by Suzanne Morris, DVM

As Valentine’s Day approaches, it seems an appropriate time to post about hearts. Cat hearts. In a manner similar to humans, cats can suffer from disease affecting the heart muscle. The most common of these in cats is hypertrophic cardiomyopathy (HCM). HCM is an abnormal thickening of the wall of the lower left chamber of the heart. As the chamber wall thickens inward, there is less space for blood flow through the chamber. This alteration of the blood flow through the heart can lead to complications including blood clot formation and congestive heart failure. Sudden death can affect patients with myocardial disease—human and cats alike. Many cats who suffer from these complications of HCM will have no medical history of heart disease. –They may not have any heart arrhythmia or murmur detected on physical exam or any outward signs of the disease, and their heart size and shape may appear within normal limits on chest x-ray films, which can make HCM a silent killer.

It is not fully understood what causes HCM in all cats. Genetic mutations have been reported in Maine Coon cats and genetic factors have been reported in other purebred cats (Ragdolls and British Shorthairs). A distinction is made between HCM that results from (is secondary to) an underlying condition (such as hyperthyroidism or chronic steroid administration) and HCM wherein there is no underlying disease (and is a primary disease).

The major complications of HCM include the previously-mentioned sudden death, congestive heart failure (CHF), and arterial thromboembolus (ATE) formation, also known as “saddle thrombus.” In ATE, a clot forms in the upper left heart chamber, which can dislodge from the heart, travel down the aorta, and lodge at some point along the vessel (classically, at the point where the aorta branches into the vessels of the legs), thereby disrupting circulation to the “downstream” tissues (often the limbs). Owners often will discover cats affected by this condition dragging a limb or both hind limbs and vocalizing (as it is a very painful condition).  With treatment, sometimes these patients can be helped through these ATE and CHF crises, but the long-term prognosis is often poor, as there is an underlying heart disease that will likely progress.

The best tool at this point in time for detecting HCM is ultrasound imaging of the heart (echocardiography), which allows for measurements to be taken of the heart walls.  This imaging will often be recommended for patients with detected abnormalities such as heart murmurs on physical exam—the difficulty with this is that not all patients with HCM will have detectable heart murmurs on physical exam. Echocardiography is often performed by a cardiologist who can then create a plan for management of the patient, which may consist of medications (such as beta blockers) or simply routine echocardiographic monitoring.

Your veterinarian can help to determine a diagnostic plan for your kitty if you have concerns. In the meantime, your kitty will be relying on your big heart for a little extra attention this Valentine’s Day…


Ferasin L. Feline Myocardial Disease: Classification, Pathophysiology, and Clinical Presentation. Journal of Feline Medicine and Surgery 2009;11: 3-13.

Ferasin L, Feline Myocardial Disease 2: Diagnosis, Prognosis, and Clinical Management. Journal of Feline Medicine and Surgery 2009; 11: 183-194.