Heart Disease in Dogs: Diagnosis and Treatment of Mitral Valve Disease

Diagnosis of mitral valve disease in the dog

The rapid, turbulent blood flow created by mitral regurgitation (think of the force and soundHeart Disease in Dogs: Diagnosis and Treatment of Mitral Valve Disease created when placing your thumb over a garden hose) can be heard through a stethoscope.  When your pet is examined by your veterinarian, the normal “lub-dub” sound includes a murmur, which sounds like “lub-squish-dub”.  Louder murmurs in dogs usually indicate more severe disease.  Click here  to listen to normal and abnormal heart sounds from humans, which are similar to dogs.

As the heart becomes more inefficient, the ventricular muscle thickens and the chambers enlarge in an effort to maintain cardiac output.  Chest x-rays may therefore show left ventricle and left atrial enlargement.  In the case of heart failure, fluid accumulation in and around the airways in the lungs would also be seen.

Echocardiography is a real-time video of the heart.  It is the only diagnostic tool capable of demonstrating mitral regurgitation, measuring left atrial size, and testing for portal hypertension.  A thorough echocardiogram is also important to find concurrent heart abnormalities.  This tool should be used in conjunction with electrocardiography (ECG)  to detect and evaluate abnormal heart rate and rhythm.  Click here to see part of a normal canine echocardiogram.

Treatment of mitral valve disease in the dog

MMVD is irreversible, and will become more severe with time regardless of treatment, though at an unknown rate in each case.  The goal of treatment, therefore, is to reduce your pet’s clinical signs by reducing the work required of the heart.  The single most important and effective treatment of your pets condition when heart failure is diagnosed is to reduce excess fluid accumulation in the lungs.

Furosimide (trade name Lasix) is used to reduce blood volume by increasing urine production (diuresis).  This often works well for months or years, but such aggressive diuresis may be required that kidney damage occurs.  The delicate balance between “dry for the heart” and “wet for the kidneys” is unique to each dog, so kidney function tests must be performed regularly from the start.

Enalapril is an angiotensin-converting enzyme (ACE) inhibitor.  Along with other drugs in this class, enalapril inhibits blood vessel constriction, allowing the heart to function more efficiently.

Pimobendan may be prescribed for your pet as well. This class of drugs, called “inodilators”, is used to increase the strength of heart contraction while also dilating arteries.  This makes blood flow more easily forward, resulting in less regurgitation through the mitral valve.

Humans with diseased mitral valves commonly them replaced artificial or animal valves. Though some universities are experimenting with valve replacement for dogs, it is not widely available and is far from being perfected.

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Dr Roger Johnson and Dr Derek Calhoon

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. Derek Calhoon, DVM is a veterinary general practitioner.

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