Donor heart refusal after circulatory death: An analysis of United Network for Organ Sharing refusal codes.

Objective: Donor hearts procured after circulatory death (DCD) may significantly increase the number of hearts available for transplantation. The purpose of this study was to analyze current DCD and brain-dead donor (DBD) heart transplantation rates and characterize organ refusal using the most up-to-date United Network for Organ Sharing (UNOS) and Organ Procurement and Transplantation Network data. Methods: We analyzed UNOS and Organ Procurement and Transplantation Network DBD and DCD candidate, transplantation, and demographic data from 2020 through 2022 and 2022 refusal code data to characterize DCD heart use and refusal. Subanalyses were performed to characterize DCD donor demographics and regional transplantation rate variance. Results: DCD hearts were declined 3.37 times more often than DBD hearts. The most frequently used code for DCD refusal was neurologic function, related to concerns of a prolonged dying process and organ preservation. In 2022, 92% (1329/1452) of all DCD refusals were attributed to neurologic function. When compared with DBD, DCD donor hearts were more frequently declined as the result of prolonged warm ischemic time (odds ratio, 5.65; 95% confidence interval, 4.07-7.86) and other concerns over organ preservation (odds ratio, 4.06; 95% confidence interval, 3.33-4.94). Transplantation rate variation was observed between demographic groups and UNOS regions. DCD transplantation rates are currently experiencing second order polynomial growth. Conclusions: DCD donor hearts are declined more frequently than DBD. DCD heart refusals result from concerns over a prolonged dying process and organ preservation. Heart transplantation rates may be substantially improved by ex situ hemodynamic assessment, adoption of normothermic regional perfusion guidelines, and quality initiatives.

Extending heart preservation to 24†h with normothermic perfusion.

Cold static storage (CSS) for up to 6 h is the gold standard in heart preservation. Although some hearts stored over 6 h have been transplanted, longer CSS times have increased posttransplant morbimortality. Transmedics® Organ Care System (OCS™) is the only FDA-approved commercial system that provides an alternative to CSS using normothermic ex situ heart perfusion (NEHP) in resting mode with aortic perfusion (Langendorff method). However, it is also limited to 6 h and lacks an objective assessment of cardiac function. Developing a system that can perfuse hearts under NEHP conditions for >24 h can facilitate organ rehabilitation, expansion of the donor pool, and objective functional evaluation. The Extracorporeal Life Support Laboratory at the University of Michigan has worked to prolong NEHP to >24 h with an objective assessment of heart viability during NEHP. An NEHP system was developed for aortic (Langendorff) perfusion using a blood-derived perfusate (leukocyte/thrombocyte-depleted blood). Porcine hearts (n = 42) of different sizes (6-55 kg) were divided into five groups and studied during 24 h NEHP with various interventions in three piglets (small-size) heart groups: (1) Control NEHP without interventions (n = 15); (2) NEHP + plasma exchange (n = 5); (3) NEHP + hemofiltration (n = 10) and two adult-size (juvenile pigs) heart groups (to demonstrate the support of larger hearts); (4) NEHP + hemofiltration (n = 5); and (5) NEHP with intermittent left atrial (iLA) perfusion (n = 7). All hearts with NEHP + interventions (n = 27) were successfully perfused for 24 h, whereas 14 (93.3%) control hearts failed between 10 and 21 h, and 1 control heart (6.6%) lasted 24 h. Hearts in the piglet hemofiltration and plasma exchange groups performed better than those in the control group. The larger hearts in the iLA perfusion group (n = 7) allowed for real-time heart functional assessment and remained stable throughout the 24 h of NEHP. These results demonstrate that heart preservation for 24 h is feasible with our NEHP perfusion technique. Increasing the preservation period beyond 24 h, infection control, and nutritional support all need optimization. This proves the concept that NEHP has the potential to increase the organ pool by (1) considering previously discarded hearts; (2) performing an objective assessment of heart function; (3) increasing the donor/recipient distance; and (4) developing heart-specific perfusion therapies.

Twenty-four-hour Normothermic Ex Vivo Heart Perfusion With Low Flow Functional Assessment in an Adult Porcine Model.

BACKGROUND: Cold static storage and normothermic ex vivo heart perfusion are routinely limited to 6 h. This report describes intermittent left atrial (LA) perfusion that allows cardiac functional assessment in a working heart mode. METHODS: Using our adult porcine model, general anesthesia was induced and a complete cardiectomy was performed following cardioplegic arrest. Back-table instrumentation was completed and normothermic ex vivo heart perfusion (NEHP) was initiated in a nonworking heart mode (Langendorff). After 1 h of resuscitation and recovery, LA perfusion was initiated and the heart was transitioned to a coronary flow-only working heart mode for 30 min. Baseline working heart parameters were documented and the heart was returned to nonworking mode. Working heart assessments were performed for 30 min every 6 h for 24 h. RESULTS: Twenty-four-hour NEHP on 9 consecutive hearts (280 ±â€…42.1 g) was successful and no significant differences were found between working heart parameters at baseline and after 24 h of perfusion. There was no difference between initial and final measurements of LA mean pressures (5.0 ±â€…3.1 versus 9.0 ±â€…6.5 mm Hg, P = 0.22), left ventricular systolic pressures (44.3 ±â€…7.2 versus 39.1 ±â€…9.0 mm Hg, P = 0.13), mean aortic pressures (30.9 ±â€…5.8 versus 28.1 ±â€…8.1 mm Hg, P = 0.37), and coronary resistance (0.174 ±â€…0.046 versus 0.173 ±â€…0.066 mL/min/g, P = 0.90). There were also no significant differences between lactate (2.4 ±â€…0.5 versus 2.6 ±â€…0.4 mmol/L, P = 0.17) and glucose (173 ±â€…75 versus 156 ±â€…70 mg/dL, P = 0.37). CONCLUSIONS: A novel model using intermittent LA perfusion to create a coronary flow-only working heart mode for assessment of ex vivo cardiac function has been successfully developed.

Anatomic, stage-based repair of secondary mitral valve disease.

OBJECTIVE: Intervention for repair of secondary mitral valve disease is frequently associated with recurrent regurgitation. We sought to determine if there was sufficient evidence to support inclusion of anatomic indices of leaflet dysfunction in the management of secondary mitral valve disease. METHODS: We performed a systematic review and meta-analysis of published reports comparing anatomic indices of leaflet dysfunction with the complexity of valve repair and the outcome from intervention. Patients were stratified by the severity of leaflet dysfunction. A secondary analysis was performed comparing outcomes when procedural complexity was optimally matched to severity of leaflet dysfunction and when intervention was not matched to dysfunction. RESULTS: We identified 6864 publications, of which 65 met inclusion criteria. An association between the severity of leaflet dysfunction and the procedural complexity was highly predictive of satisfactory freedom from recurrent regurgitation. Patients were categorized into 4 groups based on stratification of leaflet dysfunction. Satisfactory results were achieved in 93.7% of patients in whom repair complexity was appropriately matched to severity of leaflet dysfunction and in 68.8% in whom repair was not matched to dysfunction (odds ratio, 0.148; 95% confidence interval, 0.119-0.184; P < .0001). CONCLUSIONS: For patients with secondary mitral valve disease, satisfactory outcome from valve repair improves when procedural complexity is matched to anatomic indices of leaflet dysfunction. Anatomic indices of leaflet dysfunction should be considered when planning interventions for secondary mitral regurgitation. Routine inclusion of anatomic indices in trial design and reporting should facilitate comparison of results and strengthen guidelines. There are sufficient data to support anatomic staging of secondary mitral valve disease.

Twenty-Four Hour Normothermic Ex Vivo Heart Perfusion With Hemofiltration In an Adult Porcine Model.

BACKGROUND: Historically, cardiac transplantation relied on cold static storage at 5 °C for ex vivo myocardial preservation. Currently, machine perfusion is the standard of care at many transplant centers. These storage methods are limited to 12 hours. We sought to evaluate the efficacy of hemofiltration and filtrate replacement in adult porcine hearts using normothermic heart perfusion (NEVHP) for 24 hours. METHODS: We performed 24-hour NEVHP on 5 consecutive hearts. After anesthetic induction, sternotomy, cardioplegia administration, explantation, and back-table instrumentation, NEVHP was initiated in beating, unloaded mode. After 1 hour, plasma exchange was performed, and hemofiltration was initiated. Heart function parameters and arterial blood gasses were obtained hourly. RESULTS: All hearts (n = 5) were viable at the 24-hour mark. The average left ventricular systolic pressure at the beginning of the prep was 36.6 ± 7.9 mm Hg compared with 27 ± 5.5 mm Hg at the end. Coronary resistance at the beginning of prep was 0.79 ± 0.10 mm Hg/L/min and 0.93 ± 0.28 mm Hg/L/min at the end. Glucose levels averaged 223 ± 13.9 mg/dL, and the lactate average at the termination of prep was 2.6 ± 0.3 mmol/L. CONCLUSIONS: We successfully perfused adult porcine hearts at normothermic temperatures for 24 hours with results comparable to our pediatric porcine heart model. The next step in our research is NEVHP evaluation in a working mode using left atrial perfusion.

Prolonged (24-hour) Normothermic ex vivo Heart Perfusion Facilitated by Perfusate Hemofiltration.

Currently, normothermic ex vivo heart perfusion (NEVHP) is limited to 6-12 hours. NEVHP for 24 hours or more would allow organ treatment, assessment of organ function, and near-perfect recipient matching. We present a model of NEVHP using continuous hemofiltration (HFn) with sustained myocardial viability up to 24 hours. Twenty hearts from 6-10 kg piglets were procured and maintained on our NEVHP circuit. HFn hearts (n = 10) underwent NEVHP with HFn, whereas controls (n = 10) used NEVHP alone. All HFn vs. four controls were viable at 24 h (p = 0.004). At end perfusion, HFn hearts had higher left ventricular systolic pressure (51.5 ± 6.8 mm Hg, 38.3 ± 5.2 mm Hg, p = 0.05), lower coronary resistance (0.83 ± 0.11 mm Hg/mL/min, 1.18 ± 0.21mmHg/mL/min, p < 0.05), and lower serum lactate levels (2.9 ± 0.4 mmol/L, 4.1 ± 0.6 mmol/L, p < 0.0001) when compared to control hearts. HFn hearts also had less extensive myocardial damage and significantly less edema than control hearts with lower weight gain and wet-dry ratios. Using our circuit, NEVHP for 24 hours is possible with HFn and allows for preservation of myocardial function, improved tissue viability, decreased tissue edema, and less myocardial injury.

Novel Left Atrial Cannulation Technique for Attachment of a Pumpless Artificial Lung.

A pumpless artificial lung has the potential to provide a bridge to recovery or transplantation in children with respiratory failure. Pulmonary artery inflow and left atrial outflow are necessary for low-gradient, pumpless systems; however, long-term cannulation of the fragile left atrium remains problematic. In this technique, the left atrium and pulmonary artery were exposed through a left anterior thoracotomy. Inflow to the artificial lung was created using an end-to-side anastomosis with the pulmonary artery. Device outflow was established through the left atrium. A single-stage venous cannula was passed through a free PTFE graft. Using polypropylene with pledgets, two concentric purse-string sutures were placed in the dome of the left atrium. The venous cannula was inserted. The graft was slid down the cannula and circumferentially secured to the adjacent left atrial tissue and pledgets. The other end of the graft was secured to the cannula with silk ties. The procedure was successful in 10 sheep. Initial device blood flow was 969 ± 222 ml/min, which remained stable for up to 7 days with no anastomotic complications. This is an effective method of achieving secure, long-term left atrial cannulation without cardiopulmonary bypass for use in a low-resistance, pumpless artificial lung. And, most importantly, improves the ease and safety of cannula replacement and final decannulation when AL support is no longer required.

Clinical xenotransplantation seems close: Ethical issues persist.

Scientific barriers that have prevented successful xenotransplantation are being breached, yet many ethical issues remain. Some are broad issues that accompany the adoption of novel and expensive technologies, and some are unique to xenotransplantation. Major ethical questions include areas such as: viral transmission; zoonoses and lifetime surveillance; interfering with nature; efficacy, access, and expense; treatment of animals; regulation and oversight.

Echocardiography in Pandemic: Front-Line Perspective, Expanding Role of Ultrasound, and Ethics of Resource Allocation.

The grave clinical context of the coronavirus disease 2019 (COVID-19) pandemic must be understood. Italy is immersed in the COVID-19 pandemic. Most of the world will soon follow. The United States currently has the most documented cases of COVID-19 of any nation. Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)-associated acute cardiomyopathy is common in critical care patients and is associated with a high mortality rate. Patients with COVID-19 frequently require mechanical support for adequate oxygenation. A severe shortfall of ventilators is predicted. Of equal concern is the projected shortage of trained professionals required to care for patients on mechanical ventilation. Ultrasonography is proving to be a valuable tool for identifying the pulmonary manifestations and progression of COVID-19. Lung ultrasound also facilitates successful weaning from mechanical ventilation. Ultrasonography of the lung, pleura, and diaphragm are easily mastered by experienced echocardiographers. Echocardiography has an established role for optimal fluid management and recognition of cardiac disease, including SARS-CoV-2-associated acute cardiomyopathy. Cardiologists, anesthesiologists, sonographers, and all providers should be prepared to commit their full spectrum of skills to mitigate the consequences of the pandemic. We should also be prepared to collaborate and cross-train to expand professional services as necessary. During a declared health care crisis, providers must be familiar with the ethical principles, organizational structure, practical application, and gravity of limited resource allocation.