Low-voltage shock impedance measurements: A false sense of security.

BACKGROUND: Implantable cardioverter defibrillators use low-voltage shock impedance measurements to monitor the lead integrity. However, previous case reports suggest that low-voltage shock impedance measurements may fail to detect insulation breaches that can cause life-threatening electrical short circuits. METHODS AND RESULTS: We report six cases of insulation breaches in transvenous defibrillation leads that were not obvious during standard interrogations and testing of the lead beforehand. In two cases, an electrical short circuit during commanded shock delivery for internal electrical cardioversion resulted in a total damage of the ICD generator. In one of these cases, commanded shock delivery induced ventricular fibrillation, which required external defibrillation. In two cases, a shock due to ventricular tachycardia was aborted as the shock impedance was less than 20 Ω. However, in both cases the tiny residual shock energy terminated the ventricular tachycardia. In contrast, in one case the residual energy of the aborted shock did not end ventricular fibrillation induced at defibrillator threshold testing. In one case, the ICD indicated an error code for a short circuit condition detected during an adequate shock delivery. CONCLUSIONS: This case series illustrates that low-voltage shock impedance measurements can fail to detect insulation breaches. These data suggest that in patients without a contraindication, traditional defibrillator threshold testing or high voltage synchronized shock at the time of device replacement should be considered.

Enhancing Guidewire Efficacy for Trans-radial Access: The EAGER Randomized Controlled Trial.

Background: The 1.5mm 'Baby J' hydrophilic narrow J tipped wire is a development of the standard 0.035" 3mm J tipped peripheral guidewire, designed to improve efficiency of transradial coronary procedures by safely navigating small caliber radial arteries to the aorta. There is currently a lack of evidence comparing the procedural success and safety of different peripheral guidewires used in transradial cardiac procedures. We compared the efficacy and safety of a narrow J tipped hydrophilic 0.035" wire (intervention - Radifocus™ 'Baby J' guidewire, TERUMO Co., Tokyo, Japan). versus standard fixed core (FC) 0.035" J wire (control). Methods: Investigator initiated, blinded, Australian, multicenter randomized trial in patients undergoing clinically indicated coronary angiography and/or PCI. Randomized 1:1 via sealed envelope method to use either the control or the intervention guidewire. The primary endpoint (technical success) was defined as gaining aortic root access with the randomized guidewire. Results: 330 patients were randomized between October 2022 - June 2023 (median age 69 years, 36% female, BMI 29 kg/m²). The primary endpoint was achieved more frequently in the intervention group [96% v 84%; mean difference 12% (95% CI 5.7-18.3); p<0.001]. Women assigned to the control wire experienced a higher failure rate compared to men (31% v 8% in men; p<0.001). Fluoroscopy time was significantly shorter in the baby J group (median 344 versus 491 seconds; p=0.024). The main mechanisms of failure using the control wire were radial artery spasm (15/26; 57%) and subclavian tortuosity (5/26; 19.2%). There were no differences in overall procedure times, MACE, or vascular complications between guidewires. Conclusions: A narrow 1.5mm J tipped hydrophilic guidewire resulted in greater technical success and reduced fluoroscopy time compared to the standard 3mm J tip non-hydrophilic guidewire. The guidewire is safe and demonstrated key incremental benefits for the trans-radial approach particularly in women.