Faculty Bibliography

BACKGROUND:Heart utilization from donation after circulatory death (DCD) donors remains highly variable across the United States, potentially resulting in missed transplantation opportunities. This study aimed to quantify the frequency of clinically viable, non-utilized DCD hearts and identify usage barriers. METHODS:We conducted a retrospective, national registry analysis of donors ≤55 years old who donated ≥1 organ, focusing primarily on DCDs. Donor characteristics, particularly age, warm ischemic time (WIT), and EF, as well as reasons for non-recovery and offer refusal, were analyzed. SRTR's heart yield model was employed to identify non-utilized DCD hearts clinically comparable to transplanted DCD hearts. RESULTS:In 2023, 613 DCD hearts were transplanted, accounting for 13.5% of all heart transplants. Only 15.5% of DCD hearts from donors ≤55 years old were utilized. Marked variation in risk-adjusted DCD heart yield was observed between states, OPOs, and Regions. Donors of transplanted DCD hearts had a median age of 32, WIT 24 minutes, and EF 63%. The yield model identified between 701-1,243 non-utilized DCD hearts with characteristics comparable to transplanted cases. Concerns about delayed progression to circulatory arrest after life support withdrawal was a key reason for non-utilization. CONCLUSIONS:Despite wider acceptance of DCD heart transplantation, an increasing proportion of DCD hearts remain unused despite favorable characteristics. Concerns related to delayed progression to circulatory arrest are a significant barrier to heart utilization. Addressing geographic variability and improving predictive models for donor viability could double DCD heart utilization and expand heart transplantation volume by approximately 700-1,200 (15-27%) annually.

PURPOSE OF REVIEW/OBJECTIVE:Hypertension is one of the most common comorbidities affecting patients after solid organ transplantation. Here we review the mechanisms leading to hypertension, along with common practices in terms of medical management. Glucagon-like peptide-1 receptor (GLP-1R) agonists, baroreflex therapy, and renal denervation are common interventions utilized prior to heart transplant. Special considerations for their management throughout the perioperative and postoperative period are covered here. RECENT FINDINGS/RESULTS:Most common medical management includes utilization of calcium channel blockers, followed by angiotensin-converting enzyme inhibitors and angiotensin receptor blockers. GLP-1R agonists have shown significant benefit in recent cardiovascular outcome trials. Preoperative management centers around risks associated with slowed gastric emptying, while reinitiation after heart transplant must take into consideration initiation and tolerance of immunosuppressive therapies. Baroreflex activation therapy has been approved for therapy of heart failure, with many patients proceeding to heart transplant. The device is frequently deactivated after transplantation, with little published experience regarding reinitiation of therapy after heart transplant. There is renewed interest in renal denervation as a treatment for refractory hypertension. The incidence of hypertension after heart transplant in those patients that have undergone previous renal denervation remains unknown, however there is limited experience with its use after renal transplant. SUMMARY/CONCLUSIONS:Further studies are required to elucidate optimal medical management of hypertension following heart transplantation. GLP-1R agonists, baroreflex activation therapy, and renal denervation are emerging therapies prior to transplant that require further investigation.

Guideline-directed medical therapy is the backbone of heart failure treatment. However, patients continue to experience heart failure symptoms, impaired quality of life, and reduced functional status despite guideline-directed medical and device treatment. There is a void in treatment alternatives between guideline-directed therapy and the advanced heart failure surgical options of heart transplant (HT) and left ventricular assist device (LVAD). Cardiac contractility modulation and baroreceptor activation therapies are shown to improve heart failure symptoms, quality of life, and exertional capacity in select patients and complement our current treatment paradigm. The purpose of this paper is to review these novel Food and Drug Administration (FDA)-approved heart failure therapies and facilitate the identification of appropriate candidates.

CLINICAL CONDITION/UNASSIGNED:The authors present the case of a young man who presented with cardiogenic shock requiring venoarterial extracorporeal membrane oxygenation and microaxial flow pump complicated by acute spinal cord infarction (SCI) leading to bilateral lower extremity paraplegia. KEY QUESTIONS/UNASSIGNED:The key questions included the following: 1) What is the incidence and pathophysiology for SCI with mechanical circulatory support (MCS)?; 2) Which configurations of MCS carry a greater risk of SCI? How do we approach MCS escalation, recognizing that with each device we carry additive risk of complications?; 3) What data guide anticoagulation strategies for MCS?; and 4) What strategies can we implement to support patients who have suffered SCI from MCS? OUTCOME/RESULTS:Our patient was transitioned to a right ventricular assist device with Impella 5.5 as a bridge to therapy, and underwent cardiac transplantation 4 weeks after presentation with ongoing inpatient rehabilitation. TAKE-HOME MESSAGES/CONCLUSIONS:Contemporary MCS carries a small but significant risk of SCI which is often irreversible. More data are required to guide anticoagulation strategies for MCS and mitigate risk.

Heart transplantation remains a critical therapy for patients with end-stage heart failure, offering incremental survival and improved quality of life. One of the key components behind the success of heart transplantation is the condition and preservation of the donor heart. In this review, we provide a comprehensive overview of ischemic reperfusion injury, risk factors associated with primary graft dysfunction, current use of various preservation solutions for organ procurement and recent advancements in donor heart procurement technologies. This State-of-the-Art review will explore factors associated with bringing the "ideal" donor heart to the operating room in the contemporary era.

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.

Cardiogenic shock (CS) is a complex, multisystem disorder precipitated by hypoperfusion from cardiac dysfunction. Our current approach to defining and treating CS encompasses all patients under 1 umbrella regardless of phenotype. This has created challenges for clinical trials and patient care owing to the heterogeneity of the patient population with CS. The Society of Coronary Angiography and Interventions shock classification has created a universal language for CS that has been rapidly adopted by researchers and clinicians. Its latest iteration established the 3-axis model incorporating shock severity, risk modifiers, and phenotypes. Phenotypes of CS have unique hemodynamic profiles that require nuanced adjustment approaches. In this study, we discuss representative cases including acute myocardial infarction, acute-on-chronic heart failure, fulminant myocarditis, and right ventricular failure. For each phenotype, specific hemodynamic parameters may help confirm appropriate diagnosis and direct to therapeutic targets signaling stability and recovery. The underlying pathophysiology of each phenotype can also help predict the extent of stabilization with pharmacologic interventions or the need to escalate to mechanical circulatory support. In conclusion, this tailored approach to CS, rather than a 1-size-fits-all approach, could help improve outcomes.

The baroreflex system is involved in modulating several physiological functions of the cardiovascular system and can modulate cardiac output, blood pressure, and cardiac electrophysiology directly and indirectly. In addition, it is involved in regulating neurohormonal pathways involved in the cardiovascular function, such as the renin-angiotensin-aldosterone system and vasopressin release. Baroreflex dysfunction is characterized by sympathetic overactivation and parasympathetic withdrawal and is associated with several cardiovascular diseases, such as hypertension, heart failure, and coronary artery disease. Targeting the baroreflex system via invasive (eg, baroreflex activation therapy and endovascular baroreceptor amplification) and noninvasive approaches (eg, slow breathing exercises and exercise training) has emerged as a novel pathway to manage cardiovascular diseases. Studies examining the long-term safety and efficacy of such interventions in various cardiovascular diseases are needed.

The first heart transplantation in the United States was performed in 1968. The first national heart allocation system was developed two decades later in 1988 as a two-tiered system. Our current heart allocation system, adopted in 2018 as a six-tiered system, is evolving to become a continuous distribution model. Herein, we review the history of the Organ Procurement and Transplantation Network, the evolution of the cardiac allocation system, modern day challenges of the current heart allocation system policy, and the future of transplantation given ongoing implementation of the modernization initiative.