Measured Lead Parameters and Electrogram Sensing Over Time in Patients With Cardiac Sarcoidosis and an Implanted Cardiac-Defibrillator

ObjectivesThe study sought to characterize the performance of implanted leads among a cohort of patients with cardiac sarcoidosis (CS) and implantable cardiac-defibrillators (ICDs).BackgroundAn ICD is indicated for some patients with CS for the prevention of sudden cardiac death. CS can lead to myocardial inflammation and scar that may interfere with lead performance.MethodsWe performed a case-control study within the cohort of patients at the University of Colorado Hospital with CS and an ICD (n = 48) compared with randomly selected controls (n = 117) who had other indications for an ICD. We compared the measured lead parameters at the time of routine interrogation to assess the differences between groups over time. The mean duration of follow-up was 51 months. Survival analysis was performed by the method of Kaplan and Meier and by Cox proportional hazards regression.ResultsThere was no significant difference in measured lead impedance, capture thresholds, or sensed electrograms at implantation between the CS and control groups. There were no significant differences between the mean parameters between groups over the follow-up period. However, patients with CS have a high incidence of significant (>50%) drop in measured electrograms (16 of 46 [33%] CS patients vs. 4 of 117 [3.4%] controls; hazard ratio: 10.49, 95% confidence interval: 3.47 to 31.67). As a result of alterations in lead parameters, 2 patients (4.3%) required lead revision, and 6 patients (13%) required ICD testing to ensure adequate detection of induced ventricular fibrillation.ConclusionsReductions over time in ICD sensing of P- and/or R-wave electrograms are common in patients with CS. Although further investigation is needed to determine the mechanism of these changes, these findings suggest that patients with CS who have an ICD should be closely monitored for clinically relevant changes in P- and R-wave amplitudes.