Fibrosis Entropy Is Associated With Life-Threatening Arrhythmia in Nonischemic Cardiomyopathy

Abstract

Background: Greater precision is required for arrhythmic risk stratification of patients with nonischemic cardiomyopathy (NICM). We sought to evaluate whether fibrosis entropy, a measure of scar texture heterogeneity derived from late gadolinium enhancement cardiovascular magnetic resonance, has incremental utility to fibrosis presence for arrhythmic risk prediction in NICM.  Methods: In this prospective observational cohort study, fibrosis entropy was calculated for patients with NICM and fibrosis (late gadolinium enhancement positive, LGE+), including regions of core fibrosis, gray zone fibrosis and combined core and gray zone fibrosis. Patients with NICM and no fibrosis (LGE-) were included as a comparator group. Adjudicated follow-up for life-threatening arrhythmia included sudden cardiac death, aborted sudden cardiac death, or sustained ventricular tachycardia.  Results: Of 291 patients with LGE+ NICM, 38 (13.1%) experienced life-threatening arrhythmia over a median follow-up of 6.3 years. Core fibrosis entropy (per-SD hazard ratio [HR], 1.77 [95% CI, 1.25-2.52]; =0.001), gray zone fibrosis entropy (HR, 1.97 [95% CI, 1.20-2.54]; =0.004), and combined fibrosis entropy (HR, 1.98 [95% CI, 1.30-3.02]; =0.004) were each associated with life-threatening arrhythmia after adjustment for variables used to determine implantable cardioverter-defibrillator candidacy in clinical practice (left ventricular ejection fraction ≤35% and New York Heart Association class >1) and remained associated after accounting for core and gray zone fibrosis mass. Left ventricular ejection fraction ≤35% was not associated with life-threatening arrhythmia (HR, 1.45 [95% CI, 0.77-2.74]; =0.250). Integration of fibrosis presence with fibrosis entropy classified patients into low-, intermediate-, and high-arrhythmic-risk groups.  Conclusions: Deeper phenotypic characterization of scar using fibrosis entropy offers incremental utility to left ventricular ejection fraction and fibrosis presence for arrhythmic risk stratification in NICM.