Ultrasound-guided S-ICD implantation: a proof-of-concept study and clinical experience

Background Subcutaneous implantable cardioverter-defibrillator (S-ICD) implantation currently requires fluoroscopy for lead and device positioning. Postoperative chest X-ray is needed for PRAETORIAN score calculation for a post-hoc assessment of shock conversion failure probability. Lead implantation depth is the strongest predictor of shock conversion success, and a recent analysis proposes a simplified PRAETORIAN score that only relies on lead depth measurement. Ultrasound (US) guidance for preoperative positioning could potentially reduce radiation exposure while maintaining optimal implant quality. Intraoperative US may help to assess lead implantation quality during implantation procedure, thus potentially providing an immediate assessment of the risk of conversion failure. Purpose 1) To assess the feasibility and accuracy of a novel US-guided approach to S-ICD implantation for lead and device positioning. 2) To explore the feasibility of a novel intraoperative US-based assessment of lead implantation depth. Methods In a single-center proof-of-concept study, 20 consecutive patients underwent S-ICD implantation with US-guided positioning. The aortic valve (AoV) position was identified by transthoracic echocardiography to guide lead and device placement. Fluoroscopic confirmation was performed for validation. Intraoperative US measurements of sternum-electrode distance were compared with postoperative lateral chest X-rays. Two blinded external reviewers assessed implantation quality on postoperative X-rays against a cohort of patients implanted according to the standard method. After conclusion of the study the US-based method was implemented into clinical practice. Results We report the results of the initial pilot study and the clinical experience thereafter. AoV visualization and placement was successful in all patients (pilot study = 20 pts, clinical patients = 10 pts). US-guided positioning required non-significant repositioning in only 1 patient (0.5 cm adjustment of the generator) after fluoroscopic confirmation. Intraoperative US measurements of sternum-electrode distance demonstrated statistical equivalence with postoperative X-ray measurements (equivalence margin ±1.5mm) (fig.1). External reviewers found no significant difference in implantation quality between US-guided and standard fluoroscopy-guided cases during blinded postoperative X-ray assessment. (Fig.2) Conclusions The novel Ultrasound-guided S-ICD lead and device positioning approach is feasible and achieves equivalent implantation quality to the fluoroscopy-guided approach. Intraoperative US assessment of lead depth correlates well with postoperative X-ray. These findings suggest: 1) potential for radiation reduction in future S-ICD implantation practice pending larger validation studies, and 2) potential for intraoperative assessment of conversion failure risk by measuring lead implantation depth during the surgical procedure.Fig2.independent reviewer assessmentFig1.