Substrates of scar-related ventricular arrhythmia in patients with hypertrophic cardiomyopathy: a cardiac magnetic resonance study

Contrast-enhanced cardiac magnetic resonance (CMR) with late gadolinium enhancement (LGE) detects myocardial fibrosis in patients with hypertro- phic cardiomyopathy (HCM). We conducted a retrospective analysis of a pro- spectively collected and followed up cohort of consecutive patients with HCM implanted with a cardioverter defibrillator (ICD) that underwent pre- implant CMR. We sought to describe scar architecture and assess scar composition as a predictor of ven- tricular tachycardia/ventricular fibrillation (VT/VF). High scar mass (>15% of LV mass) showed 44.8% positive predictive value (PPV) and 89.7% negative predictive value (NPV) for VT/VF, whereas BZ chan- nels identified VT/VF patients with 55.6% PPV and 96.8% NPV. Indeed, of 28 patients with scar <15%, 3 had VT/VF, and 2 of them had BZ channels. The C-statistic was 0.77 (95% CI: 0.64-0.89) for scar mass and 0.88 (95% CI: 0.76-0.96) for BZ channels (P 1⁄4 0.11). Using scar channels instead of scar mass to stratify the risk of VT/VF allowed us to reclassify 12.5% of the cases and 12.0% of the controls (net reclassification index [NRI]: 0.24; SE: 0.10; P 1⁄4 0.01). High-risk patients with HCM displayed extensive LV scar with predominance of BZ tissue and relatively common BZ channels in the scar volume, possibly serving as substrates for re-entrant VA.