The influence of ischemia and reperfusion time on outcome in heart transplantation

Overcoming the Boundaries of Heart Warm Ischemia in Donation After Circulatory Death: The Padua Case

A 45 year old male obese patient with a previous history of repaired congenital heart disease developed worsening heart failure making heart transplantation listing mandatory. Unfortunately, due to his anthropometric measures, the search for a suitable brain-dead donor was unsuccessful. For this reason, he accepted to be enrolled in the controlled donation after circulatory death (cDCD) program. According to the Italian Law regulating death declaration after cardiac arrest (no-touch period of 20 minutes-one of the longest in the world), we faced a 34 minute cardiac asystole, after which the heart was recovered through a thoraco-abdominal normothermic regional perfusion excluding the epiaortic vessels. The heart was then preserved by means of cold static storage. Heart transplantation was performed successfully without any signs of primary graft failure. Postoperative endomyocardial biopsies were negative for acute cellular and antibody-mediated rejection. Furthermore, echocardiographic and cardiac magnetic resonance evaluation of the heart did not show any functional abnormalities. The patient was discharged on post-operative day (POD) #39 in good clinical conditions.

Four decades of progress in heart-lung transplantation: Two hundred seventy-one cases at a single institution

OBJECTIVE

The objective of this study is to evaluate survival for combined heart-lung transplant (HLTx) recipients across 4 decades at a single institution. We aim to summarize our contemporary practice based on more than 271 HLTx procedures over 40 years.

METHODS

Data were collected from a departmental database and the United Network for Organ Sharing. Recipients younger than age 18 years, those undergoing redo HLTx, or triple-organ system transplantation were excluded, leaving 271 patients for analysis. The pioneering era was defined by date of transplant between 1981 and 2000 (n = 155), and the modern era between 2001 and 2022 (n = 116). Survival analysis was performed using cardinality matching of populations based on donor and recipient age, donor and recipient sex, ischemic time, and sex matching.

RESULTS

Between 1981 and 2022, 271 HLTx were performed at a single institution. Recipients in the modern era were older (age 42 vs 34 y; P < .001) and had shorter waitlist times (78 vs 234 days; P < .001). Allografts from female donors were more common in the modern era (59% vs 39%; P = .002). In the matched survival analysis, 30-day survival (97% vs 84%; P = .005), 1-year survival (89% vs 77%; P = .041), and 10-year survival (53% vs 26%; P = .012) significantly improved in the modern era relative to the pioneering era, respectively.

CONCLUSIONS

Long-term survival in HLTx is achievable with institutional experience and may continue to improve in the coming decades. Advances in mechanical circulatory support, improved maintenance immunosuppression, and early recognition and management of acute complications such as primary graft dysfunction and acute rejection have dramatically improved the prognosis for recipients of HLTx in our contemporary institutional experience.

Acute rejection in donation after circulatory death (DCD) heart transplants

BACKGROUND

Donation after circulatory death (DCD) heart transplantation has promising early survival, but the effects on rejection remain unclear.

METHODS

The United Network for Organ Sharing database was queried for adult heart transplants from December 1, 2019, to December 31, 2021. Multiorgan transplants and loss to follow-up were excluded. The primary outcome was acute rejection, comparing DCD and donation after brain death (DBD) transplants.

RESULTS

A total of 292 DCD and 5,582 DBD transplants met study criteria. Most DCD transplants were transplanted at status 3-4 (61.0%) compared to 58.6% of DBD recipients at status 1-2. DCD recipients were less likely to be hospitalized at transplant (26.7% vs 58.3%, p < 0.001) and to require intra-aortic balloon pumping (IABP; 9.6% vs 28.9%, p < 0.001), extracorporeal membrane oxygenation (ECMO; 0.3% vs 5.9%, p < 0.001) or temporary left ventricular assist device (LVAD; 1.0% vs 2.7%, p < 0.001). DCD recipients were more likely to have acute rejection prior to discharge (23.3% vs 18.4%, p = 0.044) and to be hospitalized for rejection (23.4% vs 11.4%, p = 0.003) at a median follow-up of 15 months; the latter remained significant after propensity matching. On multivariable logistic regression, DCD donation was an independent predictor of acute rejection (odds ratio [OR] 1.47, 95% confidence interval [CI] 1.00-2.15, p = 0.048) and hospitalization for rejection (OR 2.03, 95% CI 1.06-3.70, p = 0.026). On center-specific subgroup analysis, DCD recipients continued to have higher rates of hospitalization for rejection (23.4% vs 13.8%, p = 0.043).

CONCLUSIONS

DCD recipients are more likely to experience acute rejection. Early survival is similar between DCD and DBD recipients, but long-term implications of increased early rejection in DCD recipients require further investigation.

Short-term outcomes after heart transplantation using donor hearts preserved with ex vivo perfusion

The standard Conventional Cold Storage (CCS) during heart transplantation procurement is associated with time-dependent ischemic injury to the graft, which is a significant independent risk factor for post-transplant early morbidity and mortality - especially when cold ischemic time exceeds four hours. Since 2018, Rigshospitalet (Copenhagen, Denmark) has been utilising ex vivo perfusion (Organ Care System, OCS) in selected cases. The objective of this study was to compare the short-term clinical outcomes of patients transplanted with OCS compared to CCS. Methods: This retrospective single-centre study was based on consecutive patients undergoing a heart transplant between January 2018 and April 2021. Patients were selected for the OCS group when the cold ischemic time was expected to exceed four hours. The primary outcome measure was six-month event-free survival. Results: In total, 48 patients were included in the study; nine were transplanted with an OCS heart. The two groups had no significant differences in baseline characteristics. Six-month event-free survival was 77.8% [95% CI: 54.9-100%] in the OCS group and 79.5% [95% CI: 67.8-93.2%] in the CCS group (p = 0.91). While the OCS group had a median out-of-body time that was 183 min longer (p < 0.0001), the cold ischemic time was reduced by 51 min (p = 0.007). Conclusion: In a Scandinavian setting, our data confirms that utilising OCS in heart procurement allows for a longer out-of-body time and a reduced cold ischemic time without negatively affecting safety or early post-transplant outcomes.

Graft function and incidence of cardiac allograft vasculopathy in donation after circulatory-determined death heart transplant recipients

Experience in donation after circulatory-determined death (DCD) heart transplantation (HTx) is expanding. There is limited information on the functional outcomes of DCD HTx recipients. We sought to evaluate functional outcomes in our cohort of DCD recipients. We performed a single-center, retrospective, observational cohort study comparing outcomes in consecutive DCD and donation after brain death (DBD) HTx recipients between 2015 and 2019. Primary outcome was allograft function by echocardiography at 12 and 24 months. Secondary outcomes included incidence of cardiac allograft vasculopathy, treated rejection, renal function, and survival. Seventy-seven DCD and 153 DBD recipients were included. There was no difference in left ventricular ejection fraction at 12 months (59% vs 59%, P = .57) and 24 months (58% vs 58%, P = .87). There was no significant difference in right ventricular function at 12 and 24 months. Unadjusted survival between DCD and DBD recipients at 5 years (85.7% DCD and 81% DBD recipients; P = .45) was similar. There were no significant differences in incidence of cardiac allograft vasculopathy (odds ratio 1.59, P = .21, 95% confidence interval 0.77-3.3) or treated rejection (odds ratio 0.60, P = .12, 95% confidence interval 0.32-1.15) between DBD and DCD recipients. Post-transplant renal function was similar at 1 and 2 years. In conclusion, cardiac allografts from DCD donors perform similarly to a contemporary population of DBD allografts in the medium term.

Nonischemic Donor Heart Preservation: New Milestone in Heart Transplantation History

Heart transplantation is considered the gold standard for the treatment of advanced end-stage heart failure. However, standard donors after brain death are decreasing, whereas patients on the heart transplant waitlist are constantly rising. The introduction of the ex vivo machine perfusion device has been a turning point; in fact, these systems are able to significantly reduce ischemic times and have a potential effect on ischemia-related damage reduction. From a clinical standpoint, these machines show emerging results in terms of heart donor pool expansion, making marginal donors and donor grafts after circulatory death suitable for donation. This article aims to review mechanisms and preclinical and clinical outcomes of currently available ex vivo perfusion systems, and to explore the future fields of application of these technologies.

Early trends in cardiac allograft vasculopathy after implementation of the 2018 donor heart allocation policy in the United States

STUDY OBJECTIVE

To evaluate the impact of the new donor heart allocation system implemented in the United States in October 2018 on development of early cardiac allograft vasculopathy (CAV).

DESIGN

Retrospective cohort study.

PARTICIPANTS

Adult (≥ 18 years) heart transplant recipients registered in the United Network for Organ Sharing database between October 18, 2015 and October 17, 2018 (old system) and October 18, 2018 and May 31, 2020 (new system).

MAIN OUTCOME MEASURE

Incidence of angiographic CAV at 1 year (accelerated CAV) in the overall transplant population and among the highest acuity subgroup-Status 1A (old) and Status 1 or 2 (new). We included recipient and donor demographic, cardiovascular, and transplant factors in multivariable logistic regression models to identify predictors of accelerated CAV.

RESULTS

Of 10,375 transplant recipients, 6,660 (64%) and 3,715 (36%) were listed in the old and new allocation cohorts, respectively. The incidence of accelerated CAV was 521 (8%) in the old period compared with 272 (7%) in the new period (P = .36). Similar incidence rates were observed in the highest acuity subgroup-363 (8%) compared with 143 (7%), respectively (P = .13). In adjusted analyses of the high-acuity cohort, the new allocation system was not associated with a higher likelihood of accelerated CAV (odds ratio = 0.87, 95% confidence interval: 0.70-1.08, P = .20).

CONCLUSIONS

The new donor heart allocation system is not associated with development of accelerated angiographic CAV at 1 year, including among recipients requiring the most urgent transplants.

Improvement of Left Ventricular Graft Function Using an Iron-Chelator-Supplemented Bretschneider Solution in a Canine Model of Orthotopic Heart Transplantation

Demand for organs is increasing while the number of donors remains constant. Nevertheless, not all organs are utilized due to the limited time window for heart transplantation (HTX). Therefore, we aimed to evaluate whether an iron-chelator-supplemented Bretschneider solution could protect the graft in a clinically relevant canine model of HTX with prolonged ischemic storage. HTX was performed in foxhounds. The ischemic time was standardized to 4 h, 8 h, 12 h or 16 h, depending on the experimental group. Left ventricular (LV) and vascular function were measured. Additionally, the myocardial high energy phosphate and iron content and the in-vitro myocyte force were evaluated. Iron chelator supplementation proved superior at a routine preservation time of 4 h, as well as for prolonged times of 8 h and longer. The supplementation groups recovered quickly compared to their controls. The LV function was preserved and coronary blood flow increased. This was also confirmed by in vitro myocyte force and vasorelaxation experiments. Additionally, the biochemical results showed significantly higher adenosine triphosphate content in the supplementation groups. The iron chelator LK614 played an important role in this mechanism by reducing the chelatable iron content. This study shows that an iron-chelator-supplemented Bretschneider solution effectively prevents myocardial/endothelial damage during short- as well as long-term conservation.

Ischemic time and patient outcomes after the 2018 UNOS donor heart allocation system change

BACKGROUND

The allocation system for heart donors in the United States changed on October 18, 2018. The typical distance from donor hospitals to recipient hospitals has increased as has the ischemic time. We investigated patient outcomes with the new allocation system and the differential effects of ischemic time under both the old and new allocation schemas.

METHODS

The United Network for Organ Sharing Registry (UNOS) was queried for data regarding heart transplants occurring from October 1, 1987 to March 1, 2021. In total, 62,301 adult heart transplants were examined. Survival outcomes at 30 days and 1 year and ischemic times were compared via adjusted logistic and Cox models (overall survival and time until post-transplant rejection).

RESULTS

Mean ischemic time was slightly increased in the new system (3.43 h vs. 3.03 h, p < .001). Survival differences between old versus new systems were not observed in adjusted models (p = .818). However, there was evidence to suggest longer ischemic times are more detrimental to long-term survival under the new system (hazard ratio [HR] = 1.15 per hour increase; p = .001) versus the old system (HR = 1.08 per hour increase; p < .001), although this relationship did not reach statistical significance (p = .150).

CONCLUSIONS

Although travel distances have significantly increased under the new allocation system, survival outcomes remain largely unchanged. Ischemic time is an influential factor in recipient survival that should be limited during organ transport. Further studies on the impact of travel distances and ischemic time under the new allocation system are needed.

Determining optimal donor heart ischemic times in adult cardiac transplantation

Objectives

Unsupervised statistical determination of optimal allograft ischemic time (IT) on heart transplant outcomes among ABO donor heart types.

Methods

We identified 36,145 heart transplants (2000–2018) from the United Network for Organ Sharing database. Continuous and categorical variables were analyzed with parametric and nonparametric testing. Determination of IT cutoffs for survival analysis was performed using Contal and O'Quigley univariable method and Vito Muggeo multivariable segmented modeling.

Results

Univariable and multivariable IT threshold determination revealed a cutoff at about 3 h. The hourly increase in survival risk with ≥3 h IT is asymmetrically experienced at the early 90 days (hazard ratio [HR] = 1.29, p < .001) and up to 1‐year time point (HR = 1.16, p < .001). Beyond 1 year the risk of prolonged IT is less impactful (HR = 1.04, p = .022). Longer IT was associated with more postoperative complications such as stroke (2.7% vs. 2.3, p = .042), dialysis (11.6% vs. 9.1%, p < .001) and death from primary graft dysfunction (1.8% vs. 1.2%, p < .001). O blood type donor hearts with IT ≥ 3 h has significantly increased hourly mortality risk at 90 days (HR = 1.27, p < .001), 90 days to 1 year (HR = 1.22, p < .001) and >1 year (HR = 1.05, p = .041). For non‐O blood types with ≥3 h IT hourly mortality risk was increased at 90 days (HR = 1.33, p < .001), but not at 90 days to 1 year (HR = 1.09, p = .146) nor ≥1 year (HR = 1.08, p = .237).

Conclusions

The donor heart IT threshold for survival determined from unbiased statistical modeling occurs at 3 h. With longer preservation times, transplantation with O donor hearts was associated with worse survival.

New Insight Into the Cardioprotective Effects of Allium ursinum L. Extract Against Myocardial Ischemia-Reperfusion Injury

This study aimed to estimate the effects of increasing doses of Allium ursinum methanol extract on cardiac ischemia/reperfusion injury (I/R) with a special emphasis on the role of oxidative stress. Fifty rats were randomly divided into five groups (10 animals per group) depending on the applied treatment as follows: sham, rats who drank only tap water for 28 days and hearts were retrogradely perfused for 80 min without I/R injury, I/R, rats who drank only tap water for 28 days and hearts were exposed to ex vivo I/R injury and rats who consumed increasing doses of A. ursinum 125, 250, and 500 mg/kg for 28 days before I/R injury. Hearts from all rats were isolated and retrogradely perfused according to the Langendorff technique. Parameters of oxidative stress were spectrophotometrically measured in blood, coronary venous effluent, and heart tissue samples. Intake of wild garlic extract for 28 days significantly contributed to the recovery of cardiac function, which was reflected through preserved cardiac contractility, systolic function, and coronary vasodilatory response after ischemia. Also, wild garlic extract showed the potential to modulate the systemic redox balance and stood out as a powerful antioxidant. The highest dose led to the most efficient decrease in cardiac oxidative stress and improve recovery of myocardial function after I/R injury. We might conclude that wild garlic possesses a significant role in cardioprotection and strong antioxidant activity, which implicates the possibility of its use alone in the prevention or as adjuvant antioxidant therapy in cardiovascular diseases (CVD).

LncRNA HCP5 in hBMSC-derived exosomes alleviates myocardial ischemia reperfusion injury by sponging miR-497 to activate IGF1/PI3K/AKT pathway

Ischemia/reperfusion (I/R) injury is an inevitable process during heart transplant and suppressing I/R injury could greatly improve the survival rate of recipients. Mesenchymal stem cells (MSCs) have positive effects on I/R. We aimed to investigate the mechanisms underlying the protective roles of MSCs in I/R. Both cell model and rat model of myocardial I/R were used. MTT assay and flow cytometry were used to measure cell viability and apoptosis, respectively. QRT-PCR and western blotting were employed to measure levels of lncRNA HCP5 (HLA complex P5), miR-497, apoptosis-related proteins, and insulin-like growth factor (IGF1)/PI3K/AKT pathway. Dual luciferase assay was used to validate interactions of HCP5 and miR-497, miR-497 and IGF1. Echocardiography was performed to evaluate cardiac function of rats. Serum levels of CK-MB and LDH were measured. H&E and Masson staining were used to examine morphology of myocardial tissues. hBMSC-derived exosomes (hBMSC-Exos) increased the viability of cardiomyocytes following hypoxia/reperfusion (H/R) and decreased apoptosis. H/R diminished HCP5 expression in cardiomyocytes while hBMSC-Exos recovered the level. Overexpression of HCP5 in hBMSC-Exos further enhanced the protective effects in H/R while HCP5 knockdown suppressed. HCP5 directly bound miR-497 and miR-497 targeted IGF1. miR-497 mimics or si-IGF1 blocked the effects of HCP5 overexpression. Further, hBMSC-Exos alleviated I/R injury in vivo and knockdown of HCP5 in hBMSC-Exos decreased the beneficial effects. AntagomiR-497 blocked the effects of HCP5 knockdown. HCP5 from hBMSC-Exos protects cardiomyocytes against I/R injury via sponging miR-497 to disinhibit IGF1/PI3K/AKT pathway. These results shed light on mechanisms underlying the protective role of hBMSC-Exos in I/R.

Use of paclitaxel carried in lipid nanoparticles to treat aortic allograft transplantation in rats

OBJECTIVES

The aim of this study was to test whether lipid core nanoparticles loaded with paclitaxel (LDE-PTX) protect rat aortic allograft from immunological damage.

METHODS

Fisher and Lewis rats were used differing in minor histocompatibility loci. Sixteen Lewis rats were allocated to four-animal groups: SYNG (syngeneic), Lewis rats receiving aorta grafts from Lewis rats; ALLO (allogeneic), Lewis rats receiving aortas from Fisher rats; ALLO+LDE (allogeneic transplant treated with LDE), Lewis rats receiving aortas from Fisher rats, treated with LDE (weekly injection for 3 weeks); ALLO+LDE-PTX (allogeneic transplant treated with LDE-PTX), Lewis rats receiving aortas from Fisher rats treated with LDE-PTX (4 mg/kg weekly for 3 weeks). Treatments began on transplantation day.

RESULTS

Thirty days post-transplantation, SYNG showed intact aortas. ALLO and ALLO+LDE presented intense neointimal formation. In ALLO+LDE-PTX, treatment inhibited neointimal formation; narrowing of aortic lumen was prevented in ALLO and ALLO+LDE. LDE-PTX strongly inhibited proliferation and intimal invasion by smooth muscle cells, diminished 4-fold presence of apoptotic/dead cells in the intima, reduced the invasion of aorta by macrophages and T-cells and gene expression of pro-inflammatory tumour necrosis factor-alpha (TNFα), interferon gamma (IFNγ) and interleukin-1 beta (IL-1β).

CONCLUSIONS

LDE-PTX was effective in preventing the vasculopathy associated with rejection and may offer a potent therapeutic tool for post-transplantation.

Influence of Induction Therapy Using Basiliximab With Delayed Tacrolimus Administration in Heart Transplant Recipients - Comparison With Standard Tacrolimus-Based Triple Immunosuppression

BACKGROUND

Appropriate indications and protocols for induction therapy using basiliximab have not been fully established in heart transplant (HTx) recipients. This study elucidated the influence of induction therapy using basiliximab along with delayed tacrolimus (Tac) initiation on the outcomes of high-risk HTx recipients.Methods and Results:A total of 86 HTx recipients treated with Tac-based immunosuppression were retrospectively reviewed. Induction therapy was administered to 46 recipients (53.5%) with impaired renal function, pre-transplant sensitization, and recipient- and donor-related risk factors (Induction group). Tac administration was delayed in the Induction group. Induction group subjects showed a lower cumulative incidence of acute cellular rejection grade ≥1R after propensity score adjustment, but this was not significantly different (hazard ratio [HR]: 0.63, 95% confidence interval [CI]: 0.37-1.08, P=0.093). Renal dysfunction in the Induction group significantly improved 6 months post-transplantation (P=0.029). The cumulative incidence of bacterial or fungal infections was significantly higher in the Induction group (HR: 10.6, 95% CI: 1.28-88.2, P=0.029).

CONCLUSIONS

These results suggest that basiliximab-based induction therapy with delayed Tac initiation may suppress mild acute cellular rejection and improve renal function in recipients with renal dysfunction, resulting in its non-inferior outcome, even in high-risk patients, when applied to the appropriate recipients. However, it should be carefully considered in recipients at a high risk of bacterial and fungal infections.