Left ventricular excessive trabeculation: pathophysiology, diagnostic challenges, and prognostic significance

Excessive trabeculation has been considered the morphological hallmark of left ventricular non-compaction (LVNC), traditionally viewed as a primary cardiomyopathy resulting from an arrest in myocardial compaction during embryonic development. However, more recent evidence suggests that excessive trabeculation of the left ventricle (LVET) may represent a phenotypic trait with heterogeneous etiologies, which can be observed in both physiological and pathological conditions. LVET phenotype may represent the result of a complex interaction between genetic factors, embryonic developmental processes, and acquired hemodynamic adaptations. Additionally, it could represent a secondary morphological remodeling in response to increased preload or afterload Finally, it could be a morphological expression of shared genotype-phenotype continuum encompassing dilated, hypertrophic, and arrhythmogenic cardiomyopathies. Due to its heterogeneity, the clinical significance and the practical management remain unclear, including a significant potential for overdiagnosis, and unnecessary follow-up. The bulk of current evidence suggests that the phenotypic feature of excessive trabeculation has no independent prognostic relevance in otherwise healthy individuals in absence of specific cardiac and extracardiac conditions or symptoms. Moreover, the relationship between excessive LVET and arrhythmic risk remains controversial and appears highly dependent on the underlying cardiomyopathic substrate rather than trabecular morphology per se. However genetic studies have substantially reshaped the conceptual framework of excessive trabeculation; several genes and multiple signaling pathways have been described to clarify the peculiar morpho-tissue organization that characterizes this myocardial phenotype. This review summarizes current evidence on the prevalence, imaging characterization, genetic background, and clinical impact of excessive trabeculation in physiological phenotypes and in cardiomyopathies, and discusses whether this feature represents a remodelling response, or a phenotypic modifier influencing outcomes.