A 315-variant atrial fibrillation polygenic risk score (AF-PRS) demonstrated predictive power for non-ischemic cardiomyopathy (NICM) in 16,801 European ancestry adults, with each 15% quartile increase in genetic risk conferring a 9% higher hazard of developing heart muscle disease. Among participants, 418 (2.5%) developed NICM over the study period. This finding represents a significant advance in cardiovascular risk prediction, potentially enabling earlier identification of heart failure susceptibility before clinical symptoms emerge. The genetic overlap between atrial fibrillation and cardiomyopathy suggests shared biological pathways that could revolutionize preventive cardiology. However, several limitations temper enthusiasm: the cohort was 99% Caucasian, limiting generalizability to diverse populations where genetic risk variants may differ substantially. The retrospective design cannot establish whether AF genetic risk directly causes cardiomyopathy or reflects shared underlying mechanisms. As a preprint awaiting peer review, these results require independent validation before clinical implementation. The modest 9% risk increment per quartile, while statistically significant in this large cohort, may have limited practical utility for individual risk assessment. This work is confirmatory rather than paradigm-shifting, building incrementally on established AF-cardiomyopathy connections through a genetic lens.