PO-05-084 MANAGEMENT OF GRADUAL ELEVATED SHOCK IMPEDANCE IN ENDOTAK RELIANCE ICD LEADS

Abstract

Elevated shock impedance might indicate structural compromise to implantable cardioverter-defibrillator (ICD) leads. Defibrillation or shock impedance can be measured in two ways: through high output therapy termed true shock impedance (TSI); or through a calculated value using a low voltage sub-threshold measurement (LVSM). We have identified 3 cases of gradual LVSM shock impedance rises (>130 ohm) in patients with Endotak Reliance ICD leads at our institution who subsequently had an open circuit fault code at commanded TSI testing. Literature search revealed case series (Hauser RG et al 2020 and Monkhouse C et al 2019) highlighting this phenomenon. We sought to understand the scope and establish potential recommendations for commanded shock TSI testing in patients with Endotak Reliance ICD leads and high LVSM shock impedance by reviewing cases reported in the FDA Manufacturer and User Facility Device Experience (MAUDE) database. We searched the MAUDE database from 2008 to 2021 for “high impedance” or “impedance problem” while filtering for Endotak Reliance ICD leads. Of these 1369 patients, we identified those who underwent commanded shock testing. The MAUDE search identified 117 ICD leads with high shock impedance (majority > 125 ohm) that underwent DFT or commanded shock. Of those, 69 (59%) had successful DFT or what was deemed as acceptable impedance after commanded shock and remain in service. 18 dual coil leads (15%) underwent shock vector change prior to testing with 16 (87%) of those remaining in service. 30 (26%) of the leads had open circuit fault code, continued high shock impedance or failed defibrillation with testing. These leads were extracted or abandoned with new leads implanted. 1 death was reported as a complication of lead extraction. Endotak Reliance ICD leads can show gradual rise in LVSM shock impedance although the etiology is uncertain. Potential theories include fibrotic encapsulation or calcification of the SVC/RV coil. It is important that these patients are identified, monitored, and risk stratified. We recommend high voltage TSI commanded shock testing in high-risk patients with a gradual rise in LVSM shock impedance that is above the acceptable range. If the impedance is within normal limits during testing, continued surveillance might suffice with repeat testing if further increase in impedance is observed. If the impedance remains elevated with TSI commanded shock testing, then lead replacement should be considered.