Clinical and genetic characterization of patients with catecholaminergic polymorphic ventricular tachycardia: a case series

AIM: of the study was to evaluate the clinical and genetic characteristics, including the development of adverse events and outcomes in patients with catecholaminergic polymorphic ventricular tachycardia (CPVT). MATERIALS AND METHODS: The clinical phenotype of eight patients with CPVT, two of whom were relatives of probands, was observed over 4 years. The clinical and instrumental study included ECG-12, 24-hour Holter ECG monitoring, genealogical history collection and family history of sudden cardiac death (SCD), transthoracic echocardiography and cardiac magnetic resonance imaging to detect structural myocardial changes, electrophysiologic study according to indications, and ICD monitoring. High-throughput sequencing (NGS) was utilized to search for mutations in genes linked to the onset of channelopathies and other inherited rhythm disorders. RESULTS: In 8 patients, nucleotide variants of pathogenicity classes III-V were identified according to the ACMG (2015) criteria in the RYR2 gene associated with CPVT. Pathogenic (IV-V class) and likely pathogenic (IV class) mutations in the RYR2 gene were found in 6 (75%) probands, variants with uncertain clinical significance (VUS, class III) were found in 2 patients. At the time of diagnosis, transient QTc interval prolongation of more than 480 ms was detected in 4 (50%) patients; bradycardia less than 54 beats/min — in 2 (25%) patients, sequences of supraventricular tachycardia and ventricular tachyarrhythmia — in 2 (25%) patients. The most severe form of the disease with marked clinical manifestations and an episode of clinical death with subsequent resuscitation, as well as a transient QTc interval prolongation exceeding 500 ms was observed in patients with mutations c.11814C A (p.Ser3938Arg, rs794728704); c.463G A (p.Gly155Arg) and c.14876G A (p.Arg4959Gln, rs794728811) in the RYR2 gene. Three (37.5%) patients underwent ICD implantation; one for primary SCD prevention and two for secondary prevention. CONCLUSION: In this study, the spectrum of clinical manifestations in patients with genetically confirmed CPVT was examined. The findings highlight transient QTc interval extensions, significant sinus bradycardia, and sequences of supraventricular tachyarrhythmias, which can escalate into life-threatening ventricular tachyarrhythmias in CPVT patients.