Outcomes in Patients Bridged With Univentricular and Biventricular Devices in the Modern Era of Heart Transplantation

Waitlist and transplant outcomes in heart transplant candidates bridged with temporary endovascular right ventricular assist devices

BACKGROUND

Advances in mechanical circulatory support and changes in allocation policy have shifted waitlisting practices for heart transplantation (HT) in the United States. This analysis reports waitlist and transplant outcomes among HT candidates bridged with temporary endovascular right ventricular assist devices (tRVADs).

METHODS

Patients awaiting HT from 2008 to 2022 in the United Network of Organ Sharing registry were grouped by the presence of tRVAD while waitlisted and propensity matched. Waitlist outcomes were HT and a competing outcome of death/deterioration requiring waitlist inactivation. Competing-risks regression was used to model waitlist outcomes. Subanalyses were performed to compare waitlist outcomes among patients with durable and temporary left ventricular assist devices (LVADs) with and without concomitant tRVADs. One-year posttransplant mortality was estimated using Kaplan-Meier analysis.

RESULTS

Of 41,507 HT candidates, 133 (0.3%) had tRVADs. After propensity matching, patients with tRVAD had a similar likelihood of HT and an elevated hazard for death/deterioration (hazard ratio 2.2, 95% confidence interval 1.4-3.2, p < 0.001) compared to those without tRVAD. Most patients with tRVAD (84%) had concomitant LVADs. tRVAD was associated with an elevated risk for deterioration/death among those with temporary LVADs but not durable LVADs. For patients undergoing HT, tRVAD was associated with an increased risk for 1-year mortality compared to propensity-matched recipients.

CONCLUSIONS

Bridging with tRVAD is uncommon and primarily used in patients requiring biventricular support. tRVADs are associated with waitlist inactivation or death, particularly with concomitant temporary LVAD support. As temporary devices are increasingly used as a bridge to HT, outcomes of patients with tRVADs should inform future allocation policy, particularly for candidates with biventricular failure.

Current and future options for adult biventricular assistance: a review of literature

In cardiogenic shock various short-term mechanical assistances may be employed, including an Extra Corporeal Membrane Oxygenator and other non-dischargeable devices. Once hemodynamic stabilization is achieved and the patient evolves towards a persisting biventricular dysfunction or an underlying long-standing end-stage disease is present, aside from Orthotopic Heart Transplantation, a limited number of long-term therapeutic options may be offered. So far, only the Syncardia Total Artificial Heart and the Berlin Heart EXCOR (which is not approved for adult use in the United States unlike in Europe) are available for extensive implantation. In addition to this, the strategy providing two continuous-flow Left Ventricular Assist Devices is still off-label despite its widespread use. Nevertheless, every solution ensures at best a 70% survival rate (reflecting both the severity of the condition and the limits of mechanical support) with patients suffering from heavy complications and a poor quality of life. The aim of the present paper is to summarize the features, implantation techniques, and results of current devices used for adult Biventricular Mechanical Circulatory Support, as well as a glance to future options.

Biventricular Assist Devices as a Bridge to Heart Transplantation Under the New Donor Heart Allocation System in the United States

Biventricular assist devices (BiVADs) for pre-heart transplant care is rare. The outcomes of pretransplant BiVAD support after the 2018 heart transplant allocation policy change are entirely unknown at this time. The United Network of Organ Sharing database was retrospectively queried from October 2018 to June 2022 to identify patients supported to transplant with BiVADs. They were compared to patients listed as Status 2 for heart transplantation with an isolated VAD (uni-VAD). The primary outcome of interest was 1 year survival. Secondary outcomes included length of stay, posttransplant stroke, dialysis, and pacemaker implantation. The frequency of BiVAD use for heart transplantation has remained unchanged after the 2018 allocation policy change, making up approximately 2% of transplant recipients annually. Patients supported with BiVADs appeared to be similar to patients supported with uni-VADs. One year survival was similar between the groups (88.57% vs. 87.90%). Length of stay was longer and there was a trend toward higher frequencies of posttransplant dialysis use. Patients supported to transplant with BiVADs appear to have posttransplant outcomes comparable to patients commonly listed as Status 2 with an isolated VAD. Compared to past analyses, there is a suggestion of improved survival with the 2018 allocation policy change.

Right and left ventricular assist devices are an option for bridge to heart transplant

Background

Patients with a left ventricular assist device with right ventricular failure are prioritized on the heart transplant waitlist; however, their post-transplant survival is less well characterized. We aimed to determine whether pretransplant right ventricular failure affects postoperative survival in patients with a left ventricular assist device as a bridge to transplant.

Methods

We performed a retrospective review of the 2005-2018 Organ Procurement and Transplantation Network/United Network for Organ Sharing registry for candidates aged 18 years or more waitlisted for first-time isolated heart transplantation after left ventricular assist device implantation. Candidates were stratified on the basis of having right ventricular failure, defined as the need for right ventricular assist device or intravenous inotropes. Baseline demographic and clinical characteristics were compared among the 3 groups, and post-transplant survival was assessed.

Results

Our cohort included 5605 candidates who met inclusion criteria, including 450 patients with right ventricular failure, 344 patients with a left ventricular assist device and intravenous inotropes as a bridge to transplant, 106 patients with a left ventricular assist device and right ventricular assist device, and 5155 patients with a left ventricular assist device as a bridge to transplant without the need for right side support. Compared with patients without right ventricular failure, patients with a left ventricular assist device as a bridge to transplant with right ventricular failure were younger (median age 51 years, 55 vs 56 years, P < .001) and waited less time for organs (median 51 days, 93.5 vs 125 days, P < .001). These patients also had longer post-transplant length of stay (median 18 days, 20 vs 16 days, P < .001). Right ventricular failure was not associated with decreased post-transplant long-term survival on unadjusted Kaplan–Meier analysis (P = .18). Neither preoperative right ventricular assist device nor intravenous inotropes independently predicted worse survival on multivariate Cox proportional hazards analysis. However, pretransplant liver dysfunction (total bilirubin >2) was an independent predictor of worse survival (hazard ratio, 1.74; 95% confidence interval, 1.39-2.17; P < .001), specifically in the left ventricular assist device group and not in the left ventricular assist device + right ventricular assist device/intravenous inotropes group.

Conclusions

Patients with biventricular failure are prioritized on the waiting list, because their critical pretransplant condition has limited impact on their post-transplant survival (short-term effect only); thus, surgeons should be confident to perform transplantation in these severely ill patients. Because liver dysfunction (a surrogate marker of right ventricular failure) was found to affect long-term survival in patients with a left ventricular assist device, surgeons should be encouraged to perform transplantation in these severely ill patients after a recipient's optimization by inotropes or a right ventricular assist device because even when the bilirubin level is elevated in these patients (treated with right ventricular assist device/inotropes), their long-term survival is not affected. Future studies should assess recipients' optimization before organ acceptance to improve long-term survival.

Pediatric Heart Transplant Recipients Bridged with Biventricular Assist Device Have Worse 1 Year Graft Survival

There are little data on postheart transplant (HT) outcomes for pediatric patients that were supported to HT with biventricular assist device (BiVAD). The United Network for Organ Sharing database was queried for patients <18 years old at time of HT between January 2005 and March 2018, excluding patients bridged with total artificial hearts and right ventricular assist device (VAD). Of 4,904 pediatric HT recipients, patients were grouped by no VAD support (3,934; 80.2%), left ventricular assist device only (736; 15%), and BiVAD (234; 4.8%). Overall graft survival analysis indicates crossing hazard rates between groups over time with the BiVAD group having a significantly lower graft survival at 1 year post-HT. A Cox model adjusted for age, era, diagnosis, and time by group interaction demonstrated increased 1 year hazard ratio (HR) of 8.5 (95% confidence intervals [CI]: 6.15-11.79) comparing BiVAD to no VAD. Comparable hazard between BiVAD and no VAD groups were found at 5 years (HR 1.01; 95% CI: 0.67-1.51), while lower hazard for the BiVAD group was found at 10 years post-HT (HR 0.07; 95% CI: 0.03-0.18). Although pre-HT BiVAD support leads to worse graft survival 1 year post-HT, long-term survival is acceptable.

Contemporary Mechanical Circulatory Support with Continuous Flow Biventricular Assist Devices: A Systematic Review

As the incidence of heart failure increases, so too has that of biventricular failure. While transplantation remains the gold standard therapy for end-stage heart failure, the limited organ supply has increased the need for durable mechanical circulatory support. We therefore sought to conduct a systematic review of continuous flow ventricular assist devices in a biventricular configuration (CF-BiVAD). An electronic search of PubMed and Cumulative Index to Nursing and Allied Health Literature (CINAHL) databases was performed using the keyword "BIVAD". Studies were reviewed to identify discrete variables, including implant indication, INTERMACs profile, timing of implant, mean age and BMI, and the anticoagulation/antiplatelet regimens employed post implant. Outcomes of interest included mortality and the incidence of thrombus, bleeding, infection, stroke and renal failure. A total of 25 studies met inclusion criteria. No single variable was consistently reported, with only four studies reporting all five adverse effects. INTERMACs profile at implant and anticoagulation/antiplatelet regimen were reported in less than 50% of studies. Of those reporting mortality, there was a wide range of follow-up, from less than six months to >10 years, and the survival rate was similarly widely variable. Additionally, more than 50% of studies failed to isolate CF-BiVAD from alternative means of biventricular support, such as temporary support platforms, TAH, and pulsatile VADs. Therefore high-quality quantitative analysis is not possible. In summary, CF-BiVAD literature has a very heterogenous reporting of data. Standard reporting criteria may allow for future analyses to determine which patient characteristics portend a favorable outcome with CF-BiVAD implantation.

Overview of Ventricular Assist Devices and the Total Artificial Heart

BACKGROUND

Patients with isolated left ventricular failure may have positive outcomes after being implanted with a left ventricular assist device. Unfortunately, almost half of patients with heart failure and reduced ejection fraction also have evidence of right ventricular dysfunction. For a subset of this population with severe biventricular failure, or those who develop right ventricular dysfunction after left ventricular assist device implantation, patients may necessitate biventricular assist devices or the total artificial heart.

OBJECTIVES

This overview of mechanical circulatory support devices will enhance nurses' ability to differentiate criteria for implantation, current practice, and outcomes with a focus on durable ventricular assist devices and the total artificial heart.

METHODS

A review of the literature involved searching CINAHL and PubMed databases using keywords biventricular assist devices, total artificial heart, and durable mechanical circulatory support. Results were narrowed to articles based on adults, 18 years or older. Seventy-eight relevant articles were identified, and 8 articles compared the durable biventricular assist devices.

RESULTS

Similar patient outcomes were found when comparing the use of left ventricular assist devices as biventricular support versus the total artificial heart.

DISCUSSION

The decision to implant the appropriate durable mechanical circulatory support for a patient in biventricular failure is complex and dependent on patient factors.

The Total Artificial Heart: Where Are We?

The total artificial heart (TAH) is a device that replaces the failing ventricles. There have been numerous TAHs designed over the last few decades, but the one with the largest patient experience is the SynCardia temporary TAH. The 50-mL and 70-mL sizes have been approved in the United States, Europe, and Canada as a bridge to transplantation. It is indicated in patients with severe biventricular failure or structural heart issues that preclude the use of a left ventricular assist device. The majority of the patients implanted are Interagency Registry for Mechanically Assisted Circulatory Support profile 1 or 2. The 1-year survival in experienced centers that have implanted over 10 TAHs is 73%. The risk factors for death include older age, need for preimplantation dialysis, and malnutrition. The most common causes of death are multiple organ failure, usually the result of physiologic deterioration before implantation, and neurologic dysfunction. The device allows the patient to be discharged home and managed as an outpatient. Proper patient selection, the timing of intervention, patient care, and device management are essential for a suitable outcome. In addition, the CARMAT TAH is another device that will soon be studied in a clinical trial in the United States. The BiVACOR TAH is a revolutionary design utilizing electromagnetic levitation that is expected to enter a clinical trial in the next few years.

2019 EACTS Expert Consensus on long-term mechanical circulatory support

Long-term mechanical circulatory support (LT-MCS) is an important treatment modality for patients with severe heart failure. Different devices are available, and many-sometimes contradictory-observations regarding patient selection, surgical techniques, perioperative management and follow-up have been published. With the growing expertise in this field, the European Association for Cardio-Thoracic Surgery (EACTS) recognized a need for a structured multidisciplinary consensus about the approach to patients with LT-MCS. However, the evidence published so far is insufficient to allow for generation of meaningful guidelines complying with EACTS requirements. Instead, the EACTS presents an expert opinion in the LT-MCS field. This expert opinion addresses patient evaluation and preoperative optimization as well as management of cardiac and non-cardiac comorbidities. Further, extensive operative implantation techniques are summarized and evaluated by leading experts, depending on both patient characteristics and device selection. The faculty recognized that postoperative management is multidisciplinary and includes aspects of intensive care unit stay, rehabilitation, ambulatory care, myocardial recovery and end-of-life care and mirrored this fact in this paper. Additionally, the opinions of experts on diagnosis and management of adverse events including bleeding, cerebrovascular accidents and device malfunction are presented. In this expert consensus, the evidence for the complete management from patient selection to end-of-life care is carefully reviewed with the aim of guiding clinicians in optimizing management of patients considered for or supported by an LT-MCS device.

Implantation of Two HVADs Used as a Total Artificial Heart: A New Approach

A 30-year-old patient had angiosarcoma of the right atrium with a negative outcome. The use of a SynCardia or Carmat was not possible due to invasion of the right atrium by the tumor, so we implanted two HeartWare ventricular assist devices (Medtronic, Minneapolis, MN) in a total artificial heart configuration using a technique not previously described. The surgical follow-up was simple, and the patient remained alive 30 days postoperatively. The technique we describe herein offers new prospects for the implantation of two HeartWare ventricular assist devices in a total artificial heart configuration.

Extracorporeal life support in preoperative and postoperative heart transplant management

Increased experience with extracorporeal life support (ECLS) as a mode of cardiac support has expanded its use to diverse patient populations including patients requiring a bridge to heart transplantation and patients requiring posttransplant support for primary graft dysfunction (PGD). The use of ECLS is associated with acceptable outcomes in well-selected patients. While outcomes with the use of extracorporeal membrane oxygenation (ECMO) as a bridge to heart transplant have been variable, several series have confirmed the safe use of ECLS to stabilize patients prior to left ventricular assist device (LVAD) implantation. These patients are then considered later, when in stable condition, for heart transplant. When ECLS is used prior to heart transplant, mortality is greatest during the first 6 months posttransplant. Patients who are alive 6 months after transplant appear to have similar survival rates as patients who were not supported with ECLS prior to transplant. ECLS support is a reliable therapeutic option for severe PGD and early graft failure after heart transplantation. In patients who require support for severe PGD, venoarterial-ECMO appears to result in better clinical outcomes than LVAD support. ECLS use for PGD after heart transplant continues to be the first line of support. Further studies are necessary to understand the optimal role of ECLS in heart transplantation.

Noteworthy Literature Published in 2016 for Thoracic Organ Transplantation Anesthesiologists

This article is first in the series to review the published literature on perioperative issues in patients undergoing thoracic solid organ transplantations. We present recent literature from 2016 on preoperative considerations, organ preservation, intraoperative anesthesia management, surgical techniques, postoperative complications, and the impact of perioperative management on short- and long-term outcomes that are pertinent to thoracic transplantation anesthesiologists.