Electrocardiography

Electrocardiography, in medicine, procedure by which a physician obtains a tracing of the electrical activity of the heart. The rhythmic beating of the heart is maintained by an orderly series of discharges originating in the sinus node of the right atrium and proceeding through the atrioventricular node and the bundle of neuromuscular fibers (the bundle of His) to the ventricles. By attaching electrodes to various parts of the body, a record of this current can be obtained. This record is called an electrocardiogram, or ECG or EKG for short. Prominent parts of the ECG are the P wave, a deflection caused by the current originating in the atrium; the QRS complex, showing the passage of the electrical activity into the ventricles; and the T wave, as the ventricles reset themselves. The ECG is often helpful in showing the cause of an abnormal heart rhythm or an evolving heart attack.