Non-Dilated Left Ventricular Cardiomyopathy: Exploring the Spectrum from Phenotype to Disease Entity.

Non-dilated left ventricular cardiomyopathy has recently emerged as a distinct morpho-functional phenotype defined by non-ischemic left ventricular scarring or fatty replacement or by isolated global left ventricular hypokinesia without scarring in the absence of ventricular dilatation. Whether it represents a distinct biological entity or a shared phenotypic expression across cardiomyopathies remains unresolved. This narrative review examines evidence from genetics, multimodality imaging, natural history, and outcomes. Overlap with dilated and arrhythmogenic cardiomyopathies is extensive: no currently validated genetic, imaging, histological, or circulating marker uniquely identifies the phenotype, and longitudinal studies describe heterogeneous trajectories from reverse remodeling to dilated or predominantly arrhythmogenic evolution. Genetics argues in both directions, as the genes involved are shared yet their distribution differs, pro-arrhythmogenic variants being more frequent than in dilated cardiomyopathy. We propose a hypothesis-generating framework of three probable trajectories, evolving dilated cardiomyopathy, evolving arrhythmogenic cardiomyopathy, or stable non-dilated disease, integrating genotype, multiparametric cardiac magnetic resonance, longitudinal remodeling, and arrhythmic phenotype.