Overview of Congestive Heart Failure (CHF) in Dogs
Heart failure is a condition, caused by an abnormality in the structure or the function of the heart, in which it is unable to pump normal quantities of blood to the tissues of the body. The heart is a pump, and when it fails, it often leads to fluid retention in the lung and the body cavities leading to congestive heart failure.
There are many causes of heart failure in dogs, including:
Birth (congenital) defects of the heart
Degeneration of the heart valves
Heart muscle disease (cardiomyopathy)
Diseases of the pericardium (the lining around the heart)
Irregular electrical rhythms of the heart arrhythmia
Dogs of any age and any breed can develop heart failure. There is certainly a predisposition for heart failure caused by cardiomyopathy in giant canine breeds. Many older, small breed dogs develop heart failure from abnormal function of the heart valves as the valve tissue degenerates.
Heart failure affects your dog by reducing the amount of blood that is pumped to the muscles, leading to fatigue. In addition, most cases of heart failure are associated with the accumulation of fluid in the lungs (pulmonary edema), the chest cavity (pleural effusion), or the abdominal cavity (ascites). This fluid accumulation can lead to shortness of breath and other problems such as coughing and difficult breathing.
What To Watch For
Some of the symptoms of heart failure, and the progression of heart failure in a dog, are related to increased activity of the nervous system and to increased concentrations of circulating hormones (and related chemicals). These include:
Shortness of breath
Difficult breathing (dyspnea)
Diagnosis of Congestive Heart Failure (CHF) in Dogs
Your veterinarian may suspect CHF after examining your dog, but he will probably run several diagnostic tests to confirm the diagnosis and underlying cause. Tests may include:
General physical examination with emphasis on stethoscope examination (auscultation) of the heart and lungs
A chest radiograph (X-ray)
Measurement of blood pressure
An electrocardiogram (EKG)
Ultrasound examination of the heart (echocardiogram)
Treatment of Congestive Heart Failure (CHF) in Dogs
Treatment for congestive heart failure will vary depending on the underlying cause. This may include one or more of the following:
Initial treatment may require hospitalization with a diuretic, oxygen, and other drugs such nitroglycerine paste.
A diuretic (“water-pill”) such as the drug furosemide (Lasix®)
Pleural effusion (fluid around the lungs) may require thoracocentesis, which is insertion of a small needle in order to drain some of the fluid. This often improves breathing and makes your dog more comfortable.
Nitroglycerine, which comes in the form of a paste, is often used topically (spread on the ear or abdomen or other relatively hairless area).
Other diuretics, such as spironolactone.
Angiotensin converting enzyme inhibitor such as enalapril (Enacard) or benazepril. These drugs block some of the harmful hormones that circulate in heart failure and prevent salt retention.
A diet limiting sodium intake and preventing fluid retention.
Use of digoxin (Lanoxin; Cardoxin)
At home, administer all veterinary prescribed medications on a regular basis. Be aware of your dog’s general activity, exercise capacity and interest in the family activities. Keep a record of his appetite and ability to breathe comfortably (or not), and note the presence of any symptoms such as coughing or severe tiring.
Do not stop medication or change the dosage without checking with your veterinarian. Most medications are for the life of your dog. And never withhold water, even if your pet urinates more than normal, unless specifically instructed to do so.
Difficult breathing is usually an emergency. See your veterinarian immediately.
In general, heart failure cannot be prevented, although early diagnosis of the underlying cause can provide an improved quality of life. Once diagnosed, you should prevent excessive physical activity or excitement, avoid high heat/humidity and avoid high salt (sodium) foods or treats.
In-depth Information on Congestive Heart Failure (CHF) in Dogs
Congestive heart failure leads to inadequate blood flow to the tissues of the body, resulting in lethargy and fatigue. Accumulation of fluid often impairs breathing. When the fluid accumulates in the lungs (pulmonary edema) or around the lungs (pleural effusion), the condition can become life threatening. Though dramatic, the symptoms of congestive heart failure are not specific for only that condition.
As there are dozens of reasons for coughing, difficult breathing and fatigue; therefore, your veterinarian will formulate a diagnostic plan to make a correct diagnosis.
The conditions most often confused with heart failure are diseases of the airways, the lung and the chest cavity (pleural space) including:
Tracheal (windpipe) collapse, a common condition in small breed dogs, frequently leads to chronic coughing.
Chronic bronchitis in dogs is an inflammation of the bronchial tree that resembles the smoker’s cough of human beings. The cause of most canine cases of bronchitis is not known, but treatment is different than for heart failure.
Pneumonia or infection of the lung can lead to symptoms that are similar to those of heart failure.
Pulmonary fibrosis in dogs is the deposition of scar tissue in the lungs. Symptoms are similar to those of pulmonary edema.
Heartworm disease, a parasitic infection of the blood vessels of the lungs, must be excluded as a possible diagnosis. This infection can also lead to heart failure as well as lung injury.
Tumors of the chest can cause symptoms that resemble those of heart failure.
Fluid accumulation within the chest cavity that surrounds the lungs (pleural effusion) can cause shortness of breath. Some cases are caused by heart failure, but others are not.
Veterinary care should include diagnostic tests and subsequent treatment recommendations.
Diagnosis In-depth of Congestive Heart Failure (CHF) in Dogs
Diagnostic tests are needed to properly diagnose congestive heart failure. Tests may include:
Complete medical history and physical examination, with emphasis on stethoscope examination (auscultation) of the heart and lungs. Of particular importance is the identification of abnormal heart sounds such as heart murmurs or irregular heart rhythms (arrhythmia).
A chest radiograph (X-ray) is usually needed to identify heart enlargement, fluid accumulation in the lung and exclude some of the previously mentioned conditions that can mimic heart failure.
The blood pressure is usually measured. This is done with the special device that measures blood flow, noninvasively, through the legs. Both high and low blood pressure values usually need to be identified as either can occur in patients with heart failure.
An electrocardiogram (EKG) is often obtained to identify heart enlargement and determine the electrical activity of the heart. The electrocardiogram is a noninvasive test done by attaching small contact electrodes to the limbs and body.
Ultrasound examination of the heart (echocardiogram) may be needed for a definitive diagnosis. This noninvasive test requires sophisticated equipment that creates high frequency sound waves much like the sonar of a submarine. An image of the heart is created. The echocardiogram is usually the test of choice to establish the final diagnosis of the cause of congestive heart failure, but this examination may require referral to a specialist.
Laboratory (blood) tests are often recommended to evaluate other organ function, such as the kidney, and exclude anemia as a complicating factor. This can be critical to evaluate the effect of heart failure on other organs such as the kidneys and to monitor the effects of treatment. A blood test to detect heartworm infection may be recommended in some patients.
Your veterinarian may recommend additional diagnostic tests to insure optimal medical care. These are selected on a case-by-case basis. Examples may include:
Specialized blood tests such as blood taurine in cases of dilated cardiomyopathy.
Thyroid tests to exclude abnormal function of the thyroid gland.
Blood cultures in suspected infection of the heart valves.
Doppler studies, which are a special type of echocardiography and often require referral to a specialist. Doppler studies more accurately diagnosed blood flow disturbances.
Thoracocentesis (draining fluid from around the lung) or abdominal paracentesis (draining fluid from the abdominal cavity) may be necessary to provide relief from the excessive fluid and determine the cause of the abnormal fluid accumulation. Tests on the fluid can help determine its cause.
Treatment In-depth of Congestive Heart Failure (CHF) in Dogs
The principles of therapy for congestive heart failure include improving heart function, preventing fluid accumulation, preventing further deterioration of the heart muscle and antagonizing chemicals and hormones produced in excessive quantities in heart failure. Rarely is it possible to “cure” the heart disease. The most important causes of heart failure in dogs are valve degeneration and cardiomyopathy (heart muscle disease). Definitive treatment usually requires valve replacement (which is rarely done in dogs) or heart transplantation (not done currently). Heart failure caused by fluid accumulation in the sac around the heart (pericardial effusion) is not treated by drugs but instead requires drainage of the fluid or removal of a portion of the pericardial membrane. Congenital heart defects (heart problems present at birth) should be referred to a specialist for management.
Initial treatment for heart failure may require hospitalization with a diuretic, oxygen and other hospital-administered treatments. Vasodilator drugs, such as nitroglycerine or nitroprusside, may be administered. In some forms of heart failure, the use of dobutamine or other potent stimulators of the heart muscle may be necessary. Fluid accumulation around the lungs (pleural effusion) may require drainage with a needle (thoracocentesis).
Treatment usually includes a diuretic (“water-pill”) such as the drug furosemide (Lasix). Diuretics prevent the kidney from retaining excessive salt (sodium) and water leading to increased volume of urine is produced. Diuretics are usually prescribed for home care to prevent fluid retention. The dose must be sufficient to prevent fluid retention but, at the same time, cannot be so high as to cause kidney failure or excessive loss of potassium.
Other diuretics may be prescribed in selected patients. For example, spironolactone prevents fluid retention and may protect the heart muscle for further damage in dilated cardiomyopathy.
A potassium supplement may be recommended in some patients.
Most patients with chronic heart failure are treated with an angiotensin-converting enzyme inhibitor such as enalapril (Enacard) or benazepril. Enalapril, benazepril and related drugs block some of the harmful hormones that circulate in heart failure, prolong life and reduce clinical symptoms in canine heart failure. This class of drug treatment, sometimes called ACE-inhibitors, prevents salt retention as well. Dosing is critical as these drugs can excessively lower blood pressure or lead to kidney failure.
The diet may be modified to limit sodium intake and prevent fluid retention. There are specialized diets available for this purpose though some senior diets are also relatively low in sodium.
The drug digoxin (Lanoxin; Cardoxin) is prescribed in some patients. The dose of this drug must be critically determined to prevent side effects such as loss of appetite and vomiting.
Dietary supplements are used in some forms of cardiomyopathy. The amino acids taurine is sometimes prescribed for cardiomyopathy in spaniel breeds. L-carnitine is sometimes recommended for treatment of dilated cardiomyopathy. Other nutritional supplements, such as vitamin E and coenzyme Q10, are recommended by some but there is no evidence of their benefit in heart failure in dogs.
Special treatments are needed for some causes of heart failure. Antiarrhythmic drugs are used to control the heart rhythm. Beta-blockers, such as metoprolol, propranolol or atenolol, may be prescribed to control heart rate, to control arrhythmias and protect the heart muscle. Calcium channel blockers, such as the drug diltiazem or amlodipine, are used in some circumstances. Direct vasodilator drugs are sometimes prescribed for dogs with advanced heart failure. There are special circumstances for the recommendation of these treatments and the use of some of these drugs is best guided by a specialist.
Follow-up Care for Dogs with Congestive Heart Failure (CHF)
Optimal treatment for the dog with congestive heart failure requires a combination of home and professional veterinary care. Follow-up can be critical. Administer prescribed medication(s) as directed and be certain to alert your veterinarian if you are experiencing problems treating your dog. Optimal follow- up veterinary care for heart failure often involves the following:
Regular examinations that include an interview about clinical symptoms and quality of life. Be prepared to answer questions about your dog’s activity, appetite, ability to sleep comfortably, breathing rate and effort, coughing, exercise tolerance and overall “quality of life.”
BRING YOUR MEDICATIONS with you to show your veterinarian. Dosing is critical for heart medication.
Measurement of arterial blood pressure is often done.
Blood tests to examine kidney function and blood electrolytes are routinely recommended.
A blood digoxin test should be done periodically if that drug is prescribed.
A chest X-ray may be needed to evaluate the lungs for fluid.
An electrocardiogram is recommended if there is a heart arrhythmia.