Heart Disease in Dogs: Treatment for Atrial Defibrillation

Treatment goals for dogs in atrial fibrillation are to slow the heart rate and to manage theHeart Disease in Dogs: Treatment for Atrial Defibrillation congestive heart failure.  Atrial fibrillation is a disease that is cured (with rare exceptions), rather managed for the lifetime of the dog.

Medications to slow the heart rate in dogs with atrial fibrillation

Digoxin – This drug is a very old and very effective drug derived from the plant Digitalis.  It also works by slowing the heart rate.  Other beneficial side effects include increasing contractility of the heart to a small degree.  This is beneficial especially in cases of congestive heart failure.

Beta blockers – This class of drug is one of the most powerful drugs to slow the heart rate which is primary way that atrial fibrillation causes adverse effects. Unfortunately beta blockers also exert profound depression of the contractility of the heart (systolic function). Most dogs in atrial fibrillation also have decreased strength of the heart muscle to contract making the use of beta blockers such as atenolol and sotalol poor choices in most dogs with atrial fibrillation.

Diltiazem – This drug also works by slowing the heart rate and has minimal if any decrease inHeart Disease in Dogs: Treatment for Atrial Defibrillation contraction of the heart.  Therefore diltiazem is a very useful drug for slowing the heart rate in dogs with atrial fibrillation. Digoxin (digitalis) and diltiazem are frequently used in combination to decrease the heart rate in dogs with atrial fibrillation.

Medications to treat heart failure in dogs with atrial fibrillation

Furosemide (Lasix) – This drug works by eliminating fluid through the kidneys.  Unfortunately, this drug can damage the kidneys when used chronically.

Enalapril – This drug works by preventing the kidneys from retaining fluid. In addition it serves to dilate the arteries thereby lessening the work that the failing heart has to overcome.   This drug is also effective at preventing protein loss in through the kidneys.
Pimobendan (Vetmedin) – This drug has two separate mechanisms of action and is in a class of drugs called inodilators. As with enalapril, is helps to dilate the arteries decreasing resistance to blood flow. In addition, it serves to increase contractility of the ventricle. These two functions have made it a very commonly prescribed drug for dogs in heart failure that have decreased ability of the heart to contract. Pimobendan is used to treat heart failure that is usually associated with atrial fibrillation but has no specific effects on atrial fibrillation.

Defibrillationto treat dogs with atrial fibrillation

Defibrillation is virtually an electrical shock to the heart to “reset” the rhythm of the heart to a “normal sinus rhythm”. This procedure is beginning to fall out of favor in humans as a recent study has shown no significant benefit over medical management. Unfortunately, defibrillation in dogs is typically very ineffective due to the advanced heart disease and enlargement that is not reversible. On very rare occasion, a congenital disease that can be corrected with surgery or stinting (Cor Triatriatum Dexter/Sinister) may benefit from defibrillation.

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Dr Roger Johnson and Dr Kyle Marano

Roger K. Johnson, DVM, Diplomate ACVIM (internal medicine) is a board-certified veterinary internal medicine specialist. His professional interests include cardiology as well as using advanced diagnostics to help his patients. His particular favorites include echocardiography, abdominal ultrasonography, and endoscopy. Kyle Marano, DVM is a small animal veterinarian practicing out of Northern Colorado. He has written pieces ranging from sports commentary and analysis to quips on the every day life of veterinary medicine. His furry family includes a chocolate lab mix and an overly nosy cat.

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