Introduction: Delayed enhancement - magnetic resonance imaging (DE-MRI) has demonstrated that nonischemic cardiomyopathy is mainly characterized by intramural or epicardial fibrosis whereas global endomyocardial fibrosis suggests cardiac involvement in autoimmune rheumatic diseases or amyloidosis. Conduction disorders and sudden cardiac death are important manifestations of autoimmune rheumatic diseases with cardiac involvement but the substrates of ventricular arrhythmias in autoimmune rheumatic diseases have not been fully elucidated. Methods and Results: 20 patients with autoimmune rheumatic diseases presenting with ventricular tachycardia (VT) (n=11) or frequent ventricular extrasystoles (n=9) underwent DE-MRI and / or endocardial electroanatomical mapping of the left ventricle (LV). 10 patients with autoimmune rheumatic diseases underwent VT ablation. Global endomyocardial fibrosis without myocardial thickening and unrelated to coronary territories was detected by DE-MRI or electroanatomical voltage mapping in 9 of 20 patients with autoimmune rheumatic diseases. In the other patients with autoimmune rheumatic diseases, limited regions of predominantly epicardial (n = 4) and intramyocardial (n = 5) fibrosis or only minimal fibrosis (n = 2) were found using DE-MRI. Endocardial low-amplitude diastolic potentials and pre-systolic Purkinje or fascicular potentials, mostly within fibrotic areas, were identified as the targets of successful VT ablation in 7 of 10 patients with autoimmune rheumatic diseases. Conclusion: Global endomyocardial fibrosis can be a tool to diagnose severe cardiac involvement in autoimmune rheumatic diseases and may serve as the substrate of ventricular arrhythmias in a substantial part of patients.

Introduction: In patients with left ventricular (LV) nonischemic cardiomyopathy and monomorphic ventricular tachycardia (VT), midmyocardial and epicardial substrates are often involved but endocardial structures may also be affected. Delayed enhancement – magnetic resonance imaging (DE–MRI) was used to characterize the substrates of predominantly epicardial VT to improve identification of target sites for ablation. Methods and Results: 12 patients with LV nonischemic cardiomyopathy and monomorphic VT (prior myocarditis in 9) had a predominantly epicardial (n = 8) or epicardial-only DE-MRI substrate (n = 4). Modest-sized endocardial involvement in predominantly epicardial substrates was identified by DE-MRI in 8 patients. Mapping of 22 VTs was performed in 12 patients using an endo-epicardial approach in 6 patients and an endocardial-only approach in 6 patients. Endocardial VT reentry circuit exit sites as defined by entrainment and pace mapping criteria corresponded to endocardial breakthroughs from predominantly epicardial DE-MRI substrates in 7 patients. The endocardial VT exits were located at the ventricular base near the mitral annulus in 6 patients. Successful endocardial ablation of at least one VT was accomplished in 5 patients. Epicardial ablation as a part of an endo-epicardial approach or as epicardial-only ablation was performed in 6 patients and was successful in 4 patients. Conclusion: Endocardial breakthroughs from predominantly epicardial DE-MRI substrates are often located near the ventricular base in the perivalvular region and correlate with endocardial VT reentry circuit exit sites amenable to ablation.