MEDICAL ANIMATION TRANSCRIPT: Depending on activity level, the heart beats about 60 to 100 times per minute. It may be higher during exercise or lower at rest. A normal heart rate and rhythm ensures the delivery of oxygen-rich blood to all of the body's organs, such as the brain and lungs. A group of cells in the heart, called the cardiac conduction system, uses electrical impulses to control the speed and rhythm of each heartbeat. Each heartbeat starts in the right atrium in the sinoatrial, or SA node, then spreads through the walls of the heart chambers, called the atria, and ventricles causing them to contract. This process repeats with each heartbeat. Problems with the cardiac conduction system cause the heart to have an abnormal rhythm called an arrhythmia. This may cause an irregular pulse. Arrhythmias may happen in the atria or ventricles. Types of arrhythmia include fibrillation, which is an irregular heartbeat rhythm, tachycardia, which is a fast heartbeat of more than 100 beats per minute, and bradycardia, which is a slow heartbeat of less than 60 beats per minute. Atrial fibrillation is the most common type of arrhythmia. Random impulses cause the atria to fibrillate, or twitch, rapidly and randomly. Tachycardia in the atria is called supraventricular tachycardia. In focal atrial tachycardia, small areas within the atria wall, start or pass along impulses that cause the atria to contract rapidly, but with a regular rhythm. In atrial flutter, larger areas within the atrial wall start or pass along impulses that cause the atria to contract rapidly, but with a regular rhythm. Tachycardia may also happen in the ventricles with rapid and regular contractions. The body may not receive enough blood because the ventricles contract before completely filling with blood. The most serious arrhythmia is ventricular fibrillation where many random impulses fire rapidly within the ventricular walls. In ventricular fibrillation, the ventricles are quivering instead of beating. This is a medical emergency because the heart cannot effectively pump blood to the body or itself. Sometimes, problems with the SA node or problems with the pathway of the electrical impulses to the ventricles can cause the slow heartbeat in bradycardia. If the heart beats too slowly, the body may not receive enough oxygen-rich blood. Depending on the type of arrhythmia, a doctor may recommend one or more of the following treatments, lifestyle changes, such as eating a heart healthy diet, exercising, and quitting smoking, medication, such as antiarrhythmic drugs and beta blockers, catheter ablation where thin wires inserted into the heart destroy the tissue causing the arrhythmia with hot or cold energy, and implantable devices, such as a pacemaker or defibrillator to correct the pace or rhythm of the heart.