Yoneda ZT, Anderson KC, Quintana JA, et al. - The use of genetic testing in early-onset atrial fibrillation (AF) is supported as genetic testing performed in these patients identified pathogenic variants linked with more serious inherited cardiomyopathy and arrhythmia syndromes.

• Early-onset AF can be the initial presentation of a more grave underlying inherited cardiomyopathy or arrhythmia syndrome.

• This is a prospective, observational cohort study of 1293 patients with AF diagnosed before 66 years of age and who had whole genome sequencing done.

• A disease-associated variant was identified, through genetic testing, in 10% of patients with early-onset AF (a higher percentage was obtained if diagnosed before the age of 30 years and lower percentage if diagnosed after the age of 60 years).

• Genetic testing also identified a variant of undetermined significance in 812 (62.8%) participants, 92 (7.1%) as heterozygous carriers for an autosomal recessive disorder, and no suspicious variant in 258 (20.0%).

• Most pathogenic/likely pathogenic variants were in genes linked with cardiomyopathy.

• TTN, MYH7, MYH6, LMNA, and KCNQ1 were revealed as the most common genes.