Congestive Heart Failure in Dogs
Congestive heart failure is the inability of the heart to provide adequate circulation to meet the body's needs. It is the end result of a weakened heart muscle. The health of the liver, kidneys, lungs, and other organs is impaired by the circulatory failure, resulting in a problem involving multiple organs.
A diseased heart can compensate for many months or years without signs of failure. When failure does occur, it may appear suddenly and unexpectedly-sometimes immediately after strenuous exercise, when the heart is unable to keep up with the body's demands.
In toy and small-breed dogs, chronicvalvular disease with mitral regurgitation is the most common cause of congestive heart failure. In large-breed dogs it is dilated cardiomyopathy.
The early signs of congestive heart failure are tiring easily, a decrease in activity level, and intermittent coughing. The coughing occurs during periods of exertion or excitation. It also tends to occur at night, usually about two hours after the dog goes to bed. Dogs may be restless-pacing instead of quickly settling down to sleep.
These early signs are nonspecific and may even be considered normal for the dog's age. As heart failure progresses the dog develops other signs, such as lack of appetite, rapid breathing, abdominal swelling, and a marked loss of weight.
Because the heart no longer pumps effectively, blood backs up in the lungs, liver, legs, and other organs. Increased pressure in the veins causes fluid to leak into the lungs and peritoneal cavity. Fluid in the lungs is the cause of the coughing. A rapid accumulation of fluid in the small airways can cause the dog to cough up a bubbly red fluid, a condition called pulmonary edema. Pulmonary edema indicates failure of the left ventricle.
With failure of the right ventricle, fluid leaks into the abdomen, giving the belly a characteristic swelling or potbellied appearance (called ascites). This may be accompanied by swelling of the legs (dependent edema). An accumulation of fluid in the chest cavity (pleural effusion) also occurs with right-sided heart failure.
In the late stages of congestive heart failure the dog sits with his elbows spread and his head extended. Breathing is labored. The pulse is rapid, thready, and often irregular. The mucous membranes of the gums and tongue are bluish-gray and cool. A thrill may be felt over the chest. Fainting can occur with stress or exertion.
An accurate diagnosis is established through chest X-rays, ECG, echocardiography,and other tests (such as a heartworm antigen test) as indicated.
Treatment: It is important to correct any underlying cause whenever possible. Heartworms, bacterial endocarditis,and some forms of congenital heart disease are potentially curable if they are treated before the heart is damaged.
Treatment of congestive heart failure involves feeding the dog a low-salt diet, restricting exercise, and giving appropriate medications to increase heart function and prevent cardiac arrhythmias.
Most commercial diets contain excessive amounts of salt. Your veterinarian may prescribe a low-salt prescription diet such as Hill's h/d, Purina CV, or Royal Canin EC. In dogs with mild symptoms, salt restriction may be the only treatment required.
Exercise is beneficial, but only for dogs who are not symptomatic. If symptoms such as easy tiring, coughing, or rapid breathing appear with exercise, do not allow your dog to engage in activities that elicit these symptoms.
Various drugs are available that increase the force and contraction of the heart muscle or decrease the workload. They include the digitalis glycosides, calcium channel blockers, angiotensin-converting enzyme (ACE) inhibitors, beta blockers, and anti-arrhythmics. These are the same drugs used in people. ACE inhibitors such as enalapril maleate (Enacard) and benazepril (Fortekor) may prolong the life of dogs with valvular heart disease and cardiomyopathy, and are commonly used in dogs with these diseases. Fluid accumulation in the lungs and elsewhere is managed by diuretics such as furosemide (Lasix). Potassium supplements may be necessary when giving certain diuretics. A diuretic that spares the potassium the body needs is spironolactone (Aldactone).
Dogs with congestive heart failure may benefit from vitamin-B supplements and taurine or carnitine. Coenzyme Q is another supplement that may help dogs with cardiac problems.
When treating cardiac arrhythmias, it is important to search for and correct any underlying electrolyte or metabolic problems that might trigger an attack. A number of cardiac drugs, including digitalis, lidocaine, diltiazem, procainamide, atropine, and propanalol (Inderal), are used to control arrhythmias in dogs. Dogs whose primary problem is an arrhythmia may be able to have a pacemaker implanted to help control the heart rate.
With proper treatment, a dog with congestive heart failure can live a longer and more comfortable life. However, heart disease requires close monitoring. You will need to return to your veterinarian regularly for checkups.
This article is excerpted from “Dog Owner’s Home Veterinary Handbook” with permission from Wiley Publishing, Inc.
Copyright © 2007 by Howell Book House. All rights reserved.