A Visual LGE Extent Cutoff for Mortality Risk Stratification in Ischemic Cardiomyopathy.

Abstract

Background: Late gadolinium enhancement (LGE) extent has been linked to adverse outcomes in ischemic cardiomyopathy (ICM). While quantitative methods of LGE assessment are widely accepted, semi-quantitative methods remain debated but still hold value. This study aimed to determine an optimal LGE segments cutoff for ICM patients with left ventricular ejection fraction (LVEF) <50% in a large bicentric cohort.

Methods: This bicentric retrospective French study included 3,591 patients with ICM (defined by prior myocardial infarction and/or coronary revascularization), LVEF <50%, and ischemic-LGE on cardiovascular magnetic resonance performed between 2008 and 2022. Ischemic LGE extent was assessed semi-quantitatively using the 17-segment model. An optimal cutoff for LGE extent was derived in the derivation cohort (Center 1, N=2,900) using a conditional inference tree and externally validated in an independent cohort (Center 2, N=691). The primary outcome was all-cause mortality. Prognostic performance was compared between a conventional model based on LVEF ≤35% alone and a combined model integrating LVEF ≤35% with the newly identified ischemic-LGE cutoff. Model discrimination and reclassification were assessed using Harrell's C-index, continuous net reclassification improvement (NRI), and integrated discrimination improvement (IDI).

Results: During a median follow-up of 9 years, 549 patients (15.3%) died. The optimal cutoff of visual LGE extent to predict mortality was 5 segments. Patients with high ischemic LGE extent (>5 segments) had a markedly increased risk of all-cause mortality compared with those with ≤5 segments (adjusted hazard ratio, 3.8; 95% CI: 3.0-4.8; p<0.001). Survival discrimination according to this cutoff was consistent across derivation and validation cohorts. Compared with the conventional LVEF ≤35% model alone, the combined model integrating the >5 ischemic-LGE segment cutoff significantly improved risk discrimination and patient reclassification (ΔC-index: +16%; continuous NRI: +36%; IDI: +4%; all p<0.001).

Conclusion: In patients with ICM, reduced LVEF (<50%), and detectable ischemic LGE, a visually assessed segment-based cutoff of >5 ischemic-LGE segments was independently associated with all-cause mortality and validated in an independent second-center cohort. This pragmatic, software-independent assessment may complement conventional risk stratification, although prospective studies are required before integration into clinical decision-making.