Atrial fibrillation

Atrial fibrillation (AF) is an electrical rhythm disturbance of the heart affecting the atria. Abnormal electrical impulses in the atria cause the muscle to contract erratically and pump blood inefficiently. The atrial chambers are thus not able to completely empty blood into the ventricles.

Pooling of blood in the atria can cause red blood cells to stick together and form a clot. Clots can be released into the circulatory system and lodge in the blood vessels of the brain. Interruption of blood flow to the brain can result in a cerebrovascular accident, more commonly known as a stroke. Patients with severe cases of AF typically take an anticlotting drug such as coumadin to prevent the occurrence of strokes.

A type of AF, termed paroxysmal, is when the arrhythmia occurs on an unexpected, intermittent basis. These patients tend to have less heart damage than those with chronic (sustained) AF.

Causes

AF is an intermediate-phase disease, meaning that the condition usually develops in response to damage to the heart or from other changes in the cardiovascular system. These include:

• Untreated hypertension
• Abnormal mitral valve function
• Heart surgery
• Coronary heart disease
• Excessive alcohol consumption (“binge drinking”)

In turn, untreated AF can precipitate further damage to the heart by weakening the muscles of the ventricles. This weakened condition of the ventricles is termed cardiomyopathy, which in turn leads to an end-stage condition called heart failure.

The descriptions below are for informational purposes only. For specific treatment advice, consult a qualified medical professional.

Treatment

A highly effective, safe treatment for AF is still an unmet medical need. Nonetheless, current AF treatments, which are somewhat effective, include medication or invasive procedures, or some combination of the two. Because AF is a complex heart condition, the treatment program is typically managed by a physician who specializes in heart disease.

• Medication – beta blockers work by slowing the heart rate, as do calcium channel blockers. Additionally some calcium blockers act to correct the electrical pathways of the heart. Digoxin, from the digitalis class, is useful for two reasons: it slows electrical conduction from the atria to the ventricles; it also strengthens ventricular pumping, making it is useful in AF patients with heart failure.

• Cardioversion – in this technique, the physician attempts to convert the heart to a normal rhythm. Several drugs are available to do this, although the degree of success with these medications can vary. An external defibrillator, applied to the chest while the patient is sedated, works in principal by a sudden electrical shock to the heart, which can induce a normal rhythm. Like medications, this procedure has variable results.

• Ablation – this procedure uses radiofrequency energy to destroy abnormal electrical pathways in heart tissue. The energy emitting probe (electrode) is placed into the heart through a catheter. The practitioner first “maps” an area of the heart to locate the abnormal electrical activity before the responsible tissue is eliminated. Ablation is a newer technique and has shown some promise for cases unresponsive to conventional treatments.