Atrial fibrillation (A-fib)
Atrial fibrillation occurs when the atrium has lost the ability to beat in a coordinated fashion. Instead of the SA node generating a single electrical signal, numerous areas of the atrium become irritated and produce electrical impulses. This causes the atrium to jiggle, or fibrillate, instead of beating. The AV node sees all the electrical signals, but because there are so many, and because they are so erratic, only some of the hundreds of signals per minute are passed through to the ventricle. The ventricles then fire irregularly and often very quickly.
As in PSVT, the symptoms may include palpitations, lightheadedness, and shortness of breath. The cause of atrial fibrillation, however, may be more significant, since it may be due to aging of the conducting system of the heart and there may be associated atherosclerotic heart disease. Therefore, atrial fibrillation with rapid ventricular response associated with chest pain or shortness of breath may need emergent cardioversion (a procedure that uses electricity to shock the heart back into a normal rhythm) or intravenous medications to control the heart rate.
One significant complication of atrial fibrillation is the formation of blood clots along the inside of the heart wall. These clots may break off and travel to different organs in the body (embolize), blocking blood vessels and causing the affected organs to malfunction because of the loss of blood supply. A common complication is a clot traveling to the brain, resulting in a stroke.
The treatment of atrial fibrillation depends upon many factors including how long it has been present, what symptoms it causes, and the underlying health of the individual. The patient and his or her doctor will decide whether or not to restore a normal sinus rhythm or to simply keep the heart rate under control.
Atrial fibrillation can be a safe rhythm and not life threatening when the rate is controlled. Medications are used to slow the electrical impulses through the AV node, so that the ventricles do not try to capture each signal being produced. The reason to return people to a regular rhythm has to do with cardiac output. In atrial fibrillation, the atria do not beat and pump blood to the ventricles. Instead, blood flows into the ventricles by gravity alone. This lack of atrial kick can decrease the heart's efficiency and cardiac output by 10% to 15%.
Blood thinning, or anticoagulation, may be recommended for those patients with atrial fibrillation and elevated risk for stroke. Oral drugs that anticoagulate are warfarin (Coumadin), dabigatran (Pradaxa), rivaroxaban (Xarelto), and apixaban (Eliquis). There are other injectable drugs that are used in a hospital setting. If the patient is at low risk, the doctor may recommend aspirin alone for stroke prevention. If atrial fibrillation is poorly tolerated due to symptomatic palpitations or symptoms of reduced cardiac output, or if there are concerns with lifelong anticoagulation therapy, more definitive therapy may include specific medications, electrical cardioversion, or catheter based ablation (sometimes with a pacemaker inserted). Atrial fibrillation is a common condition, with many implications, and the best plan for each patient should be discussed at length with one's physician.