Sporadic high pacing and shock impedance on remote monitoring in hybrid implantable cardioverter-defibrillator systems: clinical impact and management

Background: Sporadic high impedance values without other anomalies detected by remote monitoring of hybrid cardiac implantable electronic device systems have been described recently. The clinical significance and related hazard of this phenomenon are not fully understood. Objective: The purpose of this study was to describe the prevalence, management, and outcomes associated with hybrid implantable cardioverter-defibrillator (ICD) systems. Methods: We collected data on patients with sporadic high lead impedance alert on remote monitoring who had undergone implantation with a hybrid ICD system between January 2015 and December 2019. Pacing thresholds, sensing and impedance values, and temporal pattern of impedance values were collected by remote monitoring, at implantation, and during an in-office visit. Results: Among 92 patients receiving a hybrid ICD, 15 (16.3%) had high impedance alert on remote monitoring (14 Boston Scientific and 1 St. Jude Medical ICD canisters paired with Medtronic or Biotronik DF-1 leads). Four patients had a cardiac resynchronization therapy–defibrillator (CRT-D), 7 a dual-chamber ICD, and 4 a single-chamber ICD. Three patients presented with high atrial lead impedance, 7 high right ventricular lead impedance, 1 high left ventricular impedance, and 2 high shock impedance values. All patients underwent follow-up by remote monitoring. Sporadic high impedance values were not associated with an adverse outcome or need for revision in all but 1 patient, who had continuously increasing pacing thresholds due to lead microfracture. Conclusion: In the absence of clear signs of lead fracture or connection issues, sporadic high pacing and shock impedance in hybrid implantable defibrillator systems can be safely managed by close follow-up.