About Hypertrophic Cardiomyopathy (HCM)

Many people may be unfamiliar with HCM, but it’s actually the most commonly inherited heart disease.¹ You may have heard of the term ‘oHCM’ or ‘HOCM’, a type of HCM that causes obstruction and affects how blood flows out of the heart, which is explained further down the page. It is important to note that not all people with HCM have this obstruction.

Here you will learn about who may be at risk of HCM, how it affects the heart, and the difference between the two types of HCM.

Who is at risk of HCM?

HCM can affect anyone regardless of age, gender or ethnicity.

The reported prevalence of HCM ranges from 1 in 200 to 1 in 500 people in the general population^1-2*†

In Australia, a minimum of 15,971 men (~17 cases/10,000) and
8,057 women (~8 cases/10,000) were estimated to have HCM in the year 2021^3‡

HCM can be an inherited disease, meaning it can run in families. However, not all cases of HCM are genetic

^*The 1995 CARDIA study, a multicenter, US-population-based echocardiography study of 4111 subjects (aged 23-35), identified the prevalence of HCM as 1:500 people in the general population.²
^†The 2015 Semsarian publication identified that the prevalence of HCM gene carriers could be as high as 1:200.¹
^‡Results from the multicentre National Echo Database Australia (NEDA) extrapolated to the Australian population.³

What causes the symptoms of HCM?

The heart is a muscle that pumps oxygen around the body by contracting and relaxing.

In HCM, the heart muscle becomes thickened and stiff. Depending on where and how much the heart muscle thickens, it can reduce the amount of oxygen-rich blood that is pumped out to the rest of the body, resulting in symptoms of HCM.

Understanding the types of HCM

There are two main types of HCM:

Non-obstructive HCM, where the heart muscle thickens but it doesn't affect the flow of blood out of the heart.
Obstructive HCM, also known as oHCM or HOCM, where the thickened heart muscle makes it harder to pump blood around the body. It is estimated that obstructive HCM accounts for roughly 70% of all HCM cases.⁴

Obstructive HCM

Non-obstructive HCM

References: 1. Semsarian C, et al. J Am Coll Cardiol 2015;65:1249–1254. 2. Maron BJ, et al. Circulation 1995;92:785–789. 3. Playford D, et al. Heart Lung Circ 2024;33:212–221. 4. Ommen SR, et al. J Am Coll Cardiol 2020;76:e159–e240.

CV-AU-2500002. April 2025.