About 1% to 5% of patients with dilated cardiomyopathy (DCM) have an illness caused by variations in myosin heavy chain 7 (MYH7); however, the clinical features and natural history of MYH7-related DCM are poorly understood. For a study, researchers sought to identify the phenotype and prognosis of DCM associated with MYH7. Additionally, they assessed the impact of variation position on phenotypic expression.

A total of 147 DCM-causing MYH7 variant carriers (35.6±19.2 years; 47.6% female; 29 foreign locations) were investigated clinically.

At the time of the first assessment, 106 (72.1%) individuals had DCM (Left ventricular ejection fraction: 34.5%±11.7%). 23.7% of carriers who were originally phenotype-negative acquired DCM during the median follow-up of 4.5 years (IQR: 1.7-8.0 years). By the ages of 40 and 60, phenotypic expression was 46% and 88%, respectively, with 18 individuals (16%) receiving their initial diagnosis before the age of 18. 36% of DCM patients had imaging evidence of LV noncompaction. 28% of the patients had left ventricular reversal remodeling during follow-up. At 5 years, the incidence of adverse cardiac events among DCM patients was 11.6%, with 5 (4.6%) fatalities brought on by end-stage heart failure (ESHF) and 5 (4.6%) patients needing a heart transplant. Major ventricular arrhythmia rates were minimal (1.0% and 2.1% at 5 years in patients with DCM and in those with LVEF of ≤35%, respectively). ESHF and primary ventricular arrhythmia were also dramatically reduced compared to DCM brought on by TTN truncating mutations and LMNA-related DCM.

Early age of start, strong phenotypic expression, modest left ventricular reverse remodeling, and frequent progression to ESHF were characteristics of MYH7-related DCM. Ventricular arrhythmias, which were uncommon, were overshadowed by the consequences of heart failure.

Reference: jacc.org/doi/10.1016/j.jacc.2022.07.023