Profile of arrhythmias and conduction disorders in patients with familial hypertrophic cardiomyopathy: data from a multicenter registry

Aim . To analyze the profile of cardiac arrhythmias and conduction disorders in patients with familial hypertrophic cardiomyopathy (HCM) based on data from the registry of the National Medical Research Center for Therapy and Preventive Medicine and the Lomonosov Moscow State University (2021-2026). Material and methods . The analysis included 136 patients (48 men, 88 women; aged 19-78 years) — probands and relatives with a verified diagnosis or pathogenic variants in genes associated with HCM. All patients underwent additional examination, including electrocardiography (ECG) and Holter ECG monitoring. Based on this examination, 81 patients with arrhythmias and conduction disorders were identified. Genetic testing identified variants in the MYH7 , MYBPC3 , MYL2 , DSG2 , JPH2 , FLNC , ALPK3 , CACNA1C , ACTC1 , LDB3 , and TNNI3 genes in 60 patients. Results . Atrial fibrillation was recorded in 13,9% of cases (permanent in 3,7%, paroxysmal in 9,6%), ventricular premature beats in 59,6%, and ventricular fibrillation in 2,2%. Ventricular tachycardia (VT) was detected in 24,3% of all registry patients and in 34% of patients with gene variants (n=60). Degree I atrioventricular (AV) block was detected in 11% of cases, and degree II-III AV block — in 4,4%, left bundle branch block — in 5,9%. In genetic analysis, VT (80 vs 20%, p=0,001) and first degree AV block (45 vs 8%, padj=0,027) were more common in carriers of variants in the MYBPC3 gene (n=20) compared with MYH7 (n=25). The groups did not differ in interventricular septal thickness and left ventricular mass index after adjustment for sex, age and body mass index (BMI), whereas LV posterior wall thickness was higher in the MYBPC3 group (padj=0,028). The median risk of sudden cardiac death, calculated according to the Hypertrophic Cardiomyopathy. Risk-Sudden Cardiac Death (HCM Risk-SCD) score was 4,9% [3,4; 7,2] over 5 years n carriers in the MYBPC3 gene variants, compared to 3,1% [2,2; 6,8] (p=0,916) in carriers of MYH7 variants. However, no significant differences were found between the groups. Conclusion . The incidence of VT in familial HCM varies significantly depending on the genotype, reaching 80% in carriers of MYBPC3 variants. Patients with familial HCM, especially those carrying MYBPC3 variants, are recommended to undergo follow-up monitoring with Holter ECG every 6-12 months for the early detection of VT. Detection of VT allows for stratification of sudden cardiac death risk according to the HCM Risk-SCD score and determines indications for implantable cardioverter-defibrillator (ICD).