The surface electrocardiogram and clinical cardiac electrophysiology

Normal pacemaker cell and conduction system function is fundamentally important in maintaining cardiac mechanical performance. Cardiac arrhythmias consist of a group of electrical disturbances in the heart, including abnormal spontaneous depolarization, irregular conduction (short circuits), and conduction blocks. The resultant fast, slow, or irregular heart rhythm can cause significant hemodynamic compromise, discomfort, and/or death. Importantly, a thorough understanding of cardiac electrophysiology is essential for management of any cardiac patient. The electrocardiogram, as recorded from electrodes placed on the surface of the chest and extremities, is a simple, yet important diagnostic technique for identification of cardiac arrhythmias. It can also be useful in the diagnosis of electrolyte abnormalities, medication toxicity, ischemic heart disease, and enlargement of cardiac chambers.