Disease-associated variants were more common in genes associated with cardiomyopathies than channelopathies, and the most affected genes were TTN, MYH7, MYH6, LMNA, and KCNQ1. The results of this study help to inform decisions regarding genetic testing in patients presenting with early-onset AF. The gene discussed is KCNQ1; the disease is cardiomyopathy.