Prior to having anesthesia, my cat’s veterinarian gave her an ECG due to her advanced age. The ECG showed an abnormal heart rhythm that my veterinarian called “atrial fibrillation”, and we did not proceed with anesthesia. What is atrial fibrillation?
The heart is a hollow organ with four separate chambers that pump blood throughout the body. The bottom chambers are the right and left ventricles, and they pump the blood to the lungs and to the rest of the body, respectively. The top chambers are the right and left atria, and they accept blood from the general circulation and from the lungs, respectively. When the heart relaxes, the valves between the atria and the ventricles open, allowing the blood to move from the atria to the ventricles. When the heart is beating normally, the contractions of the atria and the ventricles are coordinated to move the blood smoothly around the body, as well as into the lungs where carbon dioxide is exhaled, and oxygen is acquired by the red blood cells.
“Atrial fibrillation describes very rapid contractions,
or ‘twitching’, of the heart muscle, confined to the
atria, or the top chambers of the heart.”
Atrial fibrillation describes very rapid contractions, or ‘twitching’, of the heart muscle, confined to the atria, or the top chambers of the heart. Most of the time, atrial fibrillation in cats occur secondary to heart disease. Sometimes, in large breed cats, atrial fibrillation will occur as a primary heart problem. In those cases, the ventricles will contract more rapidly than normal, and the rhythm may be either regular or irregular.
What are the signs and symptoms of atrial fibrillation?
Most cats who develop atrial fibrillation have underlying heart disease, so the signs that are observed are often related to that condition. If the cat is experiencing congestive heart failure, the heart cannot pump blood effectively enough to provide adequate oxygen to the tissues and to keep the body’s fluids balanced. The cat may be exercise intolerant, becoming exhausted after very little exertion. The cat may cough or have difficulty breathing. Atrial fibrillation causes an erratic heart rhythm that may sound like an extra heart sound is present, when heard through a stethoscope. Your veterinarian may mention what is called a “pulse deficit”. This is when there are fewer pulses felt in an artery (like the femoral artery in the rear leg) than are heard through a stethoscope.
What causes atrial fibrillation?
Sometimes, no specific cause is determined for atrial fibrillation. In that case it is called “idiopathic”. Atrial fibrillation can be the result of chronic heart valve disease, or disease of the heart muscle itself. Atrial fibrillation can also (rarely) be caused by heart disease that is present at birth.
What are treatment options for atrial fibrillation?
For a cat with primary atrial fibrillation that has not been present for an overly long period of time, quinidine medication may help to return the heart to a normal rhythm.
For a cat with secondary atrial fibrillation, the focus of medical management is to treat the underlying heart disease. For congestive heart failure, medication is given to relieve the body of excess fluid, to control hypertension (if present), and to help the heart beat more effectively. Another goal of therapy is to slow the contraction rate of the ventricles to help the blood circulate better. It is best to restrict the cat’s activity until the rapid heart rate is under control.
Your veterinarian may recommend a special diet for your cat with atrial fibrillation. If the cat is experiencing congestive heart failure, then a mild to moderate restriction of sodium in the diet may be in order.
Is there any monitoring or follow-up for cats with atrial fibrillation?
Heart rate is monitored closely, and there will be follow-up ECGs to measure the success of treatment. Over time, heart function will deteriorate, ultimately leading to congestive heart failure that cannot be managed. Eventually, euthanasia will be appropriate. That said, many cats can live quite a long time with medical management of their congestive heart failure and atrial fibrillation.