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.