An overview of heart disease in cats
Integrative Pet Vet
The heart is a marvel of engineering and function. In the resting cat, it is a muscle that contracts on average almost 190,000 times per day (130-140 times per minute) only resting briefly between contractions. In addition, the heart has the ability to increase its rate to meet the needs of the exercising body.
The heart is designed to force blood to move forward with each contraction for efficient movement throughout the body and lungs. This forward movement of the blood is made possible because of the valves in the heart and in the large arteries leaving the heart along with the elastic fibers in the major arteries. Valves in the veins prevent blood from moving backward while muscle contraction acts to squeeze blood forward toward the heart.
In order to efficiently circulate blood to all parts of the body, the heart is divided into two sides. Each side has its own circulation path — the right side pumps to the lungs and left side pumps to the rest of the body. Oxygenated blood from the lungs returns to the left side of the heart to be pumped to the rest of the body. Deoxygenated blood from the body moves into the lung circulation through the right side of the heart.
The general term for heart muscle problems in cats is cardiomyopathy. This means heart (cardio-) muscle (myo-) disease (pathy). These diseases can be categorized as primary or secondary. Primary cardiomyopathy is a problem specific to the heart muscle, while secondary cardiomyopathies are caused by another health issue, such as an overactive thyroid.
Primary cardiomyopathies include: 1) hypertrophic, 2) restrictive and 3) dilated.
Hypertrophic cardiomyopathy (HCM) is the most common, accounting for 85-90 percent of primary patients. HCM is a condition where the heart muscle becomes abnormally thickened. This thickening reduces the volume of blood filling the heart chamber and prevents the heart muscle from relaxing between contractions. It mainly affects the left side of the heart. There is no clear explanation for its cause, but a genetic component is likely.
In the restrictive cardiomyopathy (RCM), the heart muscle has increased amounts of fibrosis (scar type tissue), making the heart walls stiff so the chambers cannot fill with blood properly or empty completely with a contraction. RCM occurs in about 10 percent of primary cardiomyopathy patients and mainly affects geriatric cats.
Dilated cardiomyopathy (DCM) is just as it sounds. The heart muscle is thinner than normal and cannot contract properly. DCM is relatively uncommon, accounting for about 1-2 percent of the patients. DCM was once more common until it was determined that the cause was a taurine deficiency. Pet foods generally contain appropriate levels of taurine now.
Secondary cardiomyopathies occur when the heart is affected by a problem that exists in another part of the body. These include nutritional imbalances, hyperthyroidism, cancer, infections, immune reactions and toxicities.
Indications that a cat is affected by cardiomyopathy include difficult or rapid breathing, general weakness, lethargy, poor appetite, and sudden weakness or paralysis in the back legs. Gallop sounds or abnormal rhythm may be heard when listening to the heart. Lung sounds may be muffled or harsh. Body temperature may be low due to poor blood circulation.
Evaluation for a diagnosis generally includes blood tests, chest X-rays, ultrasound of the heart and electrical recordings of the heart. Treatment recommendations depend on the diagnosis and how advanced the problem is. For example, in life-threatening congestive heart failure, a rapid response is indicated and may include the use of diuretic drugs, oxygen therapy, blood pressure medication and drugs to improve heart contractions. Treatment for blood clots may be important. Factors contributing to the heart problem, like an overactive thyroid or an infection should be addressed.
Cats that are in early stages of cardiomyopathy or not in a life-threatening situation may benefit from long-term support in addition to any medications that are necessary. Supportive care may include nutrients that are beneficial for the heart muscle like vitamins E and C, taurine, L-carnitine, and appropriate levels of minerals including magnesium and calcium. Herbal therapies like hawthorn may be helpful for improving blood flow to the heart muscle and increasing the strength of contraction.
With reduced heart function, the kidneys may be compromised. In addition, ongoing stress places more demands on the adrenal glands. Support for both the kidneys and adrenal glands should be considered as part of an overall care plan.
If you have questions about heart disease in cats, contact your veterinarian.
Ron Carsten, DVM, PhD, CVA, CCRT was one of the first veterinarians in Colorado to use the integrative approach, has lectured widely to veterinarians, and has been a pioneer in the therapeutic use of food concentrates. He has a Doctor of Veterinary Medicine, a PhD in Cell and Molecular Biology, and is a Certified Veterinary Acupuncturist and Canine Rehabilitation Therapist. He practices integrative veterinary medicine in Glenwood Springs.
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