Genotype-phenotype relationship in hypertrophic cardiomyopathy

Abstract Background/Introduction Hypertrophic cardiomyopathy (HCM) is an inherited highly heterogeneous disease with variable penetrance and expression, but the exact relationship between the underlying genetic cause and the clinical course remains elusive. Purpose The aim of our study was to analyse the phenotypic and molecular characteristics of individuals with HCM examined and treated at our University Hospital. Methods Clinical data from adult HCM patients treated at our hospital between 2005 and 2023 were analysed. Informed consents to participate in the study were obtained from all participants. Clinical manifestation, instrumental examination and next generation sequencing (NGS) data of HCM related genes were collected. The Mann–Whitney U for two groups and Kruskal–Wallis tests for more than two groups were used to compare continuous variables. Univariate logistic regression was used to analyze categorical variables. Results The study involved 191 unrelated individuals, 58.6% males, the median age at HCM diagnosis was 50, interquartile range 37 – 60 years. A median follow-up was 3.9 [1.6-6.4] years. Pathogenic and likely pathogenic (P/LP) variants were identified in 45.5% (N=87) of affected individuals. Truncating variants were observed in 31 individuals. MYBPC3 P/LP variants were the most common (N=47), following by MYH7 (N=22) and other (N=18). Individuals with MYBPC3 P/LP truncating variants had higher HCM estimated 5-year risk of sudden cardiac death (SCD) during primary evaluation (3.1 [2.5-4.6]) compared to individuals with P/LP variants in other genes (2.4 [1.9-3.7]) and individuals with negative NGS results (1.8 [1.5-2.7], p<0,001). Patients with MYBPC3 P/LP variants experienced the earliest onset of symptoms (median age 37.0 [30.5-50.0] years) and HCM diagnosis (median age 38.0 [31.0-51.5] years) compared to individuals with other genes P/LP variants (median age 46.0 [31.0-56.2] years and 47.5 [31.5 – 59.5] years, respectively) and genotype negative individuals (median age 51.5 [44.0-61.0] years and 52.0 [45.0-63.2] years, respectively), p>0,001). The presence of P/LP variant was associated with significantly thicker left ventricular wall (maximal thickness) on cardiac imaging in comparison with negative NGS results (18.0 [15.0-21.0] mm vs. 16.0 [14.0-18.0] mm, p=0.002 on transthoracic echocardiography and 20.0 [17.0-22.5] mm vs. 18.0 [16.0-20.0] mm, p<0,001 on cardiac magnetic resonance). The presence of MYBPC3 truncating variants were associated with the greatest risk of ventricular tachycardia in comparison with negative NGS results (OR 3.05, 95% CI:1.3, 8.0, p=0.025). Conclusion More severe HCM phenotype is associated with detection of P/LP variants in HCM related genes. The presence of the MYBPC3 P/LP variant is associated with an earlier onset of the disease and truncating variants of this gene are related to a higher risk for ventricular tachycardia and an estimated 5-year risk of SCD.