Figure 35-9 Electromagnetic interference from the monopolar electrosurgery (i.e., Bovie) caused an implantable cardioverter-defibrillator (ICD) to detect ventricular fibrillation (VF). This stored electrogram was one of 73 found at the end of a 4-hour surgical procedure in which considerable monopolar electrosurgery (ESU) was used. This patient had a Guidant Medical ICD in the VOE-VVI mode. This patient's ICD had been placed in a "monitor only" mode before surgery. As a result, the ICD recorded any instance of ventricular dysrhythmia that would have triggered therapy, but it could not deliver therapy. The electrogram demonstrates a ventricular rate of 70 beats/min but with considerable noise on the baseline (1); a ventricular fibrillation (VF) event was declared for the detected heart rate of 345 beats/min, and the ICD charged its capacitor (2); the ICD was programmed to "reconfirm before shock," and the ventricular rate remains 70 beats/min with noise on the baseline (3); the noise caused the ICD to believe that the patient remained in VF, and the ICD would have delivered a shock, except it was programmed to monitor only (4); and because the noise is gone (i.e., the ESU had stopped), the ICD declares the event over after a "successful" defibrillation (5).