The urgent priority for transplantation is to trim the waiting list

Heart Transplantation: A Bibliometric Review From 1990-2021

BACKGROUND

As the rapidly aging population and the rising incidence of end-stage heart failure (HF), extensive research has been conducted on heart transplantation (HTx). Bibliometrics harbors the function for describing the relationships of knowledge structures in different research fields and predicting the growth trend .

METHODS

The publications were searched and filtered based on the WOS core database. The target literature was visualized and analyzed by CiteSpace or VOSviewer .

RESULTS

In total, 19,998 published papers were obtained. There is a wave-like growth in HTx development. Most advanced research results are concentrated in a few developed countries, while the interactions with developing countries are still in infancy. The United States occupies a strong dominant position among active countries on HTx. Early research hotpots mostly focused on primary disease, survival risk factors, and complications. In recent years, the research frontiers have shifted steadily to clinical evaluation of immunosuppressants and diagnosis of acute rejection, cardiac re-injury with COVID-19, innovations in ventricular assist devices(VAD), and donation allocation strategies. The research directions of HTx are gradually shifting from observational studies to intervention research.

Amiodarone Use Prior to Cardiac Transplant Impacts Early Post-Transplant Survival

PURPOSE

It remains unclear if use of amiodarone pre-cardiac transplantation impacts early post-transplant survival.

METHODS

We selected all patients undergoing heart transplant from 2004 to 2006 with available information using the United Network for Organ Sharing database (n = 4057). Multivariable Cox models compared the risk of death within 30 days post-transplant in patients who were taking amiodarone at the time of transplant listing (n = 1227) to those who were not (n = 2830).

RESULTS

Mean age was 52 (± 12) years, and 23% were women. Patients who died within 30 days (n = 168) were older; had higher panel reactive antibody levels, higher bilirubin levels, and higher prevalence of prior cardiac surgery; were often at status 1B; and had higher use of amiodarone at listing compared to those who survived (5.3% versus 3.6%; p = 0.02). Cause of death was unknown in 49% and was reported as graft failure in 43% of cases. In multivariable Cox models, patients on amiodarone at the time of listing had 1.56-fold higher risk of post-transplant death within 30 days (95% confidence intervals 1.08-2.27) compared to patients who were not on amiodarone at listing (C-statistic 0.70).

CONCLUSION

In conclusion, patients who reported taking amiodarone at the time of listing for transplant had a higher risk of death within 30 days post-transplant.

Geographic Variation in the Treatment of U.S. Adult Heart Transplant Candidates

BACKGROUND

The current U.S. priority ranking for heart candidates is based on treatment intensity, not objective markers of severity of illness. This system may encourage centers to overtreat candidates.

OBJECTIVES

This study sought to describe national variation in the intensity of treatment of adult heart transplantation candidates and identify center-level predictors of potential overtreatment.

METHODS

The registrations of all U.S. adult heart transplantation candidates from 2010 to 2015 were collected from the SRTR (Scientific Registry of Transplant Recipients). "Potential overtreatment" was defined as treatment of a candidate who did not meet American Heart Association cardiogenic shock criteria with either high-dose inotropes or an intra-aortic balloon pump. Multilevel logistic regression and propensity score models were used to adjust for candidate variability at each center. Center-level variables associated with potential overtreatment were identified.

RESULTS

From 2010 to 2015, 108 centers listed 12,762 adult candidates who were not in cardiogenic shock for heart transplantation. Of these, 1,471 (11.6%) were potentially overtreated with high-dose inotropes or intra-aortic balloon pumps. In the bottom quartile of centers, only 2.1% of candidates were potentially overtreated compared with 27.6% at top quartile centers, an interquartile difference of 25.5% (95% confidence interval: 21% to 30%). Adjusting for candidate differences did not significantly alter the interquartile difference. Local competition with 2 or more centers increased the odds of potential overtreatment by 50% (adjusted odds ratio: 1.50; 95% confidence interval: 1.07 to 2.11).

CONCLUSIONS

There is wide variation in the treatment practices of adult heart transplantation centers. Competition for transplantable donor hearts is associated with the potential overtreatment of hemodynamically stable candidates. Overtreatment may compromise the fair and efficient allocation of scarce deceased donor hearts.

Performing diagnostic coronary angiography to evaluate high-risk cardiac donors: A French nationwide cohort study

BACKGROUND

Allograft shortage might be overcome by the use of hearts from expanded-criteria donors (ECD) but their estimated high-risk of coronary artery disease (CAD) results in a limited utilization of these hearts for transplantation. We aimed to determine if performing coronary angiography (CA) in ECD enhances cardiac procurement and to develop a predictive model estimating their probability of absence of CAD.

METHODS

We retrospectively used the French National Transplant Registry CRISTAL and considered all donors aged 45 to 70 with ≥ 1 organ harvested between March 2012 and June 2014 to derive a high-risk donor population. Of 515 donors with ≥ 1 CAD risk factor and no obvious contraindication for cardiac procurement, 230 underwent CA. Coefficients estimated by multivariate logistic regression models were used to evaluate the impact of CA on procurement and build the predictive model.

RESULTS

Among CA donors, 133 had CAD, 53 (23%) with at least one stenosis ≥ 50%. Predictors of cardiac graft offer were female gender, age below 60, no cardiac arrest, no intravenous adrenaline/dobutamine requirement and no treated hypercholesterolemia. CA increased the probability of procurement by 9% (p = 0.028). Female gender, non-vascular cause of death, absence of diabetes and BMI ≥ 25 kg/m² (p < 0.05) were associated with a normal CA and used for the prediction model. The area under the ROC curve of the model was 0.70. Specificity for the highest quartile was 82%.

CONCLUSION

Performing CA in ECD enhances cardiac procurement. When CA is not feasible, we defined a clinical score allowing accurate estimation of normal CA probability.

Adverse Effects of Delayed Transplant Listing Among Patients With Implantable Left Ventricular Assist Devices

BACKGROUND

The timing of transplant listing after implantation of a left ventricular assist device (LVAD) remains uncertain, given high device complication rates and apparent stability of some LVAD-supported patients. This investigation quantifies the effect of delayed transplant listing and transplantation rates on medium-term survival and LVAD complications.

METHODS AND RESULTS

A Markov model was used to simulate the effects of delaying initial transplant listing after LVAD implantation. Modeled parameters were derived from the Standard Transplant Analysis and Research file. When transplant listing was delayed and 5-year results were examined, fewer persons underwent transplantation (53% in base model vs 51% in 180-day-delay model) and the fraction of deaths while waiting increased (17% in base model vs 21% in 180-day delay model). Life expectancy changed minimally from the base model (3.50 y) when initial listing was delayed by 180 days (3.51 y).

CONCLUSIONS

Delaying initial transplant listing increased the likelihood of death while waiting for a transplant and decreased the likelihood of transplantation. In aggregate, life expectancy was unchanged by delays in listing. This study suggests that delaying transplant listing with the expectation of providing additional life expectancy is not likely with current LVAD technology.

Trends in the Use of Inotropes to List Adult Heart Transplant Candidates at Status 1A

BACKGROUND

The number of adult heart transplant candidates waiting at the most urgent status 1A has increased over time despite the expansion of geographic sharing of hearts in 2006. We aimed to determine whether candidates listed with inotropes contribute to the excess status 1A candidates.

METHODS AND RESULTS

The initial registrations of all adult heart-only candidates listed from 2000 to 2015 were analyzed using the Scientific Registry of Transplant Recipients data set. Trends in listing status, justifications, and candidate factors were measured. Adjusted trends in listing status pre- and post-geographic sharing were estimated using multilevel logistic regression. Competing risks models provided trends in transplant-free waitlist survival. There were 46 853 adult heart-alone listings during 2000 to 2015. Pre-sharing, status 1A listing was unchanged over time (adjusted odds ratio, 0.98; 95% confidence interval, 0.78-1.23). Post-sharing, the adjusted odds of status 1A listing increased 117% over 9 years (adjusted odds ratio 2.17, 95% confidence interval, 1.82-2.58). The number of candidates listed as status 1A with inotropes increased by 193 a year, whereas the dobutamine, dopamine, and milrinone doses used decreased 49%, 55%, and 29% (P<0.001). The risk of waitlist death or deterioration of status 1A inotrope candidates relative to status 2 candidates decreased 62% for 2006 to 2010 and 70% for 2011 to 2015 compared with that for 2003 to 2006.

CONCLUSIONS

After the wider geographic sharing of hearts in 2006, transplant programs used multiple inotropes to list candidates at status 1A more frequently with progressively lower doses. Concurrently, the status 1A inotrope candidate waitlist outcomes improved substantially. These trends suggest that overtreatment with multiple inotropes contributes to the current critical excess of status 1A candidates.

Access to Heart Transplantation: A Proper Analysis of the Competing Risks of Death and Transplantation Is Required to Optimize Graft Allocation

Supplemental digital content is available in the text.

Background

Heart allocation systems are usually urgency-based, offering grafts to candidates at high risk of waitlist mortality. In the context of a revision of the heart allocation rules, we determined observed predictors of 1-year waitlist mortality in France, considering the competing risk of transplantation, to determine which candidate subgroups are favored or disadvantaged by the current allocation system.

Methods

Patients registered on the French heart waitlist between 2010 and 2013 were included. Cox cause-specific hazards and Fine and Gray subdistribution hazards were used to determine candidate characteristics associated with waitlist mortality and access to transplantation.

Results

Of the 2053 candidates, 7 variables were associated with 1-year waitlist mortality by the Fine and Gray method including 4 candidate characteristics related to heart failure severity (hospitalization at listing, serum natriuretic peptide level, systolic pulmonary artery pressure, and glomerular filtration rate) and 3 characteristics not associated with heart failure severity but with lower access to transplantation (blood type, age, and body mass index). Observed waitlist mortality for candidates on mechanical circulatory support was like that of others.

Conclusions

The heart allocation system strongly modifies the risk of pretransplant mortality related to heart failure severity. An in-depth competing risk analysis is therefore a more appropriate method to evaluate graft allocation systems. This knowledge should help to prioritize candidates in the context of a limited donor pool.

The Impact of Obesity on Patients Bridged to Transplantation With Continuous-Flow Left Ventricular Assist Devices

OBJECTIVES

This study sought to determine if obese patients had worse post-left ventricular assist device (LVAD) implantation outcomes and if the implantation of an LVAD allowed for weight loss.

BACKGROUND

Obesity is a risk factor for cardiovascular disease including heart failure. Obese heart failure patients have better outcomes than those with normal weight; however, obese patients have worse outcomes after heart transplantation.

METHODS

Patients were identified in the United Network for Organ Sharing (UNOS) database that underwent LVAD implantation as bridge to transplantation from May 2004 and April 2014, with follow-up through June 2014. Patients were grouped according to body mass index (BMI) based on the World Health Organization classification.

RESULTS

Among 3,856 patients, the risk of death or delisting was not significantly different between BMI groups (p = 0.347). There was no increased risk of death (p = 0.234) or delisting (p = 0.918). The risk of complication requiring UNOS status upgrade was increased for those with class II obesity or greater (hazard ratio: 1.48; p = 0.004), driven by increased infection and thromboembolism. Obese patients had worse post-transplantation outcomes. Weight loss substantial enough to decrease BMI group was achieved by a small proportion of patients listed with class I obesity or greater (9.6% to 15.5%).

CONCLUSIONS

Patients with obesity had similar freedom from death or delisting while on LVAD support. However, class II obese or greater patients had an increased risk of complications requiring UNOS status upgrade compared with those with normal BMI during LVAD support and decreased post-transplantation survival. Weight loss on device therapy was possible, but uncommon. Careful consideration is needed when a bridge to weight loss strategy is proposed.

Acellular human heart matrix: A critical step toward whole heart grafts

The best definitive treatment option for end-stage heart failure currently is transplantation, which is limited by donor availability and immunorejection. Generating an autologous bioartificial heart could overcome these limitations. Here, we have decellularized a human heart, preserving its 3-dimensional architecture and vascularity, and recellularized the decellularized extracellular matrix (dECM). We decellularized 39 human hearts with sodium-dodecyl-sulfate for 4-8 days. Cell removal and architectural integrity were determined anatomically, functionally, and histologically. To assess cytocompatibility, we cultured human cardiac-progenitor cells (hCPC), bone-marrow mesenchymal cells (hMSCs), human endothelial cells (HUVECs), and H9c1 and HL-1 cardiomyocytes in vitro on dECM ventricles up to 21 days. Cell survival, gene expression, organization and/or electrical coupling were analyzed and compared to conventional 2-dimensional cultures. Decellularization removed cells but preserved the 3-dimensional cardiac macro and microstructure and the native vascular network in a perfusable state. Cell survival was observed on dECM for 21 days. hCPCs and hMSCs expressed cardiocyte genes but did not adopt cardiocyte morphology or organization; HUVECs formed a lining of endocardium and vasculature; differentiated cardiomyocytes organized into nascent muscle bundles and displayed mature calcium dynamics and electrical coupling in recellularized dECM. In summary, decellularization of human hearts provides a biocompatible scaffold that retains 3-dimensional architecture and vascularity and that can be recellularized with parenchymal and vascular cells. dECM promotes cardiocyte gene expression in stem cells and organizes existing cardiomyocytes into nascent muscle showing electrical coupling. These findings represent a first step toward manufacturing human heart grafts or matrix components for treating cardiovascular disease.

Pretransplant coagulopathy and in-hospital outcomes among heart transplant recipients: a propensity-matched nationwide inpatient sample study

BACKGROUND

The prevalence and contemporary trends of pre-heart transplantation (HT) coagulopathy and associated clinical outcomes have not been studied from a national database.

HYPOTHESIS

Pre-HT coagulopathy is associated with increased in-hospital mortality.

METHODS

Among 2454 adult HT recipients from the 2003 to 2010 Nationwide Inpatient Sample databases, 707 (29%) had pre-HT coagulopathy (defined as a comorbidity variable, based on International Classification of Diseases, Ninthe Revision, Clinical Modification and Diagnosis Related Group codes). We used propensity scores for coagulopathy to assemble a matched cohort of 664 pairs of patients with and without coagulopathy balanced in 54 baseline characteristics.

RESULTS

The prevalence of pre-HT coagulopathy increased from 17% in 2003 to 44% in 2010 (P for trend <0.001). In-hospital mortality occurred in 8.6% and 4.7% of matched HT recipients with and without coagulopathy, respectively (hazard ratio: 1.81; 95% confidence interval [CI]: 1.17-2.80; P = 0.008). Coagulopathy was not significantly associated with post-HT graft complications (odds ratio [OR]: 1.20; 95% CI: 0.95-1.52; P = 0.131) but was associated with increased blood transfusions (OR: 1.92; 95% CI, 1.54-2.41; P < 0.001). Coagulopathy and no-coagulopathy groups had no difference in median length of stay (22 days in each group, P = 0.746), but median total hospital charges were higher among patients with coagulopathy compared to those without (US$425 643 vs US$389 656; P = 0.008).

CONCLUSIONS

In this national study of HT recipients, pretransplant coagulopathy was common, increased over time, and was not significantly associated with post-HT graft complications or increased hospital stay. However, it was associated with increased bleeding risk, in-hospital mortality, and total hospital charges. These findings may have implications for the selection of patients for HT.

Considerations for patients awaiting heart transplantation-Insights from the UK experience

The nature and size of the heart transplant waiting list has changed over recent years, most obviously with a larger number of patients on the list with ventricular assist devices (VADs). Given the limited numbers of available donors it is time to re-evaluate who is actually placed on the list. Evidence suggests that many patients with stable ambulatory heart failure might have a limited survival benefit from heart transplantation, so these patients may be an obvious target when considering how to reduce the size of the list. How stable VAD patients or adult congenital heart disease patients with declining symptoms should be prioritized for transplantation is unclear. Nevertheless we do need effective and simple models that can predict which of these disparate groups would benefit from transplantation so that we can fairly distribute this scarce commodity to the sickest patients that would benefit the most from transplantation.

The future direction of the adult heart allocation system in the United States

Ensuring equitable and fair organ allocation is a central charge of the United Network for Organ Sharing (UNOS) as the Organ Procurement and Transplantation Network (OPTN) through its contract with the Department of Health and Human Services (DHHS). The OPTN/UNOS Board initiated a reassessment of the current allocation system. This paper describes the efforts of the OPTN/UNOS Heart Subcommittee, acting on behalf of the OPTN/UNOS Thoracic Organ Transplantation Committee, to modify the current allocation system. The Subcommittee assessed the limitations of the current three-tiered system, outcomes of patients with status exceptions, emerging ventricular assist device (VAD) population, options for improved geographic sharing and status of potentially disenfranchised groups. They analyzed waiting list and posttransplant mortality rates of a contemporary cohort of patient groups at risk, in collaboration with the Scientific Registry of Transplant Recipients to develop a proposed multi-tiered allocation scheme. This proposal provides a framework for simulation modeling to project whether candidates would have better waitlist survival in the revised allocation system, and whether posttransplant survival would remain stable. The tiers are subject to change, based on further analysis by the Heart Subcommittee and will lead to the development of a more effective and equitable heart allocation system.

Four-year outcomes with third-generation centrifugal left ventricular assist devices in an era of restricted transplantation

OBJECTIVES

Third-generation ventricular assist devices (VADs) are associated with improved outcomes, though in recent clinical trials bridge-to-transplant (BTT) rates are ∼30% at 6 months, so that transplantation can be used as a ‘bail out’ for serious complications. In the UK, there was a significant reduction in heart transplantation rates over the last decade, so that transplantation from VADs is much less frequent. The objective of this study was to determine outcomes and their predictors in this situation of low BTT rates, and as patients were exposed to long-term support, the incidence and outcomes of VAD thrombosis.

METHODS

We analysed outcomes for 102 consecutive patients between 2009 and 2013 (mean age 47 ± 13; VentrAssist n = 6 and HeartWare n = 96). The median duration of support was 462 ± 426 days.

RESULTS

Survival rates on the device were 75 and 66% at 1 and 2 years, respectively. Older age and more acute INTERMACS groups were significantly related to reduced survival within the first 90 days (P = 0.030 and 0.010, respectively). Poor preoperative right ventricular (RV) function had a negative effect on survival after 1 year (P = 0.009), though not earlier. VAD thrombosis (n = 24 HeartWare and n = 1 VentrAssist) occurred at 0.18 events per patient-year for HeartWare and 0.07 for VentrAssist devices at a median time of onset at 404 ± 281 days. There was no significant effect of VAD thrombosis on survival. Only 14 of 102 patients were transplanted at a median of 334 ± 347 days, and only 3 were transplanted within the first 6 months.

CONCLUSIONS

Third-generation left ventricular assist device implants with a low rate of transplantation have similar survival to destination therapy, and are susceptible to long-term complications of VAD thrombosis and right heart failure.

The unsolved problem of organ allocation in times of organ shortage: the German solution?

The concept of the International and Inter-Society Co-ordination Committee (I2C2) has been introduced at the International Society for Heart and Lung Transplantation (ISHLT) annual meeting in Prague. It is a pivotal role of I2C2 to develop formal relationships with other societies involved in the field of thoracic transplantation to attain mutual benefits, share membership, and achieve common goals. This editorial is on behalf of an initiative of the I2C2 committee chairs to report about a specific problem related to thoracic transplantation in 1 European country and the approach chosen by the local national authorities, together with the transplant community, to address this issue.

The vexing problem of thrombosis in long-term mechanical circulatory support

Durable left ventricular assist devices (LVADs) have not only enhanced longevity but also conferred sustained improvements in quality of life, symptom control, and functional capacity in patients with medically refractory advanced heart failure. Problems with device-related infection, bleeding, neurologic events, right-sided heart failure, and device malfunction have dominated the clinical care of patients living on mechanical support. Even as adoption of durable LVADs accelerated globally, we began to encounter a growing dilemma of pump malfunction caused by thrombosis. In early 2011, clinicians began to notice a spike in the incidence of pump thrombosis with the HeartMate II (Thoratec Corp, Pleasanton, CA) LVAD. By 2012, the problem of thrombosis in LVADs began to consume most of the scientific direction as centers and collaborative groups began to dissect this nascent phenomenon. In this perspective, we describe the magnitude and implications of pump thrombosis, discuss secular and management trends in this unique population, attempt to dissect the problem at its root, offer guidance on surveillance and therapeutic principles, and outline issues that deserve our immediate and collaborative attention.