Xiu-Gui Lu

Saphenous Vein Conduits Harvested by Endoscopic Technique Exhibit Structural and Functional Damage

BACKGROUND Injury to the saphenous vein endothelium during harvest impacts patency after coronary artery bypass graft surgery. Many centers are adopting endoscopic saphenous vein harvest (ESVH) instead of using the traditional open saphenous vein harvest (OSVH) technique. Our objective was to compare the effects of ESVH and OSVH on the structural and functional viability of saphenous vein endothelium using multiphoton imaging, immunofluorescence, and biochemical techniques. METHODS Ten patients scheduled for coronary artery bypass graft surgery were prospectively identified. Each underwent ESVH for one portion and OSVH for another portion of the saphenous vein. A 1-cm segment from each portion was immediately transported to the laboratory for processing. The vessel segments were labeled with fluorescent markers to quantify cell viability (esterase activity), calcium mobilization, and generation of nitric oxide. Samples were also labeled with immunofluorescent antibodies to visualize caveolin, endothelial nitric oxide synthase, von Willebrand factor, and cadherin, and extracted to identify these proteins using Western blot techniques. All labeling, imaging, and image analysis was done in a blinded fashion. RESULTS Esterase activity was significantly higher in the OSVH group (p < 0.0001). Similarly, calcium mobilization and nitric oxide production were significantly greater in the OSVH group (p = 0.0209, p < 0.0001, respectively). Immunofluoresence and Western blot techniques demonstrated an abnormal alteration in distribution of caveolin and endothelial nitric oxide synthase in the ESVH group. CONCLUSIONS Our study indicates that ESVH has a detrimental effect on the saphenous vein endothelium, which may lead to decreased graft patency and worse patient outcomes.

Development and Evaluation of a Novel Solution, Somah, for the Procurement and Preservation of Beating and Nonbeating Donor Hearts for Transplantation

Background— Injury to myocytes, endocardium, and the coronary endothelium during harvesting and storage can compromise outcomes after heart transplantation. Safeguarding of structure and function of cardiomyocytes and endothelium in donor hearts may lead to improved patient survival after transplantation. Information gained from porcine hearts stored in standard transplant solution was used to design a superior preservation solution that would optimally protect and maintain organs from beating heart and/or nonbeating heart donors during long-term storage. Methods and Results— Multiphoton microscopy was used to image deep within cardiac biopsies and coronary artery tissue harvested from porcine hearts obtained from beating heart and nonbeating heart donors for analysis of myocyte and endothelial cell structure and function. Cell structural integrity and viability, calcium mobilization, and nitric oxide generation were determined with fluorescence viability markers, immunofluorescence, and Western blots. During hypothermic storage in standard preservation solution, Celsior, myocyte, and endothelial viability was markedly attenuated in hearts obtained from beating heart donors. In contrast, hearts from beating and nonbeating heart donors stored in the newly formulated Somah solution demonstrated an increase in high-energy phosphate levels, protection of cardiac myocyte viability, mitochondrial membrane polarization, and structural proteins. Similarly, coronary artery endothelial organization and function, calcium mobilization, and nitric oxide generation were well maintained during temporal storage in Somah. Conclusions— The Celsior preservation solution in clinical use today has led to a profound decline in cardiomyocyte and endothelial cell viability, whereas the newly designed Somah solution has safeguarded myocyte and endothelial integrity and function during organ storage. Use of Somah as a storage medium may lead to optimized graft function and long-term patient survival after transplantation.

Evaluation of blood components exposed to coated arterial filters in extracorporeal circuits

Background: Biocompatible surfaces play an important role in the inflammatory response during cardiopulmonary bypass (CBP), with the arterial filter contributing a large surface area of the circuit. Different filter-coating materials designed to improve blood-filter biocompatibility are currently used in CPB circuits. This study evaluates eight biocompatible coatings used for arterial filters and their effects on blood components during circulation. Methods: Arterial filters were randomly assigned in eight independent heparin-bonded tubing loops and perfused by a single swine (n=8). Arterial blood was routed simultaneously, but separately, into each circuit and circulated for 30 minutes at 37°C. Blood samples were drawn for CBC, ACT, and TAT III measurements at baseline, post-heparinization and post-circulation. At study completion, filters were imaged using multiphoton microscopy. Results: RBC, platelet, and WBC counts, and TAT III complex were all decreased after 30 minutes of circulation; however, WBC count was the only parameter that showed statistically significant differences between the filters. Circulating WBC reduction ranged from 6% (Carmeda and Trillium) to 41% (Terumo-X-coating) with corresponding microscopic confirmation of increased WBC entrapment. Conclusion: All eight filter coatings altered the blood components to varying degrees. Selection of the most effective filter, in conjunction with a heparin-bonded circuit for CPB, may decrease the intraoperative foreign-surface activation of blood cells.

Subnormothermic Preservation in Somah: A Novel Approach for Enhanced Functional Resuscitation of Donor Hearts for Transplant

Organ preservation at 4°C results in temporally irreversible injury to cellular structure and function. This study was designed to evaluate the possibility of storing hearts at ambient temperatures in novel organ preservation solution Somah to prevent damage and preserve optimum function by maintaining cellular energy over the temperature range of storage. Porcine hearts were stored in Celsior at 4°C and Somah at 4°C, 13°C and 21°C for 5 h thereafter reperfused and reanimated in vitro for 3 h. Heart weights, histopathology, ultrastructure and 2‐dimensional echocardiography (2D‐Echo) assessments showed preservation of structure in Somah groups. Tissue high‐energy phosphate levels in Somah groups after storage were significantly greater than the Celsior hearts (p < 0.05) and highest in the 21°C Somah hearts. Upon reperfusion, myocardial O2 consumption and lactate levels quickly achieved steady state in 21°C hearts, but were delayed in Somah 4/13°C groups and severely depressed in the Celsior group. Inotrope and electroconversion requirements were inversely related to storage temperature. In vitro 2D Echo demonstrated a discordantly attenuated function in the Celsior group, moderate functionality in 4°C Somah group and superior reestablishment of performance in the Somah higher temperature groups. Hearts stored in Somah at 21°C were metabolically and functionally superior to any other groups.

Further evaluation of Somah: long-term preservation, temperature effect, and prevention of ischemia-reperfusion injury in rat hearts harvested after cardiocirculatory death.

OBJECTIVE To identify and evaluate the ideal temperature for long-term storage of hearts from donation after cardiocirculatory death, in the novel organ preservation solution Somah. METHODS DCD hearts from Sprague-Dawley rats were harvested after 30 minutes of euthanasia, preserved in Somah at 4°C, 10°C, 21°C, or 37°C for 24 hours and then reperfused with blood:Somah (3:1) perfusate at 37°C for 30 minutes. Myocardial biopsies were taken during storage and before and after reperfusion to assess the structural and functional viability of tissue using multiphoton imaging, biochemistry, and immunofluorescence. RESULTS Myocyte viability, determined by Live-Dead and esterase assays, was similar at 4°C, 10°C, and 21°C (193, 198 and 217 normalized fluorescence counts [NFC]) with a significant decrease at 37°C (131 NFC). Upon reperfusion, esterase activity was enhanced in DCD hearts stored in Somah at 21°C but noticeably decreased at all other temperatures. High-energy adenosine triphosphate/creatine phosphate (ATP/CP) syntheses and the expression of structural/contractile proteins was well preserved at 21°C, both after 24-hour storage and upon reperfusion. In contrast, hearts stored at all other temperatures demonstrated variable degenerative changes, loss of protein expression, and/or deranged ATP/CP synthesis after 24 hours of storage and/or upon reperfusion. CONCLUSION The robust maintenance of structural/functional integrity of cardiac tissue and the preservation of protein expression and cellular energy metabolism in DCD hearts after long-term preservation at subnormothermic temperature suggests that 21°C is ideal for long-term storage of DCD hearts in Somah solution.

Sub-normothermic preservation of donor hearts for transplantation using a novel solution, Somah: A comparative pre-clinical study

BACKGROUND Hearts preserved ex vivo at extreme hypothermia (4°C) undergo time-dependent irreversible injury. Our studies using a novel solution, Somah, suggest that hearts are viably preserved at 21°C. In this study we evaluate the relative efficacy of Somah for preservation of hearts at 21°C when compared with the clinically used Celsior and University of Wisconsin (UWS) solutions. METHODS Porcine hearts arrested by cardioplegia at 21°C using Somah, Celsior or UWS solution were stored in the respective solutions at 21°C (n = 5) for 5 hours and then reperfused ex vivo for functional assessment. We assessed development of edema, cardiac tissue high-energy phosphate (HEP; ATP + creatine phosphate) levels and release of cardiac enzymes. Alterations in left ventricular wall thicknesses and functional parameters were examined by 2-dimensional (2D) echocardiography. Changes in myocardial oxygen consumption (MVO2) and lactate utilization were assessed at reperfusion. RESULTS Heart weights were unaltered during 5-hour storage in all groups. After storage, HEP levels were 28.33 ± 5.51, 10.20 ± 2.78 and 5.92 ± 1.46 nmol/liter per milligram protein (p < 0.001) in the Somah, Celsior and UWS group hearts, respectively. Upon reanimation, 2D echocardiography showed edema in the Celsior and UWS hearts; prompt attainment of physiologic function was associated with rapid establishment of aerobic metabolism not requiring stimulatory interventions in the Somah hearts, but not in the Celsior/UWS hearts. Percent fractional area change, ejection fraction and stroke volume were significantly higher (p < 0.001) in Somah hearts than in Celsior and UWS group hearts. CONCLUSIONS Increased synthesis of HEP, rapid metabolic switch and optimal function together provide evidence that hearts procured for transplantation are preserved in a superior viable condition at 21°C with Somah, but not with other commonly used clinical preservation solutions.

The Progression of Isoflurane-induced Malignant Hyperthermia and ItsAttenuation by Cisatracurium in a Pre-clinical Porcine Model of HeartTransplant

Background: Even after several years of study, the intra-operative diagnosis of Malignant Hyperthermia (MH) and the approach to anesthesia in MH-susceptible individuals has remained a challenge. In this study we present the pre-operative and intra-operative findings of development and progression of MH in a porcine model that was assigned for heart transplants. Methods: Female Yorkshire swine were assigned as either donor or recipient and anesthetized with inhalational isoflurane with or without cisatracurium. The inadvertent development of signs indicating MH, including, alterations required in ventilator/bypass machine settings, arterial and venous blood tests, gross- and histo-pathology, were followed through the surgeries that lasted for variable durations between donors and recipients. Results: Both donors and the recipients were apparently MH-susceptible, and showed systemic intraoperative signs of variable severity, that were greater in longer duration recipient surgeries, and in those in which cisatracurium was not administered. These included features of hypermetabolism such as elevated pCO2 and serum lactate, increased requirements for O2 (FIO2), and multi-organ changes, including pulmonary congestion, features of intestinal pseudo-obstruction, and inflammatory infiltrates in livers and hearts. Conclusions: The isoflurane-induced MH progressed temporally in severity with the duration of surgery. Use of cisatracurium was directly beneficial in attenuating and/or delaying the progress of MH.

Multifactorial Comparison of Modified and Conventional Perfusion Strategies in A Porcine Model of Cardiopulmonary Bypass

BACKGROUND Utilization of thromboresistant circuits in cardiopulmonary bypass (CPB) surgery has been controversial. However, due to the advantages associated with these types of circuits, we sought to evaluate the efficacy of use of low-dose heparin in conjunction with thromboresistant surfaces, closed perfusion system, elimination of blood-gas interface, maintenance of hematocrit to >25%, and systemic normothermia, with respect to the conventional strategy of non-thromboresistant open circuits with high-dose heparin, during 3 h of CPB in an animal model. METHODS Using an open-chest swine model, animals were placed on CPB for 3 h with additional monitoring for 1 h post-CPB. Pigs were randomized into either a heparin-bonded circuit (HBC) group (n = 10) or a non-HBC (NHB) group (n = 10). Hemodynamic, hematologic, and biochemical parameters and multiphoton microscopy were used to compare the two groups. RESULTS Pigs in the HBC group showed a 38.4% reduction in post-CPB blood loss in comparison with the NHB group (P = 0.0007). Additionally, compared with the HBC group, the NHB group exhibited a 32.7% post-CPB reduction in platelets (P < 0.001) and significant increases in alkaline phosphatase, aspartate aminotransferase, and creatine phosphokinase enzymes (P < 0.0202, P = 0.0015, P < 0.0001; respectively). Multiphoton imaging of the arterial filters revealed no entrapment of RBC, WBC, and platelets in the HBC group, while the filters in the NHB group were clogged by these cells. CONCLUSION Utilization of modified perfusion strategy employing low-dose heparin and closed thromboresistant circuits is successful in ameliorating the potential adverse hematologic and pro-inflammatory elements induced with open perfusion system of non-thromboresistant circuits most commonly used in cardiac surgery.