MEDICAL ANIMATION TRANSCRIPT: Atrial fibrillation is a type of arrhythmia, which is an abnormality in the pace or force of your heartbeat. If you have atrial fibrillation, the heart's upper chambers contract in a fast, twitchy fashion, resulting in an irregular, uncoordinated heartbeat. Your heart is a muscular organ made up of four chambers: the right and left atria, and the right and left ventricles. During a normal heartbeat, the chambers of your heart contract and relax in a rhythmic pattern to deliver a consistent flow of blood throughout your body. The right atrium collects blood from the body and the right ventricle pumps it to the lungs which bring oxygen to and remove carbon dioxide from the blood. At the same time, the left atrium receives blood from the lungs, and the left ventricle pumps it out to supply your body's tissues with oxygen and nutrients. Each heartbeat begins in the heart’s “natural” pacemaker, called the sinoatrial, or SA, node, located in the wall of the right atrium. An electrical signal starts here, then spreads across both atria, causing them to contract and push blood into the ventricles. As the atria relax, the signal travels through the atrioventricular, or AV, node, to the ventricular walls, causing them to contract. The ventricles relax, completing one full heartbeat. Immediately, the SA node generates a new electrical impulse, repeating the pattern. In atrial fibrillation, the electrical signals originate from unusual locations in the atria and nearby pulmonary veins. These abnormal signals travel through the atria haphazardly, causing the atria to contract in a jumble of rapid quivers and twitches. The signals bombard the AV node, causing the ventricles to contract rapidly. Even at a faster pace, the ventricular contractions cannot keep up with the rapid atrial contractions, resulting in an uncoordinated heartbeat. After these irregular contractions, the chambers may not empty completely. When blood collects in the atria, clots may form. A clot can flow out of your heart, through your neck into your brain, where it can cause a stroke. Blood pooling in your ventricles deprives your body's tissues of oxygen and nutrients. If your heart is consistently unable to pump enough blood to meet the body's needs, you can develop heart failure. Your doctor may treat your atrial fibrillation with anti-arrhythmic medications. Anti-arrhythmic medications control the electrical signals sent to your atria, which help your heart beat in a regular rhythm. After treatment, your heart may still beat too quickly. In this case, your doctor may give you beta-blocker medications to slow your heart rate down to normal. In addition, your doctor may recommend procedures that restore your heart's normal rhythm and rate, such as cardioversion, ablation, or pacemaker placement. In electrical cardioversion, your doctor will give your heart a shock to start a normal heart rhythm. During ablation, your surgeon will use radio wave energy to destroy the heart tissue generating the abnormal electrical signals. In pacemaker placement, your surgeon will implant a small device under the skin near your heart to regulate your heart's rhythm.