitivity and 100% specificity for MAE in the study population. All-cause mortality was significantly higher in the No LGE/CRT-P group versus the LGE/CRT-D group (15 [34.9%] vs. 2 [11.8%], p = 0.076). In patients with NICM candidates for biventricular pacing, the presence of LGE on CMR, irrespective of the extent or segmental pattern, is independently associated with an MAE and is associated with worse heart failure outcomes. However, the absence of LGE did not rule out MAE, and implanting CRT-P based on lack of fibrosis may result in higher all-cause mortality.