Temporary Mechanical Circulatory Support as a Bridge to Transplant: Return of the Intra-Aortic Balloon Pump

Impella 5.5 as a bridge to heart transplantation: Waitlist outcomes in the United States

OBJECTIVES

The 2018 United Network for Organ Sharing allocation policy change has led to a significant increase in the use of mechanical circulatory support devices in patients listed for orthotopic heart transplantation. However, there has been a paucity of data regarding the newest generation Impella 5.5, which received FDA approval in 2019.

METHODS

The United Network for Organ Sharing registry was queried for all adults awaiting orthotopic heart transplantation who received Impella 5.5 support during their listing period. Waitlist, device, and early post-transplant outcomes were assessed.

RESULTS

A total of 464 patients received Impella 5.5 support during their listing period with a median waitlist time of 19 days. Among them, 402 (87%) patients were ultimately transplanted, with 378 (81%) being directly bridged to transplant with the device. Waitlist death (7%) and clinical deterioration (5%) were the most common reasons for waitlist removal. Device complications and failure were uncommon (<5%). The most common post-transplant complication was acute kidney injury requiring dialysis (16%). Survival at 1-year post-transplant survival was 89.5%.

CONCLUSION

Since its approval, the Impella 5.5 has been increasingly used as a bridge to transplant. This analysis demonstrates robust waitlist and post-transplant outcomes with minimal device-related and postoperative complications.

Review of Pathophysiology of Cardiogenic Shock and Escalation of Mechanical Circulatory Support Devices

PURPOSE OF REVIEW

Cardiogenic shock (CS) is a complex clinical entity that continues to carry a high risk of mortality. The landscape of CS management has changed with the advent of several temporary mechanical circulatory support (MCS) devices designed to provide hemodynamic support. It remains challenging to understand the role of different temporary MCS devices in patients with CS, as many of these patients are critically ill, requiring complex care with multiple MCS device options. Each temporary MCS device can provide different types and levels of hemodynamic support. It is important to understand the risk/benefit profile of each one of them for appropriate device selection in patients with CS.

RECENT FINDINGS

MCS may be beneficial in CS patients through augmentation of cardiac output with subsequent improvement of systemic perfusion. Selecting the optimal MCS device depends on several variables including the underlying etiology of CS, clinical strategy of MCS use (bridge to recovery, bridge to transplant or durable MCS, or abridge to decision), amount of hemodynamic support needed, associated respiratory failure, and institutional preference. Furthermore, it is even more challenging to determine the appropriate time to escalate from one MCS device to another or combine different MCS devices. In this review, we discuss the current available data published in the literature on the management of CS and propose a standardized approach for escalation of MCS devices in patients with CS. Shock teams can play an important role to help in hemodynamic-guided management and algorithm-based step-by-step approach in early initiation and escalation of temporary MCS devices at different stages of CS. It is important to define the etiology of CS, and stage of shock and recognize univentricular vs biventricular shock for appropriate device selection and escalation of therapy.

Bivalirudin Versus Unfractionated Heparin in Patients With Cardiogenic Shock Requiring Venoarterial Extracorporeal Membrane Oxygenation

This study evaluated differences in efficacy and safety outcomes with bivalirudin compared with unfractionated heparin (UFH) in patients with cardiogenic shock requiring venoarterial extracorporeal membrane oxygenation (VA ECMO). We performed a retrospective study at an academic medical center that included patients greater than 18 years of age supported with VA ECMO due to cardiogenic shock from January 2009 to February 2021. The primary endpoint was ECMO-associated thrombotic events normalized to duration of ECMO support. Secondary safety endpoints included major bleeding (per ELSO criteria) and blood product administration. Overall, 143 patients were included in our analysis with 54 having received bivalirudin and 89 having received UFH. Median duration of ECMO support was 92 (interquartile range, 56-172) hours. ECMO-associated thrombotic events per ECMO day were significantly less among those that received bivalirudin ( P < 0.001). In adjusted regression, bivalirudin was independently associated with an increased time to thrombosis when compared with UFH (Exp[B] -3.8; 95% confidence interval, 1.7-8.8; P = 0.002). Patients receiving bivalirudin experienced less major bleeding events ( P = 0.02) with less total red blood cell and fresh frozen plasma administration ( P = 0.04 and P = 0.03, respectively). Bivalirudin is a safe and efficacious alternative to UFH in patients requiring VA ECMO for cardiogenic shock.

Bridge to transplantation from mechanical circulatory support: a narrative review

Objective

To highlight recent developments in the utilization of mechanical circulatory support (MCS) devices as bridge-to-transplant strategies and to discuss trends in MCS use following the changes to the United Network for Organ Sharing (UNOS) heart allocation system.

Background

MCS devices have played an increasingly important role in the treatment of heart failure patients. Over the past several years, technological advancements have led to new developments in MCS devices and expanding indications for MCS use. In October of 2018, the UNOS heart allocation policy was revised to prioritize higher-urgency patients, including those supported with temporary MCS devices. Since then, changes in trends of MCS utilization have been observed.

Methods

Articles from the PubMed database regarding the use of MCS devices as bridge-to-transplant strategies were reviewed.

Conclusions

Over the past decade, utilization of temporary MCS devices, which include the intra-aortic balloon pump (IABP), percutaneous ventricular assist devices (pVADs), and extracorporeal membrane oxygenation (ECMO), has become increasingly common. Recent advancements in MCS include the development of pVADs that can fully unload the left ventricle (LV) as well as devices designed to provide right-sided support. Technological advancements in durable left ventricular assist devices (LVADs) have also led to improved outcomes both on the device and following heart transplantation. Following the 2018 UNOS heart allocation policy revision, the utilization of temporary MCS in advanced heart failure patients has further increased and the proportion of patients bridged directly from a temporary MCS device has exponentially risen. However, following the start of the COVID-19 pandemic, the trends have reversed, with a decrease in the percentage of patients bridged from a temporary MCS device. As long-term data following the allocation policy revision becomes available, future studies should investigate how trends in MCS use for patients with advanced heart failure continue to evolve.

Decreased frequency of transplantation and lower post-transplant survival free of re-transplantation in LVAD patients with the new heart transplant allocation system

PURPOSE

To evaluate the effect of the new heart transplant (HT) allocation system in left ventricular assist device (LVAD) supported patients listed as bridge to transplantation (BTT).

METHODS

Adult patients who were listed for HT between October 18, 2016 and October 17, 2019, and were supported with an LVAD, enrolled in the UNOS database were included in this study. Patients were classified in the old or new system if they were listed or transplanted before or after October 18, 2018, respectively.

RESULTS

A total of 3261 LVAD patients were listed for transplant. Of these, 2257 were classified in the old and 1004 in the new system. The cumulative incidence of death or removal from the transplant list due to worsening clinical status at 360-days after listing was lower in the new system (4% vs. 7%, P = .011). LVAD Patients listed in the new system had a lower frequency of transplantation within 360-days of listing (52% vs. 61%, P < .001). A total of 1843 LVAD patients were transplanted, 1004 patients in the old system and 839 patients in the new system. The post-transplant survival at 360 days was similar between old and new systems (92.3% vs. 90%, P = .08). However, LVAD patients transplanted in the new system had lower frequency of the combined endpoint, freedom of death or re-transplantation at 360 days (92.2% vs. 89.6%, P = .046).

CONCLUSION

The new HT allocation system has affected the LVAD-BTT population significantly. On the waitlist, LVAD patients have a decreased cumulative frequency of transplantation and a concomitant decrease in death or delisting due to worsening status. In the new system, LVAD patients have a decreased survival free of re-transplantation at 360 days post-transplant.