Although the application of electrical energy to the heart had been investigated in the 18th century, it was not until the first half of the 20th century that reference was made to the clinical use of electrical shocks to revert abnormal cardiac rhythms. Several recent reviews have summarized historical milestones in the development of devices capable of delivering specified electrical charges to the heart [1–4]. Early studies utilized alternating current (AC), employing 60-cycle AC of 1.5 to 2.0 amperes and 120 to 130 volts. Although AC discharges are capable of transthoracic defibrillation of the human heart, they are not suitable for correcting arrhythmias in man because they may lead to substantial deterioration in ventricular function and expose the patient to the risk of ventricular fibrillation [5]. The development of capacitors capable of delivering single-pulse discharges set the stage for the production of the cardioversion/defibrillation apparatus in use today (figure 7–1).