A Review of Cardiomyopathy Gene Variants as Drivers of Early-Onset Atrial Fibrillation: Linking Genotype to Phenotype in Precision Medicine.

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia worldwide, typically driven by age, obesity and other conventional cardiovascular risk factors. However, a subset of patients develop early-onset AF-often before 65 years of age in the absence of structural heart disease-suggesting alternative mechanisms beyond acquired risk. Emerging evidence implicates pathogenic variants in cardiomyopathy-associated genes as key drivers in this population. This review synthesises contemporary evidence linking cardiomyopathy gene variants, particularly in TTN, LMNA, MYH7, and PKP2, to early-onset AF. Across multiple sequencing cohorts, pathogenic or likely pathogenic variants are identified in 5-20% of young AF patients, with prevalence rising sharply at younger ages. TTN truncating variants confer up to a twofold increased risk of AF and a tenfold higher risk of subsequent dilated cardiomyopathy, whereas LMNA mutations are associated with aggressive atrial fibrosis, conduction disease, and early recurrence after catheter ablation. Longitudinal studies demonstrate that genotype-positive AF patients face higher risks of heart failure, sudden cardiac death, and progression to overt cardiomyopathy. These findings redefine early-onset AF as a potential sentinel manifestation of inherited myocardial disease rather than an isolated electrical disorder. Genetic testing-especially in individuals with AF onset ≤45 years or a family history of cardiomyopathy-enables early detection, cascade screening, and personalized surveillance. Integrating genomics, advanced imaging, and electrophysiologic management supports a precision medicine framework that may improve outcomes by identifying and intervening before structural disease develops.