Intracardiac Echocardiography for Transvenous Lead Extractions: Evaluating its Utility in a Vascular Phantom Model

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Transvenous lead extractions (TLEs) are minimally invasive procedures in which pacing or implantable cardioverter defibrillator leads are extracted under guidance of 2D X-ray fluoroscopy. Despite the fact that fluoroscopy is currently the gold standard for TLEs, it has several limitations in terms of visualization of anatomical structures, areas of high risk and complications. Since TLEs carry a small but distinct risk of major complications including laceration of the Superior Vena Cava (SVC), bleeding and death, this study aimed to evaluate the utility of intracardiac echocardiography (ICE) to overcome current problems of fluoroscopy and to reduce major complications during TLEs. Hereby the presented work first had the objective of designing and constructing a tissue-mimicking vascular phantom model with realistic geometry and echogenicity to simulate a real-life lead extraction environment suitable for ultrasound imaging and second, of evaluating the utility of ICE for different visualization planes of the lead-tissue interface whilst using the phantom model. In order to accomplish this, different mould prototypes were designed and constructed with additive manufacturing in order to enable polyvinyl alcohol (PVA) pouring of the phantom. Following several iteration steps of the prototypes, an ultrasound compatible PVA phantom model of the SVC and approximate innominate veins with realistic geometry could be constructed according a developed methodology, adopted and modified from previous protocols. Subsequently, its suitability to serve as a real-life lead extraction environment in terms of echogenicity was assessed by comparison of its results with findings from previous conducted clinical studies. Ultimately, both the constructed phantom and a porcine model were used to evaluate the performance of ICE in three experiments whereby several visualization planes of the lead-tissue interface were examined. The results of this study demonstrate that a side-looking phased-array ICE catheter could image different structures of the lead-tissue interface including the vessel wall of the SVC, area of scar tissue, free-floating and adherent cardiac leads as well as the advancement of an extraction sheath over the lead. It was found that the structures could be clearly distinguished from each other in terms of echogenicity. The scar tissue along the lead-tissue interface was visualized as an echo dense signal, characterized by a linear echogenic shadow, and equivalent to prior clinical observations. From the results, it also appeared that a parallel view and cross-sectional view outside the SVC gave more insight into lead binding sites and their location with respect to the vessel wall than a conventional parallel view inside the SVC. It can be concluded that it is feasible to design and construct a vascular phantom model with realistic geometry and echogenicity, adequate for the simulation of a real-life lead extraction environment and to evaluate the utility of ICE for TLEs. This study has demonstrated that ICE is a valuable tool to visualize and assess the lead-tissue interface, which is crucial to avoid major complications during TLEs. Thus, implementation of ICE imaging into TLEs has the potential to add to a more effective and safer procedure.