Utility and safety of axillo-subclavian venous imaging with carbon dioxide (CO) prior to chronic lead system revisions.

Background: Prior to attempting placement of one or more electrodes to revise existing rhythm control devices, patency of the central veins should be documented, in view of a high incidence of significant chronic occlusions. Since iodinated contrast venography may be contraindicated in select situations, imaging of the axillo-subclavian venous system with gaseous carbon dioxide (CO(2)) was evaluated prospectively in 23 consecutive individuals who were considered for revision of previously implanted pacemaker or automatic cardioverter defibrillator lead systems.

Methods: Approximately 20 mL of CO(2) were manually infused via CO(2) primed injection tubing into a vein at or above the level of the antecubital fossa ipsilateral to the side of prior lead placements.

Inappropriate defibrillator shocks from depolarization--repolarization mismatch in a patient with hypertrophy cardiomyopathy.

Despite wide use of dedicated bipolar sensing electrodes in implantable cardioverter-defibrillator (ICD) systems, oversensing occasionally occurs, leading to unwarranted shocks or antitachycardia pacing. This case report highlights an individual with hypertrophic cardiomyopathy (HCM) who experienced inappropriate shocks from oversensing of repolarization electrograms (T-waves). During the implantation procedure, no excessive T-wave amplitudes were detected during sinus rhythm, ventricular pacing, or induced ventricular fibrillation.