Abstract 13083: Anatomy Characterization Informs Implant Procedure Design for a Novel Extravascular ICD System
Introduction: Extravascular approaches to ICD therapy in some clinical situations require unique implant methods. Current systems require high energy and don’t provide anti-tachycardia pacing. A new extravascular approach involves placement of a defibrillation lead between the heart and sternum. Due to the unfamiliarity most ICD implanters have with this space, quantification of the anatomy there is crucial for development of a safe and effective procedure.
Methods: CT scans were segmented and analyzed to characterize relative locations of structures in or near the substernal space including heart, lungs, sternum, and mammary arteries. Segmentation resulted in faceted 3D surface models. A lead was virtually implanted behind the sternum in the intended location. Proximity distributions from the lead to various structures in the space were characterized at multiple levels of the sternum (up to the 3rd intercostal space (ICS)). Additionally, the location along the right ventricular (RV) long axis where the lead was closest to the heart was measured.
Results: Analysis was completed in 68 patients. The myocardium was closest on average to the virtual lead at the level of the xiphisternal junction (Fig. 1)(5th- 95th percentile: 1.0 - 9.9 mm) and furthest away at the 3rd ICS (4.2 - 47.5 mm). It was closest to lung tissue at the 3rd ICS (1.2 -14.7 mm) and furthest away at the tip of the xiphoid process (20.7 - 73.9 mm). The mammary arteries were found to be no closer than 11.5 mm to either margin of the sternum at any level. At the xiphisternal junction, the lead sat at ~60% along the RV long axis (0%=RV apex, 100%=tricuspid valve), suggesting close proximity to the central portion of the RV.
Conclusions: Meaningful variation exists in the geometric relationships between many of the anatomical structures of the substernal space. Despite this variation, these results support that a lead can be placed in the substernal space close to myocardium while avoiding other organs.
Author Disclosures: R. Lahm: Employment; Significant; Medtronic plc. V. Bhatia: Employment; Significant; Employee. M. Harris: Employment; Significant; Employee.
- © 2016 by American Heart Association, Inc.