The Normal Cardiac Cycle During each heartbeat, the two upper chambers (right and left atria) contract, followed by contraction of the two lower pumping chambers (right and left ventricles). This action is coordinated by the heart's electrical system. Normal electrical activation of the heart occurs in an orderly fashion. With each beat, the electrical impulse starts in the sinus (or sinoatrial) node (in the right atrium). The impulse spreads through the atria, stimulating the atria …showed first 75 words of 2053 total…

…showed last 75 words of 2053 total…be useful in people with atrial fibrillation and ventricular rates that cannot be well controlled on medication. Open heart surgery - May be indicated to correct valvular disease or to bypass coronary artery disease that may predispose to arrhythmias. In addition, surgical procedures are available to potentially cure some arrhythmias in appropriately selected people. For example, the Maze procedure is designed to cure atrial fibrillation in some people with very hard to control atrial fibrillation.