Heart Failure Due to Valve Defect in Dogs

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.

Causes

Obscure or unknown cause.

Diagnosis

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.

Treatment

This is a progressive disease with no single treatment plan that will work for all patients. Individualized treatment will be recommended on the basis of your dog's current health status, how far the disease has progressed, and what existing complications need to be treated to stabilize your dog. Your veterinarian will discuss all of the available treatment options with you so that you can make an informed decision on how to progress. In some patients little or no treatment is required, with only regular monitoring, while others may need to be admitted for immediate emergency treatment. In still other patients, extensive medical treatment, or even surgery, may be recommended. Medical treatment will be focused on the primary disease as well as any other complications that need to be addressed immediately. Surgery to replace the defective valve may be attempted for some patients but you may need to search for a surgeon skilled in this specialized surgical technique.

The results of surgery are not promising at present, though the success rate has improved with the advancement of surgery techniques and improved surgery skills in this area of medicine.

Living and Management

Initially, absolute cage rest may be recommended. Once your dog's health has stabilized it may be allowed to have slow leash walks. You will also need to closely observe your dog's behavior, calling your veterinarian as soon as any unusual symptoms or behaviors are noticed.

Due to the progressive nature of this disease, a high level of commitment and care is required on your part for the successful management and treatment of the condition. Your veterinarian will give you a detailed plan for the administration of medications, exercise, diet, and any other vital information for treating your dog at home. Dogs that are affected with atrioventricular valve endocardiosis generally need an individualized sodium restricted diet plan during treatment.

You may need to visit your veterinarian every week during the first month of treatment. At each visit your veterinarian will check your dog's progress with standard laboratory testing, including radiographs and ECG. You will need to familiarize yourself with the drugs that have been prescribed for your dog and be especially vigilant about the time and frequency of dispensing these drugs. Follow your veterinarian's guidelines strictly regarding your dog's at home health management.

Long-term prognosis depends upon many factors, including the age of your dog, the current status of the disease, concurrent diseases, and management.

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