Prognostic Value of Non-Ischemic Ring-Like Left Ventricular Scar in Patients with Apparently Idiopathic Non-Sustained Ventricular Arrhythmias

Background: Left ventricular (LV) scar on late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) has been correlated with life-threatening arrhythmic events in patients with apparently idiopathic ventricular arrhythmias (VA). We investigated the prognostic significance of a specific LV-LGE phenotype characterized by a ring-like pattern of fibrosis. Methods: 686 patients with apparently idiopathic non-sustained VA underwent contrast enhanced CMR. A ring-like pattern of LV scar was defined as LV subepicardial/midmyocardial LGE involving at least 3 contiguous segments in the same short-axis slice. The endpoint of the study was time to the composite outcome of all cause death, resuscitated cardiac arrest due to ventricular fibrillation (VF) or hemodynamically unstable ventricular tachycardia (VT) and appropriate implantable cardioverter defibrillator therapy. Results: A total of 28 (4%) patients had a ring-like pattern of scar (Group A), 78 (11%) a non ring-like pattern (Group B), and 580 (85%) had normal CMR with no LGE (Group C). Group A patients were younger compared to Group B and Group C (median age 40 vs. 52 vs. 45 years, p<0.01), more frequently males (96% vs. 82% vs. 55%, p<0.01) with a higher prevalence of family history of sudden cardiac death/cardiomyopathy (39% vs. 14% vs. 6%; p<0.01), and more frequent history of unexplained syncope (18% vs. 9% vs. 3%, p<0.01). All patients in Group A showed VA with a right bundle branch block morphology vs. 69% in Group B and 21% in Group C (p<0.01). Multifocal VA were observed in 46% of Group A patients compared to 26% of Group B and 4% of Group C (p<0.01). After a median follow-up of 61 (34-84) months, the composite outcome occurred in 14 patients (50%) in Group A vs. 15 (19%) in Group B and 2 (0.3%) in Group C (p<0.01). After multivariable adjustment, the presence of LGE with ring-like pattern remained independently associated with increased risk of the composite endpoint (HR 68.98, 95% CI 14.67-324.39, p<0.01). Conclusions: In patients with apparently idiopathic non-sustained VA, nonischemic LV scar with a ring-like pattern is associated with malignant arrhythmic events.