Bridging With Extracorporeal Membrane Oxygenation Under the New Heart Allocation System: A United Network for Organ Sharing Database Analysis

Three-year outcomes after bridge to transplantation ECMO-pre- and post-2018 UNOS revised heart allocation system

BACKGROUND

Utilization of temporary mechanical circulatory support, including veno-arterial extra-corporeal membrane oxygenation as a bridge to heart transplantation (HT) has increased significantly under the revised United Network for Organ Sharing (UNOS) donor heart allocation system. The revised heart allocation system aimed to lower waitlist times and mortality for the most critically ill patients requiring biventricular, nondischargeable, mechanical circulatory support. While previous reports have shown improved 1-year post-HT survival in the current era, 3-year survival and factors associated with mortality among bridge-to-transplant (BTT) extra-corporeal membrane oxygenation (ECMO) patients are not well described.

METHODS

We queried the UNOS database for all adult (age ≥ 18 years) heart-only transplants performed between 2010 and 2019. Patients were stratified as either pre- (January 2010-September 2018; era 1) or post-allocation change (November 2018-December 2019; era 2) cohort based on their HT date. Baseline recipient characteristics and post-transplant outcomes were compared. A Cox regression analysis was performed to explore risk factors for 3-year mortality among BTT-ECMO patients in era 2. For each era, 3-year mortality was also compared between BTT ECMO patients and those transplanted without ECMO support.

RESULTS

During the study period, 116 patients were BTT ECMO during era 1 and 154 patients during era 2. Baseline recipient characteristics were similar in both groups. Median age was 48 (36-58 interquartile range (IQR)) years in era 2, while it was 51 (27-58 IQR) years in era 1. The majority of BTT-ECMO patients were males in both era 2 and era 1 (77.7% vs 71.5%, p = 0.28). Median ECMO run times while listed for HT were significantly shorter (4 days vs 7 days, p < 0.001) in era 2. Waitlist mortality among BTT ECMO patients was also significantly lower in era 2 (6.3% vs 19.3%, p < 0.001). Post-HT survival at 6 months (94.2% vs 75.9%, p < 0.001), 1 year (90.3% vs 74.2%, p < 0.001), and 3 years (87% vs 66.4%, p < 0.001) was significantly improved in era 2 as compared to era 1. Graft failure at 1 year (10.3% vs 25.8%, p = 0.0006) and 3 years (13.6% vs 33.6%, p = 0.0001) was also significantly lower in era 2 compared to era 1. Three-year survival among BTT ECMO patients in era 2 was similar to that of patients transplanted in era 2 without ECMO support (87% vs 85.7%, p = 0.75). In multivariable analysis of BTT-ECMO patients in era 2, every 1 kg/m2 increase in body mass index was associated with higher mortality at 3 years (hazard ratio (HR) 1.09, 95% CI 1.02-1.15, p = 0.006). Similarly, both post-HT stroke (HR 5.58, 95% CI 2.57-12.14, p < 0.001) and post-HT renal failure requiring hemodialysis (HR 4.36, 95% CI 2.43-7.82, p < 0.001) were also associated with 3-year mortality.

CONCLUSIONS

Three years post-HT survival in patients bridged with ECMO has significantly improved under the revised donor heart allocation system compared to prior system. BTT ECMO recipients under the revised system have significantly shorter ECMO waitlist run times, lower waitlist mortality and 3-year survival similar to those not bridged with ECMO. Overall, the revised allocation system has allowed more rapid transplantation of the sickest patients without a higher post-HT mortality.

Impact of left ventricular unloading on postheart transplantation outcomes in patients bridged with VA-ECMO

INTRODUCTION AND OBJECTIVES

The impact of preoperative left ventricular (LV) unloading on postoperative outcomes in patients bridged with venoarterial extracorporeal membrane oxygenation (VA-ECMO) to heart transplantation (HT) is unknown. Our aim was to compare posttransplant outcomes in patients bridged to HT with VA-ECMO, with or without the use of different mechanical strategies for LV decompression.

METHODS

We conducted a retrospective analysis of the postoperative outcomes of consecutive HT candidates bridged with VA-ECMO, with or without concomitant LV unloading. Patients were included from 16 Spanish centers from 2010 to 2020. The primary endpoint was 1-year post-HT survival, which was assessed using Cox regression.

RESULTS

Overall, 245 patients underwent high-emergency HT while supported with VA-ECMO. A mechanical strategy for LV unloading was used in 133 (54.3%) patients, with the intra-aortic balloon pump being the most commonly used method (n=112; 84.2%). One-year posttransplant survival was 74.4% in the LV unloading group and 59.8% in the control group (P=.025). In multivariate analyses, preoperative LV unloading was independently associated with lower 1-year mortality (adjusted HR, 0.50; 95%CI, 0.32-0.78; P=.003). This association was observed both in patients managed with an intra-aortic balloon pump alone (adjusted HR, 0.52; 95%CI, 0.32-0.84; P=.007) and with other strategies for mechanical LV unloading (adjusted HR, 0.43; 95%CI, 0.19-0.97; P=.042). No significant differences were found between groups regarding other postoperative complications.

CONCLUSIONS

Preoperative LV unloading was independently associated with increased 1-year posttransplant survival in candidates bridged with VA-ECMO.

Extracorporeal membrane oxygenation as a bridge to thoracic multiorgan transplantation

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) has emerged as a crucial tool in the care of patients with multiorgan failure and is increasingly utilized as a bridge to transplantation. While data on ECMO as a bridge to isolated heart and lung transplantation have been described, our emerging experience with ECMO as a bridge to thoracic multiorgan transplantation is not yet well understood.

METHODS

The United Network for Organ Sharing database was used to identify adult patients undergoing thoracic multiorgan transplantation between 1987 and 2022. Exclusion criteria were recipient age <18 and bridging with other non-ECMO mechanical circulatory support, Survival analysis was performed to compare outcomes between patients bridged to transplantation with ECMO and those who were not bridged.

RESULTS

Of 3,927 patients undergoing thoracic multiorgan transplantation, a total of 203 (5.2%) patients received ECMO as a bridge to transplantation. Among ECMO recipients, patients were most commonly bridged to heart-lung (45.8%), followed by heart-kidney (34.5%), and lung-kidney transplantation (11.8%). At a median follow-up of 35.5 months, unadjusted survival among patients bridged with ECMO was decreased versus multiorgan transplant recipients who were not bridged (p < 0.001). Among patients surviving past 30 days following transplantation, conditional long-term survival was similar between ECMO and non-ECMO patients (p = 0.82).

CONCLUSIONS

ECMO is increasingly utilized as a bridge to thoracic multiorgan transplantation and is associated with increased 30 day mortality and decreased long-term survival. In select patients surviving to 30 days following transplantation, similar long-term survival is seen between patients bridged with ECMO and those not bridged.

Impact of Heart Failure Etiology on Waitlist Mortality in Heart Transplant Candidates Supported With Extracorporeal Membrane Oxygenation

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) has gained traction as a bridge to heart transplantation (HT) but remains associated with increased waitlist mortality. This study explores whether this risk is modified by underlying heart failure (HF) etiology.

METHODS

Using the Organ Procurement and Transplantation Network registry, we conducted a retrospective review of first-time adult HT candidates from 2018 through 2022. Patients were categorized as "ECMO", if ECMO was utilized during the waitlisting period, or "No ECMO" otherwise. Patients were then stratified according to the following HF etiology: ischemic cardiomyopathy (CMP), dilated nonischemic CMP, restrictive CMP, hypertrophic CMP, and congenital heart disease (CHD). After baseline comparisons, waitlist mortality was characterized for ECMO and HF etiology using the Fine-Gray regression.

RESULTS

A total of 16 143 patients were identified of whom 7.0% (n = 1063) were bridged with ECMO. Compared to No ECMO patients, ECMO patients had shorter waitlist durations (46.3 vs. 185.0 days, p < 0.01) and were more likely to undergo transplantation (75.3% vs. 70.3%, p < 0.01). Outcomes analysis revealed that ECMO was associated with increased mortality risk (subdistribution hazard ratio [SHR]: 3.42, p < 0.01), a risk that persisted in all subgroups and was notably high in CHD (SHR: 4.83, p < 0.01) and hypertrophic CMP (SHR: 9.78, p < 0.01). HF etiology comparison within ECMO patients revealed increased mortality risk with CHD (SHR: 3.22, p < 0.01). Within No ECMO patients, hypertrophic CMP patients had lower mortality risk (SHR: 0.64, p = 0.03).

CONCLUSIONS

The increased waitlist mortality risk with ECMO persisted after stratification by HF etiology. These findings can help decision-making surrounding candidacy for cannulation and prognostic evaluation.

Contemporary Bridge to Heart Transplantation With Venoarterial Extracorporeal Membrane Oxygenation

Objective: In October 2018, the United Network for Organ Sharing changed their heart allocation criteria to prioritize patients on temporary mechanical circulatory support. This study assesses outcomes of patients bridged to orthotopic heart transplantation (OHT) with venoarterial extracorporeal membrane oxygenation (VA ECMO) since this change. Methods: We conducted a retrospective single-center study of adults (≥18 years) supported with VA ECMO at the time of OHT (October 1, 2018, to December 31, 2021). The primary outcome was midterm survival. Results: During the study period, 117 patients underwent OHT including 52 adults ≥18 years (44%) and 65 children <18 years (56%). Among adults, 8 (15%) were supported with VA ECMO at the time of OHT and are included in this study; 75% were male (n = 6), and the median age was 52.5 (interquartile range [IQR] = 23.5 to 57.25) years. Most patients were peripherally cannulated (75%, n = 6) and supported with an intra-aortic balloon pump during the pretransplant period (87.5%, n = 7). The median ECMO duration was 7 (IQR = 4.5 to 25.25) days. Three patients experienced complications on ECMO (37.5%), including thromboembolic bowel infarction (12.5%, n = 1) and bleeding requiring reintervention (25%, n = 2). All patients survived to discharge without posttransplantation complications and were alive at the latest follow-up. The median follow-up time was 24.8 (IQR = 19.5 to 28.2) months. Conclusions: Patients can be successfully bridged with VA ECMO directly to OHT with excellent midterm results. Key contributors to our outcomes include early extubation, use of bivalirudin over heparin, ambulation, and rehabilitation while on ECMO.

Impact of Left Ventricular Unloading on Outcome of Heart Transplant Bridging With Extracorporeal Membrane Oxygenation Support in New Allocation Policy

BACKGROUND

The new heart allocation policy places veno-arterial extracorporeal membrane oxygenation (VA-ECMO)-supported heart transplant (HT) candidates at the highest priority status. Despite increasing evidence supporting left ventricular (LV) unloading during VA-ECMO, the effect of LV unloading on transplant outcomes following bridging to HT with VA-ECMO remains unknown.

METHODS AND RESULTS

From October 18, 2018 to March 21, 2023, 624 patients on VA-ECMO at the time of HT were identified in the United Network for Organ Sharing database and were divided into 2 groups: VA-ECMO alone (N=384) versus VA-ECMO with LV unloading (N=240). Subanalysis was performed in the LV unloading group: Impella (N=106) versus intra-aortic balloon pump (N=134). Recipient age was younger in the VA-ECMO alone group (48 versus 53 years, P=0.018), as was donor age (VA-ECMO alone, 29 years versus LV unloading, 32 years, P=0.041). One-year survival was comparable between groups (VA-ECMO alone, 88.0±1.8% versus LV unloading, 90.4±2.1%; P=0.92). Multivariable Cox hazard model showed LV unloading was not associated with posttransplant mortality after HT (hazard ratio, 0.92; P=0.70). Different LV unloading methods had similar 1-year survival (intra-aortic balloon pump, 89.2±3.0% versus Impella, 92.4±2.8%; P=0.65). Posttransplant survival was comparable between different Impella versions (Impella 2.5, versus Impella CP, versus Impella 5.0, versus Impella 5.5).

CONCLUSIONS

Under the current allocation policy, LV unloading did not impact waitlist outcome and posttransplant survival in patients bridged to HT with VA-ECMO, nor did mode of LV unloading. This highlights the importance of a tailored approach in HT candidates on VA-ECMO, where routine LV unloading may not be universally necessary.

Improved waitlist and comparable post-transplant outcomes in simultaneous heart-kidney transplantation under the 2018 heart allocation system

OBJECTIVE

This study aimed to investigate the clinical trends and the impact of the 2018 heart allocation policy change on both waitlist and post-transplant outcomes in simultaneous heart-kidney transplantation in the United States.

METHODS

The United Network for Organ Sharing registry was queried to compare adult patients before and after the allocation policy change. This study included 2 separate analyses evaluating the waitlist and post-transplant outcomes. Multivariable analyses were performed to determine the 2018 allocation system's risk-adjusted hazards for 1-year waitlist and post-transplant mortality.

RESULTS

The initial analysis investigating the waitlist outcomes included 1779 patients listed for simultaneous heart-kidney transplantation. Of these, 1075 patients (60.4%) were listed after the 2018 allocation policy change. After the policy change, the waitlist outcomes significantly improved with a shorter waitlist time, lower likelihood of de-listing, and higher likelihood of transplantation. In the subsequent analysis investigating the post-transplant outcomes, 1130 simultaneous heart-kidney transplant recipients were included, where 738 patients (65.3%) underwent simultaneous heart-kidney transplantation after the policy change. The 90-day, 6-month, and 1-year post-transplant survival and complication rates were comparable before and after the policy change. Multivariable analyses demonstrated that the 2018 allocation system positively impacted risk-adjusted 1-year waitlist mortality (sub-hazard ratio, 0.66, 95% CI, 0.51-0.85, P < .001), but it did not significantly impact risk-adjusted 1-year post-transplant mortality (hazard ratio, 1.03; 95% CI, 0.72-1.47, P = .876).

CONCLUSIONS

This study demonstrates increased rates of simultaneous heart-kidney transplantation with a shorter waitlist time after the 2018 allocation policy change. Furthermore, there were improved waitlist outcomes and comparable early post-transplant survival after simultaneous heart-kidney transplantation under the 2018 allocation system.

Blood type O heart transplant candidates have longer waitlist time and higher delisting under the new allocation system

OBJECTIVE

Prior studies have examined the effect of blood type on heart transplantation (HTx) waitlist outcomes in cohorts through 2015. We aim to analyze the effect of blood type on contemporary waitlist outcomes with a new allocation system focus.

METHODS

Adults listed for HTx between April 2015 and December 2020 were included. Survival to HTx and waitlist death/deterioration was compared between type O and non-type O candidates using competing risks regression. Donor/recipient ABO compatibility trends were further investigated.

RESULTS

Candidates with blood type O (n = 7509) underwent HTx less frequently than candidates with blood type other than type O (n = 9699) (subhazard ratio [sHR], 0.56; 95% CI, 0.53-0.58) with higher rates of waitlist death/deterioration (sHR, 1.18; 95% CI, 1.04-1.34). Subgroup analyses demonstrated persistence of this trend under the new donor heart allocation system (HTx: sHR, 0.58; 95% CI, 0.54-0.62; death/clinical deterioration: sHR, 1.27; 95% CI, 1.02-1.60), especially among those listed at high status (1, 2, or 3) (HTx: sHR, 0.69; 95% CI, 0.63-0.75; death/deterioration: sHR, 1.61; 95% CI, 1.16-2.22). Among those listed at status 3, waitlist death/deterioration was modified by presence of a durable left ventricular assist device (left ventricular assist device: sHR, 1.57; 95% CI, 0.58-4.29; no left ventricular assist device: sHR, 3.79; 95% CI, 1.28-11.2). Type O donor heart allocation to secondary ABO candidates increased in the new system (14.5% vs 12.0%; P < .01); post-HTx survival remained comparable between recipients with blood type O and non-type O (log-rank P = .07).

CONCLUSIONS

Further logistical considerations are warranted to minimize allocation inequity regarding blood type under the new allocation system.

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.

Heart Transplant Waitlist Outcomes and Wait Time by Center Volume in the Pre-2018 Allocation Change Era

Although the transplant outcomes of centers are heavily monitored and compared, with a particular link between posttransplant outcomes and center volume demonstrated, little data exist comparing waitlist outcomes. Here, we explored waitlist outcomes by transplant center volume. We performed a retrospective analysis of adults listed for primary heart transplantation (HTx) from 2008 to 2018 using the United Network for Organ Sharing database. Transplant centers were split into low (<10 HTx/year), medium (10-30 HTx/year), and high (>30 HTx/year) volume, and waitlist outcomes were compared. Of the 35,190 patients included in our study, 23,726 (67.4%) underwent HTx, 4,915 (14.0%) died or deteriorated before receiving HTx, 1,356 (3.9%) were delisted due to recovery, and 1,336 (3.8%) underwent left ventricular assist device (LVAD) implantation. High-volume centers had higher rates of survival to transplant (71.3% vs. 60.6% for low-volume centers and 64.9% for medium-volume centers), and low rates of death or deterioration (12.6% vs. 14.6% for low-volume centers and 15.1% for medium-volume centers). Listing at a low-volume center was independently associated with death or delisting before HTx (HR 1.18, p = 0.007), whereas listing at a high-volume center (HR 0.86; p < 0.001) and prelisting LVAD (HR 0.67, p < 0.001) were protective. Death or delisting before HTx was lowest for patients listed in higher volume centers.

Extended Support With the Impella 5.5: Transplant, ECMO, and Complications

We report midterm results of Impella 5.5 use with focus placed on bridge-outcomes, venoarterial extracorporeal membrane oxygenation (VA-ECMO) transition, complications, and risk factors for mortality. A retrospective review of patients implanted with the Impella 5.5 at our medical center was conducted. Forty patients were included with varying bridge strategies. Sixteen (40%) patients were supported for <14 days, 13 (32.5%) for 14-30 days, and 11 (27.5%) for >30 days. Thirty day mortality was 22.5% (9/40). Twenty-five (62.5%) were successfully bridged to transplant or durable left ventricular assist device (LVAD), while four (10.0%) recovered without the need for any further cardiac support. Five of 11 (60%) patients initially supported with VA-ECMO were either transitioned to durable left ventricular assist device (dLVAD; n = 3, 27.3%), transplanted (n = 1, 9.1%), or recovered (n = 1, 9.1%). Of nine patients with >moderate right ventricle (RV) dysfunction, five (55.6%) were successfully bridged to transplant or LVAD. Five (12.5%) patients required interval cannulation to VA-ECMO, often in the setting of RV dysfunction, and all (100%) were successfully transplanted. Lower pulmonary artery (PA) systolic pressure ( P = 0.029), among other factors, was associated with mortality. In summary, the Impella 5.5 may be able to effectively stabilize patients in refractory left ventricular predominant cardiogenic shock for extended durations, allowing time for mechanical circulatory support (MCS) and transplant evaluations.

The Year in Cardiothoracic Transplant Anesthesia: Selected Highlights From 2021 Part II: Cardiac Transplantation

This article spotlights the research highlights of this year that specifically pertain to the specialty of anesthesia for heart transplantation. This includes the research on recent developments in the selection and optimization of donors and recipients, including the use of donation after cardiorespiratory death and extended criteria donors, the use of mechanical circulatory support and nonmechanical circulatory support as bridges to transplantation, the effect of COVID-19 on heart transplantation candidates and recipients, and new advances in the perioperative management of these patients, including the use of echocardiography and postoperative outcomes, focusing on renal and cerebral outcomes.

Simple technique of distal leg perfusion during heart transplant in patients with preoperative veno-arterial extracorporeal membrane oxygenation support

Direct heart transplant from veno-arterial extracorporeal membrane oxygenation (VA-ECMO) support is challenging. Continuation of postoperative VA-ECMO support may be required in the setting of primary graft dysfunction or severe vasoplegia. We describe a simple technique to perfuse the ipsilateral leg of an arterial ECMO cannula during heart transplant while the ECMO circuit is turned off but maintaining the arterial cannula and distal perfusion catheter in place. This technique minimizes the number of intraoperative procedures with a minimal risk of leg ischemia, and provides a smooth transition to postoperative VA-ECMO support if necessary.

Cannulation-related adverse events of peripheral veno-arterial extracorporeal membrane oxygenation support in heart transplantation: Axillary versus femoral artery cannulation

BACKGROUND

In heart transplantation (HT), peripheral veno-arterial extracorporeal membranous oxygenation (VA-ECMO) is utilized preoperatively as a direct bridge to HT or postoperatively for primary graft dysfunction (PGD). Little is known about wound complications of an arterial VA-ECMO cannulation site which can be fatal.

METHODS

From 2009 to 2021, outcomes of 80 HT recipients who were supported with peripheral VA-ECMO either preoperatively or postoperatively were compared based on the site of arterial cannulation: axillary (AX: N = 49) versus femoral artery (FA: N = 31).

RESULTS

Patients in the AX group were older (AX: 59 years vs. 52 years, p = .006), and less likely to have extracorporeal cardiopulmonary resuscitation (0% vs. 12.9%, p = .040). Survival to discharge (AX, 81.6% vs. FA. 90.3%, p = .460), incidence of stroke (10.2% vs. 6.5%, p = .863), VA-ECMO cannulation-related bleeding (6.1% vs. 12.9%, p = .522), and arm or limb ischemia (0% vs. 3.2%, p = .816) were comparable. ECMO cannulation-related wound complications were lower in the AX group (AX, 4.1% vs. FA, 45.2%, p < .001) including the wound infections (2.0% vs. 32.3%, p < .001). In FA group, all organisms were gram-negative species. In univariate logistic regression analysis, AX cannulation was associated with less ECMO cannulation-related wound complications (Odds ratio, .23, p < .001). There was no difference between cutdown and percutaneous FA insertion regarding cannulation-related complications.

CONCLUSIONS

Given the lower rate of wound complications and comparable hospital outcomes with femoral cannulation, axillary VA-ECMO may be an excellent option in HT candidates or recipients when possible.

Higher Rates of Dialysis and Subsequent Mortality in the New Allocation Era for Heart Transplants

BACKGROUND

In 2018, a United Network for Organ Sharing (UNOS) policy change increased prioritization of patients bridged with temporary mechanical circulatory support devices, such as venoarterial ECMO, for cardiac transplantation. Considering increased waitlist acuity, we sought to characterize whether this was associated with an increased risk for development of postoperative acute renal failure requiring dialysis (AKI-D) and risk of death after transplantation.

METHODS

Dialysis-naive adults receiving single-organ heart transplant between November 2009 and February 2020 were stratified by receipt of AKI-D. Era 1 and era 2 were defined by the periods of UNOS allocation before and after policy change, respectively. Multivariable logistic regression was performed to determine risk factors for AKI-D. Rates of AKI-D were compared by propensity score-matched cohorts. Survival was compared by Kaplan-Meier analysis.

RESULTS

A total of 20 698 patients were included. Venoarterial ECMO use significantly increased in era 2 (5.6% vs 0.58%; P < .01). Overall prevalence of AKI-D was greater in era 2 (13.5% vs 10.2%; P < .01). Use of preoperative ECMO, intra-aortic balloon pump, and ventilators and longer ischemia times were identified as independent risk factors for development of AKI-D. Five- and 10-year survival rates were significantly decreased for patients with AKI-D. There was no short-term survival difference of patients with AKI-D between era 2 and the more contemporary era 1.

CONCLUSIONS

Patients in whom AKI-D develops after transplantation have significantly worse short- and long-term outcomes. Preoperative use of ECMO, preoperative ventilator support, and longer ischemia times are risk factors for development of AKI-D, and their prevalence has increased since the allocation policy change.

Temporary Mechanical Circulatory Support: Left, Right, and Biventricular Devices

Temporary mechanical circulatory support (MCS) encompasses a wide array of invasive devices, which provide short-term hemodynamic support for multiple clinical indications. Although initially developed for the management of cardiogenic shock, indications for MCS have expanded to include prophylactic insertion prior to high-risk percutaneous coronary intervention, treatment of acute circulatory failure following cardiac surgery, and bridging of end-stage heart failure patients to more definitive therapies, such as left ventricular assist devices and cardiac transplantation. A wide variety of devices are available to provide left ventricular, right ventricular, or biventricular support. The choice of a temporary MCS device requires consideration of the clinical scenario, patient characteristics, institution protocols, and provider familiarity and training. In this review, the most common forms of left, right, and biventricular temporary MCS are discussed, along with their indications, contraindications, complications, cannulations, hemodynamic effects, and available clinical data.

Modern outcomes of heart-lung transplantation: assessing the impact of the updated US allocation system

OBJECTIVES

In 2018, the United Network for Organ Sharing modified their heart allocation policy to reduce waitlist mortality and prioritize patients with the greatest acuity. Considering declining rates of combined heart-lung transplantation, this study sought to investigate the impact of the new allocation system on waitlist and post-transplant outcomes of patients listed for combined heart-lung transplantation.

METHODS

Adult patients listed for combined heart-lung transplant between 2012 and 2021 were included. Patients were stratified according to listing era. Competing risk regression was used to assess waitlist outcomes. Cox proportional hazards regression was used to establish risk factors for post-transplant mortality.

RESULTS

A total of 511 patients were included, of whom 295 (57.8%) were listed in era 1 and 216 (42.2%) in era 2. Era 2 was associated with increased likelihood of transplant (adjusted standard hazard ratio (aSHR): 1.60 [1.23-2.07]; P < 0.01) and decreased waitlist mortality (aSHR: 0.43 [0.25-0.73]; P < 0.01). Despite longer ischaemic times and increased use of preoperative veno-arterial extracorporeal membrane oxygenation (ECMO) in era 2, early post-transplant survival was equivalent. Predicted heart mass ratio <0.8 (Hazard ratio (HR); 3.24; P = 0.01), ventilator support (HR: 3.83; P < 0.01) and greater ischaemic times (HR: 1.80; P < 0.01) independently predicted the mortality. Procedures at high centre volumes (HR: 0.36; P = 0.04) were associated with decreased mortality. Use of ECMO was not predictive of mortality in the modern era.

CONCLUSIONS

The allocation policy change has led to improvements in waitlist outcomes in patients listed for heart-lung transplantation. Despite increased ischaemic times and use of ECMO, early post-transplant survival was equivalent.

Prolonged waitlisting is associated with mortality in extracorporeal membrane oxygenation-supported heart transplantation candidates

OBJECTIVE

Heart transplantation (HTx) candidates supported with venoarterial extracorporeal membrane oxygenation (ECMO) may be listed at highest status 1 but are at inherent risk for ECMO-related complications. The effect of waitlist time on postlisting survival remains unclear in candidates with ECMO support who are listed using the new allocation system.

METHODS

Adult candidates listed with ECMO for a first-time, single-organ HTx from October 18, 2018, to March 21, 2021, in the Scientific Registry of Transplant Recipients database were included and stratified according to waitlist time (≤7 vs ≥8 days). Postlisting outcomes were compared between cohorts.

RESULTS

Among 175 candidates waitlisted for ≤7 days, 162 (92.6%) underwent HTx whereas 13 (7.4%) died/deteriorated compared with 41 (57.8%) and 21 (29.6%) of the 71 candidates waitlisted for ≥8 days, respectively (P < .01). Blood type O candidates (odds ratio [OR], 2.94; 95% CI, 1.54-5.61) were more likely to wait ≥8 days whereas candidates with concurrent intra-aortic balloon pump were less likely (OR, 0.30; 95% CI, 0.10-0.89). Obesity was additionally associated among those listed at status 1 (OR, 2.04; 95% CI, 1.00-4.17). Waitlisting for ≥8 days was independently associated with 90-day postlisting mortality conditional on survival to day 8 postlisting (hazard ratio, 5.59; 95% CI, 2.59-12.1). Candidates listed at status 1 showed similar trends (hazard ratio, 5.49; 95% CI, 2.39-12.6). There was no significant difference in 90-day post-HTx survival depending on whether a candidate waited for ≥8 days versus ≤7 days (92.7 vs 92.0%; log rank P = .87).

CONCLUSIONS

Among ECMO-supported candidates, obtaining HTx within 1 week of listing might improve overall survival.

Lack of volume-outcome association in ECMO bridge to heart transplantation

BACKGROUND

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is increasingly used as a bridge to cardiac transplantation. As the 2018 United Network for Organ Sharing (UNOS) heart allocation policy change elevated waitlist status for patients receiving mechanical circulatory support (MCS), we aimed to determine if a center's annual heart transplant volume was associated with ECMO-support duration and posttransplant outcomes.

METHODS

Adults heart transplant candidates between January 1, 2011, and December 31, 2021, were isolated in the UNOS database. VA-ECMO use was identified at the time of listing for transplant. Average annual transplant volume was calculated by the center, with stratification as high (≥20 cardiac transplants, high volume center [HVC]) or low (<20 cardiac transplants, low volume center [LVC]) volume centers. Results are reported as mean (interquartile range) or n (%).

RESULTS

In total, 543 patients at HVCs and 275 at LVCs were listed for transplant supported with VA-ECMO. Those listed at HVCs were more likely to be supported by intra-aortic balloon pump (103 [19%] vs. 32 [11.6%], p = .008) and inotropes (267 [49.2%] vs. 106 [38.5%], p = .004) at time of listing. Patients at HVCs received ECMO support for 6 [4-9] days, compared to 8 [4-15] days at low-volume centers (p = .030), and but were cannulated a similar time before listing (2 [1-5] vs. 3 [1-7] days, p = .517). There were no differences in rates of transplant (p = .2126), waitlist mortality (p = .8645), delisting due to clinical deterioration (p = .8419), or recovery (p = .1773) between groups. Among transplanted patients, there were no differences in support duration (6 [4-8] vs. 6 [4-10], p = .187), or time from registration to transplant (5 [2-20] vs. 7 [3-22] days, p = .560). Posttransplant survival did not vary (p = .293).

CONCLUSIONS

LVCs can successfully bridge patients to transplant with VA-ECMO and achieve comparable outcomes to HVCs.

Veno-Arterial Extracorporeal Membrane Oxygenation as a Bridge to Heart Transplant-Change of Paradigm

Despite advances in medical therapy and mechanical circulatory support (MCS), heart transplant (HT) remains the gold standard therapy for end-stage heart failure. Patients in cardiogenic shock require prompt intervention to reverse hypoperfusion and end-organ damage. When medical therapy becomes insufficient, MCS should be considered. Historically, it has been reported that critically ill patients bridged with veno-arterial extracorporeal membrane oxygenation (VA-ECMO) directly to HT have worse outcomes. However, when the heart allocation system gives the highest priority to patients on VA-ECMO support, those patients have a higher incidence of HT and a lower incidence of death or removal from the transplant list. Moreover, patients with a short waiting time on VA-ECMO have a similar hazard of mortality to non-ECMO patients. According to the reported data, bridging with VA-ECMO directly to HT may be a solution in the selection of critically ill patients when the anticipated waiting list time is short. However, when a prolonged waiting time is expected, more durable MCS should be considered. Regardless of the favorable results of the direct bridging to HT with ECMO in selected patients, the superiority of this strategy compared to the bridge-to-bridge strategy (ECMO to durable MCS) has not been established and further studies are mandatory in order to clarify this issue.

TEMPORAL TRENDS IN THE USE AND OUTCOMES OF TEMPORARY MECHANICAL CIRCULATORY SUPPORT AS A BRIDGE TO CARDIAC TRANSPLANTATION IN SPAIN. FINAL REPORT OF THE ASIS-TC STUDY

BACKGROUND

We aimed to describe recent trends in the use and outcomes of temporary mechanical circulatory support (MCS) as a bridge to heart transplantation (HTx) in Spain.

METHODS

Retrospective case-by-case analysis of 1,036 patients listed for emergency HTx while on temporary MCS in 16 Spanish institutions from January 1st, 2010 to December 31st, 2020. Patients were classified in 3 eras according to changes in donor allocation criteria (Era 1: January 2010/May 2014; Era 2: June 2014/May 2017; Era 3: June 2017/December 2020).

RESULTS

Over time, the proportion of candidates listed with intra-aortic balloon pumps decreased (Era 1 = 55.9%, Era 2 = 32%, Era 3 = 0.9%; p < 0.001), while the proportion of candidates listed with surgical continuous-flow temporary VADs (Era 1 = 10.6%, Era 2 = 32%, Era 3 = 49.1%; p < 0.001) and percutaneous VADs (Era 1 = 0.3%, Era 2 = 6.3%; Era 3 = 17.2%; p < 0.001) increased. Rates of HTx increased from Era 1 (79.4%) to Era 2 (87.8%), and Era 3 (87%) (p = 0.004), while rates of death before HTx decreased (Era 1 = 17.7%; Era 2 = 11%, Era 3 = 12.4%; p = 0.037) Median time from listing to HTx increased in patients supported with intra-aortic balloon pumps (Era 1 = 8 days, Era 2 = 15 days; p < 0.001) but remained stable in other candidates (Era 1 = 6 days; Era 2 = 5 days; Era 3 = 6 days; p = 0.134). One-year post-transplant survival was 71.4% in Era 1, 79.3% in Era 2, and 76.5% in Era 3 (p = 0.112). Preoperative bridging with ECMO was associated with increased 1-year post-transplant mortality (adjusted HR=1.71; 95% CI 1.15-2.53; p = 0.008).

CONCLUSIONS

During the period 2010 to 2020, successive changes in the Spanish organ allocation protocol were followed by a significant increase of the rate of HTx and a significant reduction of waiting list mortality in candidates supported with temporary MCS. One-year post-transplant survival rates remained acceptable.

Extracorporeal membrane oxygenation as a bridge to durable mechanical circulatory support or heart transplantation

BACKGROUND

Patients with cardiogenic shock may require extracorporeal membrane oxygenation (ECMO) prior to durable mechanical circulatory support (dMCS) or heart transplantation (HTx).

METHODS

We investigated the clinical characteristics and outcomes of adult patients with ECMO support as bridge to dMCS or HTx between 1/1/13 and 12/31/20.

RESULTS

Of 57 patients who underwent bridging ECMO, 41 (72%) received dMCS (approximately half with biventricular support) and 16 (28%) underwent HTx, 13 (81%) after the 2018 UNOS allocation system change. ECMO → HTx patients had shorter ventilatory time (3.5 vs 7.5 days; p = 0.018), ICU stay (6 vs 18 days; p = 0.001), and less need for inpatient rehabilitation (18.8% vs 57.5%; p = 0.016). The 1-year survival post HTx was 81.3% in the ECMO → HTx group and 86.4% in the ECMO → dMCS group (p = 0.11). For those patients in the ECMO → dMCS group who did not undergo HTx, 1-year survival was significantly lower, 31.6% (p = 0.001).

CONCLUSION

Patients on ECMO who undergo HTx, with or without dMCS bridge, have acceptable post-HTx survival. These findings suggest that HTx from ECMO is a viable option for carefully selected patients deemed acceptable to proceed with definitive advanced therapies, especially in the era of the new UNOS allocation system.

Association of center-level temporary mechanical circulatory support use and waitlist outcomes after the 2018 adult heart allocation policy

BACKGROUND

The present study characterizes the association of center-level temporary mechanical circulatory support use with waitlist outcomes after the 2018 adult heart allocation policy change.

METHODS

The United Network for Organ Sharing database was queried for all single-organ, adult heart transplant candidates from November 2015 to October 2021. The study population was divided into 2 cohorts, prepolicy and postpolicy, centered around the rule change on October 18, 2018. The primary study outcome was center-level rate of poor waitlist outcome, defined as death or deterioration on the waitlist. Competing-risks regression was used to generate risk-adjusted rates of poor waitlist outcome at each center, while Pearson's correlation coefficient (r) was used to assess the significance of center-level temporary mechanical circulatory support use (defined as the proportion listed with temporary mechanical circulatory support) and poor waitlist outcome.

RESULTS

Of 22,077 transplant candidates included in analysis, 50.5% were listed during postpolicy. Compared to prepolicy, postpolicy candidates were more often listed with temporary mechanical circulatory support and less commonly listed with a durable left-ventricular assist device. The proportion of hospitals not using any temporary mechanical circulatory support decreased significantly from prepolicy to postpolicy (15% to 1%, P < .001). During prepolicy, center-level temporary mechanical circulatory support use showed no correlation with adjusted poor waitlist outcome. However, center-level temporary mechanical circulatory support use showed a negative correlation with poor waitlist outcome during postpolicy (r = -0.42, P < .001).

CONCLUSION

The 2018 adult heart allocation policy appears to benefit patients listed at high temporary mechanical circulatory support using centers, with significant interhospital variation in temporary mechanical circulatory support use in the new era. Given the growing role of temporary mechanical circulatory support on the heart transplant waitlist, greater standardization of its application is warranted.

Heart transplantation: focus on donor recovery strategies, left ventricular assist devices, and novel therapies

Heart transplantation is advocated in selected patients with advanced heart failure in the absence of contraindications. Principal challenges in heart transplantation centre around an insufficient and underutilized donor organ pool, the need to individualize titration of immunosuppressive therapy, and to minimize late complications such as cardiac allograft vasculopathy, malignancy, and renal dysfunction. Advances have served to increase the organ donor pool by advocating the use of donors with underlying hepatitis C virus infection and by expanding the donor source to use hearts donated after circulatory death. New techniques to preserve the donor heart over prolonged ischaemic times, and enabling longer transport times in a safe manner, have been introduced. Mechanical circulatory support as a bridge to transplantation has allowed patients with advanced heart failure to avoid progressive deterioration in hepato-renal function while awaiting an optimal donor organ match. The management of the heart transplantation recipient remains a challenge despite advances in immunosuppression, which provide early gains in rejection avoidance but are associated with infections and late-outcome challenges. In this article, we review contemporary advances and challenges in this field to focus on donor recovery strategies, left ventricular assist devices, and immunosuppressive monitoring therapies with the potential to enhance outcomes. We also describe opportunities for future discovery to include a renewed focus on long-term survival, which continues to be an area that is under-studied and poorly characterized, non-human sources of organs for transplantation including xenotransplantation as well as chimeric transplantation, and technology competitive to human heart transplantation, such as tissue engineering.

Heart Failure-Related Cardiogenic Shock: Pathophysiology, Evaluation and Management Considerations: Review of Heart Failure-Related Cardiogenic Shock

Despite increasing prevalence in critical care units, cardiogenic shock related to HF (HF-CS) is incompletely understood and distinct from acute myocardial infarction related CS. This review highlights the pathophysiology, evaluation, and contemporary management of HF-CS.