Transtelephonic defibrillation. STUDY OBJECTIVES: This study was undertaken to assess the safety and reliability of a device for transtelephonic defibrillation. DESIGN: The transtelephonic system consists of a patient unit and a base station. The patient unit contains a monitor-defibrillator, electrode pads, microphone, microprocessor, and DC defibrillator. The base station comprises a control panel, computer, and ECG display. SETTING: Fifteen patients who were treated in our emergency department for cardiac arrest were placed on patient units that activated our base station in a remote location within the ED. TYPE OF PARTICIPANTS: Thirteen patients were treated for ventricular fibrillation, and two patients were treated for ventricular tachycardia. INTERVENTIONS: Thirty-one shocks were delivered transtelephonically. MEASUREMENTS AND MAIN RESULTS: In all cases, voice and ECG transmission were established without difficulty. CONCLUSIONS: We conclude that this system represents a safe and reliable method for the treatment of ventricular fibrillation, and we advocate additional use to study the prehospital applications of transtelephonic defibrillation. 