Temporary Mechanical Circulatory Support: Devices, Outcomes and Future Directions

Guide to Temporary Mechanical Support in Cardiogenic Shock: Choosing Wisely

Cardiogenic shock is a multisystem pathology that carries a high mortality rate, and initial pharmacotherapies include the use of vasopressors and inotropes. These agents can increase myocardial oxygen consumption and decrease tissue perfusion that can oftentimes result in a state of refractory cardiogenic shock for which temporary mechanical circulatory support can be considered. Numerous support devices are available, each with its own hemodynamic blueprint. Defining a patient's hemodynamic profile and understanding the phenotype of cardiogenic shock is important in device selection. Careful patient selection incorporating a multidisciplinary team approach should be utilized.

Bridge to Transplantation: Policies Impact Practices

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.

International Society for Heart and Lung Transplantation Guidelines for the Evaluation and Care of Cardiac Transplant Candidates-2024

The "International Society for Heart and Lung Transplantation Guidelines for the Evaluation and Care of Cardiac Transplant Candidates-2024" updates and replaces the "Listing Criteria for Heart Transplantation: International Society for Heart and Lung Transplantation Guidelines for the Care of Cardiac Transplant Candidates-2006" and the "2016 International Society for Heart Lung Transplantation Listing Criteria for Heart Transplantation: A 10-year Update." The document aims to provide tools to help integrate the numerous variables involved in evaluating patients for transplantation, emphasizing updating the collaborative treatment while waiting for a transplant. There have been significant practice-changing developments in the care of heart transplant recipients since the publication of the International Society for Heart and Lung Transplantation (ISHLT) guidelines in 2006 and the 10-year update in 2016. The changes pertain to 3 aspects of heart transplantation: (1) patient selection criteria, (2) care of selected patient populations, and (3) durable mechanical support. To address these issues, 3 task forces were assembled. Each task force was cochaired by a pediatric heart transplant physician with the specific mandate to highlight issues unique to the pediatric heart transplant population and ensure their adequate representation. This guideline was harmonized with other ISHLT guidelines published through November 2023. The 2024 ISHLT guidelines for the evaluation and care of cardiac transplant candidates provide recommendations based on contemporary scientific evidence and patient management flow diagrams. The American College of Cardiology and American Heart Association modular knowledge chunk format has been implemented, allowing guideline information to be grouped into discrete packages (or modules) of information on a disease-specific topic or management issue. Aiming to improve the quality of care for heart transplant candidates, the recommendations present an evidence-based approach.

Year in Review 2023: Noteworthy Literature in Cardiothoracic Transplantation

This review highlights key studies examining perioperative management of cardiothoracic transplantation published in 2023. Articles were manually screened after searching Scopus, PubMed, and Google Scholar databases for manuscripts related to cardiothoracic transplantation, which yielded 343 papers with 15 qualitatively selected as the most salient for readers. Overarching themes include differences in outcomes across the various etiologies of end-stage lung disease, novel developments to expand the donor pool, and multi-organ transplantation.

An explainable machine learning approach using contemporary UNOS data to identify patients who fail to bridge to heart transplantation

Background

The use of Intra-aortic Balloon Pump (IABP) and Impella devices as a bridge to heart transplantation (HTx) has increased significantly in recent times. This study aimed to create and validate an explainable machine learning (ML) model that can predict the failure of status two listings and identify the clinical features that significantly impact this outcome.

Methods

We used the UNOS registry database to identify HTx candidates listed as UNOS Status 2 between 2018 and 2022 and supported with either Impella (5.0 or 5.5) or IABP. We used the eXtreme Gradient Boosting (XGBoost) algorithm to build and validate ML models. We developed two models: (1) a comprehensive model that included all patients in our cohort and (2) separate models designed for each of the 11 UNOS regions.

Results

We analyzed data from 4,178 patients listed as Status 2. Out of them, 12% had primary outcomes indicating Status 2 failure. Our ML models were based on 19 variables from the UNOS data. The comprehensive model had an area under the curve (AUC) of 0.71 (±0.03), with a range between 0.44 (±0.08) and 0.74 (±0.01) across different regions. The models' specificity ranged from 0.75 to 0.96. The top five most important predictors were the number of inotropes, creatinine, sodium, BMI, and blood group.

Conclusion

Using ML is clinically valuable for highlighting patients at risk, enabling healthcare providers to offer intensified monitoring, optimization, and care escalation selectively.

Temporary ventricular assist device support with a catheter-based axial pump: Changing the paradigm at a pediatric heart center

OBJECTIVE

We report the largest pediatric single-center experience with an Impella (Abiomed Inc) catheter-based axial pump support.

METHODS

We conducted a retrospective cohort study of all patients with acute decompensated heart failure or cardiogenic shock requiring catheter-based axial pump support between October 2014 and February 2022. The primary outcome per individual encounter (hospital admission) was defined as bridge-to-recovery, bridge-to-durable ventricular assist device support, bridge-to-cardiac transplantation, or death at 6 months after catheter-based axial pump explantation. Adverse events were defined according to the Pediatric Interagency Registry for Mechanical Circulatory Support criteria.

RESULTS

Our final study cohort included 37 encounters with 43 catheter-based axial pump implantations. A single catheter-based axial pump device was used for support in 33 encounters (89%), with 2 catheter-based axial pump devices used in 3 (8%) separate encounters and 3 catheter-based axial pump devices used in 1 (3%) encounter. The median [range] age, weight, and body surface area at implantation were 16.8 [6.9-42.8] years, 61.1 [23.1-123.8] kg, and 1.7 [0.8-2.5] m2, respectively. The predominant causes of circulatory failure were graft failure/rejection in 16 patients (43%), followed by cardiomyopathy in 7 patients (19%), arrhythmia refractory to medical therapies in 6 patients (16%), myocarditis/endocarditis in 4 patients (11%), and heart failure due to congenital heart disease in 4 patients (11%). Competing outcomes analysis showed a positive outcome with bridge-to-recovery in 58%, bridge-to-durable VAD support in 14%, and bridge-to-cardiac transplantation in 14% at 6 months. Fourteen percent of encounters resulted in death at 6 months.

CONCLUSIONS

We demonstrate that catheter-based axial pump support in children results in excellent 1- and 6-month survival with an acceptable adverse event profile.

Guide to Temporary Mechanical Support in Cardiogenic Shock: Choosing Wisely

Cardiogenic shock is a multisystem pathology that carries a high mortality rate, and initial pharmacotherapies include the use of vasopressors and inotropes. These agents can increase myocardial oxygen consumption and decrease tissue perfusion that can oftentimes result in a state of refractory cardiogenic shock for which temporary mechanical circulatory support can be considered. Numerous support devices are available, each with its own hemodynamic blueprint. Defining a patient's hemodynamic profile and understanding the phenotype of cardiogenic shock is important in device selection. Careful patient selection incorporating a multidisciplinary team approach should be utilized.

Utilization of the percutaneous left ventricular support as bridge to heart transplantation across the United States: In-depth UNOS database analysis

BACKGROUND

Intra-aortic balloon pump (IABP) and Impella device utilization as a bridge to heart transplantation (HTx) have risen exponentially. We aimed to explore the influence of device selection on HTx outcomes, considering regional practice variation.

METHODS

A retrospective longitudinal study was performed on a United Network for Organ Sharing (UNOS) registry dataset. We included adult patients listed for HTx between October 2018 and April 2022 as status 2, as justified by requiring IABP or Impella support. The primary end-point was successful bridging to HTx as status 2.

RESULTS

Of 32,806 HTx during the study period, 4178 met inclusion criteria (Impella n = 650, IABP n = 3528). Waitlist mortality increased from a nadir of 16 (in 2019) to a peak of 36 (in 2022) per thousand status 2 listed patients. Impella annual use increased from 8% in 2019 to 19% in 2021. Compared to IABP, Impella patients demonstrated higher medical acuity and lower success rate of transplantation as status 2 (92.1% vs 88.9%, p < 0.001). The IABP:Impella utilization ratio varied widely between regions, ranging from 1.77 to 21.31, with high Impella use in Southern and Western states. However, this difference was not justified by medical acuity, regional transplant volume, or waitlist time and did not correlate with waitlist mortality.

CONCLUSIONS

The shift in utilizing Impella as opposed to IABP did not improve waitlist outcomes. Our results suggest that clinical practice patterns beyond mere device selection determine successful bridging to HTx. There is a critical need for objective evidence to guide tMCS utilization and a paradigm shift in the UNOS allocation system to achieve equitable HTx practice across the United States.

Kidney health and function with left ventricular assist devices

PURPOSE OF REVIEW

Mechanical circulatory support (MCS) is a group of evolving therapies used for indications ranging from temporary support during a cardiac procedure to permanent treatment of advanced heart failure. MCS is primarily used to support left ventricle function, in which case the devices are termed left ventricular assist devices (LVADs). Kidney dysfunction is common in patients requiring these devices, yet the impact of MCS itself on kidney health in many settings remains uncertain.

RECENT FINDINGS

Kidney dysfunction can manifest in many different forms in patients requiring MCS. It can be because of preexisting systemic disorders, acute illness, procedural complications, device complications, and long-term LVAD support. After durable LVAD implantation, most persons have improvement in kidney function; however, individuals can have markedly different kidney outcomes, and novel phenotypes of kidney outcomes have been identified.

SUMMARY

MCS is a rapidly evolving field. Kidney health and function before, during, and after MCS is relevant to outcomes from an epidemiologic perspective, yet the pathophysiology underlying this is uncertain. Improved understanding of the relationship between MCS use and kidney health is important to improving patient outcomes.

Optimal, Early Postoperative Management of Cardiac Transplant and Durable Left Ventricular Assist Recipients

PURPOSE OF REVIEW

Summarize developments in the early postoperative care of patients undergoing cardiac transplantation or left ventricular assist device implantation. Provide a practical approach with personal insights to highly complex patients at risk for prolonged hospitalization.

RECENT FINDINGS

Advancements in technology allow for percutaneous mechanical circulatory support of both the right and left ventricles either isolated or combined via subclavian and neck vessels. Since the adult heart allocation system has been changed to reduce waitlist mortality, the use of temporary mechanical circulatory support has increased. This has influenced preoperative optimization by enabling ambulation and majorly changed postoperative strategy. New doors have been opened for a multidisciplinary approach to facilitate rapid weaning of inotropic medications, limitation of sedation, early liberation from mechanical ventilation, and mobilization. Individualized percutaneous mechanical circulatory support offers new possibilities for the early postoperative management of highly complex patients undergoing cardiac transplantation or durable left ventricular assist device implantation.