Pacemaker/implantable cardioverter-defibrillator interaction

We describe a case of pacemaker/implantable cardioverter-defibrillator (ICD) interaction in a single system causing failure to detect induced ventricular fibrillation (VF) in an 83-year-old man with ischemic cardiomyopathy. He underwent an ICD generator replacement due to battery depletion. In addition, a right atrial lead was placed to treat symptomatic bradycardia. Appropriate sensing and pacing parameters were observed in both leads during implant, and there was no cross-talk between the leads. A defibrillation threshold (DFT) test was performed (sense 1.5 mV, shock on T) with induction of VF that was not detected by the device, ultimately requiring an external defibrillation to terminate the arrhythmia. The device printout during testing showed atrial/ventricular lead cross-talk caused by the 1.1-J shock to induce VF, sensed beats in the noise window activating the noise suppression algorithm and preventing initial VF detection, and recurrent resetting of the automatic gain control due to ventricular sensing of the atrial pacing artifact preventing detection and perpetuating atrioventricular (AV) pacing at a rate of 60 bpm. In conclusion, pacemaker/ICD interaction can occur in a dual-chamber ICD system. This can be prevented by programming a shorter AV delay, increasing sensitivity (i.e., more sensitive value), and programming a pause before initiating pacing after an ICD discharge.