Synchronized Electrical Cardioversion

Synchronized cardioversion is a procedure similar to electrical defibrillation in that a transthoracic electrical current is applied to the anterior chest to terminate a life-threatening or unstable tachycardic arrhythmia. Unlike defibrillation, which is used in cardiac arrest patients, synchronized cardioversion is performed on patients who still have a pulse but are hemodynamically unstable. It is used to treat both hemodynamically unstable ventricular and supraventricular rhythms. Each year, almost 350,000 Americans die from heart disease. Half of these die suddenly, outside of a hospital, because of the sudden cessation of spontaneous, organized cardiac function. The most common cause of sudden cardiac arrest in adults is pulseless ventricular tachycardia or ventricular fibrillation. Ventricular tachycardia can also occur in the presence of a pulse; often, it is the precursor to ventricular fibrillation. Ventricular tachycardia is characterized by rapid, wide (greater than 0.12 seconds) QRS complexes. Supraventricular Tachycardia (SVT) refers to a cardiac rhythm greater than 100 beats per minute, which originates above the bundle of His. SVT is characterized by rapid, narrow (less than 0.12 seconds wide) QRS complexes. Any tachycardic rhythm that does not originate in the ventricles is called SVT. This includes sinus tachycardia, junctional tachycardia, reentrant tachycardias, multiple atrial tachycardia (MAT), atrial fibrillation, and atrial flutter. Although various supraventricular rhythms can cause SVT, they are treated with the same clinical approach.