Genotyping Protocol
Venipuncture was performed and DNA was extracted using the Illustra Nucleon BACC3 Genomic DNA Extraction kit (GE Healthcare, Chicago, IL, USA). Samples were genotyped for the AF-associated variants using TaqMan (Applied Biosystems, Foster City, CA), a plate-based, 1-step reaction that identifies the SNP allele during polymerase chain reaction amplification. An AF genetic risk score was calculated using the literature risk estimates as weights for the minor allele of each of the 12 SNPs as previously reported4. All 12 SNPs were genotyped in all subjects without genotype imputation. In the atrial appendage cohort subgroup, we classified patients based on genetic risk score as well as the status of the RS2200733 SNV (a component of the polygenic risk score). This SNP was chosen as a stratifier for morphologic evaluation analysis given the known role of PITx2 in Left-Right signaling. Patients were categorized as SNV carriers if they were heterozygous (CT) or homozygous (TT) for the RS2200733 variant. Patients with the CC genotype were classified as non-carriers. Investigators were fully blinded to the genotype status of each subject until data analysis was complete.

Modeling of genetic risk score

The polygenic risk score utilized here includes 12 SNPs (Table 1), and is the most commonly studied such score as originally published by Tada et al and subsequently validated3, 5-9. The linkage disequilibrium between these SNPs is captured in the implementation of the score components4. The AF- genetic risk score (GRS) for each individual in the current study was calculated: for each SNP the natural log transformed risk estimate for the minor allele was multiplied by the number of minor alleles carried by that individual; these 12 products were then summed. The risk estimate for the minor allele at each SNP was obtained from the largest available data set.