RYR2 and cardiac arrhythmia: Variable expression in CPVT has been illustrated in a description of an extended family with CPVT due to a p.G14876A variant in RYR2. In this family with an apparent highly penetrant variant, 10 of 11 variant carriers experienced syncope (including two sudden cardiac deaths during sleep) and were also found to have arrhythmia during EST ranging from isolated PVCs to ventricular fibrillation (Allouis, Probst, Jaafar, Schott, & Le Marec, 2005).