Heart Healthy Pets: Part Two

By Dr. Laura Hady

Last month, I covered some basic facts about the heart and how it works. This month I’m discussing the most common heart and circulatory diseases of dogs and cats. While symptoms of heart disease, such as cough, can mimic other diseases, such as pneumonia, there are particular symptoms that can help you and your veterinarian treat your pet properly.

  • Mitral valve disease, also known as mitral valve regurgitation, is the most common form of heart disease in dogs. Your dog may or may not show clinical signs until the later stages. Toy breeds are more prone to have this disease where the collagen protein in the mitral valves becomes weaker. Using a stethoscope, your veterinarian may hear a left-sided murmur that sounds like a washing machine. At the later stages of abnormal blood flow through the valves, there is a back-up of oxygenated blood into the lungs. This oxygenated blood mixes with the unoxygenated blood, meaning less oxygenated blood gets to the tissues. Some pets will also have a cough because of lung congestion that can result. Medications that help with this issue include pimobendan, blood pressure medication, and diuretics to decrease the fluid build-up in the lungs.
  • High blood pressure (hypertension) can occur in both dogs and cats. Hypertension not only increases the work of the heart, but it can also affect the kidneys, lungs, and vision. Blood pressure consists of two numbers. The top number is the systolic pressure in your pet’s blood vessels when their heart beats. The bottom number is the diastolic pressure in their vessels between heart beats. A higher pressure reflects increased work or pressure against the artery walls during each heart contraction. Animal vessels harden and can narrow as they age, which makes the vessels less elastic. Your veterinarian can screen your pet for high blood pressure as part of senior wellness programs, and if it is high, your veterinarian may treat your pets with medications that are similar to those used in human medicine.
  • Hypertrophic cardiomyopathy is more commonly found in cats but can also be found in small-breed dogs. The term simply means that the heart muscle, usually in the left ventricle, has nearly doubled. The problem is that the left ventricle space is so much smaller that only one-fifth of the normal amount of oxygenated blood can reach the tissues in the body. Clinical signs in cats include less energy, decreased appetite, and/or a possible sudden loss of the use of the one or both hind limbs due to a saddle thrombus (think blood clot) in the femoral artery. This causes loss of oxygenated blood to the muscles and nerves of the back legs. Your veterinarian may hear an increased heart rate sounding like a gallop rhythm when they listen to your cat’s heart. While ultrasound of the heart is the best way to diagnose this condition, your veterinarian may also want to take radiographs of your cat’s chest as well as draw blood to check the liver and kidney function. Medications include drugs to help slow the heart rate and drugs to decrease blood pressure.
  • Dilated cardiomyopathy is more likely to affect cocker spaniels and larger breeds of dogs (Doberman pinschers, Great Danes, German shepherds, and retrievers). In this disease, the heart muscle wall has become thinner; there is death of the heart muscle cells; and the heart becomes less efficient at pumping oxygenated blood to the tissues. The heart and brain will compensate for this by increasing the heart rate to keep blood going to the tissues. A subset of dogs and cats will have dilated cardiomyopathy due to a decreased amount or absorption of the amino acid taurine in their diet, while others have decreased carnitine in their heart muscle. Pet owners may notice weakness, weight loss, cough, a distended abdomen (from fluid backing up into the liver and abdomen), and sudden death. Your veterinarian will notice an increased heart rate, a different type of heart beat (arrhythmia), abnormal lung sounds, and a pale color to the gums in the mouth. Diagnosis is made with electrocardiogram (EKG), radiographs showing an enlarged heart, and a less efficient ejection of blood from the heart to the rest of the body. Medications for dilated cardiomyopathy include drugs that increase the efficiency of the heart contraction, decrease the abnormal heart rhythm, ACE (angiotensin converting enzyme) inhibitors to open up the blood vessels and thus decrease the work of the heart, and diuretics if your dog is in heart failure.
  • Heartworm disease affects dogs more than cats. The immature heartworms are injected into a dog (microfilarial stage) when a mosquito takes a blood meal. Without prevention, they grow and move throughout the bloodstream to take up residence in the right ventricle and pulmonary artery causing coughing, weakness, and kidney damage. With the microfilarae comes bacteria that must be treated with the antibiotic doxycycline and steroids to decrease the inflammation in the heart and lungs. Once the bacteria have been killed, then your veterinarian can treat the adult heartworms with a drug called Immiticide administered in stages, while giving the heartworm preventative to kill the microfilarae. Please talk to your veterinarian about the prevention recommendations for your environmental area.

While heart disease can sound alarming as a diagnosis in your pet, know that medical breakthroughs have given your veterinarian better methods of diagnosis, safer treatments, and a wider choice of preventative measures. Please discuss with your family veterinarian any weight, diet, and exercise recommendations for your pet with heart disease, especially as we enter into the more active months of spring and summer.

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