Structural and biomechanical characterizations of acellular porcine mitral valve scaffolds: anterior leaflets, posterior leaflets, and chordae tendineae.

Mitral valve (MV) tissue engineering is still in its early stage, and one major challenge in MV tissue engineering is to identify appropriate scaffold materials. With the potential of acellular MV scaffolds being demonstrated recently, it is important to have a full understanding of the biomechanics of the native MV components and their acellular scaffolds. In this study, we have successfully characterized the structural and mechanical properties of porcine MV components, including anterior leaflet (AL), posterior leaflet (PL), strut chordae, and basal chordae, before and after decellularization. Quantitative DNA assay showed more than 90% reduction in DNA content, and Griffonia simplicifolia (GS) lectin immunohistochemistry confirmed the complete lack of porcine α-Gal antigen in the acellular MV components. In the acellular AL and PL, the atrialis, spongiosa, and fibrosa trilayered structure, along with its ECM constitutes, i.e., collagen fibers, elastin fibers, and portion of GAGs, were preserved. Nevertheless, the ECM of both AL and PL experienced a certain degree of disruption, exhibiting a less dense, porous ECM morphology. The overall anatomical morphology of the strut and basal chordae were also maintained after decellularization, with longitudinal morphology experiencing minimum disruption, but the cross-sectional morphology exhibiting evenly-distributed porous structure. In the acellular AL and PL, the nonlinear anisotropic biaxial mechanical behavior was overall preserved; however, uniaxial tensile tests showed that the removal of cellular content and the disruption of structural ECM did result in small decreases in maximum tensile modulus, tissue extensibility, failure stress, and failure strain for both MV leaflets and chordae.

Differences in Organ Donation and Transplantation in States Within the United States and in European Countries: Is There a Benefit to Opting Out?

BACKGROUND: Organ donation in the United States currently requires explicit consent by an "opt-in" approach. Some European countries have reported an increase in donation rates with an "opt-out" strategy. We hypothesized that regional differences in decision making affect organ donation rates in different countries and suggest no single approach will reliably increase organ donation rates. METHODS: Donation and transplantation rates in European countries and states within the United States with populations of >10 million and a minimum organ donation rate of 10 donors per million were compared. 2016 International Registry in Organ Donation and Transplantation data and the 2016 Scientific Registry of Transplant Recipients annual report were used for European countries and US states, respectively. Comparisons by region and donation model were made. RESULTS: Deceased organ donor rates and transplants did not differ between opt-in and opt-out models. Living donation was increased in all opt-in entities. When comparing European countries, there was a trend toward higher organ donation rates in opt-out countries than in opt-in countries. Donation and transplantation rates of US states were higher than both European opt-in and opt-out countries. CONCLUSION: There were no differences in deceased donor organ donation when considering the donation consent model. These data do not support that an opt-out approach will increase the number of transplants in the United States.

Cardiac transplantation in adults with congenital heart disease: A single center case series.

BACKGROUND: Adult congenital heart disease (CHD) transplant recipients historically experienced worse survival early after transplantation. We aim to review updated trends in adult CHD transplantation. METHODS: We performed a single center case series of adult cardiac transplants from January 2013 through July 2020. Outcomes of patients with CHD were compared to non-CHD. The primary outcome was overall survival. Secondary outcomes included a variety of post-operative complications. RESULTS: 18/262 (7%) transplants were CHD recipients. CHD patients were younger with median age 41 (32-47) versus 58 (48-65) (P < .001). Fontan circulation for single ventricle physiology was present in 4/18 (22%) of CHD recipients, while 16/18 (89%) had systemic right ventricles. CHD recipients had higher rates of previous cardiovascular operations (94% vs. 51%, P < .001). 9/18 (50%) of CHD patients required reconstructive procedures at the time of transplant. Operative and cardiopulmonary bypass times were longer for the CHD cohort (7.5 h [6.6-8.5] vs. 5.6 h [4.6-7] P < .001) and (197 min [158-240] vs. 130 [105-167] P < .001), respectively. There were no differences in operative complications or survival between CHD and non-CHD recipients. CONCLUSIONS: These data highlight the added technical challenges of performing adult CHD transplants. However, similar outcomes can be achieved as for non-CHD recipients. SUMMARY: Modern advances in palliation of congenital heart defects (CHD) has led to increased survival into adulthood. Many of these patients require heart transplantation as adults. There are limited data on adult CHD transplantation. Historically, these patients have had worse perioperative outcomes with improved long-term survival. We retrospectively analyzed 262 heart transplants at a single center, 18 of which were for adult CHD. Here, we report our series of 18 CHD recipients. We detail the palliative history of all CHD patients and highlight the added technical challenges for each of the 18 patients at transplant. In our analysis, CHD patients had more prior cardiovascular surgeries as well as longer transplant operative and bypass times. Despite this, there were no differences in perioperative and long-term outcomes. We have added patient and institution specific data for transplanting patients with adult CHD. We hope that our experience will add to the growing body of literature on adult CHD transplantation.

Myocardial Substrate Oxidation and Tricarboxylic Acid Cycle Intermediates During Hypothermic Machine Perfusion.

BACKGROUND: The optimal substrate for hypothermic machine perfusion preservation of donor hearts is unknown. Fatty acids, acetate, and ketones are preferred substrates of the heart during normothermic perfusion, but cannot replete the tricarboxylic acid (TCA) cycle directly. Propionate, an anaplerotic substrate, can replenish TCA cycle intermediates and may affect cardiac metabolism. The purpose of this study was to determine myocardial substrate preferences during hypothermic machine perfusion and to assess if an anaplerotic substrate was required to maintain the TCA cycle intermediate pool in perfused hearts. METHODS: Groups of rat hearts were perfused with carbon-13 (13C)-labeled substrates (acetate, ß-hydroxybutyrate, octanoate, with and without propionate) at low and high concentrations. TCA cycle intermediate concentrations, substrate selection, and TCA cycle flux were determined by gas chromatography/mass spectroscopy and 13C magnetic resonance spectroscopy. RESULTS: Acetate and octanoate were preferentially oxidized, whereas ß-hydroxybutyrate was a minor substrate. TCA cycle intermediate concentrations except fumarate were higher in substrate-containing perfusion groups compared with either the no-substrate perfusion group or the no-ischemia control group. CONCLUSIONS: The presence of an exogenous, oxidizable substrate is required to support metabolism in the cold perfused heart. An anaplerotic substrate is not essential to maintain the TCA cycle intermediate pool and support oxidative metabolism under these conditions.

A comparison of cholecystitis grading scales.

BACKGROUND: Previously, our group developed the Parkland grading scale for cholecystitis (PGS) to stratify gallbladder (GB) disease severity that can be determined immediately when performing laparoscopic cholecystectomy (LC). In prior studies, PGS demonstrated excellent interrater reliability and was internally validated as an accurate measure of LC outcomes. Here, we compare PGS against a more complex cholecystitis severity score developed by the national trauma society, American Association for the Surgery of Trauma (AAST), which requires clinical, operative, imaging, and pathologic inputs, as a predictor of LC outcomes. METHODS: Eleven acute care surgeons prospectively graded 179 GBs using PGS and filled out a postoperative questionnaire regarding the difficulty of the surgery. Three independent raters retrospectively graded these GBs using PGS from images stored in the electronic medical record. Three additional surgeons then assigned separate AAST scores to each GB. The intraclass correlation coefficient statistic assessed rater reliability for both PGS and AAST. The PGS score and the median AAST score became predictors in separate linear, logistic, and negative binomial regression models to estimate perioperative outcomes. RESULTS: The average intraclass correlation coefficient of PGS and AAST was 0.8647 and 0.8341, respectively. Parkland grading scale for cholecystitis was found to be a superior predictor of increasing operative difficulty (R, 0.566 vs. 0.202), case length (R, 0.217 vs. 0.037), open conversion rates (area under the curve, 0.904 vs. 0.757), and complication rates (area under the curve, 0.7039 vs. 0.6474) defined as retained stone, small-bowel obstruction, wound infection, or postoperative biliary leak. Parkland grading scale for cholecystitis performed similar to AAST in predicting partial cholecystectomy, readmission, bile leak rates, and length of stay. CONCLUSION: Both PGS and AAST are accurate predictors of LC outcomes. Parkland grading scale for cholecystitis was found to be a superior predictor of subjective operative difficulty, case length, open conversion rates, and complication rates. Parkland grading scale for cholecystitis has the advantage of being a simpler, operative-based scale which can be scored at a single point in time. LEVEL OF EVIDENCE: Single institution, retrospective review, level IV.

Right ventricular outflow tract obstruction: a quest for ideal management.

Management of right ventricular outflow tract obstruction has undergone much change over the last century. Techniques described in the literature include anatomical repairs and the use of various patches, conduits, and innovative grafts. However, many of these approaches require reoperations or catheter-based interventions, leading to increased morbidity, mortality, and cost. The search for the ideal long-lasting conduit continues and there are new techniques on the horizon, using genetic engineering and nanotechnology. This review discusses the evolution of various techniques for repair of right ventricular outflow tract obstruction, past and current conduits, as well as ongoing research.

Ipsilateral arcuate foramen and high-riding vertebral artery: implication on C1-C2 instrumentation.

BACKGROUND CONTEXT: Several methods for C1-C2 stabilization have been described in the literature. These include C1-C2 transarticular and C1 lateral mass screws. In patients with aberrant anatomy such as a high-riding vertebral artery (VA) or the presence of an arcuate foramen at C1, there exists a higher risk of VA injury. This may lead to excessive bleeding, stroke, and possibly death. There have been several studies determining the incidence of arcuate foramen and high-riding VA occurring individually in the general population, but none have determined their occurrence simultaneously. PURPOSE: To determine the prevalence of ponticulus posticus and high-riding VA occurring simultaneously in the general population. STUDY DESIGN: Radiological study. METHODS: One hundred consecutive computed tomography (CT) scans of the cervical spine were reviewed. Scans that contained an arcuate foramen were identified, and it was indicated whether the foramen was right sided, left sided, or bilateral. In the same group, the thickness of the isthmus and the internal height of the lateral mass of C2 were measured. The VA was considered high riding if the isthmus thickness was less than 5 mm or the isthmus internal height was less than 2 mm. RESULTS: Fourteen out of one hundred (14%) patients had a fully formed arcuate foramen. Of these, six were left sided, three were right sided, and five were bilateral. In addition, there were 24 (24%) patients with partially formed ponticulus posticus. Thirty-two (32%) patients were identified to have a high-riding VA. Of these, 13 were left sided, 9 were right sided, and 10 were bilateral. Five (5%) had an ipsilateral arcuate foramen and high-riding VA. CONCLUSIONS: The arcuate foramen and high-riding VA are common anomalies that are often not recognized. Although ipsilateral high-riding VA and arcuate foramen rarely occur in the general population, proper identification of these anomalies on preoperative CT scan facilitates planning the safest technique for C1-C2 instrumentation.