Be still my beating heart: Atrial fibrillation
Column by Dr. Tim Moser
Molly was doing her usual Tuesday morning housework. As she bent over to clean under the table, she suddenly felt a little dizzy - not enough to pass out, but as she stood up, she grasped for a chair to steady herself. The remainder of the day her heart would flutter on occasion. This was especially noticeable when she was sitting quietly in the armchair working on her needlepoint, or when lying in her bead trying to take a nap. Molly really did not have chest pain, but there was some chest discomfort present that worried her.
By dinnertime, she became more concerned since her symptoms did not go away. Reluctantly, Molly called her daughter for a ride to the emergency room. A kind and competent medical staff performed a complete evaluation, which showed atrial fibrillation. Since Molly's heart rate was too fast, medication was given through an IV, which slowed her heart. An ultrasound of her heart was performed, and several treatment options were discussed. After a short hospital stay, Molly returned home symptom free.
Atrial fibrillation (often abbreviated as "A Fib" by medical personnel) is the most common abnormal heart beat in the general population. As we age, the chance of developing atrial fibrillation is greatly increased. Some patients with atrial fibrillation are completely unaware the problem exists. Others know immediately that something is wrong, and seek medical attention.
Normal Heart Conduction
The heart is an organ that is very polite and orderly when it comes to the signals that tell the muscle when to contract. During a normal heart beat, an electrical signal that makes the heart muscle contract originates in the upper portion of the heart, known as the right atrium. As the electrical signal makes its way down the heart, the muscle contracts in an orderly fashion from the top to the bottom, allowing the heart to pump blood to the body. After a brief pause, the process is repeated. The next electrical signal is seldom initiated until the previous signal has made it entirely through the heart.
In contrast, atrial fibrillation is an abnormal conduction of electrical signals in the heart. This results in an irregular heart rate, where the pulse may feel erratic. Instead of an orderly, regular signal telling the heart muscle to contract, atrial fibrillation is caused by the rude, chaotic crescendo of competing electrical impulses originating in the upper portion of the heart. The electrical signals crowd together and all try to push into the lower portion of the heart at the same time, much like a mob of screaming Elvis fans pushing their way through a small door attempting to get into a theater in Vegas. The result is the heart beat becomes irregular, as the electrical impulses are conducted in a random and erratic manner through the heart.
Symptoms of Atrial Fibrillation
Since Atrial Fibrillation is be definition an irregular heart rhythm, most patients will feel their heart skip a beat. Doctors call this irregular heart rate "palpitations." This can be barely noticeable, or very distressing with symptoms of chest pain and shortness of breath. At an extreme, the heart rate may beat so fast that the heart is in danger of damage if left unchecked.
The most devastating consequence of untreated atrial fibrillation is stroke. Since the upper portion of the heart is not contracting properly, blood can pool and eventually form clots on the lining of the heart chamber. When the clots break loose, they flow through the arteries until trapped in a blood vessel. If the affected vessel happens to be in the brain, then a stroke results. The formation of blood clots in the heart and possible stroke is more common with increasing age. Persons over age 65 increase their risk of stroke significantly as they grow older.
There are a variety of medications used when treating atrial fibrillation. First, the heart has to be slowed to an acceptable level. For most patients, a heart rate as high as 110 is probably okay, as long as no bothersome palpitations are present. If the heart rate is too fast, common drug types used to slow things down may include either a beta blocker, calcium channel blocker, or Digoxin.
Since a devastating effect of being in atrial fibrillation can include having a stroke, "blood thinners" are often prescribed to prevent a blood clot from forming in the chambers of the upper heart. The most common drug is Warfarin (generic for Coumadin). This requires frequent blood tests (such as an INR or PT) to make sure the dose is correct. Warfarin's effects are influenced by many factors, to include diet and taking other medications.
At times atrial fibrillation can be eliminated or kept under good control by using oral medications, such as Amiodorone. These medications target the heart conduction system itself, and try to maintain a normal heart rhythm.
More aggressive treatment options might include shocking the heart back into a normal rhythm using electricity. This is called "cardioversion," and is performed under special circumstances only.
The "take no prisoners" approach is RFA, or radio frequency ablation. This is a relatively new procedure, where the large blood vessels that enter the upper chambers of the heart (known as the pulmonary veins) are closely examined using a heart catheter. Since the abnormal electrical signals causing atrial fibrillation originate in this location, destruction of very small areas of heart tissue using radio waves can prevent the abnormal signals from occurring again. Most patents that have this procedure remain in a normal heart rhythm and do quite well.
Want more information about atrial fibrillation?http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001236/