Faculty Bibliography

BACKGROUND:Studies have not explored consciousness during deep hypothermic circulatory arrest (DHCA). However, as studies in cardiac arrest have identified a spectrum of consciousness, we sought to establish the feasibility of studying consciousness during DHCA. METHODS:This was a prospective study across 10 hospitals with 36 DHCA patients undergoing thoracic aortic aneurysm repair or pulmonary endarterectomy. A tablet computer delivered audiovisual stimuli (images and names of three fruits) using headphones during each procedure as a potential test of implicit learning and explicit recall. We also established electroencephalography (EEG) and near-infrared spectroscopy (NIRS) to measure electrocortical markers of consciousness and cerebral oxygenation. Post-procedure interviews were carried out to test patients' ability to recall the audiovisual stimuli as well other explicit memories. PRIMARY OUTCOMES/METHODS:1) Feasibility of establishing tests of explicit recall and implicit learning, 2) Electroencephalography testing during DHCA. SECONDARY OUTCOMES/RESULTS:1) Signs of explicit recall of memories or implicit learning, and 2) identification of electrocortical biomarkers of consciousness during DHCA. RESULTS:Overall, 29/36 (81%) had the tablet set up. All 36 had NIRS and EEG set up, but 9 (25%) had useable EEG data, and 23 (66%) NIRS data. Delta EEG waves were observed during circulatory arrest in 3/9 (33%) patients, while 1/9 (11%) had theta waves just prior to circulatory arrest. All others showed isoelectric pattern. 35/36 (97%) agreed to follow up interviews. None had explicit recall of the names of the three fruits, but 3/36 (9%) correctly guessed them as a potential sign of implicit learning and 3 (9%) recalled other memories including events around the procedure and themes consistent with a recalled experience of death. CONCLUSIONS:A spectrum of consciousness and awareness, including signs of implicit learning and electrocortical biomarkers of consciousness may be present during DHCA, despite absence of visible signs of consciousness. This can be further used to help explain the negative psychological outcomes that cardiac arrest survivors face.

BACKGROUND/UNASSIGNED:Donation after circulatory death (DCD) with cardiopulmonary bypass for thoracoabdominal normothermic regional perfusion (TA-NRP) has led to increased use of donor hearts. Rejection rates and long-term survival outcomes are not known. METHODS/UNASSIGNED:A single-center retrospective cohort review of patients who underwent DCD heart transplantation from January 2020 to December 2023 was performed. Donor and recipient characteristics, operative characteristics, and posttransplantation outcomes were analyzed. Subgroup analysis comparing co-localized vs distant donors and recipients was performed. The primary end point was 1-year survival. Secondary end points included incidences of primary graft dysfunction (PGD), cardiac allograft vasculopathy (CAV), rejection rate, and overall mortality. Our TA-NRP protocol has remained the same, consisting of sternotomy, ligation of aortic arch vessels, establishment of cardiopulmonary bypass, reintubation, resuscitation of the heart, and cold static storage during transport. RESULTS/UNASSIGNED:< .005) ischemia times, without any other differences. CONCLUSIONS/UNASSIGNED:Outcomes after DCD heart transplantation using TA-NRP remain encouraging with acceptable rates of rejection, PGD, CAV, and survival at 1 year.

OBJECTIVE/UNASSIGNED:Anticoagulation monitoring in patients supported on extracorporeal membrane oxygenation is challenging given the risks of both bleeding and thrombotic complications. Based on our early clinical experience, we revised our heparin protocol by reducing our target anti-factor Xa assay from 0.3 to 0.7 U/mL to 0.15 to 0.5 U/mL, while instituting a partial thromboplastin time cutoff of 70 seconds. We evaluated the impact of this change on bleeding/thrombotic complications. METHODS/UNASSIGNED:A single-center retrospective study of adult patients on extracorporeal membrane oxygenation support was conducted from January 2015 to August 2022. Patients were stratified into groups based on protocol revision: Pre-Revision (2015-2018) or Post-Revision (2019-2022). Our primary end point was the incidence of bleeding/thrombotic complications. Time in therapeutic range was calculated to determine protocol adherence. Poisson regression was performed to correlate time in therapeutic range with the likelihood of complication. RESULTS/UNASSIGNED:008). CONCLUSIONS/UNASSIGNED:A modified heparin monitoring protocol defined by a lower therapeutic anti-factor Xa assay target and a set partial thromboplastin time cutoff correlated with decreases in bleeding/thrombotic complications in patients on extracorporeal membrane oxygenation.

Perspective Statement: Beyond the Society of Thoracic Surgery's (STS) quality metrics, many other operative measures, such as completeness of revascularization, and patient care measures add quality and value for patients undergoing coronary artery bypass surgery; and Enhanced Recovery after Surgery (ERAS) protocols have improved patient experience and recovery, leading to better outcomes and significant healthcare savings.

The physiologic impact of pulsatile flow (PF) on end-organ perfusion during cardiopulmonary bypass (CPB) is controversial. Using an intra-aortic balloon pump (IABP) to maintain PF during CPB for patients undergoing heart transplantation (HT) may impact end-organ perfusion, with implications for postoperative outcomes. A single-center retrospective study of 76 patients bridged to HT with IABP was conducted between January 2018 and December 2022. Beginning in May 2022, patients received IABP-generated PF during CPB at an internal rate of 80 beats/minute. Fifty-eight patients underwent HT with the IABP turned off (IABP-Off), whereas 18 patients underwent HT with IABP-generated PF (IABP-On). The unmatched IABP-On group experienced shorter organ ischemia times (180 vs. 203 minutes, p = 0.015) and CPB times (104 vs. 116 minutes, p = 0.022). The cohort was propensity matched according to age, organ ischemia time, and CPB time. Elevations in postoperative lactates in the immediate (2.8 vs. 1.5, p = 0.062) and 24 hour (4.7 vs. 2.4, p = 0.084) postoperative periods trended toward significance in the matched IABP-Off group. There was no difference in postoperative vasoactive inotropic score (VIS), postoperative creatinine, or length of stay. This limited preliminary data suggest that maintaining counterpulsation to generate PF during CPB may improve end-organ perfusion in this patient population as suggested by lower postoperative lactate levels.

Since the development of the first heart allocation system in 1988 to the most recent heart allocation system in 2018, the road to heart transplantation has continued to evolve. Policies were shaped with advances in temporary and durable left ventricular assist devices as well as prioritization of patients based on degree of illness. Herein, we review the changes in the heart allocation system over the past several decades and the impact of practice patterns across the United States.

BACKGROUND:Recent studies suggest the transplantation of Hepatitis C (HCV) hearts from viremic donors is associated with comparable 1 year survival to nonviremic donors. Though HCV viremia is a known risk factor for accelerated atherosclerosis, data on cardiac allograft vasculopathy (CAV) outcomes are limited. We compared the incidence of CAV in heart transplant recipients from HCV viremic donors (nucleic acid amplification test positive; NAT+) compared to non-HCV infected donors (NAT-). METHODS:We retrospectively reviewed annual coronary angiograms with intravascular ultrasound from April 2017 to August 2020 at two large cardiac transplant centers. CAV was graded according to ISHLT guidelines. Maximal intimal thickness (MIT) ≥ 0.5 mm was considered significant for subclinical disease. RESULTS:Among 270 heart transplant recipients (mean age 54; 77% male), 62 patients were transplanted from NAT+ donors. CAV ≥ grade 1 was present in 8.8% of the NAT+ versus 16.8% of the NAT- group at 1 year, 20% versus 28.8% at 2 years, and 33.3% versus 41.5% at 3 years. After adjusting for donor age, donor smoking history, recipient BMI, recipient, hypertension, and recipient diabetes, NAT+ status did not confer increased risk of CAV (HR.80; 95% CI.45-1.40, p = 0.43) or subclinical IVUS disease (HR.87; 95% CI.58-1.30, p = 0.49). Additionally, there was no difference in the presence of rapidly progressive lesions on IVUS. CONCLUSION/CONCLUSIONS:Our data show that NAT+ donors conferred no increased risk for early CAV or subclinical IVUS disease following transplantation in a cohort of heart transplant patients who were treated for HCV, suggesting the short-term safety of this strategy to maximize the pool of available donor hearts.

BACKGROUND:Drug overdose (DO) deaths rose to unprecedented levels during the coronavirus disease 2019 (COVID-19) pandemic. This study examines the impact of COVID-19 on the availability of cardiac allografts from DO donors and the implications of DO donor use on recipient survival. METHODS:Heart transplants reported to the United Network for Organ Sharing from January 2017 to November 2019 ("pre-COVID") and from March 2020 to June 2021 ("COVID pandemic") were analyzed with respect to DO donor status. Outcomes were analyzed using Kaplan-Meier survival and Cox regression to identify predictors of survival. Characteristics of discarded cardiac allografts were also compared by DO donor status. RESULTS:During the COVID-19 pandemic, 27.2% of cardiac allografts were from DO donors vs 20.5% pre-COVID, a 32.7% increase (p < 0.001). During the pandemic, DO donors were younger (84.7% vs 76.3% <40 years, p < 0.001), had higher cigarette use (16.1% vs 10.8%, p < 0.001), higher cocaine use (47.4% vs 19.7%, p < 0.001), and higher incidence of hepatitis C antibodies (26.8% vs 6.1%, p < 0.001) and RNA positivity (16.2% vs 4.2%, p < 0.001). While DO donors were less likely to require inotropic support (30.8% vs 35.4%, p = 0.008), they were more likely to have received cardiopulmonary resuscitation (95.3% vs 43.2%, p < 0.001). Recipient survival was equivalent using Kaplan-Meier analysis (log-rank, p = 0.33) and survival probability at 36 months was 85.6% (n at risk = 398) for DO donors vs 83.5% (n at risk = 1,633) for all other donors. Cox regression demonstrated that DO donor status did not predict mortality (hazard ratio 1.05; 95% confidence interval 0.90-1.23, p = 0.53). CONCLUSIONS:During the COVID-19 pandemic, there was a 32.7% increase in heart transplants utilizing DO donor hearts, and DO became the most common mechanism of death for donors. The use of DO donor hearts did not have an impact on short-term recipient survival.