Heart Failure Due to Valve Defect in Dogs

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Atrioventricular Valve Endocardiosis in Dogs

The heart is divided into four chambers. The two upper chambers are the atria (singular: atrium), and two lower chambers are the ventricles. Atrioventricular (AV) valves are present between each atrial and ventricular pair. The valve between the right atrium and right ventricle is the tricuspid valve, while the valve between the left atrium and ventricle is called the mitral valve.

In endocardiosis, excessive fibrous tissue develops in the atrioventricular valves, affecting both the structure and function of the valves. Over a period of time this results in thickening, stiffing, and distortion of the AV valves, ultimately leading to congestive heart failure (CHF). As a result, the heart cannot pump adequate blood to the body, forcing it to work harder to attempt to meet the body's requirements. This cardiac behavior leads to multiple complications, including stiffening of the ventricles due to increased dilation. These changes ultimately lead to heart failure and death in affected dogs.

Commonly, small breeds are at a higher risk. The following breeds show a higher incidence of AV valve endocardiosis: Chihuahuas, Maltese, Pomeranians, cocker spaniels, Pekingese, Cavalier King Charles spaniels, Boston terriers, fox terriers, miniature poodles, miniature schnauzers, miniature pinschers, whippets, and toy poodles.

As this disease is chronic in nature, eventual heart failure is usually seen in older dogs (older than ten years), but mild cardiac abnormalities may be detected in young animals. The incidence rate of AV endocardiosis is slightly higher in male dogs than in female dogs.

Symptoms and Types

Following are some of the symptoms related to atrioventricular valve endocardiosis. Please note that severity and frequency of these symptoms may vary depending upon the severity of the disease itself.

  • Murmurs (abnormal heart sounds which can be heard by your veterinarian)
  • Cough
  • Lethargy and weakness
  • Exercise and work intolerance
  • Difficult breathing
  • Abdominal distention
  • Orthopnea (breathing become more difficulty when lying down)
  • Cyanosis (blue coloration of skin and mucous membrane)
  • Fainting
  • Loss of consciousness
  • Death

As the disease advances, cough, exercise intolerance, breathing problems and other symptoms become more severe and may occur with more frequency.


Obscure or unknown cause.


You will need to give a thorough history of your dog's health and onset of symptoms. The history you provide may give your veterinarian clues as to which organs are being affected secondarily, especially since heart failure affects all other organs of the body, notably the kidney and liver. After taking a detailed background history from you, your veterinarian will perform a complete physical examination on your dog. Laboratory testing is of high value in overall diagnostic workup, and will include complete blood tests, biochemical profiling, and urinalysis. These tests will provide important information to your veterinarian for a preliminary diagnosis, as well as information about the current status of the problem.

Further confirmation of the diagnosis may be assured by using X-ray and ultrasound imaging, along with electrocardiography (ECG), echocardiography to measure the heart's electrical impulses, and color Doppler to evaluate the blood's ability to flow freely. Together, these diagnostic tools provide vital information about the structure and function of the heart and the extent of the problem your dog is experiencing. Your veterinarian will evaluate the AV valves, as well as the other heart structures, in detail using these techniques. Modern advancements have made it possible to diagnose this condition with relative speed and ease so that treatment can begin in a timely fashion.

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