Browsing by Subject "Isolated Heart"
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Item Applications of the visible heart for cardiac valve repair and replacement devices.(2009-05) Quill, Jason LlorenThe Visible Heart® methodologies utilize an isolated heart apparatus for the investigation of large mammalian hearts, such as human, swine, canine, or sheep. In vitro, the hearts are perfused with a clear buffer, allowing for real-time, intracardiac imaging of a beating heart. These methodologies have been developed, enhanced, and employed at the University of Minnesota for over ten years, with the general methods having been previously described. The primary focus of earlier studies was on lead implantation and assessments of functional anatomy. My work was to investigate how this unique experimental setup could be optimized to better understand valve function. In addition, I designed subsequent experiments as a means to better design products for the repair and/or replacement of pathological cardiac valves. In order to achieve my desired thesis goal, it was paramount to gain a thorough understanding of cardiac anatomy. As such, a review of the four main cardiac valves is provided in Chapter 1. The goal of this chapter is to familiarize the reader with current nomenclature of the cardiac valves as well as the important anatomical features associated with each. In Chapter 2, the capabilities and limitations of the Visible Heart®, in its current state, are discussed in context of the design process for cardiac valve repair and/or replacement products. To this end, the following areas are identified as applications for the Visible Heart® that can aid valve repair and replacement: (1) Functional Anatomy, (2) Device Delivery and Device/Tissue Interactions, (3) Chronic Model Development and Acute Valve Assessment, (4) Acute Assessment of Surgical Repairs, (5) Pre-clinical Human Heart In Vitro Testing, and (6) Early Prototype Testing for Designers. Chapters 3-7 provide detailed examples of employing Visible Heart® methodologies as they relate to each of these areas. The functional anatomy affecting two percutaneous mitral valve repair procedures is discussed in Chapters 3 and 4. Chapter 5 investigates the delivery and device/tissue interactions of a transcatheter pulmonary valve. A chronic animal model of dilated cardiomyopathy was developed in which mitral regurgitation due to ventricular remodeling was observed after several weeks of pacing; this model is now available within the Visible Heart® for acute assessment of devices seeking to treat this valve pathology (Chapter 6). Chapter 7 then looks at the acute assessment of the "edge-to-edge" mitral valve repair technique following induced P2 prolapse and provides control data for any device seeking to mimic this repair procedure percutaneously. Perfusion-fixed human specimens were utilized in Chapters 3 and 4, and a reanimated human heart was utilized for in vitro testing in Chapter 5. Finally, many early prototypes have been studied and tested in our laboratories using the Visible Heart® methods, but it is beyond the scope of this thesis to discuss the details of these studies. This work has advanced our understanding of the capabilities and limitations of a large mammalian, isolated heart preparation as it relates to the design processes for valve replacement and/or repair devices. This work is not an exhaustive list, but rather the beginning of many potential studies that will now be better designed based upon the capabilities and limitations I have identified. Additionally, the Visible Heart® is a dynamic system that will continue to advance and add capabilities, which will only serve to make it more important in the field of valve assessment.Item Extending Function and Applications of Isolated Cardiopulmonary Systems(2016-11) Howard, BrianThe use of isolated mammalian hearts has a history that is responsible for a staggering amount of the basic physiological knowledge we have about the cardiovascular system and is a primary gateway between ideas and clinical treatment. Advances in cardiac physiology, surgery, transplantation, pacing, defibrillation, ablation, and pharmacology are derived from this area of research. The work outlined here takes identified issues with experimental preparations, as well as clinical applications, to investigate solutions and directions for their systematic address. Extending the utility and window of viability of the isolated heart and lungs has resulted in clinically applicable advances in drug treatments and assessment tools. Most importantly though, it has the potential to expand the population of acceptable donor organs where there is immediate need and continuous shortfall in supply. My thesis consists of chapters which progress in translational application, making use of novel and comprehensive ways of controlling and investigating isolated cardiovascular systems. In the first chapter, the Visible Heart® preparation is used to replicate and extend a classic temperature experiment in the large isolated porcine heart. This chapter also addresses the clinical applications of optimizing heart function with emerging isolated heart transportation devices; making the best use of efforts to assess and maintain the heart for transplantation. This is followed in chapters 2 using the Visible Heart® system to assess therapeutic drug delivery for treating atrial fibrillation and again preserving a heart’s function for transplantation. The advancement of the isolated heart preparation is further driven by procedural concerns with cryo-ablation technologies to include functional lungs. This comprehensive system is used on actual human heart lung-bloc combinations for investigative purposes and required its own set of unique engineering solutions to produce a viable test platform. It is also this evolution of the isolated heart preparation that was a significant factor in bringing the Lung Organ Care System (OCS™) to the Visible Heart Laboratory as a unique research tool. As a commercial device, the OCS™ device seeks to replace the storage-on-ice standard of care with warm and ventilated perfusion of the lungs independent of the heart. As a laboratory instrument it has allowed new opportunities for investigating both basic lung physiology as well as providing lessons that are clinically applicable. The completely novel thermal monitoring of the lungs in this isolated state are discussed in Chapter 5 which investigates thermal tools and profiling of lung damage for the first time. This provides a whole new paradigm for emerging lung and general organ assessment directly relating identified injury states, overall lung function, and recovery/damage profiles that may help physicians make better use of precious donor lungs. In extending the use of the isolated lungs to an underutilized population of donors, the final chapter, Chapter 6, demonstrates for the first time a controlled study and injury model for donation after cardiac death (DCD). With modification to the current clinical use protocol for the OCS™ device, the viability window for injured lungs is shown to be nearly tripled. The impact of demonstrating viable DCD lungs on this system is the potential to greatly expand the number of lungs for transplantation, which would be invaluable to many currently on a long wait list. My thesis work has produced stable isolated cardio-vasculature systems with direct impact on the design of devices, investigation, therapy and monitoring in the pursuit of bettering the standard of care and expanding the availability of the organs for transplantation. It provides new and unique combinations of heart and lungs tailored to the investigative necessity in human anatomy and a more comprehensively described large mammalian model for anatomy, physiology and acute injury.