Congestive Heart Failure in the Canine Dr. Robert Baker, DVM
Congestive heart failure (CHF) is a term that is used to define the final stage of a clinical condition characterized by a progressive, irreversible deterioration of the heart muscles. Dysfunction is associated with a decrease in blood flow from the heart. Initial compensatory body mechanisms are activated to increase blood pressure which increases the output of the heart. However, these mechanisms eventually contribute to an enlarged poorly functioning heart. Enlarged heart muscles lose contractibility; this reduces blood flow and contributes to poor cellular oxygenation which leads to congestive heart failure. There are primarily two types of congestive heart failure with different underlying causes:
- Degenerative Valvular disease (DVD)
Affects primarily the heart valves.
- Dilated Cardiomyopathy (DCM)
Affects primarily the heart muscle. More likely to have arrhythmias (irregular heart rhythm) in DCM than in DVD.
Part I: Degenerative Valvular Disease (DVD)Dr. Robert Baker, DVM
Many small breeds of dogs tend to develop degenerative enlargement of the heart valves as they age. This can lead to a progressive deformity of one or more of the heart valves. These valvular deformities allow some of the blood to back up instead of going forward through the heart. This causes abnormal heart sounds (murmurs). The presence of heart murmurs by themselves does not indicate CHF and many dogs may never develop the clinical signs of CHF. However, if valvular damage becomes more progressive, blood back up can cause heart enlargement and an increase in venous blood pressure which causes a buildup of fluid on the lungs (pulmonary edema). The clinical signs associated with pulmonary edema are as follows:
- Exercise intolerance (lack of stamina)
- Increase respiratory rate with or without increased activity
- Increase coughing particularly with exercise
- Pot belly appearance from fluid in the abdomen
PLEASE NOTE: Any of the above symptoms should be brought to the immediate attention of your veterinarian.
DVD is not painful; however difficulty in breathing may be cause fear and anxiety.
While DVD may occur at any age or in any breed, in general it tends to occur in smaller breeds of dogs. Examples are Chihuahuas, Toy Poodles, Beagles, Dachshunds, Miniature Schnauzers and Cavalier King Charles Spaniels.
Diagnostic confirmation and heart assessment is enhanced by radiographs, ultrasound and response to clinical therapy. A positive clinical response to diuretics such as furosemide aids in confirming a diagnosis of Congestive Heart Failure (CHF). Other medications, at the direction of your veterinarian, such as ace inhibitors, digoxin, spironolactone, and a new drug called pimobendan are used for treating CHF. Low salt prescription diets are often appropriate.
Administration of various amounts and combinations of these medications is often necessary to properly manage CHF. Monitoring the respiratory rate at rest is helpful in determining clinical response.
CHF due to DVD is slowly progressive and survival times average two years or longer. Since it can usually be successfully managed, if caught in the early stages, your pet should be able to enjoy a good quality of life while undergoing treatment for Congestive Heart Failure (CHF).
Part II: Dilated Cardiomyopathy (DCM)Dr. Robert Baker, DVM
This section will discuss Dilated Cardiomyopathy (DCM) as it relates to Congestive Heart Failure (CHF). (The previous section discussed DVD.)
While the exact causes of Dilated Cardiomyopathy (DCM) are unknown, a heritary or genetic factor is suspected since it occurs in primarily large breeds of dogs. DCM is most commonly seen in the Doberman Pinscher, Irish Wolfhound, Great Dane, Boxer and St. Bernard. Nutritional deficiencies of taurine and carnitine are thought to be linked to DCM in certain breeds such as the Cocker Spaniel. Dilated Cardiomyopathy (DCM) is less commonly seen than Degenerative Valvular disease (DVD).
The clinical symptoms of DCM often relate to a weakening of the heart muscle:
- Abdominal Distention from fluid accumulation (ascities) causing a “pot belly” appearance
- Weight loss
- Exercise intolerance
- Fatigue
- Fainting (syncope)
- Abnormal Heart sounds (arrhythmias or murmurs)
PLEASE NOTE: Any of the above symptoms should be brought to the immediate attention of your veterinarian.
Diagnostic evaluation in suspected cases include radiographs (x-rays), ultrasound (echocardiogram) which is very useful in evaluating the overall heart status, ECG (Electrocardiogram), and laboratory blood work to evaluate internal organ status.
While there is no cure for DCM it can usually be successfully managed for limited periods of time usually a year or less. Sudden death, while not common, can occur with this disease. Treatment is somewhat similar to treatment for Degenerative Valve Disease, with drug adjustment to meet the individual animal’s particular needs. There is no data to suggest that DCM can be prevented; however the use of ace inhibitors may increase survival rates.
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