Search for: All records

Abstract BackgroundPercutaneous coronary interventions (PCIs) within left main coronary arteries are high-risk procedures that require optimization of interactions between stent(s) and diseased vessels. Optical Coherence Tomography (OCT) is a widely accepted tool that enhances physicians’ ability to assess proper stent appositions during clinical procedures. The primary aim of this study was to develop complementary post-procedure imaging methodologies to better assess and interpret outcomes of left main PCI procedures, utilizing both reanimated and perfusion-fixed human hearts. MethodsPCIs were performed while obtaining OCT scans within the left main anatomies of six human hearts. Subsequently, each heart was scanned with a micro-CT scanner with optimized parameters to achieve resolutions up to 20 µm. Scans were reconstructed and imported into a DICOM segmentation software to generate computational models of implanted stents and associated coronary vessels. 2D images from OCT that were obtained during PCIs were compared to the 3D models generated from micro-CT reconstructions. In addition, the 3D models were utilized to create virtual reality scenes and enlarged 3D prints for development of “mixed reality” tools relative to bifurcation stenting within human left main coronary arteries. ResultsWe developed reproducible methodologies for post-implant analyses of coronary artery stenting procedures. In addition, we generated high-resolution 3D computational models, with ~ 20-micron resolutions, of PCIs performed within reanimated and perfusion-fixed heart specimens. ConclusionsGenerated computational models of left main PCIs performed in isolated human hearts can be used to obtain detailed measurements that provide further clinical insights on procedural outcomes. The 3D models from these procedures are useful for generating virtual reality scenes and 3D prints for physician training and education. 

Abstract Ex Vivo Lung Perfusion (EVLP) is now a powerful clinical technique that has facilitated the increase in successful human lung transplantation procedures. By having the abilities to assess marginal lungs, extend preservation times, and expand geographical distances for donations, EVLP has effectively both expanded the human lung transplantation donor pool and shortened times on the transplant waitlist. While clinical usage has expanded, preclinical research on EVLP has not. EVLP can be utilized as a preclinical research model, i.e., to investigate pharmacological responses (e.g., post-conditioning agents), organ preservation, device testing and/or methodology development. To facilitate the use of EVLP as a research tool, we have developed a low-cost testing system with ever increasing capabilities e.g., the use of a novel continuous weight sensor to evaluate lung edema. Real time tracking of edema allows us to hone in on potential causes of lung damage, and investigate techniques to rehabilitate and mitigate damage on a short time scale (<8 hours). This system enhances our abilities to accurately test medical devices, lung physiology, and potential treatment impacts on lungs. 

Abstract Transcatheter aortic valve replacement (TAVR) has become a popular treatment option for severe aortic stenosis (AS) patients who present a high risk for mortality should they receive a surgical aortic valve replacement (SAVR). Coronary artery occlusion (CAO) following the implantation of the device is a potential complication with a high mortality rate, as CAO causes a deterioration of coronary perfusion, followed by cardiogenic shock and electrical instability. Due to this dangerous potential complication, bailout percutaneous coronary intervention (PCI) techniques, like the snorkel and chimney techniques, have been developed as an effective strategy for ensuring coronary perfusion is maintained following a TAVR procedure. Both snorkel and chimney techniques have been implemented in a reanimated swine and human heart respectively utilizing Visible Heart® methodologies. The procedures have been recorded utilizing endoscopic cameras, echocardiography, optical coherence tomography, and fluoroscopy. Post-procedural micro-computed tomography (micro-CT) was conducted to provide post-implantation imaging with approximately 60-micron resolution. The reconstructions are then segmented and used to create 3D renderings of these complex procedures. These methodologies are repeatable and can be used in a variety of conditions to be used in subsequent educational uses. 

Abstract Preclinical research remains the essential platform in the development and optimization of medical therapies and advancements in translational medicines. However, specifically to animal research, federal laws, and institutional policies require investigators to apply the principles of the 3R's (replacement, reduction, and refinement). The concept of benchtop models utilizing isolated organs, in which multiple variables can be controlled to recreate human function, has been innovative advancements in preclinical research models that adhere to these principles. More specifically, isolated perfused kidney (IPK) models have been invaluable preclinical tools that have led to numerous advancements over the decades, including understanding renal physiology, pharmacologic therapies, and improvements in renal transplantation. However, pre‐existing IPK models are not without their own limitations, leaving areas for improvement. An isolated perfused kidney apparatus was designed to best recreate human use conditions as a preclinical tool. Porcine renal blocks were chosen over the more commonly used rodent models, due to their greater similarities to human anatomies. Sixteen porcine kidney pairs obtained en bloc were extracted and placed onto an apparatus where aortic flows, pressures, and overall systemic temperatures were controlled. Organ viability was assessed in 10 renal blocks (n = 8 fresh andn = 2 previously frozen specimens) via both urinary flows and compositions at timepoints up to 180 min. Multimodality imaging, which included fluoroscopy, ultrasound, optical coherence tomography (OCT), and video scopes, was also employed to capture internal and external images to determine renal artery orientations and dimensions. Anatomical measurements and viability assessments of porcine renal blocks were successfully achieved in our perfusion model. Renal main artery diameters averaged smaller in our sample size than in human anatomy while also having more superior takeoff angles. Yet, the average lengths of each main segment were comparable to human anatomy: 32.09 ± 7.97 mm and 42.23 ± 7.33 mm in the left and right renal main artery, respectively. Urine production and urine composition of the fresh renal blocks, when compared to the frozen blocks and baseline perfusate, showed kidney viabilities of up to 3 h via excretion and retention of various metabolites. In this paper, we described a protocol for an isolated perfused kidney apparatus using large mammalian renal blocks. We believe this protocol to be an improvement from similar pre‐existing models in better representing human physiologic function while allowing for multimodal imaging. The resulting Visible Kidney™ preclinical model, which has shown viability after isolation and reperfusion, can be a fast and reliable tool for the development of medical devices while also reducing the unnecessary use of animals for research. 

Abstract Purpose of the ReviewThe current lack of objective and quantitative assessment techniques to determine cardiac graft relative viability results in risk-averse decision-making, which negatively impact the utilization of cardiac grafts. The purpose of this review is to highlight the current deficiencies in cardiac allograft assessment before focusing on novel cardiac assessment techniques that exploit conventional and emerging imaging modalities, including ultrasound, magnetic resonance, and spectroscopy. Recent FindingsExtensive work is ongoing by the scientific community to identify improved objective metrics and tools for cardiac graft assessment, with the goal to safely increasing the number and proportion of hearts accepted for transplantation. SummaryThis review briefly discusses the in situ and ex vivo tools currently available for clinical organ assessment, before focusing on the individual capabilities of ultrasound, magnetic resonance, and spectroscopy to provide insightful, non-invasive information regarding cardiac graft functional and metabolic status that may be used to predict outcome after transplantation.