NKX2-5 and congenital heart disease: NKX2–5 is a transcription factor crucial for regulation of cardiac development,54 and genetic variants in NKX2–5, including rs2277923, are found to be associated with congenital heart disease.55 Notably, one study assessing sex-specific SNPs in patients with a bicuspid aortic valve found variants in NKX2–5 specific to women.56 Together with that finding, our results might indicate that NKX2–5 variants have an effect on RHR and possibly congenital heart disease in women.