post-05Milo is a seven-year-old feline with hypertrophic cardiomyopathy. Milo presented to our practice after already having been through quite the ordeal. What a tough little guy!

Milo presented for limping, and had several x-rays taken at his primary veterinarian. At that time, the veterinarians treating Milo felt it might best serve him to have a cardiology work-up when his balance became unsteady and his breathing became labored. Additionally, his appetite had decreased dramatically and he was unable to go to the bathroom. The x-rays revealed cardiomegaly and a complicated lung pattern that pointed toward pulmonary edema.

Dr. Orr, board certified cardiologist with VRCC Cardiology, completed a complete physical exam on Milo. Upon repeating the x-rays for comparison, the heart enlargement was unchanged but the previous lung pattern, or pulmonary edema (fluid in his lungs), had resolved. The radiographs therefore indicated that Milo’s congestive heart failure was controlled. To determine the cause for his heart failure, an echocardiogram was performed. The echocardiogram was consistent with hypertrophic cardiomyopathy, the most common form of heart disease in felines.


Hypertrophic Cardiomyopathy (HCM) is an acquired and typically idiopathic (unknown cause) heart muscle disease commonly diagnosed in felines.  It is characterized by concentric hypertrophy (thickening) of the left ventricle (LV), resulting in heart muscle stiffness and impaired relaxation. This impairs the filling of the LV leading to dilation of the top storage chambers, called the atrium.  In most cases, the primary cause is unknown, but it may occur secondary to hyperthyroidism, hypertension, acromegaly and other less common causes.

A familial and heritable form has been identified in Maine Coons and Ragdolls and a genetic test is presently available in these breeds through the veterinary cardiac genetics lab at North Carolina State. The median age for diagnosis is typically 5.5 years, and is equally distributed amongst males and females.  It is currently estimated that HCM represents about 68% of all feline cardiomyopathies.  Affected cats are at risk for the following:  arrhythmias related to heart muscle thickening and ischemia (decreased oxygen supplied to the muscle), congestive heart failure and feline arterial thromboembolism (clots) related to the left atrial enlargement.

Treatment goals are to improve the relaxation of the heart, reduce fluid accumulation if present, prevent thromboembolic disease, and treat any underlying disorder (hyperthyroidism, hypertension) if present.  If cats have obstruction to outflow of blood from the LV (caused by systolic anterior motion of the mitral valve), then beta blockers are typically prescribed. For cats who are non-obstructive, treatment with calcium channel blockers such as Diltiazem can be used to help with myocardial relaxation.

Prognosis is variable, and the median survival time is reported to be 563 days for cats with heart failure.  For those cats with feline arterial thromboembolism, survival is reported at 77-184 days.
Dr. Orr discontinued Milo’s antibiotic, which may have contributed to Milo’s lack of appetite, altered the increment for Milo’s diuretic dosage to improve kidney function, and added Clopidogrel to help prevent clot formation. This was added because Milo’s initial limping was most likely due to a blood clot. A recent study, the FAT Cat Study, revealed that Clopidogrel is superior to Aspirin for clot prevention. Cats with a history of clots are at high risk for reoccurrence, typically within 6 months. These clots can travel anywhere, but they generally affect the pelvic limbs. It is important to remember they can also affect the forelimbs and cause a transient unilateral lameness, typically the right front.

Milo was discharged to return home and has been doing well. His appetite has improved and he is taking his medication daily. Milo is back to playing with his toys, and according to his mom, back to his ornery self.