GJC1 and atrioventricular block: However, to date, in humans, only mutations in Cx43 have been reported to give rise to syndromic or non-syndromic CHD, including atrial isomerism, VSD, ASD, and pulmonary stenosis, though mutations in Cx40, Cx43, and Cx45 have been implicated with arrhythmias, such as AVB, atrial fibrillation, and sudden infant death syndrome [70,92,93,94].