Cats most commonly suffer from hypertrophic cardiomyopathy (HCM), a condition where the heart muscle becomes abnormally thick. This can reduce the heart’s ability to relax and fill properly. With time this may lead to complications such as arterial thromboembolism (where blood clots form and block circulation, often to the hind limbs), or heart failure (characterised by fluid accumulation in or around the lungs).
The cause of HCM is not fully understood, but genetics play a significant role. Certain breeds—including Maine Coon, Ragdoll, British Shorthair, American Shorthair, Sphynx, Bengal, Chartreux, Norwegian Forest, Siberian, and Persian cats—are more prone to HCM due to inherited mutations in cardiac genes. These mutations affect proteins involved in the contraction and relaxation of heart muscle cells.
In addition to genetic factors, endocrine disease, high blood pressure, inflammation of the heart and some types of cancer can also lead to heart muscle thickening that mimics HCM. These conditions must be ruled out before confirming a diagnosis of primary HCM.
Cats can also suffer from congenital defects and other less common types of heart disease.
