The combined effects of cardiac anatomy and pacing lead electrode location within left ventricular cardiac veins on resultant pacing thresholds are not well understood. The specific aims of this study were to: (1) develop a comparative electrostatic model based on previously obtained histological measurements, and (2) compare resulting electric fields and voltage gradients with in vitro experimental results. In vitro pacing thresholds measured from swine hearts were utilized to model electric fields generated from different cardiac venous pacing locations within veins of varying diameter and fat thickness. The simulated activation fields were defined as 100 V/m and all materials were defined as isotropic. The obtained results predicted larger activation fields when an electrode was oriented away from the myocardium or in free-floating positions, hence requiring more myocardial tissue to have 100 V/m than when it was oriented toward the myocardium. Thus, the resultant modeled electric fields followed the same qualitative trends as in vitro experiments performed in the swine hearts. In general, while electrode position primarily affected pacing thresholds, both vein diameter and relative epicardial fat thickness also influenced pacing thresholds. The electric fields were larger for basal regions modeled using larger vein diameters and epicardial fat thicknesses. These electrostatic field simulations provide unique insights as to how varied cardiac anatomies and relative electrode locations affect thresholds by enabling visualization of the electric fields propagating through cardiac tissues during pacing from the venous system.
The University of Minnesota's Visible Heart® Laboratory has developed a novel free‐access educational website highlighting both functional and static human cardiac anatomy: The Atlas of Human Cardiac Anatomy (http://www.vhlab.umn.edu/atlas/). This website contains freely downloadable footage from over 100 human hearts, with associated text describing these anatomies, and with various related educational tutorials. To collect these images and videos, human hearts (deemed non‐viable for transplant) were obtained from LifeSource (MN) or the U of MN's Bequest Program, as gifts for research from the organ donors and their families. To honor these donations, all obtained/developed educational information has and will be gifted back for the training of interested individuals: which may range from students in K‐12, undergraduates, post‐graduates, cardiovascular residents or fellows, physicians, or patients themselves. This library of heart images and videos, includes those obtained with videoscopes, fiberscopes, ultrasound, fluoroscopy, MRI, and/or CT: from perfusion‐fixed specimens and/or from reanimated specimens using Visible Heart® methodologies (Hill et al., 2001). “The Atlas” is a living website that is updated on a monthly basis with new educational information, images, video footage, and/or requested materials. This project was funded by NIH training grant T32AR007612 and Medtronic, Inc.
ObjectiveTo obtain unique images of left‐sided pacing lead implantations for the educational benefits of both physicians and medical device design engineers.MethodsWe employed Visible Heart® methodologies to obtain simultaneous videoscopic (internal and external) and flouroscopic footage of the device‐tissue interfaces during left‐sided pacing lead (Medtronic 4196 4F dual electrode lead) implantations within reanimated swine hearts. We targeted the lateral cardiac veins via delivery through the coronary sinus. We used an isolated cardiopleged heart from Yorkshire‐cross swines; the University of Minnesota's Animal Care and Use Committee approved all experimental protocols involved in this study.ResultsFigure 1 displays typical images obtained during the implantation of left‐sided leads: (1) fluoroscopic and videoscopic images of the initial cannulation of the coronary sinus; (2) fluoroscopic and fiberscopic images of the subselection of a target lateral vein; and (3) fluoroscopic, videoscopic, fiberscopic, and external images of a subsequently implanted left‐sided lead.ConclusionUsing Visible Heart ® methodologies, we were able to obtain novel footage of left‐sided lead implantations that are of educational value for students, patients, physicians, and left‐sided lead device design engineers.Research Support Source: The University of Minnesota's Institute for Engineering in Medicine and Medtronic Inc. (Minneapolis, MN)
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