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J.C. Hardin, DVM
It is common for the mitral valve (the 'one way door' between the left atrium and left ventricle in the heart) to fail in dogs, and occasionally in cats. When this valve starts letting blood flow backwards in the heart, the atrium enlarges, and blood is backed up into the blood vessels of the lungs. This process leads to fluid buildup in the lungs (pulmonary edema). In humans, a valve transplant is curative. Since this is not an option for pets, medications are used to try to control the problem as much as possible. The mitral valve can fail for many reasons. It may have not developed properly to begin with (aplasia), it can develop infection (endocarditis), or scar and become stiff from repeated infections (as with chronic dental disease). In the worst cases one of the cords holding one of the valve leafs in place breaks, letting the valve 'flop in the stream' (ruptured chordae tendinae). The overstretched atrium (chamber above the valve) can press on the windpipe contributing to coughing, form a clot that eventually breaks loose and clogs arteries elsewhere in the body, or starts to quiver (atrial fibrillation) instead of beating properly. With atrial fibrillation, fainting spells are common. First tier medications used to help treat and prevent congestive heart failure are furosemide and enalapril. FUROSEMIDE is a diuretic that helps clear excess fluid from the lungs. (Analogy - wringing out a damp sponge). It increases thirst and urination, and can lead to eventual loss of potassium to the point potassium supplements are needed. Muscle weakness is one sign of low potassium. It is very important that fresh water is always available to any pet, but especially those on diuretics. ENALAPRIL helps lower blood pressure (afterload) easing the heart's work load. (Analogy - imagine a fire crew putting out a fire with a high pressure water hose, then suddenly everyone in the city turns on their faucets. The water pressure in the fire hose drops as a result. By opening up all the little arteries throughout the body, blood volume is pulled away from the heart, reducing pressure within it.) Some patients on enalapril get 'light headed' and dizzy as they get used to the medicine. Sometimes nausea and diarrhea occur. DIET is important in dogs with CHF. Excess sodium needs to be avoided, but an extremely restricted sodium diet only makes things worse. For most CHF patients, K/d is recommended. High sodium snacks need to be avoided. Frozen green beans, or green beans with no salt added are usually a safe choice. A nutrient supplement (neutraceutical) called COENZYME Q10 is recommended by at least one prominent veterinary cardiologist. Coenzyme Q10 is believed to increase numbers of mitochondria in heart muscle cells, making it more efficient. You can buy Coenzyme Q10 over-the-counter at any drug or nutrition store. A very low dose of buffered ASPIRIN daily can help prevent clot formation in the left atrium. In cats, it is usually given only twice weekly. ANTIBIOTICS such as clindamycin are often recommended, especially if dental disease is present. Dogs and cats with lots of tartar and gum disease are often put on antibiotics to be given one week out of each month ('pulse therapy') to help keep the heart valves clear of bacteria. Pets with pulmonary edema are more prone to bacterial infection of the lungs, and antibiotics are often used to help prevent this as well. WEIGHT MANAGEMENT is an important part of care of pets with CHF. Overweight pets simply need to lose weight to decrease the work the heart has to do. It is better for a pet to be hungry for a few months to get weight off than experience a worsening heart problem. TEMPERATURE CONTROL of your pet's environment is important. Pets don't sweat to cool themselves, they simply move air faster through their respiratory system. For pets already having problems breathing, cooling down is much harder. Heat exhaustion occurs much more readily in pets with CHF. Despite these treatments and precautions, decompensation is always possible. There is no cure for a heart valve defect. During a DECOMPENSATION event, sudden labored breathing occurs, coughing of foamy fluid (sometimes blood tinged) may occur, the tongue or gums appear bluish, and the pet stretches its neck out to breathe. 'Crackles' are heard in the lungs with a stethoscope. Immediate care (oxygen, injectable diuretics, sometimes a nitroglycerin patch) is needed for a decompensation event. Second tier drugs for heart failure include spironolactone and pimobendan. SPIRONOLACTONE is a diuretic that works differently than furosemide. It conserves potassium, and pets that were on furosemide and taking potassium supplements often need to stop taking potassium supplements when they start spironolactone. PIMOBENDAN is a drug that helps slow heart rate but increases the force of each contraction, without making the heart muscle use more oxygen or energy to do so. It also helps open up blood vessels, further controlling blood pressure. With certain arrhythmias, DIGOXIN is used. This is also a drug that slows heart rate while increasing force of contraction. (Analogy - imagine fanning a fire with a bellows - you can either fan it with rapid, shallow motions, or slow, powerful motions. Digoxin is like the latter scenario - it slows the heart rate but makes each beat more powerful). Digoxin is especially needed when atrial fibrillation is occurring. ADDITIONAL treatments include bronchodilators and oxygen. BRONCHODILATORS such as theophylline (oral), aminophylline (injected) or terbutaline may be used to try to open the bronchi and ease breathing. The bronchi are the tubes that split off from the windpipe inside the chest and lead to the lungs. Bronchodilators usually have mild 'caffeine-like' side effects, but the benefits usually outweigh these effects. OXYGEN is sometimes kept at home by owners of CHF pets. Certain home medical supply pharmacies (Long's, Hawthorne, and others) can set you up with what you need for this. Oxygen is highly flammable, and safety precautions are needed.