Preclinical research performed on reanimated/perfused swine kidneys: The Visible Kidney™ methodologies.

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 and n = 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.

Post-procedure micro-CT analyses of coronary artery stenting in left main vessels of reanimated and perfusion-fixed human hearts.

BACKGROUND: Percutaneous 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. METHODS: PCIs 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. RESULTS: We 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. CONCLUSIONS: Generated 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.

Multimodal Imaging of a Culotte Bifurcation Procedure in the Left Main Coronary Artery of a Perfusion-Fixed Human Heart: Step-by-Step with Serial Micro-CT Analyses.

Percutaneous coronary intervention can be a high-risk procedure that would benefit from optimizing device-tissue interactions between stents and coronary vessels. Using a perfusion-fixed human heart with coronary artery disease, we performed a percutaneous coronary intervention of the left main coronary artery bifurcation. This heart was perfused and multimodal imaging was utilized to view the procedure with direct visualization, fluoroscopy, and optical coherence tomography (OCT). We followed the European Bifurcation Club's guidelines to perform a single-stent bifurcation before transitioning to a two-stent Culotte technique. After each procedural step, the heart was removed from the perfusion apparatus and transferred to a micro-CT scanner to obtain unique scans. We conducted apposition analyses of the computational 3D models from micro-CT DICOM datasets, and compared them to the results from direct visualization and commercial OCT's Apposition Indicator software. Additional measurements of resulting coronary anatomic expansions were taken to determine the potential roles of each step in improving procedural outcomes. Micro-CT images show stent deformation during a percutaneous coronary intervention (provisional to Culotte bifurcation procedure) in an isolated diseased human heart.

Assessment of single and double coronary bifurcation stenting techniques using multimodal imaging and 3D modeling in reanimated swine hearts using Visible Heart® methodologies.

Stent implantation in bifurcated coronary lesions is technically challenging so that procedural refinements are continuously investigated. Novel procedure modeling and intracoronary imaging techniques may offer critical insights on stent deformations and stent-wall interactions during bifurcation stenting procedures. Thus, we assessed coronary bifurcation stenting techniques using multimodal imaging and 3D modeling in reanimated swine hearts. Harvested swine hearts were reanimated using Visible Heart® methodologies and (under standard fluoroscopic guidance) used to test 1-stent (provisional and inverted provisional) and 2-stent (culotte, TAP and DK-crush) techniques on bifurcations within various coronary vessels using commercially available devices. Intracoronary angioscopy and frequency-domain optical-coherence-tomography (OCT) were obtained during the procedures. 3D OCT reconstruction and micro-computed tomography 3D modeling (post heart fixations) were used to assess stent deformations and stent-wall interactions. We conducted multiple stenting procedures and collected unique endoscopic and OCT images (and subsequent computational models from micro-CT) to assess stent deformations and device/wall interactions during different steps of bifurcation stenting procedures. Endoscopy, micro-CT and virtual reality processing documented that different 1- and 2-stent techniques, practiced according to experts' recommended steps, achieve optimal post-intervention stent conformation. As compared with intra-procedural endoscopy, software-generated 3D OCT images accurately depicted stent deformations during 1-stent techniques. On the opposite, during more complex 2-stent techniques, some defects were appreciated at 3D OCT reconstruction despite optimal 2D OCT images. This study provided unique insights regarding both stent deformations occurring in the course of bifurcation stenting and the efficacy of OCT to visualize them.