Treating HCM

At present there is, unfortunately, no cure for HCM.

Treatment goals, and therefore what drug is prescribed, will depend on the individual cat's situation. That is, treatment options vary depending on the cat's clinical signs and the degree and type of functional impairment resulting from the hypertrophy.

If the cat's heart is hypertrophied as the result of another disease, treatment of the primary disease might result in some improvement of the heart condition, but the potential for improvement is largely unknown and, in some cases, disproved.

Hypertrophy affects the heart's ability to function properly. In a cat with moderate to severe disease that is not in heart failure, one or more medications may be prescribed in an effort to reduce the risk of heart failure and to help the heart function as efficiently as possible. A common intent of medication is to improve the ability of the left ventricle to fill with blood. In some cases this involves slowing an abnormally fast heart rate; in others, trying to increase the ability of the heart muscle to relax; in still other cases, a combination of these goals is sought. However, there is no drug therapy that is known to actually help prior to the onset of heart failure. Recently it has been shown that while so-called ACE inhibitors are helpful in managing heart failure in cats with HCM, they are not effective at improving heart function or slowing the progression of the disease when it is mild to moderate and the cat is not in heart failure. There is no drug therapy known to prevent sudden death in cats with HCM. One should also be aware that medical opinions vary regarding the efficacy of the available medications and at which stage a particular medication is most warranted.

Given the complexity of HCM when it has progressed to clinical disease and the variety of medications available for ongoing disease management, it is strongly recommended that a veterinary cardiologist be consulted by the cat's owner or their veterinarian (or, ideally, both) for disease management options and planning. The body of knowledge about HCM and its treatment options is always evolving, and a veterinary cardiologist will be aware of the most current information about the disease and the medications that may be prescribed.

Heart failure

A diuretic must be prescribed if a cat is suffering from congestive heart failure. Fluid accumulation is lessened by forcing the kidneys to excrete more sodium and water. The diuretic dose must be carefully tailored to the severity of the heart failure and the cat's response. Treatment does not guarantee that heart failure can be controlled and the heart failure often becomes resistant to treatment over time. An ACE inhibitor should also be given to any cat with heart failure due to HCM. Vetmedin® (pimobendan), a new heart drug for dogs, should never be given to a cat with HCM as it may make things worse. A cat with a large amount of pleural effusion (i.e., fluid around the lungs in the chest cavity) should have that fluid removed using a needle or catheter and syringe. This may need to be done periodically.

Prevention of clot formation

A medication that reduces the ability of the blood to clot may be prescribed if the cat is felt to be at risk for blood clot formation. There also is no drug therapy that has been proven to reduce the risk of clot formation. Aspirin is generally regarded as ineffective for this purpose. Plavix® (clopidogrel) is currently being studied. A low molecular weight heparin may occasionally be prescribed (these drugs must be injected beneath the skin with a needle and syringe). Coumadin® (warfarin) may also be used for this purpose but must be closely monitored to ensure the cat is not placed at risk for hemorrhage. Treatment does not guarantee that a clot will not form. In fact, rethrombosis is common with both aspirin and Coumadin® in cats that have already thrown one clot.

A cat that is suffering from severe signs such as heart failure or leg paralysis requires veterinary care as quickly as possible. Ongoing disease management options can be explored when the acute problems have been brought under control.

The veterinarian will want to examine any cat with heart failure periodically to determine how it is responding to treatment. From time to time these examinations may include tests such as an echocardiogram, an electrocardiogram (ECG or EKG), and chest X-rays. Medication may be adjusted or augmented based on the cat's condition and its response to treatment.

The owner of a cat with HCM should be sensitive to changes in the cat's condition and should not hesitate to seek veterinary advice if the cat seems unwell. The veterinarian may show the owner how to check the cat's sleeping respiration (breathing) rate at home, since an increased rate could be a sign that congestive heart failure is developing or redeveloping. The owner should also take note if the cat's sides expand noticeably in and out as it breathes (to a greater than normal extent). Even if the respiration rate seems normal, labored breathing could also be a sign of heart failure. A cat that exhibits any breathing abnormalities should be seen by a veterinarian.

Never attempt to medicate your cat without veterinary instruction and supervision!

Some owners wonder if their cat might benefit from a vitamin or nutritional supplement. Currently, there is no evidence that HCM is the result of any nutritional deficiency. In addition, it is possible that some ingredient in a supplement would be inappropriate either for some aspect of your cat's condition, or in combination with a medication your cat is taking. Please discuss any questions you might have about your cat's nutrition with your veterinarian. Inappropriate supplementation could have potentially serious consequences for your pet.

Limb paralysis can be a devastating complication of HCM. For more information about the challenges of treating a thromboembolism (blood clot), please see Oakland Veterinary Referral Services' in-depth discussion about feline thromboembolic disease.

If your cat has signs of limb paralysis, please seek veterinary care as soon as possible. Blood clots are often very painful; and the cat may also have, or be at risk for, congestive heart failure. Your veterinarian will examine your cat and discuss the treatment alternatives appropriate for your cat's condition. Please do not try to "wait it out" or attempt a home remedy. Medications such as aspirin can be toxic to cats if not administered appropriately and should only be given under the direction of a veterinarian.