Atrial fibrillation is an abnormal and irregular heartbeat. The result is usually a very fast heartbeat. During a normal heartbeat, one electrical impulse travels through the upper chambers of the hart (atria). This causes the chambers to contracts. The result is a 20 to 25 percent decrease in the heart’s pumping efficiency. This means that less blood is delivered to vital organs like the brain, lungs and heart. Symptoms caused by atrial fibrillation can include dizziness, shortness of breath and fatigue.
Many patients are aware when their heart is beating fast and irregularly. They often experience symptoms of palpitations (a pounding or fluttering feeling in their chest). An episode of atrial fibrillation can last from a few seconds to weeks or longer. There are three main categories of atrial fibrillation:
Paroxysmal atrial fibrillation – an episode spontaneously stops without treatment.
Persistent atrial fibrillation – an episode stops after treatment.
Permanent atrial fibrillation – atrial fibrillation continues, despite treatment.
How Does the Heart’s Electrical System Work?
The heart has electrical cells that send signals to tell the heart when to beat. The Sinus Node starts each heartbeat by sending a signal through the upper chambers of the heart (atria). This causes the atria to contract. The electrical signal then travels to the AV Node, slowing down slightly before it travels to the lower chambers of the heart (ventricles). Next, the electrical signal travels to the Bundle of His, through the left and right bundle Branches, and through the Purkinje Fibers to signal the ventricles to contract.
What Causes Atrial Fibrillation?
- Heart disease, including coronary artery disease, heart enlargement due to many years of high blood pressure, and heart failure from other causes.
- Damaged heart valves, particularly the mitral valve
- An overactive thyroid gland
- Chronic lung disease
- Recent heart or lung surgery
- Heavy alcohol or caffeine use
- Some medications, such as theophylline
What Are The Symptoms?
- Irregular, rapid heartbeat
- Dizziness and lightheadedness
- Heart palpitations (a pounding, fluttering, or racing sensation in the chest)
- Weakness and fatigue
- Shortness of breath
- Chest pain
How Is Atrial Fibrillation Diagnosed?
If you are in atrial fibrillation when you visit your doctor, an ECG (EKG) will confirm the diagnosis. An ECG measures the electrical activity of your heart. If atrial fibrillation is occurring, the ECG will show a unique pattern. If the ECG shows a normal rhythm, your doctor may have you wear a 24-hour or 30-day portable ECG recorder. That way if the abnormal electrical activity occurs again outside the office, it will be recorded.
Once atrial fibrillation is diagnosed, the doctor uses your medical history, a physical exam, and blood tests to see if there is a cause that can be treated. An echocardiogram may be done to check for structural problems in your heart. This test sends sound waves through the chest to create an image of the structure of the heart. For example, an abnormal mitral valve can cause atrial fibrillation. This would be detected with an echocardiogram. In some cases, an electrophysiology (EP) study is also used to help determine the cause. Sometimes, no cause can be found.
What Are the Complications of Atrial Fibrillation?
The most serious complication of atrial fibrillation is a stroke. When the flow of blood slows down in the quivering atrium, the blood may form a clot. Clots may then travel in the bloodstream to the brain, blocking blood flow and causing a stroke. If you continue to have atrial fibrillation despite treatment, you are at greater risk for stroke. This is especially true if you have other heart disease or a certain type of artificial heart valve. In this case you will need to take a blood thinner to reduce the risk of a clot forming.
How is Atrial Fibrillations Treated?
There are five main components of treatment for atrial fibrillation:
Treat the underlying cause – If the underlying cause of the atrial fibrillation is treatable, treatment of the problem usually converts the rhythm to normal.
Drugs to convert the rhythm to normal – There are a variety of drugs, called antiarrhythmics, which can be used to convert the heart rhythm back to normal.
Drugs to slow the heart rate – There are a variety of drugs, including beta blockers, calcium channel blockers and digoxin that can be used to slow the heart rate.
Electrical cardioversion – A very brief electric shock is sent through the chest, reorganizing electrical activity and allowing normal heart rhythm to take over. Cardioversion is done in the hospital under anesthesia. Cardioversion is usually very effective in converting the heart’s rhythm. However, the atrial fibrillation may reoccur at some point.
Anticoagulation therapy – Because there is serious risk of blood clots and stroke with atrial fibrillation, most patients require anticoagulation therapy (thin the blood) to minimize this risk.
Catheter ablation – Several catheters are guided into the heart through leg veins while the patient is under a light anesthetic. These catheters are advanced into the left atrium, and abnormal electrical signals that originate near or in the pulmonary veins are cauterized or “ablated.” This can cure the condition in many patients.
Your doctor will evaluate your medical history and symptoms and recommend one, a couple or all of the above treatments. Some patients never convert to a normal rhythm and require medications, especially Coumadin, for the rest of their lives.