Implications of percutaneous delivery of cardiac devices on interatrial septal anatomy and biomechanics

Abstract

The anatomy and physiology of the interatrial septum in the heart is fairly well understood. However, the biomechanical properties, as they relate to percutaneous medical device therapy, have not been fully studied. The aim of this dissertation is to better understand how the anatomy and physiology of the cardiac interatrial septum interplays with medical devices such as percutaneous transseptal equipment and atrial septal occluders. To do this, we employed 2D functional imaging of human hearts as well as 3D computational modeling of the anatomy to determine the size, shape and physiology of the atrial septum. Further, the models were utilized to understand anomalous human anatomy and how atrial septal occluder devices may distort the anatomy if placed into a defect like a patent foramen ovale. The wide variability found in the anomalous anatomy will likely cause difficulty in placement of such occluder devices in a patent foramen ovale anatomy since the overlap of the two septa can range anywhere from 2-20mm in length. This knowledge of the anatomy can also feed into design considerations for occluder devices aimed specifically at this anatomy. The second portion of the thesis looks specifically at transseptal punctures and the defects that are a result of this procedure. Following an extensive literature review of reports analyzing the prevalence of iatrogenic atrial septal defects following such procedures, the data suggested that the size of the catheter, time post procedure and the procedure time all impacted its prevalence following a procedure. To further investigate the way in which the catheters interact with the septum, the biomechanical properties of the septum, tensile testing, ripping, tenting and puncturing forces were determined and related to the orientation of the septum. Ultimately it was found that the fossa ovalis will preferentially rip in the superior to inferior direction as opposed to the anterior posterior direction. This suggests that extensive manipulations in the former direction could cause a larger defect following procedures. These data should be considered and understood while performing such procedures and for designing next generation transseptal devices or computer simulations.