Scar channels in cardiac magnetic resonance to predict appropriate therapies in primary prevention

Background Scar characteristics analyzed by late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) are related with ventricular arrhythmias. Current guidelines are based only on the left ventricular ejection fraction to recommend an implantable cardioverter-defibrillator (ICD) in primary prevention. Objectives Our study aims to analyze the role of imaging to stratify arrhythmogenic risk in patients with ICD for primary prevention. Methods From 2006 to 2017, we included 200 patients with LGE-CMR before ICD implantation for primary prevention. The scar, border zone, core, and conducting channels (CCs) were automatically measured by a dedicated software. Results The mean age was 60.9 ± 10.9 years; 81.5% (163) were men; 52% (104) had ischemic cardiomyopathy. The mean left ventricular ejection fraction was 29% ± 10.1%. After a follow-up of 4.6 ± 2 years, 46 patients (22%) reached the primary end point (appropriate ICD therapy). Scar mass (36.2 ± 19 g vs 21.7 ± 10 g; P < .001), border zone mass (26.4 ± 12.5 g vs 16.0 ± 9.5 g; P < .001), core mass (9.9 ± 8.6 g vs 5.5 ± 5.7 g; P < .001), and CC mass (3.0 ± 2.6 g vs 1.6 ± 2.3 g; P < .001) were associated with appropriate therapies. Scar mass > 10 g (25.31% vs 5.26%; hazard ratio 4.74; P = .034) and the presence of CCs (34.75% vs 8.93%; hazard ratio 4.07; P = .003) were also strongly associated with the primary end point. However, patients without channels and with scar mass < 10 g had a very low rate of appropriate therapies (2.8%). Conclusion Scar characteristics analyzed by LGE-CMR are strong predictors of appropriate therapies in patients with ICD in primary prevention. The absence of channels and scar mass < 10 g can identify patients at a very low risk of ventricular arrhythmias in this population.