Sudden death after inappropriate shocks of implantable cardioverter defibrillator in a catecholaminergic polymorphic ventricular tachycardia case with a novel RyR2 mutation

Background: Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmogenic syndrome and a cause of exercise-related sudden death. CPVT has been reported to be caused by gain of function underlying a mutation of cardiac ryanodine receptor (RyR2). Methods: In a family with a CPVT patient, genomic DNA was extracted from peripheral blood lymphocytes, and the RyR2 gene underwent target gene sequence using MiSeq. The activity of wild-type (WT) and mutant RyR2 channel were evaluated by monitoring Ca2+ signals in HEK293 cells expressing WT and mutant RyR2. We investigated a role of a RyR2 mutation in the recent tertiary structure of RyR2. Results: Though a 17-year-old man diagnosed as CPVT had implantable cardioverter defibrillator (ICD) and was going to undergo catheter ablation for the control of paroxysmal atrial fibrillation, he suddenly died at the age of twenty-one because of ventricular fibrillation which was spontaneously developed after maximum inappropriate ICD shocks against rapid atrial fibrillation. The genetic test revealed a de novo RyR2 mutation, Gln4936Lys in mosaicism which was located at the alpha-helix interface between U-motif and C-terminal domain. In the functional analysis, Ca2+ release from endoplasmic reticulum via the mutant RyR2 significantly increased than that from WT. Conclusion: A RyR2 mutation, Gln4936Lys, to be documented in a CPVT patient with exercise-induced ventricular tachycardias causes an excessive Ca2+ release from the sarcoplasmic reticulum which corresponded to clinical phenotypes of CPVT. The reduction of inappropriate shocks of ICD is essential to prevent unexpected sudden death in patients with CPVT.