Risk of Collateral Lead Damage in Percutaneous Cardiac Implantable Electronic Device Extraction.

OBJECTIVES: This study sought to assess the risk of collateral lead damage during cardiac implantable electronic device extraction. BACKGROUND: With the increasing numbers of cardiovascular implantable electronic devices, there has been an increase in the number of percutaneous device and lead extractions. It is unknown how often collateral damage (defined as the need for unintended lead extraction, or loss of lead's integrity or dislodgement) occurs in the planned retained leads. METHODS: In this retrospective study, 108 patients who underwent incomplete cardiovascular implantable electronic device removal at the University of California, San Diego from September 2010 to September 2015 were included. The authors established the integrity of previously functioning leads at the end of each procedure as well as on follow-up visits using parameters including lead impedance change, threshold change, drop in P- or R-wave signal amplitude, or presence of lead noise. RESULTS: Only 4 of 143 leads (2.7%) were found to have collateral damage. One right atrial (RA) lead had a clear insulation break, the second RA lead was found dislodged, and the third RA had a constant noise. The right ventricular lead was found to have a new high pacing threshold. Collateral lead age, extracted lead implantation site, collateral lead implantation site, and mode of lead extraction (laser, traction, or rotational dilator) did not have a significant correlation with the outcome of collateral lead damage. CONCLUSIONS: Lead extraction can be performed safely; however, there is a small risk of damaging adjacent leads. Close follow-up is needed, especially for the first few months, to assess for the reconnected leads' integrity.

Abrasion and fatigue resistance of PDMS containing multiblock polyurethanes after accelerated water exposure at elevated temperature.

Segmented polyurethane multiblock polymers containing polydimethylsiloxane and polyether soft segments form tough and easily processed thermoplastic elastomers (PDMS-urethanes). Two commercially available examples, PurSil 35 (denoted as P35) and Elast-Eon E2A (denoted as E2A), were evaluated for abrasion and fatigue resistance after immersion in 85 °C buffered water for up to 80 weeks. We previously reported that water exposure in these experiments resulted in a molar mass reduction, where the kinetics of the hydrolysis reaction is supported by a straight forward Arrhenius analysis over a range of accelerated temperatures (37-85 °C). We also showed that the ultimate tensile properties of P35 and E2A were significantly compromised when the molar mass was reduced. Here, we show that the reduction in molar mass also correlated with a reduction in both the abrasion and fatigue resistance. The instantaneous wear rate of both P35 and E2A, when exposed to the reciprocating motion of an ethylene tetrafluoroethylene (ETFE) jacketed cable, increased with the inverse of the number averaged molar mass (1/Mn). Both materials showed a change in the wear surface when the number-averaged molar mass was reduced to ≈ 16 kg/mole, where a smooth wear surface transitioned to a 'spalling-like' pattern, leaving the wear surface with ≈ 0.3 mm cracks that propagated beyond the contact surface. The fatigue crack growth rate for P35 and E2A also increased in proportion to 1/Mn, after the molar mass was reduced below a critical value of ≈30 kg/mole. Interestingly, this critical molar mass coincided with that at which the single cycle stress-strain response changed from strain hardening to strain softening. The changes in both abrasion and fatigue resistance, key predictors for long term reliability of cardiac leads, after exposure of this class of PDMS-urethanes to water suggests that these materials are susceptible to mechanical compromise in vivo.