Atrial fibrillation is the most common abnormality known of the heart rhythm. Many new cases are diagnosed yearly in the U.K. Although a definitive cure is still not available in most cases, significant advances have been made in the management of atrial fibrillation.

Symptoms

Atrial fibrillation is an abnormality in the heart rhythm that involves irregular and often rapid beating of the heart. The abnormal heart rhythm leads to the diminished delivery of blood and its nutrients (oxygen and glucose) to the brain and other organs. The lack of oxygen and nutrients causes symptoms such as weakness, fatigue, dizziness, fainting spells, and shortness of breath.

Causes

The heart has an electrical system that determines the heart rate and keeps the heart chambers contracting (pumping) in an orderly and efficient manner. It is a bit like the quartz in a quartz watch, it ticks regularly to ensure the heart beats regularly. Unlike the watch, the heart can speed up or slow down, depending on whether we are exercising or relaxing. The frequency of signals generated governs the heart rate.

During atrial fibrillation, the signals are generated by many different areas in the heart rather than by one single source. These abnormal signals fire in a rapid (often more than 150 beats/minute) and chaotic manner. These rapidly firing chaotic signals cause the heart to quiver rather than contract normally. Even at an average rate of 150 contractions/minute, the heart may not have enough time to fill the chambers with blood before the next contraction. Therefore, atrial fibrillation decreases the amount of blood pumped by the heart both because of the loss of normal contractions and because of the rapid rate of contractions.

Risk factors

There are many risk factors in developing atrial fibrillation. These are:

• Coronary heart disease (including heart attack)
• High blood pressure (hypertension)
• Abnormal heart muscle function (including congestive heart failure)
• Mitral heart valve disease (including mitral valve prolapse)
• Overactive thyroid, or overdose of thyroid medication
• Low amounts of oxygen in the blood (for example, as occurs with lung diseases such as emphysema or chronic obstructive pulmonary disease (COPD)
• Inflammation of the lining surrounding the heart (pericarditis)
• Blood clots in the lung (pulmonary embolism)
• Chronic lung diseases (emphysema, asthma, COPD)
• Alcohol excess
• Stimulant drug use (cocaine or decongestants)
• Recent heart or lung surgery
• Abnormal heart structure from the time of birth (congenital heart disease)

About 1 in 10,000 otherwise healthy, young adults have atrial fibrillation without any apparent cause or underlying heart disease. Atrial fibrillation in these individuals is usually intermittent but can become chronic in 25% of those affected. This condition is referred to as lone atrial fibrillation. Stress and alcohol and tobacco use may play a role in causing lone atrial fibrillation.

Treatment

The first step in treating atrial fibrillation is control of the risk factors that can precipitate the disorder. Thus, the use of stimulant drugs and excessive alcohol intake must be stopped. High blood pressure requires treatment. Hyperthyroidism (too much thyroid hormone) and low blood oxygen levels must be corrected. Heart failure and other diseases of the heart and the lungs need to be treated.

The goals of atrial fibrillation treatment include:

• slowing the rapid heart rate (the rate of ventricular contractions);
• preventing blood clots and strokes;
• converting the irregular rhythm back to normal rhythm whenever possible. Converting atrial fibrillation back to a normal heart rhythm can be accomplished with medications (a process called chemical cardio version) or by electrical shocks (electrical cardio version)

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