Phenotype, outcomes and natural history of early‐stage non‐ischaemic cardiomyopathy

AimsTo characterize the phenotype, clinical outcomes and rate of disease progression in patients with early‐stage non‐ischaemic cardiomyopathy (early‐NICM).Methods and resultsWe conducted a prospective observational cohort study of patients with early‐NICM assessed by late gadolinium enhancement cardiovascular magnetic resonance (CMR). Cases were classified into the following subgroups: isolated left ventricular dilatation (early‐NICM H−/D+), non‐dilated left ventricular cardiomyopathy (early‐NICM H+/D−), or early dilated cardiomyopathy (early‐NICM H+/D+). Clinical follow‐up for major adverse cardiovascular events (MACE) included non‐fatal life‐threatening arrhythmia, unplanned cardiovascular hospitalization or cardiovascular death. A subset of patients (n = 119) underwent a second CMR to assess changes in cardiac structure and function. Of 254 patients with early‐NICM (median age 46 years [interquartile range 36–58], 94 [37%] women, median left ventricular ejection fraction [LVEF] 55% [52–59]), myocardial fibrosis was present in 65 (26%). There was no difference in the prevalence of fibrosis between subgroups (p = 0.90), however fibrosis mass was lowest in early‐NICM H−/D+, higher in early‐NICM H+/D− and highest in early‐NICM H+/D+ (p = 0.03). Over a median follow‐up of 7.9 (5.5–10.0) years, 28 patients (11%) experienced MACE. Non‐sustained ventricular tachycardia (hazard ratio [HR] 5.1, 95% confidence interval [CI] 2.36–11.00, p < 0.001), myocardial fibrosis (HR 3.77, 95% CI 1.73–8.20, p < 0.001) and diabetes mellitus (HR 5.12, 95% CI 1.73–15.18, p = 0.003) were associated with MACE in a multivariable model. Only 8% of patients progressed from early‐NICM to dilated cardiomyopathy with LVEF <50% over a median of 16 (11–34) months.ConclusionEarly‐NICM is not benign. Fibrosis develops early in the phenotypic course. In‐depth characterization enhances risk stratification and might aid clinical management.