[Overlapping Phenotype: Left Ventricular non-Compaction and Hypertrophic Cardiomyopathy]

Aim To study the clinical course of the mixed phenotype (hypertrophic cardiomyopathy, HCMP, and left ventricular noncompaction, LVNC); to determine its genetic causes; and to evaluate incidence of cardiovascular complications (CVC) during the follow-up period.Material and methods In screening of 286 patients with HCMP, 8 of them (2.8 %; median age, 41.5 years; 4 men and 4 women) from unrelated families were found to have the mixed phenotype (combination of HCMP and LVNC). For their 10 first-degree relatives, the most frequent phenotype was HCMP without LVNC; however, both isolated LVNC and the mixed phenotype were also observed. Criteria for HCMP and LVNC were confirmed by echocardiography and cardiac magnetic resonance imaging Genotyping was performed by high-throughput sequencing NGT using the TruSight Cardio Sequencing Panel kit.Results Probands with the HCMP+LVNC combination compared to first-degree relatives with isolated HCMP and LVNC were characterized by more pronounced left ventricular dysfunction (ejection fraction, 43.57±7.6 and 53.64±6.51 %, respectively; p<0.001), a higher risk of CVC, and a higher incidence of ventricular tachyarrhythmias (7.9 and 2.2 %, respectively; p<0.01). 11 mutations in 5 genes were found in 8 patients with the mixed phenotype. 72.7 % of mutations were in the MYH7 and MYBPC3 genes that encode the heavy chain of β-myosin and myosin-binding protein C, respectively; however, in some cases, replacements in other genes (DTNA, TGFB2) were also found.Conclusion The mixed phenotype (HCMP and LVNC) is associated with more severe clinical course of the disease and unfavorable CVC.