Waitlist and transplant outcomes for patients bridged to heart transplantation with Impella 5.0 and 5.5 devices

Bridging to orthotopic heart transplant: Reducing the risk of intra-operative blood loss

Background

Orthotopic heart transplantation remains the gold standard for patients with end-stage heart failure. Many devices exist to bridge patients with heart failure to transplant. Impella 5.5 (Abiomed, Danvers MA) is an example of a temporary mechanical assist device, which prioritizes patients as Status 2 by the 2018 UNOS policy change, increasing their likelihood of transplantation. Given the increase in device use, we sought to compare intra-operative complications, particularly blood loss, between bridging strategies to transplantation.

Methods

We conducted a single-institution retrospective analysis between January 2019 and May 2023.

Results

A transfusion requirement was defined as greater than 4 units of blood given intra- or immediately post-operatively (24%, 22/93). The transfusion group was more likely to have had a prior sternotomy (82% vs. 48% p < 0.01) and to be on a durable left ventricular assist device (LVAD) (45% vs. 21% p = 0.02). There was no difference in anticoagulation or antiplatelet use prior to the odds ratio (OR). The use of Impella 5.5 did not increase the risk of intra-operative bleeding (14% vs. 21% p = 0.44). In the adjusted outcomes, factors associated with intra-operative bleeding included average temperature and LVAD (OR 3.63 95% CI [1. -12.3], p = 0.04).

Conclusion

The shift to prioritize bridging devices has not been met with an increased risk of blood transfusion. We found that parameters such as a prior sternotomy, duration of temporary mechanical assist device (tMCS) use, and the presence of an LVAD were associated. This represents the first study to compare intra- and immediately post-operative transfusion data between bridging devices in the setting of transplantation.

Outcomes of Surgically Implanted Impella Microaxial Flow Pumps in Heart Failure-Related Cardiogenic Shock

BACKGROUND

Patients with cardiogenic shock (CS) are increasingly treated with high-profile microaxial flow pumps (Impella 5.5), but little is known about the indications and outcomes of this support strategy in patients with CS due to heart failure (HF-CS).

OBJECTIVES

We sought to describe the clinical features and outcomes of patients with HF-CS treated with Impella 5.5.

METHODS

We analyzed data from a prospective, multicenter observational study of patients with CS who had been implanted with an Impella 5.5. Adverse events, in-hospital survival rates and 6- and 12-month survival rates were analyzed in the total cohort and between patients treated with Impella 5.5 alone or with multiple temporary mechanical circulatory support (tMCS) devices. Outcomes were stratified based on native heart survival (NHS) and heart-replacement therapy (HRT).

RESULTS

Of the 804 patients with CS who received Impella 5.5, 444 had HF-CS. Prior to Impella 5.5 placement, 214 (48.1%) had received other tMCS devices. The duration of Impella support was 21.1 ± 20.1 days (median: 15; IQR: 8, 26 days). Survival to discharge was 75.0% for the total cohort, 86.5% for those receiving Impella 5.5 alone, and 65.0% for those receiving multiple tMCS devices. The need for renal-replacement therapy and thrombocytopenia requiring transfusions was more common in those receiving multiple tMCS devices. Among patients with NHS, 6- and 12-month survival rates were 71.3% and 64.4%, respectively, while patients receiving HRT had survival rates > 93%.

CONCLUSIONS

Patients with HF-CS treated with Impella 5.5 had overall favorable in-hospital, 6-month and 12-month survival, both as a bridge to NHS as HRT.

The Year in Cardiothoracic Transplant Anesthesia: Selected Highlights From 2022 Part II: Cardiac Transplantation

These highlights focus on research published in the year 2022 and is divided into preoperative, intraoperative, and postoperative sections. The preoperative section includes research on the assessment and optimization of candidates for heart transplantation; donor optimization and the use of extended donors; organ protection systems; donation after circulatory death allografts; recipient factors including cannabis use, sex, race, and comorbidities such as obesity, diabetes mellitus, and peripartum cardiomyopathy; the effects of the 2018 heart allocation policy change on waitlist and postoperative mortality; updates on heart transplantation in patients with coronavirus disease 2019; in pediatric patients; and those who require a bridge to transplant. The intraoperative section includes the use of a multidisciplinary team, a proposed transfusion algorithm, bench surgery on the allograft, and size matching. The postoperative section focuses on the research on the development and management of tricuspid regurgitation, echocardiography, arrhythmia management, and, finally, xenotransplantation.

Bridge to Heart Transplant With Temporary Mechanical Circulatory Support: Trends and Outcomes in the 2018 Allocation Policy Era

The United Network for Organ Sharing (UNOS) 2018 heart allocation policy prioritizes patients receiving temporary mechanical circulatory support (tMCS) given the high waitlist mortality rate of this group. This study evaluates national trends and waitlist outcomes for patients receiving tMCS under the UNOS 2018 allocation policy. Adult patients waitlisted for isolated heart transplantation were included using the UNOS database. The prevalence of tMCS, 90 day waitlist mortality, 90 day incidence of transplantation, and posttransplant 1 year mortality were analyzed. A total of 27,343 patients were waitlisted during the study period (pre-policy change: 13,004 vs. post-policy change: 14,339). The prevalence of tMCS increased from 7.4% (n: 956) to 22.4% (n: 3,186) after the policy change (p < 0.001). The use of Impella increased proportionally among tMCS modalities. Patients on tMCS had lower adjusted odds of waitlist mortality (p < 0.001), higher adjusted incidence of transplantation (p < 0.001), and similar posttransplant mortality (p = 0.10) under the 2018 policy. Patients on extracorporeal membrane oxygenation (ECMO) support had the highest odds of 90 day waitlist mortality (p < 0.05) but also the highest incidence of transplantation in the post-policy change cohort (p < 0.05). In conclusion, the use of tMCS as bridge to heart transplantation increased threefolds and is associated with lower waitlist mortality and higher incidence of transplantation following the UNOS 2018 allocation policy change.

A profile of the impella 5.5 for the clinical management of cardiogenic shock and a review of the current indications for use and future directions

INTRODUCTION

The Impella 5.5 device is a surgically inserted, trans-valvular, microaxial flow device capable of providing 5.5 L/min of continuous, antegrade flow from the left ventricle (LV) to the aorta. The ability of the Impella 5.5 to fully pressure and volume unload the dysfunctional LV while allowing for mobilization and rehabilitation has rapidly expanded its use. Clinical use scenarios include escalation of support for acute myocardial infarction cardiogenic shock (AMICS), transition from extracorporeal membrane oxygenation to mobile support, bridge to transplantation or durable MCS in acute decompensated heart failure, or perioperative use in post-cardiotomy cardiogenic shock (PCCS).

AREAS COVERED

This review provides a profile of the Impella 5.5 device, summarizes the current literature surrounding clinical applications, reviews active and upcoming clinical trials, and projects future applications for the device through an expert review.

EXPERT OPINION

The development of the Impella 5.5 has allowed for monitoring of left-heart recovery, optimizing right ventricular function, and rehabilitating patients to meet bridging endpoints. The 2018 heart transplant allocation system modifications have expanded the use of temporary mechanical circulatory support (tMCS) on the transplant waitlist, increasing the number of patients transplanted on support. With increased safety and durability, an expanding frontier is used in perioperative support for PCCS in high-risk cardiac surgery.

Temporary mechanical circulatory support as a bridge to transplant in peripartum cardiomyopathy

Background

Use of temporary mechanical circulatory support (tMCS) for peripartum cardiomyopathy (PPCM) shock has been described in small cohorts, but not on a national scale. This study compares tMCS, durable MCS (dMCS), and no MCS as bridge to transplant strategies for PPCM.

Methods

Female patients ≥14 years, listed for first-time isolated heart transplant (HT) between January 1, 2000 and June 30, 2021, were identified in the United Network for Organ Sharing database. Patients were stratified by receipt of MCS at any point during the waitlist period. Patients on multiple devices were excluded.

Results

A total of 1,043 PPCM patients were listed for HT, including 575 bridged on no MCS, 177 on tMCS, and 291 on dMCS. The tMCS cohort included 10 patients on extracorporeal membrane oxygenation, 113 on intra-aortic balloon pump, and 54 on nondischargeable ventricular assist device (VAD) or percutaneous device. The dMCS group primarily received durable VADs. Compared to dMCS, tMCS recipients were more likely to require inotropes, mechanical ventilation, and longer hospitalizations pretransplant (all p < 0.001). tMCS patients were more likely to be transplanted after 6 months than those on no device (adjusted subhazard ratio 1.57 [1.24-2.01]). Six hundred and eighty-one patients underwent HT. tMCS support was associated with similar 3-year graft survival compared to no MCS and dMCS (both p > 0.05). After multivariable risk adjustment, neither tMCS (adjusted hazard ratio 0.56 [0.06-5.43]) nor dMCS (adjusted hazard ratio 0.36 [0.05-2.82]) significantly predicted 3-year graft survival.

Conclusions

Compared to patients bridged to HT on dMCS or no MCS, PPCM patients receiving tMCS are higher acuity candidates but have equivalent post-transplant graft survival.

Impella 5.5 Bridge to Heart Transplant: An Institutional Series and a Closer Look at Device Removal Technique

Limited donor organ availability often necessitates mechanical circulatory support, and recently the Impella 5.5, as a bridge to heart transplant. Of 175 Impella 5.5-supported patients at our institution, 45 underwent transplantation in the largest series to date, for whom we analyzed outcomes. Two methods of complete device explant were evaluated: central Impella transection and removal via axillary graft. Median Impella days were 25 (16-41); median waitlist days were 21 (9-37). Eighty-nine percent (40/45) of patients had device placement via right axillary artery. Seventy-six percent (34/45) underwent central transection for device removal. Four patients (8.9%) required short-term venoarterial extracorporeal membranous oxygenation (VA ECMO) postoperatively for primary graft dysfunction (PGD). Two patients (4.4%) suffered postoperative stroke. Five patients (11.1%) required new RRT postoperatively. One patient (2.2%) returned to the operating room (OR) for axillary graft bleeding. A higher chance of procedural complications was found with the axillary removal technique ( p = 0.014). Median intensive care unit (ICU) days, length of stay (LOS), and postoperative days to discharge were 46 (35-63), 59 (49-80), and 18 (15-24), respectively. Ninety-eight percent (44/45) survived to discharge. Thirty-day survival was 95.6% (43/45), with 1 year survival at 90.3% (28/31). Eighty-eight percent (37/42) remain without rejection. In our institutional experience, Impella 5.5 is a safe and reliable bridge to transplant.

Impella 5.5: A Systematic Review of the Current Literature

OBJECTIVE

Impella 5.5 (Abiomed, Danvers, MA, USA) is a temporary mechanical circulatory support device used for patients in cardiogenic shock. This review provides a comprehensive overview of the device's clinical effectiveness, safety profile, patient outcomes, and relevant procedural considerations.

METHODS

We conducted a systematic review according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines using the PubMed/MEDLINE database. The search query included articles available from October 6, 2022, through January 13, 2023. Our initial search identified 75 studies. All records were screened by 2 independent reviewers using the Covidence software for adherence to our inclusion criteria, and 8 retrospective cohort studies were identified as appropriate for inclusion.

RESULTS

Across the included studies, the sample size ranged from 4 to 275, with predominantly male cohorts. Indications for Impella support varied, and the duration of support ranged from 9.8 to 70 days. Overall, Impella support appeared to be associated with favorable survival rates and manageable complications in various patient populations. Complications associated with Impella use included bleeding, stroke, and device malfunctions. Two studies compared prolonged and Food and Drug Administration-approved Impella support, showing similar outcomes and adverse events.

CONCLUSIONS

Impella 5.5 continues to be an attractive option for bridging patients to definitive therapy. Survival during and after Impella 5.5 was favorable for patients regardless of initial indication. However, device use was associated with several important complications, which calls for judicious use and a precontemplated exit strategy. Limitations of this literature review include biases inherent to the retrospective studies included, such as selection and publication bias.

Patient Characteristics and Early Clinical Outcomes With Impella 5.5: A Systematic Review and Meta-Analysis

Data regarding outcomes with Impella 5.5 are limited. The aim of this systematic review and meta-analysis was to summarize patient and treatment characteristics and early clinical outcomes among patients supported by Impella 5.5. A systematic literature search was conducted in PubMed, Scopus, and Cochrane databases from September 2019 to March 2023. Studies reporting outcomes in greater than or equal to 5 patients were included for review. Patient characteristics, treatment characteristics, and early clinical outcomes were extracted. Outcomes included adverse events, survival to hospital discharge, and 30 day survival. Random-effect models were used to estimate pooled effects for survival outcomes. Assessment for bias was performed using funnel plots and Egger's tests. Fifteen studies were included for qualitative review, representing 707 patients. Mean duration of support was 9.9 ± 8.2 days. On meta-analysis of 13 studies reporting survival outcomes, survival to hospital discharge was 68% (95% confidence interval [CI], 58-78%), and 30 day survival was 65% (95% CI, 56-74%) among patients with Impella devices predominantly supported by Impella 5.5 (>60%). There was significant study heterogeneity for these outcomes. Among 294 patients with Impella 5.5 only, survival to discharge was 78% (95% CI, 72-82%) with no significant study heterogeneity. This data present early benchmarks for outcomes with Impella 5.5 as clinical experience with these devices accrues.

Heart Transplantation

Heart transplantation (HTx) remains the last therapeutic resort for patients with advanced heart failure. The present work is a clinically focused review discussing current issues in heart transplantation. Several factors have been associated with the outcome of HTx, such as ABO and HLA compatibility, graft size, ischemic time, age, infections, and the cause of death, as well as imaging and laboratory tests. In 2018, UNOS changed the organ allocation policy for HTx. The aim of this change was to prioritize patients with a more severe clinical condition resulting in a reduction in mortality of people on the waiting list. Advanced heart failure and resistant angina are among the main indications of HTx, whereas active infection, peripheral vascular disease, malignancies, and increased body mass index (BMI) are important contraindications. The main complications of HTx include graft rejection, graft angiopathy, primary graft failure, infection, neoplasms, and retransplantation. Recent advances in the field of HTx include the first two porcine-to-human xenotransplantations, the inclusion of hepatitis C donors, donation after circulatory death, novel monitoring for acute cellular rejection and antibody-mediated rejection, and advances in donor heart preservation and transportation. Lastly, novel immunosuppression therapies such as daratumumab, belatacept, IL 6 directed therapy, and IgG endopeptidase have shown promising results.

The Year in Cardiothoracic and Vascular Anesthesia: Selected Highlights From 2023

This special article is the 16th in an annual series for the Journal of Cardiothoracic and Vascular Anesthesia. The authors thank the editor-in-chief, Dr. Kaplan, and the editorial board for the opportunity to continue this series, namely the research highlights of the past year in the specialty of cardiothoracic and vascular anesthesiology. The major themes selected for 2023 are outlined in this introduction, and each highlight is reviewed in detail in the main article. The literature highlights in the specialty for 2023 begin with an update on perioperative rehabilitation in cardiothoracic surgery, with a focus on novel methods to best assess patients in the preoperative and postoperative periods, and the impact of rehabilitation on outcomes. The second major theme is focused on cardiac surgery, with the authors discussing new insights into inhaled pulmonary vasodilators, coronary revascularization surgery, and discussion of causes of coronary graft failure after surgery. The third theme is focused on cardiothoracic transplantation, with discussions focusing on bridge-to-transplantation strategies. The fourth theme is focused on mechanical circulatory support, with discussions focusing on both temporary and durable support. The fifth and final theme is an update on medical cardiology, with a focus on outcomes of invasive approaches to heart disease. The themes selected for this article are only a few of the diverse advances in the specialty during 2023. These highlights will inform the reader of key updates on various topics, leading to improved perioperative outcomes for patients with cardiothoracic and vascular disease.