Intraoperative or Procedural Management of Implantable Cardioverter-Defibrillators

No special monitoring is required for the patient with an ICD. Electrocardiographic monitoring and the ability to deliver external cardioversion or defibrillation must be present during the time of ICD disablement. Should external cardioversion or defibrillation be needed, the defibrillator pads should be placed to avoid the pulse generator and lead system to the extent possible. Nevertheless, one should remember that the patient, not the ICD, is being treated. The recommendations in the section "Intraoperative or Procedural Management of Pacemakers" apply here as well.

No special anesthetic techniques have been championed for the patient with an ICD. Most of these patients will have severely depressed systolic function, dilated ventricular cavities, and significant valvular regurgitation. The choice of anesthetic technique should be dictated by the underlying physiologic derangements that are present. Conflicting data have been published regarding the choice of anesthetic agents and changes to defibrillation threshold (DFT). In 1992, Gill and colleagues examined DFT in dogs and concluded that neither halothane nor isoflurane changed DFT in open chest defibrillation compared to a pentobarbital infusion. ^[87] However, Weinbroum and associates recently evaluated defibrillation thresholds in humans during ICD implant

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Figure 35-8 Unexpected ventricular tachycardia with antitachycardia pacing (ATP) was found in this patient during her preoperative visit. A 65-year-old woman with a history of ventricular tachycardia (VT) had undergone implantation of a Medtronic single-chamber defibrillator about 8 months earlier. She had no dizziness or syncopal episodes since the implantable cardioverter-defibrillator (ICD) placement. Interrogation of her device in the preoperative center revealed VVE-VVI programming, along with an episode of tachycardia at 150 to 162 beats/min that was detected by the ICD as VT. The ICD delivered a 6-beat burst of antitachycardia pacing at 182 beats/min, which converted the tachycardia back to sinus rhythm. No backup antibradycardia pacing was needed after the VT was terminated. The upper tracing is a digitized ventricular electrogram that was stored in the ICD during the tachycardic event. The lower tracing is the marker channel that reports the interpretation of the ICD for each event. The numbers below the marker channel represent the interval (in milliseconds). The heart rate is calculated by dividing the interval into 60,000 msec/min. TS represents an interval in the VT zone, TD marks the final event that starts therapy, TP is an ATP event, and VS is an intrinsic ventricular depolarization with a rate that is neither too fast (short interval) nor too slow (long interval). This device was set to detect VT as 16 consecutive ventricular events with a rate between 146 and 200 beats/min and to deliver ATP at 84% of the last R-R interval. The last interval was 400 msec, so ATP was delivered at a rate of 182 beats/min (330-msec intervals).

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).

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