The American Transplant Congress (ATC) 2023, held in San Diego, California, emerged as a pivotal platform showcasing the latest advancements in organ machine perfusion, a key area in solid organ and ...tissue transplantation. This year's congress, attended by over 4500 participants, including leading experts, emphasized innovations in machine perfusion technologies across various organ types, including liver, kidney, heart, and lung. A total of 85 s on organ machine perfusion were identified. Noteworthy advancements included the use of normothermic machine perfusion in mitigating ex‐situ reperfusion injury in liver transplantation, the potential of biomarkers in assessing organ quality, and the impact of machine perfusion on graft survival and ischemic cholangiopathy incidence. Kidney transplantation saw promising developments in novel preservation methods, such as subzero storage and pulsatile perfusion. Heart and lung sessions revealed significant progress in preservation techniques, including metabolic alterations to extend organ preservation time. The conference also highlighted the growing interest in machine perfusion applications in pediatric transplantation, multi‐visceral organ recovery, Vascularized Composite Allotransplantation, and discussions on novel technologies for monitoring and optimizing perfusion protocols. Additionally, ATC 2023 included critical discussions on ethical concerns, legal implications, and the evolving definition of death in the era of machine preservation, illustrating the complex landscape of transplantation science. Overall, ATC 2023 showcased significant strides in machine perfusion and continued its tradition of fostering global knowledge exchange, further cementing machine perfusion's role as a transformative force in improving transplant outcomes and expanding the donor pool.
COVID-19 infection may lead to acute respiratory distress syndrome (CARDS) where severe gas exchange derangements may be associated, at least in the early stages, only with minor pulmonary ...infiltrates. This may suggest that the shunt associated to the gasless lung parenchyma is not sufficient to explain CARDS hypoxemia. We designed an algorithm (Vent
Q
), based on the same conceptual grounds described by J.B. West in 1969. We set 498 ventilation-perfusion (V
/Q) compartments and, after calculating their blood composition (PO
, PCO
, and pH), we randomly chose 10
combinations of five parameters controlling a bimodal distribution of blood flow. The solutions were accepted if the predicted PaO
and PaCO
were within 10% of the patient's values. We assumed that the shunt fraction equaled the fraction of non-aerated lung tissue at the CT quantitative analysis. Five critically-ill patients later deceased were studied. The PaO
/FiO
was 91.1 ± 18.6 mmHg and PaCO
69.0 ± 16.1 mmHg. Cardiac output was 9.58 ± 0.99 L/min. The fraction of non-aerated tissue was 0.33 ± 0.06. The model showed that a large fraction of the blood flow was likely distributed in regions with very low V
/Q (Q
= 0.06 ± 0.02) and a smaller fraction in regions with moderately high V
/Q. Overall LogSD, Q was 1.66 ± 0.14, suggestive of high V
/Q inequality. Our data suggest that shunt alone cannot completely account for the observed hypoxemia and a significant V
/Q inequality must be present in COVID-19. The high cardiac output and the extensive microthrombosis later found in the autopsy further support the hypothesis of a pathological perfusion of non/poorly ventilated lung tissue.
Hypothesizing that the non-aerated lung fraction as evaluated by the quantitative analysis of the lung computed tomography (CT) equals shunt (V
/Q = 0), we used a computational approach to estimate the magnitude of the ventilation-perfusion inequality in severe COVID-19. The results show that a severe hyperperfusion of poorly ventilated lung region is likely the cause of the observed hypoxemia. The extensive microthrombosis or abnormal vasodilation of the pulmonary circulation may represent the pathophysiological mechanism of such V
/Q distribution.
Blood perfusion is the supply of tissue with blood, and oxygen is a key factor in the field of minor and major wound healing. Reduced perfusion of a wound bed or transplant often causes various ...complications. Reliable methods for an objective evaluation of perfusion status are still lacking, and insufficient perfusion may remain undiscovered, resulting in chronic processes and failing transplants. Hyperspectral imaging (HSI) represents a novel method with increasing importance for clinical practice. Therefore, methods, software and algorithms for a new HSI system are presented which can be used to observe tissue oxygenation and other parameters that are of importance in supervising healing processes. This could offer an improved insight into wound perfusion allowing timely intervention.
Objectives
To evaluate the concordance between DECT perfusion and ventilation/perfusion (V/Q) scintigraphy in diagnosing chronic thromboembolic pulmonary hypertension (CTEPH).
Methods
Eighty patients ...underwent V/Q scintigraphy and DECT perfusion on a 2nd- and 3rd-generation dual-source CT system. The imaging criteria for diagnosing CTEPH relied on at least one segmental triangular perfusion defect on DECT perfusion studies and V/Q mismatch on scintigraphy examinations.
Results
Based on multidisciplinary expert decisions that did not include DECT perfusion, 36 patients were diagnosed with CTEPH and 44 patients with other aetiologies of PH. On DECT perfusion studies, there were 35 true positives, 6 false positives and 1 false negative (sensitivity 0.97, specificity 0.86, PPV 0.85, NPV 0.97). On V/Q scans, there were 35 true positives and 1 false negative (sensitivity 0.97, specificity 1, PPV 1, NPV 0.98). There was excellent agreement between CT perfusion and scintigraphy in diagnosing CTEPH (kappa value 0.80). Combined information from DECT perfusion and CT angiographic images enabled correct reclassification of the 6 false positives and the unique false negative case of DECT perfusion.
Conclusion
There is excellent agreement between DECT perfusion and V/Q scintigraphy in diagnosing CTEPH. The diagnostic accuracy of DECT perfusion is reinforced by the morpho-functional analysis of data sets.
Key Points
• Chronic thromboembolic pulmonary hypertension (CTEPH) is potentially curable by surgery.
• The triage of patients with pulmonary hypertension currently relies on scintigraphy.
• Dual-energy CT (DECT) can provide standard diagnostic information and lung perfusion from a single acquisition.
• There is excellent agreement between DECT perfusion and scintigraphy in separating CTEPH and non-CTEPH patients.
Purpose
To enable all‐systolic first‐pass rest myocardial perfusion with long saturation times. To investigate the change in perfusion contrast and dark rim artefacts through simulations and ...surrogate measurements.
Methods
Simulations were employed to investigate optimal saturation time for myocardium‐perfusion defect contrast and blood‐to‐myocardium signal ratios. Two saturation recovery blocks with long/short saturation times (LTS/STS) were employed to image 3 slices at end‐systole and diastole. Simultaneous multi‐slice balanced steady state free precession imaging and compressed sensing acceleration were combined. The sequence was compared to a 3 slice‐by‐slice clinical protocol in 10 patients. Quantitative assessment of myocardium‐peak pre contrast and blood‐to‐myocardium signal ratios, as well as qualitative assessment of perceived SNR, image quality, blurring, and dark rim artefacts, were performed.
Results
Simulations showed that with a bolus of 0.075 mmol/kg, a LTS of 240‐470 ms led to a relative increase in myocardium‐perfusion defect contrast of 34% ± 9%‐28% ± 27% than a STS = 120 ms, while reducing blood‐to‐myocardium signal ratio by 18% ± 10%‐32% ± 14% at peak myocardium. With a bolus of 0.05 mmol/kg, LTS was 320‐570 ms with an increase in myocardium‐perfusion defect contrast of 63% ± 13%‐62% ± 29%. Across patients, LTS led to an average increase in myocardium‐peak pre contrast of 59% (P < .001) at peak myocardium and a lower blood‐to‐myocardium signal ratio of 47% (P < .001) and 15% (P < .001) at peak blood/myocardium. LTS had improved motion robustness (P = .002), image quality (P < .001), and decreased dark rim artefacts (P = .008) than the clinical protocol.
Conclusion
All‐systolic rest perfusion can be achieved by combining simultaneous multi‐slice and compressed sensing acceleration, enabling 3‐slice cardiac coverage with reduced motion and dark rim artefacts. Numerical simulations indicate that myocardium‐perfusion defect contrast increases at LTS.
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•End-ischemic HOPE protected against arterial and biliary complications, resulting in significantly less graft loss.•Equivalent outcomes were achieved with HOPE as with primary DBD ...liver transplants.•HOPE after cold storage is a simple and effective method to treat high-risk DCD livers prior to implantation.
Donation after circulatory death (DCD) liver transplantation is known for potentially worse outcomes because of higher rates of graft non-function or irreversible cholangiopathy. The impact of machine liver perfusion techniques on these complications remains elusive. We aimed to provide data on 5-year outcomes in patients receiving DCD liver transplants, after donor organs had been treated by hypothermic oxygenated perfusion (HOPE).
Fifty HOPE-treated DCD liver transplants performed in Zurich between 2012 and 3/2017 were matched with 50 primary donation after brain death (DBD) liver transplants, and with 50 untreated DCD liver transplants in Birmingham. Match factors focussed on short cold ischaemia, comparable recipient age and low recipient laboratory model for end-stage liver disease scores. Primary endpoints were post-transplant complications, and non-tumour-related patient death or graft loss.
Despite extended donor warm ischaemia, HOPE-treated DCD liver transplants achieved similar overall graft survival, compared to standard DBD liver transplants. Particularly, graft loss due to any non-tumour-related causes occurred in 8% (4/50) of cases. In contrast, untreated DCD livers resulted in non-tumour-related graft failure in one-third (16/50) of cases (p = 0.005), despite significantly (p <0.001) shorter functional donor warm ischaemia. Five-year graft survival, censored for tumour death, was 94% for HOPE-treated DCD liver transplants vs. 78% in untreated DCD liver transplants (p = 0.024).
The 5-year outcomes of HOPE-treated DCD liver transplants were similar to those of DBD primary transplants and superior to those of untreated DCD liver transplants, despite much higher risk. These results suggest that a simple end-ischaemic perfusion approach is very effective and may open the field for safe utilisation of extended DCD liver grafts.
Machine perfusion techniques are currently being introduced into the clinic, with the aim of optimising injured grafts prior to implantation. While short-term effects of machine liver perfusion have been frequently reported in terms of hepatocellular enzyme release and early graft function, the long-term benefit on irreversible graft loss has been unclear. Herein, we report on 5-year graft survival in donation after cardiac death livers, treated either by conventional cold storage, or by 1–2 h of hypothermic oxygenated perfusion (HOPE) after cold storage. Graft loss was significantly less in HOPE-treated livers, despite longer donor warm ischaemia times. Therefore, HOPE after cold storage appears to be a simple and effective method to treat high-risk livers before implantation.
In this case report, we preserved human livers for up to 13 days under normothermic conditions using a modified commercial perfusion system. Two whole livers were split into two left lateral segment ...grafts and two extended right grafts without interruption to blood flow and then perfused on separate machines. Not only does this provide the basis for a meaningful study of liver function in the long term, but this could also facilitate the development of a model of ex situ liver regeneration.
The use of pre‐procurement normothermic regional perfusion (NRP) allowed us to implement controlled DCD liver transplantation with results comparable to brain death donors, but the use of ...uncontrolled DCD is declining due to logistic challenges and the high incidence of post‐transplant complications. In Italy, the mandatory stand‐off period of 20 min for DCD donors has driven the combined use of NRP and ex‐situ machine perfusion with the intent to counterbalance the negative impact of prolonged warm ischemia. Organ viability during NRP is based on duration of warm ischemia, regional perfusion flow, lactate, transaminases values and histology, and those used in Italy are the widest worldwide. However, this evaluation can be difficult, especially when the acute damage is particularly severe. The use of ex‐situ NRP could provide a safe organ evaluation. In the period from 06/2020 to 06/2022, all DCD grafts exceeding NRP viability criteria at a single center were eventually evaluated using ex‐situ normothermic machine perfusion. Machine perfusion viability criteria were based on lactate clearance, irrespectively to bile production, unless 1‐h transaminases perfusate level were not exceeding 5000 IU/L. Three cases of uncontrolled DCD grafts in excess of NRP viability criteria underwent ex‐situ graft evaluation. Two matched ex‐situ normothermic machine perfusion viability criteria and were successfully transplanted. Both recipients are doing well after 26 and 5 months after surgery with no signs of ischemic cholangiopathy. This experience suggests that the sequential use of NRP and normothermic machine perfusion may further expand the boundaries of organ viability in uncontrolled DCD liver transplantation.
The sequential use of normothermic regional perfusion (NRP) and ex‐situ normothermic machine perfusion (NMP) could promote the expansion of uncontrolled DCD (uDCD) acceptance criteria, but the assessment of liver grafts viability is critical
Three cases of uDCD grafts in excess of NRP viability criteria underwent ex‐situ NMP re‐evaluation. Two organs matched our ex‐situ NMP viability criteria and were successfully transplanted
The sequential use of NRP and NMP may further expand the boundaries of organ viability in uDCD liver transplantation
The last decade has been notable for increasing high-quality research and dramatic improvement in outcomes with dynamic liver preservation. Robust evidence from numerous randomized controlled trials ...has been pooled by meta-analyses, providing the highest available evidence on the protective effect of machine perfusion (MP) over static cold storage in liver transplantation (LT). Based on a protective effect with less complications and improved graft survival, the field has seen a paradigm shift in organ preservation. This editorial focuses on the role of MP in LT and how it could become the new "gold standard". Strong collaborative efforts are needed to explore its effects on long-term outcomes.
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