Porcine Heart Research Articles

Coronary Connector Facilitated Total Endoscopic Coronary Artery Bypass: An Ex Vivo Feasibility Study.

Totally endoscopic coronary artery bypass (TECAB) procedures pose significant challenges, motivating the development of Octocon, an automated endoscopic connector designed for coronary anastomoses in off-pump and endoscopic settings. This feasibility study aimed to assess Octocon's functionality and maneuverability in closed-chest conditions during robot-assisted TECAB simulations. The Octocon deployment comprises a 3-step procedure. Initially, delicate self-aligning microstapling technology is used to attach connector halves to individual blood vessels. Subsequently, the connector halves are joined to accomplish the anastomosis process. TECAB conditions were simulated using a dedicated box housing ex vivo porcine hearts. The study, conducted by 3 experienced surgeons, investigated the feasibility and standardization potential of a robot-assisted procedure employing Octocon. It evaluated maneuverability in closed-chest conditions and assessed the effectiveness of grafting internal mammary artery segments to different heart regions using single graft, jump graft, and Y-graft constructions. The robot-assisted procedure, using 4 standard instruments, successfully completed all 3 steps in 18 anastomotic procedures. In 96% of cases, the procedural steps were accomplished on the first attempt. The feasibility of constructing jump graft and Y-graft geometries on both anterior and posterior heart walls was demonstrated. Furthermore, experiences affirmed the device's endoscopic user-friendliness, ease of teachability, reproducibility, and potential to achieve expedient, leak-free anastomoses. This ex vivo study confirmed Octocon's potential suitability and functionality for TECAB. The device can create diverse grafting strategies and achieve wide-open vascular connections on various heart regions, highlighting its potential in advancing minimally invasive, robot-assisted coronary procedures. These promising results justify further exploration for integration into clinical practice.

"Honey pot"-like lesion formation: impact of catheter contact angle on lesion formation by novel temperature controlled ablation catheter in a porcine experimental model

Abstract Background The DiamondTemp(DT) catheter enables precise temperature-controlled ablation. However, the effects of the DT catheter's contact angle on lesion formation are poorly understood. Purpose This study evaluated lesion formation using the DT catheter at different angles in a porcine experimental model. Methods We used freshly sacrificed porcine hearts, and radiofrequency catheter ablation with DT was performed at 50 watts for 15 seconds at an upper-temperature setting of 60°C. The contact force (5, 10, and 30 grams) and catheter contact angles (30°, 45°, and 90°) were changed in each set (n = 13 each). The surface width (SW), maximum lesion width (MW), lesion depth (LD), surface area (SA), and distance from the distal edge to the widest area (DW) were evaluated. In addition, the generator impedance drop during radiofrequency application was analyzed. Results Figure 1 shows the summarized data in this study. SW and MW were longer at 30° than at 90° (SW 5 g: 6.34 ± 0.91 vs. 5.07 ± 0.87 mm; SW 10 g: 7.46 ± 0.55. vs. 5.60 ± 0.84 mm; SW 30 g: 7.42 ± 0.74. vs. 6.14 ± 0.77 mm; MW 10 g: 8.81 ± 0.55. vs. 7.89 ± 0.84 mm; MW 30 g: 9.24 ± 0.67. vs. 8.03 ± 1.04 mm, p <0.05, respectively). There were no significant differences in LD by catheter angle except at 30 g. SA was larger at 30° than at 90° (SA 5 g: 30.03 ± 0.91. vs. 23.61 ± 0.87; SA 10 g: 29.24 ± 0.55. vs. 21.27 ± 0.84; SA 30 g: 35.86 ± 0.74. vs. 31.74 ± 0.77, p <0.05, respectively). Besides, DW was longer at 30° than at 90° (DW 5 g: 4.28 ± 1.17. vs. 2.50 ± 0.32 mm; DW 10 g: 4.94 ± 0.52. vs. 2.47 ± 0.38 mm; DW 30 g: 5.34 ± 0.26. vs. 2.96 ± 0.40 mm, p <0.05, respectively). There were no significant differences in the impedance drop according to the catheter angle. Conclusion With the DT catheters, the lesion width increased at a shallower contact angle, whereas the LD did not. SA also increased at a shallower contact angle. The DT catheter created a large ablation lesion on the proximal side of the catheter, which looked like a "honey pot." (Figure 2)summarized dataImage of honey pot-like lesion formation

The mechanism of silent steam pop during radiofrequency catheter ablation: an ex-vivo porcine heart study

Abstract Background A steam pop (SP) during radiofrequency catheter ablation(RFCA) is usually assumed as an audible one and shows obvious changes of impedance, temperature or bipolar/unipolar potential of ablation catheter. Moreover, a SP generates a void which sometime penetrate the tissue and cardiac perforation. In clinical setting, we have sometimes experienced gas explosion from an ablating site detected only by intracardiac echography (ICE) without any sound or remarkable parameter changes, so called as a ‘silent’ SP (S-SP). However, the mechanism of this phenomenon is not yet to be clarified. Methods We performed RFCA of porcine ventricle using Tactiflex until a SP or 120s. In the first step, the output and the contact force (CF) of RFCA were fixed for 50W and 1g, 5g, 10g or 20g. Second, an ablation catheter was moved by every second with 50W. A SP was defined as suddenly gas explosion during RFCA detected by ICE and in case of non-audible SP by 2 persons standing 50cm away from ablation site, it was provided as a S-SP. Otherwise, we defined as audible one (A-SP). We analyzed the occurrence of S-SP and ablation parameters between S-SP and A-SP. Results In the first stage (n=24), 4 S-SPs and 17 A-SP were observed(S-SP; 3 in 1g and 1 in 20g, A-SP; 2 in 1g, 5 in 5g, 6 in 10g and 4 in 20g, p=0.0454). The ICE images of S-SP and A-SP seemed to be similar. S-SP significantly occurred in the setting of lower CF as compared with A-SP {3.0(2.25-16.5) vs. 8.0(5.0-21.5); p=0.0290}. There were no statistical differences concerning duration of RFCA, initial/final impedance, impedance drop, initial/maximum temperature. At the timing of SP, changes of potentials were relatively smaller in S-SP {bipolar: 0.975(0.565-6.410) vs. 5.700(3.680-8.915); p=0.0648, unipolar: 1.265(0.208-3.793) vs. 8.070(5.820-8.815); p=0.0003}. Voids formation after SPs were detected in 2(50%) of S-SP and 16(94%) of A-SP(p=0.0797). In the second beating stage (n=46), 14 S-SPs and 20 A-SPs were observed (Figure 1). Although there were no differences of average/maximum CF throughout RFCA, S-SP dominantly occurred when a catheter was pulling back against the tissue, or at the bottom of CF curve (Figure2). Whereas A-SP did when a catheter was pushing toward tissue, or at the end of ascending limb of CF curve. For ablated lesion, S-SP exhibited less void or smaller crack (Figure1). Conclusions S-SP was difficult to detect without ICE and occurred in the combined condition of high power (50W) and lower CF. For the setting of beating mode, just like clinical environment, S-SP was involved while an ablation catheter was moved away from the tissue. Although S-SP seemed to be safer than A-SP due to less or smaller voids, continuous RFCA after S-SP might involve a big void or perforation. Therefore, it might be better to use ICE for the detection of S-SP, especially for a site accompanied by unstable CF, like papillary muscles.Figure 1.Ablation parameters in a cathetFigure 2.The timing of steam pop

Procurement and Preservation of Neonatal Porcine Cardiac Tissue.

The porcine and human heart are remarkably similar in cardiac physiology and biochemistry. Translational research involving the porcine biomedical model is becoming increasingly applicable for the study of human cardiac function in health and disease. Presently, few protocols exist for collecting experimentally viable cardiac tissue from large animal models, particularly during neonatal maturation. To address this deficiency, we have developed a technique to procure and preserve ventricular tissue from neonatal piglets at day 3 (n=4) and day 30 (n=6) post-partum. Piglets were subjected to a strict sedation, anesthesia, and analgesia regimen. During surgery, cardiopulmonary indices of electrocardiogram, heart rate, systolic and diastolic blood pressure, respiration rate, peripheral O2 saturation, and end-tidal CO2 were monitored continuously to ensure normal cardiac function. Prior to cardiectomy, each heart was perfused with an intravenous administration of heparin (10 ml/kg) and ice-cold Custodiol HTK cardioplegia solution (10 ml/kg). After cardiac explantation, myocardial samples (dimensions: 1 x 1 x 1 cm) were dissected from the left and right ventricles and snap-frozen in liquid nitrogen. Analysis via SDS-PAGE and densitometry demonstrated that myofibrillar proteins are stable and undegraded. Western Blots showed full expression of protein. These results suggest that the detailed cardiac tissue procurement technique preserves the experimental viability of the cardiac tissue and prevents the degradation of myofibrillar proteins.

Impact of irrigation flow rates on lesion size and safety of ablation catheters: an ex vivo porcine heart study.

Radiofrequency (RF) catheter ablation is a well-established therapeutic approach for treating arrhythmias, where lesion size and safety are critical for efficacy. This study explored the impact of varying irrigation flow rates on lesion characteristics using the TactiFlex™ SE Ablation Catheter (TF) in an ex vivo porcine heart model, focusing on the size and safety outcomes associated with low versus standard flow rates. Myocardial slabs from porcine hearts were subjected to ablation using two types of irrigated catheters. Lesion formation was compared between low (8mL/min for TF) and standard irrigation flow rates (13mL/min for TF) across different power settings (30, 40, and 50 W). Outcome measures included lesion dimensions, incidence of steam pops, and impedance drops. A total of 210 lesions were generated under various settings. At low flow rates, the TF catheter safely formed larger lesions compared to the standard flow rates without a significant increase in steam pops or impedance drops. Lesions at low flow rates were comparable in size to those formed using other catheters under the standard settings. Conversely, the standard flow settings for TF produced smaller lesions but exhibited higher safety profiles, as evidenced by fewer steam pops and impedance drops. Lower irrigation flow rates using a TF catheter can achieve larger lesions without compromising safety, offering an optimization strategy for RF ablation procedures that balances efficacy and safety. These findings may guide clinicians in tailoring ablation strategies according to individual patient needs.

A rapid and robust organ repair polyacrylamide/alginate adhesive hydrogel mediated via interfacial adhesion-trigger molecules.

Adhesive hydrogels have been widely explored as tissue adhesives for wound sealing and repair. However, developing adhesive hydrogels with simple preparation techniques and strong adhesion to internal organs in a short time remains a challenge. In this study, we developed a strategy for robust and rapid tissue adhesion of internal organ sealing and repair by an interfacial adhesion-molecule triggered hydrogel system. In this system, polyphenol molecules act as adhesion-trigger reagents to achieve fast and strong adhesion of polyacrylamide/alginate hydrogels on the surface of wound tissue by rapidly forming abundant hydrogen bonds at the interface. The adhesion energy is significantly enhanced by 45 times under the mediation of polyphenol adhesion-trigger molecules, resulting in a robust (> 600Jm-2) tissue adhesion in just 30s. This interfacial adhesion system demonstrates good biocompatibility, strong sealing performance on multiple organs (porcine heart, lung, stomach, and intestine), and excellent repair properties in gastric perforation wounds of rabbits in vivo. Moreover, immunocytochemical and transcriptomic analyses reveal that this interfacial adhesion system significantly promotes vascular regeneration and inhibits inflammatory responses during wound repairing. The proposed hydrogel provides a facile strategy for rapid and robust tissue adhesion, and shows potential applications in organ sealing and repair.

Design and Assembly of a Miniature Catheter Imaging System for In Vivo Heart Endoscopic Imaging.

In this paper, we present the design and fabrication of a novel chip-on-tip catheter, which uses a microcamera and optical fibres to capture in vivo images in a beating porcine heart thanks to a saline flush to clear the blood field. Here, we demonstrate the medical utility and mechanical robustness of this catheter platform system, which could be used for other optical diagnostic techniques, surgical guidance, and clinical navigation. We also discuss some of the challenges and system requirements associated with developing a miniature prototype for such a study and present assembly instructions. Methods of clearing the blood field are discussed, including an integrated flush channel at the distal end. This permits the capture of images of the endocardial walls. The device was navigated under fluoroscopic guiding, through a guiding catheter to various locations of the heart, where images were successfully acquired. Images were captured at the intra-atrial septum, in the left atrium after a trans-septal cross procedure, and in the left ventricle, which are, to the best of our knowledge, the first images captured in an in vivo beating heart using endoscopic techniques.

Identification of pharmacological inducers of a reversible hypometabolic state for whole organ preservation

Drugs that induce reversible slowing of metabolic and physiological processes would have great value for organ preservation, especially for organs with high susceptibility to hypoxia-reperfusion injury, such as the heart. Using whole-organism screening of metabolism, mobility, and development in Xenopus, we identified an existing drug, SNC80, that rapidly and reversibly slows biochemical and metabolic activities while preserving cell and tissue viability. Although SNC80 was developed as a delta opioid receptor activator, we discovered that its ability to slow metabolism is independent of its opioid modulating activity as a novel SNC80 analog (WB3) with almost 1000 times less delta opioid receptor binding activity is equally active. Metabolic suppression was also achieved using SNC80 in microfluidic human organs-on-chips, as well as in explanted whole porcine hearts and limbs, demonstrating the cross-species relevance of this approach and potential clinical relevance for surgical transplantation. Pharmacological induction of physiological slowing in combination with organ perfusion transport systems may offer a new therapeutic approach for tissue and organ preservation for transplantation, trauma management, and enhancing patient survival in remote and low-resource locations.

Identification of pharmacological inducers of a reversible hypometabolic state for whole organ preservation.

Drugs that induce reversible slowing of metabolic and physiological processes would have great value for organ preservation, especially for organs with high susceptibility to hypoxia-reperfusion injury, such as the heart. Using whole-organism screening of metabolism, mobility, and development in Xenopus, we identified an existing drug, SNC80, that rapidly and reversibly slows biochemical and metabolic activities while preserving cell and tissue viability. Although SNC80 was developed as a delta opioid receptor activator, we discovered that its ability to slow metabolism is independent of its opioid modulating activity as a novel SNC80 analog (WB3) with almost 1000 times less delta opioid receptor binding activity is equally active. Metabolic suppression was also achieved using SNC80 in microfluidic human organs-on-chips, as well as in explanted whole porcine hearts and limbs, demonstrating the cross-species relevance of this approach and potential clinical relevance for surgical transplantation. Pharmacological induction of physiological slowing in combination with organ perfusion transport systems may offer a new therapeutic approach for tissue and organ preservation for transplantation, trauma management, and enhancing patient survival in remote and low-resource locations.

Changes in heart dimensions in decomposition using porcine and ovine animal models: a method for estimating decomposed human heart weight

ABSTRACT Heart weight is a routine measurement at post-mortem examination. An increased heart weight is associated with pre-existing heart disease and sudden cardiac death. However, during decomposition, the heart weight measured at post-mortem examination may not reflect the weight at the time of death. A previous study showed that heart dimensions can be used to estimate heart weight. This study documents the changes in heart dimensions during decomposition using porcine and ovine animal models. It shows that, in contrast to heart weight, which decreases in the post-mortem interval, the heart dimensions increase. Heart width increases and subsequently plateaus at the end of the 18 days to a mean of 6 and 8 mm in ovine and porcine hearts, whereas the length continues to increase. Using the results of this study, in conjunction with previous published literature, the heart width may be used as a parameter to estimate heart weight and determine cardiac hypertrophy at the time of death in decomposed hearts.

Effect of Silica Nanoparticle Treatment on Adhesion between Tissue-like Substrates and In Vivo Skin Wound Sealing.

Silica nanoparticles are innovative solutions of surgical glue that can readily adhere to various tissue-like substrates without the need for time-consuming chemical reactions or ultraviolet irradiation. Herein, 10 nm-sized silica nanoparticle (SiNP10) treatment exhibited maximum adhesion strength in the porcine heart tissue model, which was approximately 7.15 times higher than that of the control group of non-treatment. We assessed the effects of silica nanoparticle treatment on in vivo skin wounds by scoring tissue adhesion and inflammation using histological images. Compared to the commercial cyanoacrylate skin adhesive (Dermabond), suppression of inflammatory cytokine levels in the incision wound skin was observed. We further quantified the expression of angiogenic growth factors and connective tissue formation-related proteins. On day 5 after wound closing treatment, the expression levels of PDGF-BB growth factor were significantly higher in SiNP10 treatment (0.64 ± 0.03) compared to Dermabond (0.07 ± 0.05). This stimulated angiogenesis and connective tissue formation in the skin of the incision wound may be associated with the promoting effects of SiNP10 treatment on wound closure and tissue adhesion.

Wireless Magnetic Robot for Precise Hierarchical Control of Tissue Deformation.

Mechanotherapy has emerged as a promising treatment for tissue injury. However, existing robots for mechanotherapy are often designed on intuition, lack remote and wireless control, and have limited motion modes. Herein, through topology optimization and hybrid fabrication, wireless magneto-active soft robots are created that can achieve various modes of programmatic deformations under remote magnetic actuation and apply mechanical forces to tissues in a precise and predictable manner. These soft robots can quickly and wirelessly deform under magnetic actuation and are able to deliver compressing, stretching, shearing, and multimodal forces to the surrounding tissues. The design framework considers the hierarchical tissue-robot interaction and, therefore, can design customized soft robots for different types of tissues with varied mechanical properties. It is shown that these customized robots with different programmable motionscan induce precise deformations of porcine muscle, liver, and heart tissues with excellent durability. The soft robots, the underlying design principles, and the fabrication approach provide a new avenue for developing next-generationmechanotherapy.

Effect of Vessel Attenuation, VMI Level, and Reconstruction Kernel on Pericoronary Adipose Tissue Attenuation for EID CT and PCD CT: An Ex Vivo Porcine Heart Study.

Background: Pericoronary adipose tissue (PCAT) attenuation and fat attenuation index (FAI) may serve as markers of inflammation and risk of adverse cardiac events. However, standardization of relevant CT acquisition and reconstruction parameters is lacking. Objective: To investigate the influence of vessel attenuation, virtual monoenergetic image (VMI) level, and reconstruction kernel on PCAT attenuation and FAI using energy-integrating detector (EID) and photon-counting detector (PCD) CT systems in an ex-vivo porcine heart model. Methods: A porcine heart's right coronary artery (RCA) was injected with saline or varying contrast media dilutions to achieve vessel attenuations ranging from 0 to 1000 HU. After each injection, the heart was scanned with EID CT at 120 kVp and PCD CT at 140 kVp, at constant CTDIvol (10 mGy). For EID CT, polychromatic images were reconstructed with Qr40 kernel. For PCD CT, VMI (40-80 keV at 10-keV increments) were reconstructed with Qr40, Bv40, and Bv56 kernels. ROIs were placed to measure RCA and PCAT attenuation. FAI was determined using software; histogram analysis was performed of voxel attenuations in the volumes of interest for FAI calculation. Results: Correlations were observed between attenuation in the RCA and adjacent PCAT (r=0.3-1.0), and between vessel attenuation and FAI (r=-0.9-1.0). For PCAT attenuation and FAI, these associations became progressively weaker for progressively sharper kernels. For increasing vessel attenuation for EID CT and for increasing VMI level for PCD CT, FAI histograms showed right shifts of the peak attenuation; the percentage of histogram voxels meeting the threshold range for inclusion in FAI calculation for EID CT was 8-29% and for PCD CT at VMI levels of 70-80 keV was 5-42%. For PCD CT, sharper kernels were associated with left shifts in peak attenuations and greater percentages of voxels within the threshold range for inclusion in FAI calculations. Conclusion: PCAT attenuation and FAI are influenced by vessel lumen attenuation, VMI level, and reconstruction kernel. A minority of pericoronary voxels contribute to FAI measurements for polychromatic EID CT and for PCD CT at high VMI levels. Clinical Impact: These findings may help standardize acquisition and reconstruction parameters for PCAT attenuation and FAI measurements.

Successful Resuscitation of Porcine Hearts After 12 and 24 h of Static Cold Storage With Normothermic Ex Situ Perfusion.

Heart transplantation is always an emergency because the transplant needs to occur within 6 h after procurement to prevent primary graft dysfunction. Static cold storage (SCS) is the gold-standard preservation method. This study describes the outcomes of hearts preserved after prolonged SCS (12 and 24 h); those are then resuscitated with a novel normothermic ex situ heart perfusion (NEHP) system. Anesthetized piglets (n = 10) were used as heart donors. Hearts were procured and stored at 5 °C CoStorSol following standard SCS protocols. Two groups were studied: SCS-12 h and SCS-24 h. After SCS, 8 h of NEHP (37 °C blood-based perfusate) was performed at 0.7-1.0 mL/min/g of cardiac tissue. NEHP parameters were monitored continuously. Results were corroborated with 3 additional hearts transplanted orthotopically in healthy recipients (n = 3) after SCS (24 h) + NEHP (5 h). Recipients were observed for 90 min after weaning off cardiopulmonary bypass support. All hearts (after 12 and 24 h of SCS) regained normal function and metabolism within 10 min and retained it throughout 8 h of NEHP. No differences were observed in NEHP parameters and histopathology between groups. Three hearts were successfully transplanted after a total ~30 h of preservation (24 h of SCS + 5 h of NEHP + 1 h of second cold ischemia time). The 3 recipients were weaned off cardiopulmonary bypass with mild vasopressor support. NEHP has the potential to routinely resuscitate porcine hearts that have undergone SCS for up to 24 h, restoring them to viable function. By objectively assessing heart function before transplant, NEHP may enhance the success rate of transplants. If these resuscitated hearts can be successfully transplanted, it would support the effectiveness of NEHP in ensuring heart viability.

Novel Flowable Hemostatic Agent ActiClot: Efficacy and Safety Assessment in Rat and Porcine Models.

Background/Objectives: This study evaluated the hemostatic performance and safety of ActiClot (ATC), a new flowable hemostatic agent, through in vivo tests. Methods: ATC was compared with the commercially available FLOSEAL®. ATC consists of carboxymethyl starch, thrombin, and sorbitol powders in Syringe I, and a calcium chloride solution in Syringe II. In vivo evaluation used rat liver bleeding and porcine heart bleeding models. Safety was assessed using a rat subcutaneous implantation model. Results: ATC significantly reduced hemostasis time (70.00 ± 7.35 s) compared to gauze control (240.63 ± 32.31 s) in the rat liver model, showing a 70% reduction. There was no significant difference between ATC and FLOSEAL® (58.75 ± 13.42 s). In the porcine heart model, both agents achieved 100% hemostasis within 3 min, with no significant difference in success rates within 2 min (ATC 87.5%, FLOSEAL® 75%). The gauze control group failed in all tests. The rat subcutaneous implantation model showed no visual ATC observation after 48 h, indicating biocompatibility, with no inflammation observed. Conclusions: ATC demonstrated effective hemostatic performance similar to FLOSEAL® in two in vivo models, with faster hemostasis in the rat liver model. It also showed excellent safety and biocompatibility, indicating its potential for surgical and emergency bleeding control.

Surgical Aortic Valve Replacement Using a Porcine Model: A Low-Cost Simulation for Surgical Trainees.

Simulation experiences are valuable to the training of future successful surgeons. These experiences introduce trainees to operational concepts through hands-on engagement within a low-stress environment to promote skill, information retention, and increased competency for future success in real-life scenarios. The study aimed to develop a low-cost, reproducible surgical simulation for teaching aortic valve replacement using porcine models. This study employed a single-center educational workshop design to provide trainees with a comprehensive wet laboratory experience in surgical aortic valve replacement using a porcine model. The simulation involved step-by-step procedures using porcine hearts in a wet lab environment, emphasizing specific surgical techniques such as suturing, knot tying, and valve replacement. Simulated valves were created using insulation foaming and aluminum wiring. The study was conducted at a southeastern medical school's wet lab. Thirty-eight preclinical medical students participated. The simulation was designed to provide a comprehensive overview of the steps involved in aortic valve replacement using porcine models. It emphasized the importance of teamwork, fundamental surgical skills, and effective communication within a surgical setting. The low-cost surgical simulation allowed trainees to learn technical skills that could be tailored to their proficiency level. Simulation for cardiothoracic procedures is limited by monetary spending and the availability of adequate materials to create a beneficial learning experience. This low-cost simulation allows resource-limited institutions to provide their students an additional opportunity to practice fundamental surgical principles such as suturing.

Development of a Simple Analytical Model to Facilitate Preoperative Surgical Planning in Valve-Sparing Aortic Root Replacement.

Valve-sparing root replacement (VSRR) is attractive for aortic root dilation as it preserves the native aortic valve (AoV). Low effective height (eH) after reconstruction is a risk factor for repair failure and reoperation. We developed and validated a quantitative AoV repair strategy to reliably restore normal valve proportions to promote long-term function. Normal AoV proportions were used to derive geometric relationships for sinotubular junction diameter (DSTJ), free edge length (FEL), free edge angle, and commissure height. These relationships informed two models for predicting eH following VSRR: (1) assuming valve symmetry and (2) accounting for valve asymmetry. Porcine heart (n = 6) ex vivo validation was performed under 4 VSRR scenarios: "Ideal" (tube graft size targeting FEL/DSTJ = 1.28), "Oversized" (one graft size larger than Ideal), "Undersized" (two sizes smaller), and "Undersized + Plicated" (FEL/DSTJ = 1.28 restored with leaflet plication). Our analytical models predicted eH using preoperative measurements and estimated reconstructed dimensions. The Oversized graft exhibited similar eH to Ideal but higher regurgitation in the ex vivo model, whereas the Undersized graft demonstrated lower eH and regurgitation. Plication in the Undersized graft restored valve function (regurgitation & eH) similar to Ideal in the ex vivo model and above Ideal in the analytical models. Both analytical models predicted ex vivo eH well except in the Oversized and Undersized + Plicated conditions. Utilizing measurements from preoperative imaging and simple mathematical models, patient-specific operative plans for VSRR can be created by estimating valve dimensions necessary to achieve favorable valve features post-repair. Clinical application of this approach promises to improve consistency in achieving optimal long-term dimensions and durability.

Abstract We036: Recapitulating Cardiac Microenvironment: Elucidating the Role of ECM Components and Architecture on Cardiac Differentiation

The discovery of iPSCs was revolutionary for regenerative medicine, especially as a source to replace a cell population with limited regeneration capability, like cardiomyocytes (CMs). However, the exact mechanism(s) governing how the microenvironment influences cardiac differentiation at a cellular scale is still widely unclear. To bridge this gap, we created an in vitro fibrous model from a decellularized porcine cardiac extracellular matrix. The aim is to assess the impact of the microenvironment, specifically the effects of protein composition and micro-architecture, on the cardiac differentiation of iPSCs. To study the role of protein composition, atrial and ventricular regions of the porcine heart are manually identified and separated as their protein composition is observed to be different. To test this, the material was subjected to proteomics analysis with LS-Mass Spectrometry where about 1000 proteins were identified in the ventricular region and only 300 proteins in atria. The decellularized tissue was tested for complete removal of nuclei by staining and further validated with DNA quantification. The dECM was blended with synthetic polymer (polycaprolactone) for electrospinning. The average collected fiber diameter was 14.8 ± 3.9 μm. The fibrous scaffolds were seeded with iPSCs and differentiated towards cardiac lineage. dECM samples show comparable signs of biocompatibility as laminin-521 coated TCPS, forming clusters throughout the differentiation process indicating that the scaffolds encourage cardiac differentiation. Further analysis is being conducted to compare the cellular expressions of differentiation markers including mesoderm formation, cardiac specification, and cardiomyocyte structural and functional markers. The effects of the ECM composition will be checked with myosin light and heavy chain expressions, as their expressions vary in the atrial and ventricular regions of the heart.

Recombinant human placental growth factor-2 in post-infarction left ventricular dysfunction: a randomized, placebo-controlled, preclinical study.

Placental growth factor (PlGF)-2 induces angio- and arteriogenesis in rodents but its therapeutic potential in a clinically representative post-infarction left ventricular (LV) dysfunction model remains unclear. We, therefore, investigated the safety and efficacy of recombinant human (rh)PlGF-2 in the infarcted porcine heart in a randomized, placebo-controlled blinded study. We induced myocardial infarction (MI) in pigs using 75min mid-LAD balloon occlusion followed by reperfusion. After 4w, we randomized pigs with marked LV dysfunction (LVEF < 40%) to receive continuous intravenous infusion of 5, 15, 45µg/kg/day rhPlGF-2 or PBS (CON) for 2w using osmotic pumps. We evaluated the treatment effect at 8w using comprehensive MRI and immunohistochemistry and measured myocardial PlGF-2 receptor transcript levels. At 4w after MI, infarct size was 16-18 ± 4% of LV mass, resulting in significantly impaired systolic function (LVEF 34 ± 4%). In the pilot study (3 pigs/dose), PIGF administration showed sustained dose-dependent increases in plasma concentrations for 14days without systemic toxicity and was associated with favorable post-infarct remodeling. In the second phase (n = 42), we detected no significant differences at 8 w between CON and PlGF-treated pigs in infarct size, capillary or arteriolar density, global LV function and regional myocardial blood flow at rest or during stress. Molecular analysis showed significant downregulation of the main PlGF-2 receptor, pVEGFR-1, in dysfunctional myocardium. Chronic rhPIGF-2 infusion was safe but failed to induce therapeutic neovascularization and improve global cardiac function after myocardial infarction in pigs. Our data emphasize the critical need for properly designed trials in representative large animal models before translating presumed promising therapies to patients.

Modified Clover Technique Using Automated Suture Placement and Securing Technology in a Passive Beating Heart Model.

Tricuspid regurgitation (TR) is a prevalent finding in echocardiography and in case of severe disease is associated with impaired patient outcome. Clover repair offers a surgical solution that can be applied for the treatment of primary and secondary TR. An ex vivo passive beating porcine heart model was created to test a modified clover technique using automated suturing devices and to compare this approach to standard ring annuloplasty. Secondary TR was induced in 10 porcine hearts and the backflow of fluid was assessed. The primary endpoint of this study was regurgitant volume measured in mL at the site right atrial cannula. The baseline regurgitation was 43.3 ± 10.8 mL. The mean regurgitant volume was significantly reduced after all repair procedures to 22.2 ± 5.9 mL with isolated ring annuloplasty, 12 ± 3.9 mL with the modified clover, and 7.6 ± 3.4 mL with the combined procedure (p < 0.0001). The modified clover technique shows how to effectively reduce TR in an ex vivo model. This method may be suitable to facilitate tricuspid repair, especially for totally endoscopic valve surgery.