Extracorporeal membrane oxygenation bridge to heart transplant: Trends following the allocation change

Extended Duration of Impella 5.5 Support Does Not Adversely Impact Outcomes Following Heart Transplantation: A National Registry Analysis

Prior studies assessing the effects of Impella 5.5 support duration on posttransplant outcomes have been limited to single-center case reports and series. This study evaluates the impact of Impella 5.5 support duration on outcomes following heart transplantation using the United Network for Organ Sharing database. Adult heart transplant recipients who were directly bridged to primary isolated heart transplantation with Impella 5.5 were included. The cohort was stratified into two groups based on the duration of Impella support: less than or equal to 14 and greater than 14 days. The primary outcome was 90 day posttransplant survival. Propensity score matching was performed. Sub-analysis was conducted to evaluate the impact of greater than 30 days of Impella support on 90 day survival. Three hundred thirty-two recipients were analyzed. Of these, 212 recipients (63.9%) were directly bridged to heart transplantation with an Impella support duration of greater than 14 days. The two groups had comparable 90 day posttransplant survival and complication rates. The comparable posttransplant survival persisted in a propensity score-matched comparison. In the sub-analysis, Impella support duration of greater than or equal to 30 days did not adversely impact 90 day survival. This study demonstrates that extended duration of support with Impella 5.5 as a bridge to transplantation does not adversely impact posttransplant outcomes. Impella 5.5 is a safe and effective bridging modality to heart transplantation.

A call to action in thoracic transplant surgical training

Thoracic organ recovery and implantation is increasing in complexity. Simultaneously the logistic burden and associated cost is rising. An electronic survey distributed to the surgical directors of thoracic transplant programs in the United States indicated dissatisfaction amongst 72% of respondents with current procurement training and 85% of respondents favored a process for certification in thoracic organ transplantation. These responses highlight concerns for the current paradigm of training in thoracic transplantation. We discuss the implications of advancements in organ retrieval and implant for surgical training and propose that the thoracic transplant community might address the need through formalized training in procurement and certification in thoracic transplantation.

State of the art - Extracorporeal membrane oxygenation as a bridge to thoracic transplantation

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) has revolutionized the treatment of refractory cardiac and respiratory failure, and its use continues to increase, particularly in adults. However, ECMO-related morbidity and mortality remain high.

MAIN TEXT

In this review, we investigate and expand upon the current state of the art in thoracic transplant and extracorporeal life support (ELS). In particular, we examine recent increase in incidence of heart transplant in patients supported by ECMO; the potential changes in patient care and selection for transplant in the years prior to updated United Network for Organ Sharing (UNOS) organ allocation guidelines versus those in the years following, particularly where these guidelines pertain to ECMO; and the newly revived practice of heart-lung block transplants (HLT) and the prevalence and utility of ECMO support in patients listed for HLT.

CONCLUSIONS

Our findings highlight encouraging outcomes in patients bridged to transplant with ECMO, considerable changes in treatment surrounding the updated UNOS guidelines, and complex, diverse outcomes among different centers in their care for increasingly ill patients listed for thoracic transplant.

Left ventricular assist device bridging to heart transplantation: Comparison of temporary versus durable support

BACKGROUND

Since the revision of the United States heart allocation system, increasing use of mechanical circulatory support has been observed as a means to support acutely ill patients. We sought to compare outcomes between patients bridged to orthotopic heart transplantation (OHT) with either temporary (t-LVAD) or durable left ventricular assist devises (d-LVAD) under the revised system.

METHODS

The United States Organ Network database was queried to identify all adult OHT recipients who were bridged to transplant with either an isolated t-LVAD or d-LVAD from 10/18/2018 to 9/30/2020. The primary outcome was 1-year post-transplant survival. Predictors of mortality were also modeled, and national trends of LVAD bridging were examined across the study period.

RESULTS

About 1,734 OHT recipients were analyzed, 1,580 (91.1%) bridged with d-LVAD and 154 (8.9%) bridged with t-LVAD. At transplant, the t-LVAD cohort had higher total bilirubin levels and greater prevalence of pre-transplant intravenous inotrope usage and mechanical ventilation. Median waitlist time was also shorter for t-LVAD. At 1 year, there was a non-significant trend of increased survival in the t-LVAD cohort (94.8% vs 90.1%; p = 0.06). After risk adjustment, d-LVAD was associated with a 4-fold hazards for 1-year mortality (hazard ratio 3.96, 95% confidence interval 1.42-11.03; p = 0.009). From 2018 to 2021, t-LVAD bridging increased, though d-LVAD remained a more common bridging strategy.

CONCLUSIONS

Since the 2018 allocation change, there has been a steady increase in t-LVAD usage as a bridge to OHT. Overall, patients bridged with these devices appear to have least equivalent 1-year survival compared to those bridged with d-LVAD.

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.

Outcomes of extracorporeal membrane oxygenation following the 2018 adult heart allocation policy

Background

The purpose of the study was to characterize changes in waitlist and post-transplant outcomes of extracorporeal membrane oxygenation (ECMO) patients bridged to heart transplantation under the 2018 adult heart allocation policy.

Methods

All adult patients listed for isolated heart transplantation from August 2016 to December 2020 were identified using the United Network for Organ Sharing database. Patients were stratified into Eras (Era 1 and Era 2) centered around the policy change on October 18, 2018. Competing risk regression was used to evaluate waitlist death or deterioration across Eras. Cox proportional hazards models were used to determine associations between use of ECMO and 1-year post-transplant mortality within each Era.

Results

Of 8,902 heart transplants included in analysis, 339 (3.8%) were bridged with ECMO (Era 2: 6.1% vs Era 1: 1.2%, P<0.001). Patients bridged with ECMO in Era 2 were less frequently female (26.0% vs 42.0%, P = 0.02) and experienced shorter waitlist times (5 vs 11 days, P<0.001) along with a lower likelihood of waitlist death or deterioration (subdistribution hazard ratio, 0.45, 95% confidence interval, CI, 0.30–0.68, P<0.001) compared to those in Era 1. Use of ECMO was associated with increased post-transplant mortality at 1-year compared to all other transplants in Era 1 (hazard ratio 3.78, 95% CI 1.88–7.61, P < 0.001) but not Era 2.

Conclusions

Patients bridged with ECMO in Era 2 experience improved waitlist and post-transplant outcomes compared to Era 1, giving credence to the increased use of ECMO under the new allocation policy.

Effect of UNOS policy change and exception status request on outcomes in patients bridged to heart transplant with an intra-aortic balloon pump

BACKGROUND

Intra-aortic balloon pumps (IABP) are used to bridge select end-stage heart disease patients to heart transplant (HT). IABP use and exception requests both increased dramatically after the UNOS policy change (PC). The purpose of this study was to evaluate the effect of PC and exception status requests on waitlist and post-transplant outcomes in patients bridged to HT with IABP support.

METHODS

We analyzed adult, first-time, single-organ HT recipients from the UNOS Registry either on IABP at the time of registration for HT or at the time of HT. We compared waitlist and post-HT outcomes between patients from the PRE (October 18, 2016 to May 30, 2018) and POST (October 18, 2018 to May 30, 2020) eras using Kaplan-Meier curves and time-to-event analyses.

RESULTS

A total of 1267 patients underwent HT from IABP (261 pre-policy/1006 post-policy). On multivariate analysis, PC was associated with an increase in HT (sub-distribution hazard ratio (sdHR): 2.15, p < .001) and decrease in death/deterioration (sdHR: 0.55, p = .011) on the waitlist with no effect on 1-year post-HT survival (p = .8). The exception status of patients undergoing HT was predominantly seen in the POST era (29%, 293/1006); only four patients in the PRE era. Exception requests in the POST era did not alter patient outcomes.

CONCLUSIONS

In patients bridged to heart transplant with an IABP, policy change is associated with decreased rates of death/deterioration and increased rates of heart transplantation on the waitlist without affecting 1-year post-transplant survival. While exception status use has markedly increased post-PC, it is not associated with patient outcomes.

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.

Prolonged Ischemic Times for Heart Transplantation: Impact of the 2018 Allocation Change

BACKGROUND

In 2018, the United Network for Organ Sharing (UNOS) implemented a change in heart allocation policy resulting in increased organ ischemic times in early analyses. This study evaluated the effect of ischemic time on one-year mortality in the context of allocation policy changes implemented in 2006 and 2018.

METHODS

The UNOS registry was utilized to identify adults undergoing heart transplantation from 2000-2020. Patients were stratified by the allocation policy era in which they underwent transplant (2000-June 2006, July 2006-Oct 2018, Oct 2018-2020) and by ischemic time, defined as normal (≤4) and (>6 hours). One-year survival was compared using Kaplan-Meier analysis. Cox regression was used to determine risk-adjusted hazards for ischemic time on one-year mortality.

RESULTS

40,052 patients were included for analysis. Ischemic times were normal in 32,585 (81.36%) and prolonged in 7,467 (18.64%) patients. The proportion of transplantations with prolonged ischemic times increased with each subsequent policy era. After the 2018 policy change, one-year survival was 90.92% with normal ischemic times versus 87.52% with prolonged ischemic times (p<0.001). Ischemic time independently predicted one-year mortality in each era with a hazard ratio of 1.20 per hour (p=0.004) in the current era.

CONCLUSIONS

Prolonged ischemic times occur in a minority of cases but are increasing in frequency. The independent risk of prolonged ischemic time on one-year mortality persists despite advances in storage technology and should remain a consideration in donor-recipient matching.

Use of Extracorporeal Membrane Oxygenation as Bridge to Replacement Therapies in Cardiogenic Shock: Insights From the Extracorporeal Life Support Organization

BACKGROUND

There has been increasing use of extracorporeal membrane oxygenation (ECMO) as bridge to heart transplant (orthotopic heart transplant [OHT]) or left ventricular assist device (LVAD) over the last decade. We aimed to provide insights on the population, outcomes, and predictors for the selection of each therapy.

METHODS

Using the Extracorporeal Life Support Organization Registry between 2010 and 2019, we compared in-hospital mortality and length of stay, predictors of OHT versus LVAD, and predictors of in-hospital mortality for patients with cardiogenic shock that were bridged with ECMO to OHT or LVAD. One hundred sixty-seven patients underwent LVAD versus 234 patients who underwent OHT.

RESULTS

The overall use of ECMO has increased from 1.7% in 2010 to 22.2% in 2019. Mortality was similar between groups (LVAD: 28.7% versus OHT: 29.1%) while length of stay was longer for OHT (LVAD: 49.6 versus OHT: 59.5 days, P=0.05). Factors associated with OHT included prior transplant (odds ratio [OR]=31.26 [CI, 3.84-780.5]), use of a temporary pacemaker (OR=6.5 [CI, 1.39-50.15]), and increased use of inotropes on ECMO (OR=3.77 [CI, 1.39-11.07]), whereas LVAD use was associated with weight (OR=0.98 [CI, 0.97-0.99]), cardiogenic shock presentation (OR=0.40 [CI, 0.21-0.78]), previous LVAD (OR=0.01 [CI, 0.0001-0.22]), respiratory failure (OR=0.28 [CI, 0.11-0.70]), and milrinone infusion (OR=0.32 [CI, 0.15-0.67]). Older age (OR=1.07 [CI, 1.02-1.12]), cannulation bleeding (OR=26.1 [CI, 4.32-221.3]), and surgical bleeding (OR=6.7 [CI, 1.26-39.9]) in patients receiving LVAD and respiratory failure (OR=5 [CI, 1.17-23.1]) and continuous renal replacement therapy (OR=3.82 [CI, 1.28-11.9]) in patients receiving OHT were associated with increased mortality.

CONCLUSIONS

ECMO use as a bridge to advanced therapies has increased over time, with more patients undergoing LVAD than OHT. Mortality was equal between the 2 groups while length of stay was longer for OHT.

Changes in waitlist and posttransplant outcomes in patients with adult congenital heart disease after the new heart transplant allocation system

OBJECTIVE

In 2018, the United Network for Organ Sharing (UNOS) introduced new criteria for heart allocation. This study sought to assess the impact of this change on waitlist and posttransplant outcomes in adult congenital heart disease (ACHD) recipients.

METHODS

Between January 2010 and March 2020, we extracted first heart transplant ACHD patients listed from the UNOS database. We compared waitlist and post-transplant outcomes before and after the policy change.

RESULTS

A total of 1206 patients were listed, 951 under the old policy and 255 under the new policy. Prior to transplant, recipients under the new policy era were more likely to be treated with extracorporeal membrane oxygenation (P = .018), and have intra-aortic balloon pumps (P < .001), and less likely to have left ventricular assist devices (P = .027).Compared to patients waitlisted in the pre-policy change era, those waitlisted in the post policy change era were more likely to receive transplants (P = .001) with no significant difference in waiting list mortality (P = .267) or delisting (P = .915). There was no difference in 1-year survival post-transplant between the groups (P = .791).

CONCLUSION

The new policy altered the heart transplant cohort in the ACHD group, allowing them to receive transplants earlier with no changes in early outcomes after heart transplantation.