The Cardiac Rhythm An arrhythmia is any deviation from or disturbance of the normal heart rhythm. The basic rhythm of the heart is a tightly regulated phenomenon designed to insure maximal efficiency and optimal performance. It is a dynamic phenomenon that changes according to the metabolic needs of the body. The cardiac rhythm involves several different microscopic and macroscopic structures within the normal heart.	MORE INFO ABOUT CARDIAC RHYTHMS: Normal Atrial Tachycardia Atrial Fibrillation/Flutter AV Nodal Reentry Tachycardia Wolff-Parkinson-White Syndrome Ventricular Tachycardia
The Sino-Atrial Node The heart's normal or intrinsic pacemaker is called the sino-atrial node. It is located in the upper right chamber (right atrium). A signal or impulse is emitted to trigger the heart beat. The normal heart beat is 60-100 beats per minute. At times the heart may be slower, such as during sleep, or faster as during activity or stress. This impulse travels across the upper chambers of the heart. However, in order to trigger the pumping or lower chambers (the ventricles) the impulse must cross the specialized electrical (conduction) system. This connection between the upper and lower chambers of the heart is in a central area called the septum. Here a series of specialized tissues take the impulse from the top chamber, slow its progression down a bit, and then pass it on to specialized fibers that transmit the impulse across the pumping chambers to signal the muscles within these chambers to contract and pump. With the next heart beat, the process starts again. Arrhythmic Disturbances An arrhythmia may occur when any portion of this sequence is interrupted or disturbed. Among arrhythmic disturbances are the failure of the pacemaker or electrical system to trigger appropriately and conduct impulses properly. Other arrhythmias occur when abnormal foci within the heart interrupt the normal sequence of electrical stimulation and temporarily, or for prolonged periods of time, initiate the electrical sequence. Arrhythmias may be benign, symptomatic, life threatening or even fatal. Their consequences depend not only on their manifestation but on the presence of important abnormal structural conditions of the heart. If you have any questions or concerns about this site, please contact webmaster@docnet.org.