Blood Cardioplegia Induction, Perfusion Storage and Graft Dysfunction in Cardiac Xenotransplantation

BackgroundPerioperative cardiac xenograft dysfunction (PCXD) describes a rapidly developing loss of cardiac function after xenotransplantation. PCXD occurs despite genetic modifications to increase compatibility of the heart. We report on the incidence of PCXD using static preservation in ice slush following crystalloid or blood-based cardioplegia versus continuous cold perfusion with XVIVO© heart solution (XHS) based cardioplegia.MethodsBaboons were weight matched to genetically engineered swine heart donors. Cardioplegia volume was 30 cc/kg by donor weight, with del Nido cardioplegia and the addition of 25% by volume of donor whole blood. Continuous perfusion was performed using an XVIVO © Perfusion system with XHS to which baboon RBCs were added.ResultsPCXD was observed in 5/8 that were preserved with crystalloid cardioplegia followed by traditional cold, static storage on ice. By comparison, when blood cardioplegia was used followed by cold, static storage, PCXD occurred in 1/3 hearts and only in 1/5 hearts that were induced with XHS blood cardioplegia followed by continuous perfusion. Survival averaged 17 hours in those with traditional preservation and storage, followed by 11.47 days and 15.03 days using blood cardioplegia and XHS+continuous preservation, respectively. Traditional preservation resulted in more inotropic support and higher average peak serum lactate 14.3±1.7 mmol/L compared to blood cardioplegia 3.6±3.0 mmol/L and continuous perfusion 3.5±1.5 mmol/L.ConclusionBlood cardioplegia induction, alone or followed by XHS perfusion storage, reduced the incidence of PCXD and improved graft function and survival, relative to traditional crystalloid cardioplegia-slush storage alone.

Transparent PDMS Bioreactors for the Fabrication and Analysis of Multi-Layer Pre-vascularized Hydrogels Under Continuous Perfusion

Tissue engineering in combination with stem cell technology has the potential to revolutionize human healthcare. It aims at the generation of artificial tissues that can mimic the original with complex functions for medical applications. However, even the best current designs are limited in size, if the transport of nutrients and oxygen to the cells and the removal of cellular metabolites waste is mainly dependent on passive diffusion. Incorporation of functional biomimetic vasculature within tissue engineered constructs can overcome this shortcoming. Here, we developed a novel strategy using 3D printing and injection molding technology to customize multilayer hydrogel constructs with pre-vascularized structures in transparent Polydimethysiloxane (PDMS) bioreactors. These bioreactors can be directly connected to continuous perfusion systems without complicated construct assembling. Mimicking natural layer-structures of vascular walls, multilayer vessel constructs were fabricated with cell-laden fibrin and collagen gels, respectively. The multilayer design allows functional organization of multiple cell types, i.e., mesenchymal stem cells (MSCs) in outer layer, human umbilical vein endothelial cells (HUVECs) the inner layer and smooth muscle cells in between MSCs and HUVECs layers. Multiplex layers with different cell types showed clear boundaries and growth along the hydrogel layers. This work demonstrates a rapid, cost-effective, and practical method to fabricate customized 3D-multilayer vascular models. It allows precise design of parameters like length, thickness, diameter of lumens and the whole vessel constructs resembling the natural tissue in detail without the need of sophisticated skills or equipment. The ready-to-use bioreactor with hydrogel constructs could be used for biomedical applications including pre-vascularization for transplantable engineered tissue or studies of vascular biology.

Tissue Viability of Free Flaps after Extracorporeal Perfusion Using a Modified Hydroxyethyl Starch Solution

Background: In free flap surgery, tissue is stored under hypothermic ischemia. Extracorporeal perfusion (EP) has the potential to extend storage time and the tissue’s perspective of survival. In the present study, the aim is to improve a recently established, simplified extracorporeal perfusion system. Methods: Porcine musculus rectus abdominis were stored under different conditions. One group was perfused continuously with a simplified one-way perfusion system for six hours, while the other received only a single flush but no further treatment. A modified hydroxyethyl starch solution was used as a perfusion and flushing solution. Vitality, functionality, and metabolic activity of both groups were analyzed. Results: Perfused muscles, in contrast to the ischemically stored ones, showed no loss of vitality and significantly less functionality loss, confirming the superiority of storage under continuous perfusion over ischemic storage. Furthermore, in comparison to a previous study, the results were improved even further by using a modified hydroxyethyl starch solution. Conclusion: The use of EP has major benefits compared to the clinical standard static storage at room temperature. Continuous perfusion not only maintains the oxygen and nutrient supply but also removes toxic metabolites formed due to inadequate storage conditions.

Abstract 16765: Sustained Total All-Region Perfusion During the Norwood Operation is Associated With Improved Post-Operative Recovery

Introduction: We developed a technique for Stage 1 “Norwood” reconstruction with continuous perfusion of the head, heart, and lower body at mild hypothermia, deemed Sustained Total All-Region (STAR) perfusion. Hypothesis: We hypothesized that STAR perfusion would shorten cardiopulmonary bypass and procedural times and expedite post-operative recovery, due to lack of cooling and re-warming and decreased total body ischemia. Methods: Between 2012-2019, 65 infants underwent Norwood reconstruction at our institution. Those who underwent prior pulmonary artery banding were excluded, yielding a cohort of 51 infants who underwent primary Norwood reconstruction. Outcomes for patients who underwent Norwood reconstruction using STAR perfusion (n=21) were compared to those who underwent Norwood reconstruction with conventional techniques using regional cerebral perfusion only (n=30). STAR perfusion was performed with innominate artery cannulation as well as olive tip cannulas inserted into the opened descending aorta and native aortic root to provide continuous perfusion of the head, heart, and lower body throughout the procedure (Figure), under mild hypothermia (32-34°C). Results: Norwood reconstruction with STAR perfusion was associated with shorter median CPB times vs. conventional perfusion techniques (161 vs. 226 mins,p<0.0001) and elimination of myocardial ischemia (0 vs. 90 minutes cross-clamp time,p<0.0001). Total operative time was reduced by over 3 hours (319 vs 514 mins,p<0.0001), likely in part due to improved post-bypass coagulopathy. Improvements in post-operative recovery were noted with STAR perfusion, including more rapid normalization of serum lactate (19.3 vs. 26.5 hours, p=0.0009), lower peak serum lactate (8.6 vs.10 mmol/dL, p=0.04) and fewer days to chest closure (3 vs. 5 days, p=0.04). Survival to hospital discharge (95% vs 83%, p=0.38) was similar between groups. Conclusions: Norwood reconstruction with STAR perfusion is a safe technique that eliminates ischemic time to the heart and lower body and allows for the procedure to be performed at warmer temperatures. We found evidence of reduced CPB and operative times, as well as improved hemostasis, end-organ function, and post-operative recovery with this technique.