Successful Resuscitation of Porcine Hearts After 12 and 24 h of Static Cold Storage With Normothermic Ex Situ Perfusion.

Background: Heart transplantation is always an emergency because the transplant needs to occur within 6 h after procurement to prevent primary graft dysfunction. Static cold storage (SCS) is the gold-standard preservation method. This study describes the outcomes of hearts preserved after prolonged SCS (12 and 24 h); those are then resuscitated with a novel normothermic ex situ heart perfusion (NEHP) system. Methods: Anesthetized piglets (n = 10) were used as heart donors. Hearts were procured and stored at 5 °C CoStorSol following standard SCS protocols. Two groups were studied: SCS-12 h and SCS-24 h. After SCS, 8 h of NEHP (37 °C blood-based perfusate) was performed at 0.7-1.0 mL/min/g of cardiac tissue. NEHP parameters were monitored continuously. Results were corroborated with 3 additional hearts transplanted orthotopically in healthy recipients (n = 3) after SCS (24 h) + NEHP (5 h). Recipients were observed for 90 min after weaning off cardiopulmonary bypass support. Results: All hearts (after 12 and 24 h of SCS) regained normal function and metabolism within 10 min and retained it throughout 8 h of NEHP. No differences were observed in NEHP parameters and histopathology between groups. Three hearts were successfully transplanted after a total ~30 h of preservation (24 h of SCS + 5 h of NEHP + 1 h of second cold ischemia time). The 3 recipients were weaned off cardiopulmonary bypass with mild vasopressor support. Conclusions: NEHP has the potential to routinely resuscitate porcine hearts that have undergone SCS for up to 24 h, restoring them to viable function. By objectively assessing heart function before transplant, NEHP may enhance the success rate of transplants. If these resuscitated hearts can be successfully transplanted, it would support the effectiveness of NEHP in ensuring heart viability.

Safety Window for Effective Lesion Crossing in Patients With Chronic Thromboembolic Pulmonary Hypertension.

Background: Balloon pulmonary angioplasty for chronic thromboembolic pulmonary hypertension (CTEPH) is limited by a lack of safe and effective tools for crossing these lesions. We aim to identify a safety window for an intraluminal crossing device in this vascular bed by studying the piercing properties of pulmonary arterial vessel walls and intraluminal CTEPH lesion specimens. As a secondary objective, we also describe the histopathologic features of CTEPH lesions. Methods: Specimens were procured from 9 patients undergoing pulmonary endarterectomy. The specimens were subsampled and identified grossly as arterial wall or intraluminal CTEPH lesions. The force needed for tissue penetration was measured using a 0.38-mm (0.015-in) diameter probe in an ex vivo experimental model developed in our lab. Concurrent histology was also performed. Results: The mean force needed to penetrate the arterial wall and intraluminal CTEPH lesions was 1.75 ± 0.10 N (n = 121) and 0.30 ± 0.04 N (n = 56), respectively (P < .001). Histology confirmed the presence of intimal hyperplasia with calcium and hemosiderin deposition in the arterial wall as well as an old, organized thrombus in the lumen. Conclusions: The pulmonary arterial wall is friable and prone to perforation during instrumentation with workhorse coronary guide wires. However, the results of this study demonstrate that a much lower force is needed for the 0.38-mm (0.015-in) probe to penetrate an intraluminal CTEPH lesion compared to pulmonary arterial intima. This finding suggests the existence of a safety window for lesion-crossing devices, enabling effective balloon pulmonary angioplasty.

Practice Patterns in Sternal Closure and Evaluation of Adoption of a Novel Sternal Closure Device.

OBJECTIVE: The technique for sternal closure has remained largely unchanged owing to the efficacy, simplicity, and low cost of stainless-steel sternal wires. Despite their ubiquity, several other closure devices designed to address the complications associated with sternal wires such as sternal bleeding and dehiscence have become popular. We have developed a novel sternal closure device that reduces sternal bleeding and dehiscence. This study quantifies the use of currently available sternal closure devices and determines predicted uptake of the novel device. METHODS: An electronic survey, designed to determine practice patterns for sternal closure, was distributed to 70 US cardiac surgeons. The survey included a discrete choice section in which surgeons evaluated relative value of device attributes including cost, ease of emergent sternal reentry, and dehiscence risk. RESULTS: There were 70 surgeons from 30 states who completed the survey. The most frequent means of sternal closure was straight sternal wires (35.8%), followed by straight sternal wires plus figure-of-8 sternal wires (18.1%), double wires (10.9%), plates (10.2%), and other (25%). The relative utilization shifted from sternal wires to sternal plates as the risk for dehiscence increased. The adoption of the novel closure device was estimated at 34.6%. CONCLUSIONS: The standard stainless-steel sternal wire remains the most common means of sternal reapproximation, but its utilization is lower in patients at high risk for sternal dehiscence. Based on this survey, there is acceptance in the community for a novel sternal closure device designed to address the limitations of traditional sternal closure methods.

2022: Perioperative and critical care year in review for the cardiothoracic surgery team.

This year, we have again assembled an expert opinion on several key topics that pertain to the perioperative and critical care management of the cardiac surgery patient and for patients requiring extracorporeal membrane oxygenation. Approximately 1 in 3 patients undergoing cardiac surgery have diabetes mellitus; contemporary glycemic control management of these patients to minimize perioperative complications are reviewed. Goal directed fluid therapy remains an area on interest and controversy; the use of albumin as a resuscitation fluid and recent clinical trial data is reviewed. Delirium is characterized as an acute confusional state occurring in 20-25% of patients after cardiac surgery. Insights on integrating the whole interdisciplinary team, including the family, with the DELirium Team Approach (DELTA) program are discussed. Optimal management for refractory hypoxemia with venovenous extracorporeal membrane oxygenation (VV-ECMO) and the role of prone positioning remain a question. Data supporting this technique during VV-ECMO is reviewed-lastly, the contemporary management and supporting evidence for refractory postoperative vasoplegic shock after cardiopulmonary bypass is provided.

Mechanical Analysis of a Novel Sternal Closure System in Static Tensile Loading.

The most common means of sternal closure after sternotomy is stainless steel wire cerclage. These wires, while inexpensive and simple in design, are known to be associated with low strength and sternal dehiscence. In this biomechanical analysis, we compare single sternal wires, double sternal wires, and a novel sternal closure device we have designed to mitigate sternal dehiscence. The device uses polymer grommets at the sternal interfaces to distribute load over a large surface area of bone. Samples of each closure device were installed in a bone model and distracted at a rate of 10 mm/min while tensile forces were continuously measured and compared. Single wires generated the lowest stiffness and strength values, followed by the double wires. The novel device demonstrated significantly higher stiffness and strength at all displacements compared with the single and double wires. Clinical use of this device may result in meaningful reduction in complications associated with the use of standard sternal wires such as sternal separation and fracture.

Determinants of survival following heart transplantation in adults with congenital heart disease.

BACKGROUND: Adult patients surviving with congenital heart disease (ACHD) is growing. We examine the factors associated with heart transplant outcomes in this challenging population with complex anatomy requiring redo-surgeries. METHODS: We reviewed the United Network for Organ Sharing-Standard Transplant Analysis and Research database and analyzed 35,952 heart transplants from January 1st, 2000, to September 30th, 2018. We compared transplant characteristics for ischemic cardiomyopathy (ICM) (n = 14,236), nonischemic cardiomyopathy (NICM) (n = 20,676), and ACHD (n = 1040). Mean follow-up was 6.20 ± 4.84 years. Kaplan-Meier survival curves and Cox-proportional hazards analysis were used to analyze survival data. RESULTS: Multivariable analysis confirmed that ACHD was associated greater in-hospital death compared to ICM (HR = 0.54, P < 0.001) and NICM (HR = 0.46, P < 0.001). Notable factors associated with increased mortality were history of cerebrovascular disease (HR = 1.11, P = 0.026), prior history of malignancy (HR = 1.12, P = 0.006), pre-transplant biventricular support (HR = 1.12, P = 0.069), postoperative stroke (HR = 1.47, P < 0.001) and postoperative dialysis (HR = 1.71, P < 0.001). ACHD transplants had a longer donor heart ischemic time (P < 0.001) and trend towards more deaths from primary graft dysfunction (P = 0.07). In-hospital deaths were more likely with ACHD and use of mechanical support such as use of right ventricular assist device (HR = 2.20, P = 0.049), biventricular support (HR = 1.62, P < 0.001) and extracorporeal membrane oxygenation (HR = 2.36, P < 0.001). Conditional survival after censoring hospital deaths was significantly higher in ACHD (P < 0.001). CONCLUSION: Heart transplant in ACHD is associated with a higher post-operative mortality given anatomical complexity but a better long-term conditional survival. Normothermic donor heart perfusion may improve outcomes in the ACHD population by reducing the impact of longer ischemic times.

Gastrointestinal bleeding following Heartmate 3 left ventricular assist device implantation: The Michigan Bleeding Risk Model.

BACKGROUND: Gastrointestinal bleeding (GIB) results in frequent hospitalizations and impairs quality of life in durable left ventricular assist device (LVAD) recipients. Anticipation of these events before implantation could have important implications for patient selection and management. METHODS: The study population included all adult HeartMate 3 (HM3) primary LVAD recipients enrolled in the STS Intermacs registry from January 2017 to December 2020. Using multivariable modeling methodologies, we investigated the relationships between preimplantation characteristics and postimplant bleeding, bleeding and death, and additional bleeding episodes on subsequent bleeding episodes and created a risk score to predict the likelihood of post-LVAD GIB based solely on preimplantation factors. RESULTS: Of 6,425 patients who received an HM3 LVAD, 1,010 (15.7%) patients experienced GIB. Thirteen preimplantation factors were independent predictors of post-LVAD GIB. A risk score was created from these factors and calculated for each patient. By 3 years postimplant, GIB occurred in 11%, 26%, and 43% of low-, medium- and high-risk patients, respectively. Experiencing 1 post-LVAD GIB event was associated with an increased risk for further GIB events, with 33.9% of patients experiencing at least 1 recurrence. While post-LVAD GIB was associated with mortality, there was no relationship between number of GIB events and death. CONCLUSIONS: The Michigan Bleeding Risk Model is a simple tool, which facilitates the prediction of post-LVAD GIB in HM3 recipients using 13 preimplant variables. The implementation of this tool may help in the risk stratification process and may have therapeutic and clinical implications in HM3 LVAD recipients.

Modeling and estimating a threshold effect: An application to improving cardiac surgery practices.

Estimating thresholds when a threshold effect exists has important applications in biomedical research. However, models/methods commonly used in the biomedical literature may lead to a biased estimate. For patients undergoing coronary artery bypass grafting (CABG), it is thought that exposure to low oxygen delivery (DO2) contributes to an increased risk of avoidable acute kidney injury. This research is motivated by estimating the threshold of nadir DO2 for CABG patients to help develop an evidence-based guideline for improving cardiac surgery practices. We review several models (sudden-jump model, broken-stick model, and the constrained broken-stick model) that can be adopted to estimate the threshold and discuss modeling assumptions, scientific plausibility, and implications in estimating the threshold. Under each model, various estimation methods are studied and compared. In particular, under a constrained broken-stick model, a modified two-step Newton-Raphson algorithm is introduced. Through comprehensive simulation studies and an application to data on CABG patients from the University of Michigan, we show that the constrained broken-stick model is flexible, more robust, and able to incorporate scientific knowledge to improve efficiency. The two-step Newton-Raphson algorithm has good computational performances relative to existing methods.

Cannulation strategies for extracorporeal membrane oxygenation.

Extracorporeal membrane oxygenation (ECMO) is a type of extracorporeal life support (ECLS) in which the function of the heart and/or lungs is partially or completely replaced by a portable system that provides prolonged support to critically ill patients with respiratory or cardiac failure. There are two major variants of ECMO: veno-venous (VV) ECMO and veno-arterial (VA) ECMO. VV ECMO replaces the function of the lung in which it uses a cannula to remove venous blood and oxygenates it using the extracorporeal system, and returns the blood to the right atrium to be pumped to the body. VA ECMO is slightly different in that it replaces the function of the heart and lungs by returning oxygenated blood to the aorta. As a therapy for respiratory failure, ECMO minimizes hypoxia, diminishes lung stress and strain, and allows lung protective mechanical ventilation. As a support for acute and terminal heart failure, ECMO reduces preload, increases aortic flow, and allows for end-organ perfusion. Due to its physiological support and advantages, it is used for a variety of chronic and acute support purposes such as bridge therapy for heart/lung transplant, durable ventricular assist devices, and intermediate-term mechanical support postoperatively. Our review gives a broad overview of the two main types of ECMO strategies and their clinical indications, cannulation strategies, unique clinical utility, and their limitations.

Open Surgical Treatment of Acute and Chronic Pulmonary Embolism.

Acute pulmonary embolism (PE) is a common cause of death and morbidity in the United States and the prevalence of chronic thromboembolic pulmonary hypertension (CTEPH), a possible sequela of PE, has increased during the past decade. The mainstay treatment of CTEPH is open pulmonary endarterectomy, a procedure performed under hypothermic circulatory arrest, which entails endarterectomy of the branch, segmental and subsegmental pulmonary arteries. Acute PE may be similarly be treated with an open embolectomy in certain select circumstances.

Periprocedural Complications With Balloon Pulmonary Angioplasty: Analysis of Global Studies.

BACKGROUND: Balloon pulmonary angioplasty (BPA) was introduced as a treatment modality for patients with inoperable, medically refractory chronic thromboembolic pulmonary hypertension decades ago; however, reports of high rates of pulmonary vascular injury have led to considerable refinement in procedural technique. OBJECTIVES: The authors sought to better understand the evolution of BPA procedure-related complications over time. METHODS: The authors conducted a systematic review of original articles published by pulmonary hypertension centers globally and performed a pooled cohort analysis of procedure-related outcomes with BPA. RESULTS: This systematic review identified 26 published articles from 18 countries worldwide from 2013 to 2022. A total of 1,714 patients underwent 7,561 total BPA procedures with an average follow up of 7.3 months. From the first period (2013-2017) to the second period (2018-2022), the cumulative incidence of hemoptysis/vascular injury decreased from 14.1% (474/3,351) to 7.7% (233/3,029) (P < 0.01); lung injury/reperfusion edema decreased from 11.3% (377/3,351) to 1.4% (57/3,943) (P < 0.01); invasive mechanical ventilation decreased from 0.7% (23/3,195) to 0.1% (4/3,062) (P < 0.01); and mortality decreased from 2.0% (13/636) to 0.8% (8/1,071) (P < 0.01). CONCLUSIONS: Procedure-related complications with BPA, including hemoptysis/vascular injury, lung injury/reperfusion edema, mechanical ventilation, and death, were less common in the second period (2018-2022), compared with first period (2013-2017), likely from refinement in patient and lesion selection and procedural technique over time.

Foundations of a life support equipment exchange platform.

Background: The Extracorporeal Life Support Organization Supplies Platform (https://Supplies.ELSO.org) was created out of Extracorporeal Membrane Oxygenation (ECMO) disposable product shortage prior to and during the Coronavirus Disease 2019 (COVID-19) pandemic. This novel Platform supports Centers in obtaining disposables from other Centers when alternative avenues are exhausted. Methods: Driven by the opportunity for increased patient care by using the product availability of the 962 ELSO centers worldwide was the motivation to form an efficient online supply sharing Platform. The pandemic created by COVID-19 became a catalyst to further recognize the magnitude of the supply disruption on a global scale, impacting allocations and guidelines for institutions, practice, and patient care. Conclusions: Records kept on the Platform website are helpful to the industry by providing insights into where difficulties exist in the supply chain for needed equipment. Yet, the common thread is awareness, of how critical situations can stretch resources and challenge our resolve for the best patient care. ELSO is proud to support member centers in these situations, by providing a means of attaining needed ECMO life support products to cover supply shortages.

ECMO During COVID-19: A Society of Thoracic Surgeons/Extracorporeal Life Support Organization Survey.

Background: The Society of Thoracic Surgeons Workforce on Critical Care and the Extracorporeal Life Support Organization sought to identify how the coronavirus disease 2019 (COVID-19) pandemic has changed the practice of venoarterial (VA) and venovenous (VV) extracorporeal membrane oxygenation (ECMO) programs across North America. Methods: A 26-question survey covering 6 categories (ECMO initiation, cannulation, management, anticoagulation, triage/protocols, and credentialing) was emailed to 276 North American Extracorporeal Life Support Organization centers. ECMO practices before and during the COVID-19 pandemic were compared. Results: Responses were received from 93 (34%) programs. The percentage of high-volume (>20 cases per year) VV ECMO programs increased during the pandemic from 29% to 41% (P < .001), as did institutions requiring multiple clinicians for determining initiation of ECMO (VV ECMO, 25% to 43% [P = .001]; VA ECMO, 20% to 32% [P = .012]). During the pandemic, more institutions developed their own protocols for resource allocation (23% before to 51%; P < .001), and more programs created sharing arrangements to triage patients and equipment with other centers (31% to 57%; P < .001). Direct thrombin inhibitor use increased for both VA ECMO (13% to 18%; P = .025) and VV ECMO (12% to 24%; P = .005). Although cardiothoracic surgeons remained the primary cannulating proceduralists, VV ECMO cannulations performed by pulmonary and critical care physicians increased (13% to 17%; P = .046). Conclusions: The Society of Thoracic Surgeons/Extracorporeal Life Support Organization collaborative survey indicated that the pandemic has affected ECMO practice. Further research on these ECMO strategies and lessons learned during the COVID-19 pandemic may be useful in future global situations.

Contemporary Management of Ischemic Mitral Regurgitation at Coronary Artery Bypass Grafting.

BACKGROUND: Recent guidelines for the treatment of moderate or severe ischemic mitral regurgitation (IMR) in patients undergoing coronary artery bypass grafting (CABG) have changed. This study assessed the real-world impact of changing guidelines on the management of IMR during CABG over time. We hypothesized that the utilization of mitral valve repair for IMR would decrease over time, whereas mitral valve replacement for severe IMR would increase. METHODS: Patients undergoing CABG in a statewide collaborative database (2011-2020) were stratified by severity of IMR. Trends in mitral valve repair or replacement were evaluated. To account for differences of the patients, propensity score-matched analyses were used to compare patients with and without mitral intervention. RESULTS: A total of 11,676 patients met inclusion criteria, including 1355 (11.6%) with moderate IMR and 390 (3.3%) with severe IMR. The proportion of patients undergoing mitral intervention for moderate IMR decreased over time (2011, 17.7%; 2020, 7.5%; Ptrend = .001), whereas mitral replacement for severe IMR remained stable (2011, 11.1%; 2020, 13.3%; Ptrend = .14). Major morbidity was higher for patients with moderate IMR who underwent mitral intervention (29.1% vs 19.9%; P = .005). In a propensity analysis of 249 well-matched pairs, there was no difference in major morbidity (29.3% with mitral intervention vs 23.7% without; P = .16) or operative mortality (1.2% vs 2.4%; P = .5). CONCLUSIONS: Consistent with recent guideline updates, patients with moderate IMR were less likely to undergo mitral repair. However, the rate of replacement for severe IMR did not change. Mitral intervention during CABG did not increase operative mortality or morbidity.