Endomyocardial Gremlin-1 is associated with structural remodeling and adverse clinical outcomes in non-ischemic cardiomyopathy

BACKGROUND: Risk stratification in non-ischemic cardiomyopathies (NICM) remains challenging despite guideline-based phenotypic classification using multimodal diagnostics including endomyocardial biopsy (EMB). We aimed to identify EMB-derived histological and molecular markers that improve phenotypic characterization and long-term risk stratification in patients with NICM. METHODS: In this prospective cohort study, 703 consecutive patients with symptomatic NICM underwent standardized multimodal evaluation, including clinical assessment, cardiac imaging, and endomyocardial biopsy. Biopsy specimens were analyzed using histology, immunohistochemistry, and targeted myocardial mRNA profiling. Associations between endomyocardial markers, and fibroinflammatory remodeling, imaging parameters, and molecular signatures were assessed cross-sectionally. Long-term prognostic relevance was evaluated using survival and multivariable prediction analyses during follow-up of up to fifteen years for all-cause mortality, cardiovascular mortality, implantable cardioverter-defibrillator (ICD) implantation, and appropriate ICD discharge. RESULTS: Elevated myocardial Gremlin-1 expression was associated with increased fibrosis, adverse cardiac remodelling, reduced left ventricular function, and enrichment of pro-fibrotic and inflammatory mRNA signalling pathways. Myocardial and circulating Gremlin-1 expression was independently associated with all-cause and cardiovascular mortality, and ICD implantation and discharge. Machine learning-based phenotyping using histological EMB data identified Gremlin-1 as a key predictive feature of poor prognosis. Incorporation of Gremlin-1 into predictive models significantly improved long-term cardiovascular risk stratification in NICM patients. CONCLUSION: EMB and high plasmatic Gremlin-1 concentrations are at elevated risk to develop adverse cardiovascular events. Thus, the histological evaluation of Gremlin-1 may help to improve risk discrimination and management of NICM and HF patients.