Clinical to Population Prevalence of Hypertrophic Cardiomyopathy Phenotype: Insights From the National Echo Database Australia

BACKGROUND:There is a paucity of data describing the underlying prevalence of hypertrophic cardiomyopathy (HCM), a primary genetic disorder characterised by progressive left ventricular (LV) hypertrophy and sudden death, from both a clinical and a population perspective. METHODS:We screened the echocardiographic reports of 155,668 men and 147,880 women within the multicentre National Echo Database Australia (NEDA) (2001-2019). End-diastolic wall thickness ≥15 mm anywhere in the left ventricle was identified as a characteristic of an HCM phenotype according to current guideline recommendations. Applying a septal-to-posterior wall thickness ratio >1.3 and LV outflow tract obstruction ≥30 mmHg (when documented), we further identified asymmetric septal hypertrophy and obstructive HCM (oHCM), respectively. The observed pattern of phenotypical HCM within the overall NEDA cohort (>650,000 cases) was then extrapolated to the ∼539,000 (5.7% of adult population) and ∼474,000 (4.8%) Australian men and women, respectively, who were investigated with echocardiography in 2021 on an age-specific basis. RESULTS:Overall, 15,380 cases (mean age 71.1±14.6 years, 10,138 men [65.9%]) with the characteristic HCM phenotype within the NEDA cohort were identified. Of these 15,380 cases, 5,552 (36.1%) had asymmetric septal hypertrophy, and 2,276 of the 10,290 cases with LV outflow tract obstruction profiling data (22.1%) had obstructive HCM. A further 3,389 of 13,715 cases (24.7%) had evidence of LV systolic dysfunction (LV ejection fraction <55%). Within the entire NEDA cohort (including those without LV profiling), HCM was found in 10,138 of 342,161 men (2.96%; 95% confidence interval [CI] 2.91%-3.02%) and 5,242 of 308,539 women (1.70%; 95% CI 1.65%-1.75%). When extrapolated to the Australian population, we estimate that a minimum of 15,971 men and 8,057 women presented with echocardiographic features of phenotypical HCM in 2021. This translates into a minimum caseload/prevalence of ∼17 adult men (∼2.5 in those aged ≤50 years) and eight adult women (∼1 in those aged ≤50 years) per 10,000 population meeting phenotypical HCM criteria. CONCLUSIONS:Using contemporary Australian echocardiographic and population data, we estimate that a minimum of 15,971 (17.5 cases/10,000) men and 8,057 women (8.2 cases/10,000) had echocardiographic evidence of phenotypical HCM in 2021. These disease burden data are particularly relevant as new treatment options are emerging.