Phenotypic expression, genotypic profiling and clinical outcomes of infantile hypertrophic cardiomyopathy: a retrospective study.

Background: Infantile hypertrophic cardiomyopathy (HCM) is a heterogeneous disorder. Apart from registries in high-income nations, there is a shortage of data on the aetiological basis of infantile HCM in low- and middle-income nations. This study attempts to characterise the phenotypic expression, genetic architecture and short-term clinical outcomes of infantile HCM from a South Asian tertiary referral centre.

Methods: This study includes all infants from the Amrita HCM cohort between January 2011 and July 2021. Clinical history, ECG, echocardiographic data, and genetic analyses were evaluated.

Results: 34 patients with infantile HCM were diagnosed at a median age of 3.7 months (IQR 1-6 months). Underlying aetiologies were RASopathy (n=13; 38%), non-syndromic (n=12; 35%) and inborn errors of metabolism (n=9; 27%). Genetic analysis was done in 20 patients (59%) with a yield of 90%. Clinical presentation included failure to thrive (n=29; 85%), dyspnoea on exertion (n=23; 68%) and clinical heart failure (n=24; 71%). Echo showed concentric left ventricular hypertrophy in 22 patients (65%), obstructive HCM in 11 patients (32%) and left ventricular systolic dysfunction in 6 patients (18%). The mortality rate was 10.0 deaths per 100 patient years over a median follow-up period of 3.1 years. The main risk markers for mortality were the age at diagnosis, gender and concentric Left ventricular hypertrophy.

Conclusions: This cohort demonstrates the morphological, functional and genetical heterogeneity of infantile HCM, enunciating the need for integration of cardiology, metabolic and genetic services to achieve optimum outcomes in these patients.