Gradually increasing impedance in patients with pacemakers and implantable defibrillators: a watchful waiting strategy

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: Public hospital(s). Main funding source(s): hospital resources INTRODUCTION: Pacing impedance measurements are important in the surveillance of pacemaker and implantable cardioverter/defibrillator (ICD) devices. Whereas sudden changes in impedances can reflect lead fracture or isolation defects, gradually increasing impedances are thought to occur because of calcifications at the endomyocardial interface. In many cases, these leads are replaced prophylactically but this has not been studied systematically. PURPOSE: We aimed to identify the outcome of right ventricular (RV) electrodes with high impedances that were left active in this single center study. METHODS: All patients in the electronic patient database were screened for impedances >1200Ohms. 41,201 individual recordings led to 219 individual patients. 161 patients were excluded from the analysis due to sudden impedance increase, temporarily high impedances or wrong entry. Of the remaining 58 patients, baseline characteristics as well as pacing impedance, sensing values, pacing thresholds, and shock impedance in case of ICDs were recorded. RESULTS: There were 17 pacemaker and 41 ICD patients, 68±15 years old, 69% were male. Glomerular filtration rate at baseline was 81±22 ml/min/1.73m2. Baseline RV impedance was 597±123Ohms. During follow-up impedances increased to 1875±682Ohms (p<0,001). Pacing thresholds increased from 0,6±0,4V to 3,0±1,9V (p<0,001). Sensing remained stable. The median time from implant to impedance rise >1000Ohms was 5,5 (3,4-7)years and median follow-up thereafter 3,8 years (1,6-6,6). During follow-up, no intervention was performed for 45 leads (78%). No events occurred. 13 leads (22%) were replaced , 9 prophylactically (mostly because of ICD advisory leads), 3 because of high pacing thresholds and high percentage pacing and one lead because of noise oversensing, probably unrelated as it occurred 7 years after impedance increase. CONCLUSIONS: A watchful waiting strategy appears to be a safe option for patients with ICDs and pacemakers with low percentage pacing. As impedance increase cannot be used for surveillance for imminent lead fracture, other means such as short interval counts and non-sustained oversensing have to be employed and should be combined with remote monitoring.