Heart Valve Defect in Cats

A heart valve defect occurs when the valve, valve flaps, or controlling muscles of one or more heart valves is either malformed or unable to perform its regular function. Cats have multiple valves within the heart that control blood flow in and out of the heart’s chambers. Any defect in the valve can result in too much or too little blood flow or a condition in which the blood backflows through the valve. Defects can occur congenitally and be present at birth or may occur later in life. Heart valve defects are fairly rare in cats, only occurring in one to two percent of the population. These defects are often genetically inherited. The defect can be mild and easily tolerable, but may range to severe and in some cases fatal. Medical attention is needed in moderate to severe cases.

A cat with a defective heart valve will exhibit symptoms similar to those of congestive heart failure in humans. These symptoms can vary based on which valve is defective, the severity of the defect, and if the issue is congenital or brought on by another cause. In some cases, a mild defect will not cause any observable symptoms. In severe cases, a valve defect and its associated symptoms can be fatal. 

Symptoms Include:

• Murmurs or abnormal heart sounds
• Lethargy
• Weakness
• Increased sleeping
• Depression
• Exercise intolerance
• Vomiting
• Poor appetite
• Weight loss or difficulty gaining weight
• Stunted growth
• Loud breathing
• Difficulty breathing 
• Coughing
• Bloating or fluid in the abdomen
• Sudden hind leg paralysis
• Sudden collapse
• Death

Types

The types of heart valve defect are based on which of the valves are affected. The most common type of defect is known as dysplasia or enlargement of the valve that worsens due to poor valve performance over time. Stenosis or narrowing of the valve can also occur, and reduce blood flow. Valve defects include:

• Mitral valve defect: This is the most common type of valve defect in cats. It results in blood backing up in the left side of the heart and can cause blood to enter the lungs. 
• Tricuspid valve defect: This is another common type of valve defect in cats. It results in blood collecting in the right side of the heart and can cause blood to pool in the body. 
• Pulmonary valve defect: This is a much less common type of valve defect in cats. It results in poor blood flow to the lungs.
• Aortic valve defect: This is a much less common type of valve defect in cats. It results in poor blood flow to the body. 

Various issues can cause a heart valve defect in cats. Generally, valve defects are congenital and occur because of abnormal formation of the valves or the heart in utero. Congenital heart valve defects can be caused by:

• Inherited genetic defects
• Environmental conditions
• Infections during pregnancy
• Poisoning or toxins ingested during pregnancy
• Some medications
• Poor maternal nutrition during pregnancy

In some cases, valve defects occur later in life. Adult onset valve defects can be caused by:

• Damage to the heart or valves
• Hereditary conditions
• Cardiomyopathy or disease of the heart muscle
• Lifestyle factors including obesity, lack of exercise, and poor diet
• Some forms of cancer and tumors

Your veterinarian may need to use several diagnostic methods to determine if a heart valve defect is causing your pet’s symptoms. Be prepared to discuss your cat’s medical history, any symptoms you have observed, and the timeframes associated with those symptoms. A full physical examination will be necessary, and veterinary staff may use a stethoscope to listen to the cat’s heart sounds. A murmur is typical with many valve defects, although its presence alone is not enough to confirm the diagnosis. Electrocardiography to check for problems with electrical activity in the heart is a common diagnostic method used when any heart condition is suspected. This technique is often coupled with echocardiography, often called a cardiac echo, to map the heart and identify potential valve issues. X-rays or other imaging technology may also be used to look at the impact on other bodily systems and to search for potential causes like cancerous tissues or tumors. Depending on the symptoms and results of testing, blood work may be needed to identify potential sources of infection.

Treatment will differ based on the type of defect and its severity. Mild defects are often well tolerated and may not require medical treatment. If defects are moderate to severe in nature, medical treatment will be required. In the case of severe defects, especially in newborn or very young kittens, treatment may not be an option. Common treatment options include:

Medications to Reduce Blood Volume 

This type of medication includes diuretics and vasodilators. These drugs are designed to reduce blood volume, making it easier for the defective valves to control blood flow. They carry a mild risk of side effects and should be given with plenty of fluids. This treatment will generally be ongoing, often for the cat’s entire lifetime. 

Medications to Improve Performance

This type of medication includes positive inotropes and antiarrhythmics. These drugs are designed to improve cardiac performance, making it easier for the heart to pump normally. They carry a moderate risk of side effects and may require routine follow-up visits. This treatment is generally ongoing as well, and may be prescribed on a long-term or lifetime basis. 

Surgical Correction 

Correcting the valve defect via surgery is possible in certain cases. Very old or very young cats are at a high risk of complications with surgery, so it may not be possible to use this method in some cases. Surgical installation of a shunt is the most common form of surgical correction. 

In the event that surgical correction was a possibility, full recovery is likely. Continue to monitor your pet for signs of worsening or new symptoms. As with any surgery, some pain or discomfort is likely for several days. Follow-up visits to remove stitches and monitor the heart may be required. If medication is being used to manage your pet’s condition, be sure to provide the proper dose at your veterinarian’s recommended intervals. Do not stop your pet’s heart medication suddenly as this could cause severe complications and even death. Regardless of which method was used to treat your cat, maintaining an optimal body weight for your pet can aid in recovery and management. Consult your veterinarian about any recommended dietary changes.