MRI-LGE Extent (% LV Mass Fibrosis) Calculator

MRI-LGE Extent (% LV Mass Fibrosis): Comprehensive Explanation and Clinical Context This calculator estimates the proportion of myocardial fibrosis (late gadolinium enhancement, LGE) relative to total left ventricular (LV) mass using cardiac MRI data: %LGE = (LGE mass / LV mass) × 100. When input volumes are provided, they are converted to grams assuming a myocardial density of 1.05 g/mL. LGE reflects focal myocardial scar or fibrosis and is a powerful prognostic marker across cardiomyopathies.

In hypertrophic cardiomyopathy (HCM), the presence of extensive LGE (≥15% of LV mass) is a major risk modifier for sudden cardiac death, guiding ICD consideration. In ischemic heart disease, infarct size >30% LV mass predicts adverse remodeling and increased mortality, while smaller infarcts carry better prognosis. In dilated/non-ischemic cardiomyopathy (DCM/NICM), the presence (rather than exact % extent) of LGE, especially mid-wall, predicts arrhythmia and mortality, though standardized thresholds are lacking.

Overall, LGE quantification refines risk stratification and complements functional and clinical assessment in precision cardiology.