RYR2 and atrioventricular block: While greater than 90% of RYR2 mutations discovered to date are missense mutations, heterozygous CNVs involving the in-frame deletion of RYR2 exon 3 (35 amino acids, Asn57_Gly91) that also leads to an overall GOF of RyR2 have been reported to cause a wide spectrum of clinical phenotypes, including autosomal dominant CPVT1, sinoatrial node dysfunction, bradycardia, atrial fibrillation, atrioventricular block, dilated cardiomyopathy, left ventricular noncompaction, and SCA (3, 8–11).