Hypertrophic cardiomyopathy (HCM)
The most common heart disease in cats — thickening of the heart muscle. Often silent until decompensation. Maine Coons, Ragdolls, British Shorthairs predisposed.
Hypertrophic cardiomyopathy is a thickening of the heart's ventricular walls, reducing the chamber size and the heart's ability to fill properly. It is the most common acquired heart disease in cats and often silent for years before decompensating.
Predisposed breeds include Maine Coon, Ragdoll, British Shorthair, Sphynx, Persian, and Norwegian Forest Cat. Many lines have a genetic mutation that can be tested for.
Most cats present in one of three ways: an incidental heart murmur on routine exam, a sudden arterial thromboembolism (a clot lodging in the back-leg arteries, causing sudden paralysis and severe pain — an emergency), or congestive heart failure (rapid breathing, lethargy, anorexia).
Diagnosis is by echocardiogram. NT-proBNP blood test is a useful screening tool but not definitive. Once diagnosed, treatment depends on stage — beta-blockers, ACE inhibitors, antithrombotic drugs (clopidogrel), and diuretics for heart-failure cases.
Annual cardiac auscultation from kittenhood, and proactive echocardiography in predisposed breeds, gives the best chance of catching HCM early. There is no cure, but staged management substantially extends quality of life.