A Single Center Study of 1,179 Heart Transplant Patients-Factors Affecting Pacemaker Implantation

A case report of transthyretin amyloidosis following cardiac transplantation: thick ventricles that look alike

Background

Transthyretin (ATTR) amyloidosis is more prevalent than initially thought. As much as 13% of patients hospitalized with heart failure with preserved ejection fraction may have ATTR-cardiomyopathy (CM). Conversely, heart transplant patients may manifest left ventricular hypertrophy or diastolic dysfunction, especially late after transplantation.

Case summary

We present a case of a 82-year-old male heart transplant patient, 31 years following orthotopic heart transplantation. While he was satisfied with his exercise capacity as an octogenarian, several years before, he required pacemaker implantation due to third-degree atrioventricular block, had bilateral carpal tunnel syndrome treated with carpal tunnel release surgery, and experienced idiopathic sudden deafness. Based on increasing left ventricular wall thickness during routine follow-up, a diagnosis of ATTR amyloidosis was suspected. Ultimately, the diagnosis was confirmed non-invasively with a specific scintigraphic exam, while an additional physicochemical stain on an endomyocardial biopsy taken several years before provided pathological proof. We initiated tafamidis, yet stopped this treatment after 1 month because of gastrointestinal intolerance. Ultimately, our patient died 2 years later due to heart failure.

Discussion

Our case shows the long delay between the onset of ATTR deposition, the presence of clinical signs, and the final diagnosis. Echocardiographic findings suggestive for ATTR-CM include left ventricular hypertrophy and diastolic dysfunction, which are both common in heart transplant patients. Yet, ATTR-CM should be considered in the differential diagnosis, especially late after transplantation, in this closely monitored population.

Pacemaker Implantation Following Heart Transplantation - Incidence and Risk Factors. Single-Center Experience

BACKGROUND

Bradyarrhythmias, requiring pacemaker (PM) implantation, are common complications following orthotopic heart transplantation (HTx). Currently used heart transplantation methods are primarily the bicaval technique and the total heart transplantation technique. The aim of the study was to assess the incidence and risk factors, including donor parameters, of conduction disorders requiring pacing after HTx.

METHODS

A population of 111 (52 ± 13 years, 91 (82%) men) heart recipients was divided into a group requiring PM implantation post-HTx and a group not requiring PM. We compared groups in terms of donor parameters, time of graft ischemia, transport and transplantation, and surgical techniques as the potential risk factors for significant bradyarrhythmias.

RESULTS

Ten of 111 patients with HTx (9%) required PM implantation. The indication in 7 cases was sinus node dysfunction (SND), in 3 patients it was complete atrioventricular block (AV-block). In the PM group, the age of 48 ± 6 vs 40 ± 11 years (P = .0227) and the body mass index (BMI) 28 ± 3 vs 26 ± 4 kg/m2 (P = .0297) of the donor were significantly higher. There was no influence of organ transport time, ischemia time, and transplantation time. All patients requiring PM implantation were transplanted using the bicaval anastomosis: 10 (100%) vs 71 (70%) in the group not requiring PM (P = .044).

CONCLUSIONS

The need for PM implantation post-HTx despite using new techniques is still common, especially in the group operated with the bicaval method. In addition, higher donor's age and BMI are risk factors of PM implantation, what is of importance as qualification criteria of donor hearts have been gradually extended.

Cardiac resynchronization therapy with conduction system pacing in a long-term heart transplant recipient: A case report

We performed cardiac resynchronization therapy by means of conduction system pacing in a heart transplant patient suffering from heart failure with reduced ejection fraction and atrial fibrillation with conduction disturbance (bifascicular block and QRS >160 ms). ECG monitoring showed paroxysmal atrioventricular block. Biventricular pacing was not feasible due to the absence of a suitable coronary sinus branch for pacing. His bundle pacing was performed, and an implantable cardioverter-defibrillator was implanted due to severe left ventricular dysfunction. Cardiac allograft vasculopathy was excluded. During follow-up, the patient's left ventricular function improved, and symptoms alleviated with a high percentage of ventricular stimulation.

Need for cardiac implantable electronic devices and long-term follow-up in recipients of orthotopic heart transplants

BACKGROUND

Cardiac pacemaker implantation after orthotopic heart transplantation declined dramatically after development of the bicaval anastomosis technique. However, much less is known about the rate, indications, and predictors of device implantation procedures with the current surgical technique.

OBJECTIVE

The purpose of this study was to evaluate the indications, patient characteristics, incidence, and survival related to cardiac implantable electronic device (CIED) implantation after heart transplantation.

METHODS

This was a single-center study of 399 consecutive adult recipients of orthotopic heart transplants with bicaval anastomosis from 1991 to 2017. The primary end point was freedom from pacemaker or implantable cardioverter-defibrillator (ICD) implantation, and the secondary end point was all-cause mortality.

RESULTS

At the time of transplantation, the mean age of recipients was 50 ± 12 years and that of donors 31 ± 12 years. CIEDs were implanted in 8% of recipients (n = 31): 11 pacemakers (35%) for sinus node dysfunction, 17 (55%) for high-grade heart block, and 3 ICDs (10%) for the primary prevention of sudden cardiac death. Early CIED implantation (<30 days) was rare and absent for sinus node dysfunction. The risk for CIED implantation increased progressively during follow-up (0-30 years; median 11 years), with low-, moderate-, and high-risk periods between 0 and 10, between 10 and 20, and between 20 and 30 years, respectively. Recipients receiving CIEDs survived longer after transplantation (21 years vs 13 years; P < .01). Recipients receiving pacemakers for heart block were more likely to receive older donor hearts at the time of transplantation.

CONCLUSION

The risk of pacemaker implantation increases progressively, while ICD implantation is rare. Donor age is the predominant risk factor for subsequent heart block. Early sinus node dysfunction requiring permanent pacing is rare.

Heart transplantation and biomarkers: a review about their usefulness in clinical practice

Advanced heart failure (AdvHF) can only be treated definitively by heart transplantation (HTx), yet problems such right ventricle dysfunction (RVD), rejection, cardiac allograft vasculopathy (CAV), and primary graft dysfunction (PGD) are linked to a poor prognosis. As a result, numerous biomarkers have been investigated in an effort to identify and prevent certain diseases sooner. We looked at both established biomarkers, such as NT-proBNP, hs-troponins, and pro-inflammatory cytokines, and newer ones, such as extracellular vesicles (EVs), donor specific antibodies (DSA), gene expression profile (GEP), donor-derived cell free DNA (dd-cfDNA), microRNA (miRNA), and soluble suppression of tumorigenicity 2 (sST2). These biomarkers are typically linked to complications from HTX. We also highlight the relationships between each biomarker and one or more problems, as well as their applicability in routine clinical practice.

Long-Term Outcomes of Permanent Pacemaker Implantation in Bicaval Heart Transplant Recipients

BACKGROUND

Permanent pacemakers (PPMs) may be necessary in up to 10% of patients after heart transplantation (HT).

OBJECTIVES

The purpose of this study was to evaluate long-term outcomes and clinical courses of heart transplant recipients who received PPM.

METHODS

All patients who required PPM after bicaval HT at Columbia University between January 2005 and December 2021 were included. Cases were compared to matched heart transplant recipients by age, sex, and year of transplantation. Patient and device characteristics including complications and device interrogations were reviewed. Outcomes of re-transplantation or graft failure/death were compared between groups.

RESULTS

Of 1,082 heart transplant recipients, 41 (3.8%) received PPMs. The median time from transplantation to PPM was 118 days (IQR: 18-920 days). The most common indications were sinus node dysfunction (60%, n = 25) and atrioventricular (AV) nodal disease (41.5%, n = 17). Post-implantation complications included pocket hematoma (n = 3), lead under-sensing (n = 2), and pocket infection requiring explant (n = 1). Rates of death and re-transplantation at 10 years post-HT were similar between groups. In multivariable analysis, after adjustment for mechanical circulatory support, pretransplantation amiodarone use, donor ischemic time and age, only older donor age was associated with increased risk of PPM implantation (P = 0.03). There was a significant decrease in PPM placement after 2018 (1.2% vs 4.4%, P = 0.02), largely driven by a decline in early PPM placement. There were no differences in mortality or need for re-transplantation between groups.

CONCLUSIONS

PPMs are implanted after HT for sinus and atrioventricular node dysfunctions with low incidence of device-related complications. Our study shows a decrease in PPM implantation after 2018, likely attributable to expectant management in the early postoperative period.

Outcomes in orthotopic heart transplantation following pacemaker implantation

BACKGROUND

Bradyarrhythmias including sinus node dysfunction (SND) and atrioventricular block (AVB) can necessitate pacemaker (PPM) implantation in orthotopic heart transplant (OHT) recipients. Prior studies have shown conflicting findings regarding the effect of PPM implantation on survival. We evaluated the effect of PPM indication on long-term re-transplant-free survival in OHT patients.

METHODS

We conducted a retrospective cohort study of OHT patients at UCLA Medical Center from 1985 to 2018. Indication for PPM (SND, AVB) was identified. Cox proportional hazards model with pacemaker implantation as a time-varying covariate was used to evaluate its effect on the primary endpoint of retransplant or death. We included 1609 OHTs in 1511 adult patients with median follow-up of 12 years.

RESULTS

At transplant, patients were aged 53 ± 13 years and 1125 (74.5%) were male. Pacemakers were implanted in 109 (7.2%) patients; 65 for SND (4.3%) and 43 for AVB (2.8%). Repeat OHT was performed in 103 (6.4%) cases and 798 (52.8%) patients died during the follow-up period. The risk of the primary endpoint was significantly higher in patients requiring PPM for AVB (HR 3.0, 95% CI 2.1-4.2, p < .01) after controlling for age at OHT, gender, hypertension, diabetes, renal disease, history of repeat OHT, acute rejection, transplant coronary vasculopathy, and atrial fibrillation, but not PPM for SND (HR 1.0, 95% CI 0.70-1.4, p = 1.0).

CONCLUSIONS

Patients who required PPM for AVB, but not SND, were at significantly higher risk of death or retransplant compared to patients who did not require PPM.

Pacemaker Implantation following Heart Transplantation: Analysis of a Nation-Wide Database

BACKGROUND

The 2018 United-Network-for-Organ-Sharing (UNOS) allocation-system changes resulted in greater recognition of mechanical circulatory support (MCS), leading to more heart transplantations (HTx) in patients with MCS. We aimed to investigate the effect of the new UNOS allocation system on the need for a permanent pacemaker and associated complications following HTx.

METHODS

The UNOS Registry was questioned, to identify patients that received HTx in the US between 2000 and 2021. The primary objectives were to identify risk factors for the need for a pacemaker implantation following HTx.

RESULTS

49,529 HTx patients were identified, 1421 (2.9%) requiring a pacemaker post-HTx. Patients who required a pacemaker were older (53.9 ± 11.5 vs. 52.6 ± 12.8 years, p < 0.001), more frequently white (73% vs. 67%; p < 0.001) and less frequently black (18% vs. 20%; p < 0.001). In the pacemaker group, UNOS status 1A (46% vs. 41%; p < 0.001) and 1B (31% vs. 27%; p < 0.001) were more prevalent, and donor age was higher (34.4 ± 12.4 vs. 31.8 ± 11.5 years; p < 0.001). One-year survival was no different between the groups (HR: 1.08; 95% CI: 0.85, 1.37; p = 0.515). An era effect was observed (per year: OR: 0.97; 95% CI: 0.96, 0.98; p = 0.003), while ECMO pre-transplant was associated with lower risk of a pacemaker (OR: 0.41; 95% CI: 0.19, 0.86; p < 0.001).

CONCLUSIONS

While associated with various patient and transplant characteristics, pacemaker implantation does not seem to impact one-year survival after HTx. The need for pacemaker implantation was lower in the more recent era and in patients who required ECMO pre-transplant, a finding explained by recent advances in perioperative care.

Transient central hypoxemia due to intermittent high-degree atrioventricular block in a heart-transplanted patient diagnosed during routine electroencephalography: a case report

BACKGROUND

Bradycardia frequently occurs in heart-transplanted patients, mainly as a temporally restricted manifestation early after transplantation and often without symptoms. A high-degree atrioventricular block is mostly symptomatic through cerebral hypoxia induced through cerebral hypoperfusion. Only a few published cases show this specific electroencephalography result in this context. The purpose of this case is to bring attention to atypical manifestations of typical cardiac complications after heart transplantation and the importance of perseverance in the diagnostic.

CASE PRESENTATION

A Central European man in his 50s with history of heart transplantation 31 years previously was admitted to the internal medicine ward for short-lived recurrent episodes of generalized weakness with multiple falls but without loss of consciousness. During routine electroencephalography, the patient perceived this recurrent sensation. This episode coincided with a transient third-degree atrioventricular block followed 8-10 seconds later by a generalized slowing of the electroencephalography, reflecting cerebral hypoxia due to cerebral hypoperfusion. Holter monitoring confirmed the diagnosis. A pacemaker was implanted, consequently resolving the episodes.

CONCLUSION

This case report illustrates the pathophysiological central hypoxemic origin of episodes of generalized weakness caused by a high-degree atrioventricular block in a patient surviving 29 years after heart transplant. It highlights the benefit of electroencephalography as a diagnostic tool in well-selected patients.

Review of Postoperative Care for Heart Transplant Recipients

The early postoperative management strategies after heart transplantation include optimizing the function of the denervated heart, correcting the causes of hemodynamic instability, and initiating and maintaining immunosuppressive therapy, allograft rejection surveillance, and prophylaxis against infections caused by immunosuppression. The course of postoperative support is influenced by the quality of allograft myocardial protection prior to implantation and reperfusion, donor-recipient heart size matching, surgical technique of orthotopic heart transplantation, and patient factors (eg, preoperative condition, immunologic compatibility, postoperative vasomotor tone, severity and reversibility of pulmonary vascular hypertension, pulmonary function, mediastinal blood loss, and end-organ perfusion). This review provides an overview of the early postoperative care of recipients and includes a brief description of the surgical techniques for orthotopic heart transplantation.

Cardiac allograft vasculopathy and donor age affecting permanent pacemaker implantation after heart transplantation

Aims

The need for permanent pacemakers (PMs) after heart transplantation (HT) is increasing. The aim was to determine the influence of cardiac allograft vasculopathy (CAV), donor age, and other risk factors on PM implantations early and late after HT and its effect on survival.

Methods and results

A retrospective, single‐centre study was performed including HTs from 1984 to July 2018. Early PM was defined as PM implantation ≤90 days and late PM as PM > 90 days. Risk factors for PM and survival after PM were determined with (time‐dependent) multivariable Cox regression. Out of 720 HTs performed, 62 were excluded (55 mortalities ≤30 days and 7 retransplantations). Of the remaining 658 patients, 95 (14%) needed a PM: 38 (6%) early and 57 (9%) late during follow‐up (median 9.3 years). Early PM risk factors were donor age [hazard ratio (HR) 1.06, P < 0.001], ischaemic time (HR 1.01, P < 0.001), and in adults amiodarone use before HT (HR 2.02, P = 0.045). Late PM risk factors were donor age (HR 1.03, P = 0.024) and CAV (HR 3.59, P < 0.001). Late PM compromised survival (HR 2.05, P < 0.001), while early PM did not (HR 0.77, P = 0.41).

Conclusions

Risk factors for early PM implantation were donor age, ischaemic time, and in adults amiodarone use before HT. Late PM implantation risk factors were donor age and CAV. Late PM diminished survival, which is probably a surrogate marker for underlying progressive cardiac disease.

Effect of novel bicaval anastomosis technique for transplantation with and without prior cardiac surgery history

Background

To evaluate the graft outcomes after orthotopic heart transplantation (HTx) with a novel bicaval anastomosis technique between recipients with and without a history of prior cardiac surgery.

Methods

Of 70 patients who underwent HTx with a novel four-corners traction bicaval anastomosis technique from August 2017 to November 2019, 60 recipients underwent the HTx procedure as their first cardiac surgery (group A), while 10 recipients underwent HTx after prior cardiac surgery (group B). Patients in the two groups were compared in terms of their preoperative baseline variables such as etiological categories, history of blood transfusion and panel reactive antibody (PRA), intraoperative operation time and blood infusion volume, postoperative treatment time, and complications such as acute rejection and 30-day mortality as well as survival rates.

Results

Preoperative variables were comparable in group A and group B except for the history of blood transfusion (0% vs. 90.0%, P<0.001, respectively); the level of PRA was 7.5%±5.8% and 9.5%±10.9% for group A and B, respectively (P=0.583), but the time of the operation was nearly 1 hour longer for group B than group A (all P<0.05). No cases of left atrial thrombosis and donor heart distortion were observed in either group. Reoperation (1.7% vs. 10.0%, P=0.267), infection (0% vs. 10.0%, P=0.142), other postoperative complications as well as the 30-day mortality (1.7% vs. 10.0%, P=0.267), and postoperative survival rates (91.5% vs. 90.0%, P=0.805) were comparable between the two groups (all P>0.05).

Conclusions

Four-corner traction bicaval anastomosis combined with a continuous everting suture technique may result in approximately comparable prognoses for heart recipients with a history of cardiac surgery when compared with those without a history of cardiac surgery and this technique may reduce the incidence of left atrial thrombosis and distortion. Further follow-up of the long-term outcomes will be required to validate these results.

A primer for managing cardiac transplant patients in the emergency department setting

BACKGROUND

Cardiac transplant is an effective long-term management option for several severe cardiac diseases. These cardiac transplant patients may present to the emergency department with a range of issues involving the cardiac transplantation, including complications due to their transplant as well as altered presentations of disease resulting from their transplant.

OBJECTIVE

This narrative review provides a focused guide to the evaluation and management of patients with cardiac transplantation and its complications.

DISCUSSION

Cardiac transplant is an effective therapy for end-stage heart failure. A transplanted heart varies both anatomically and physiologically from a native heart. Several significant complications may occur. Graft failure, rejection, and infection are common causes of morbidity and mortality within the first year of transplant. As these patients are on significant immunosuppressive medication regimens, they are at risk of infection, but inadequate immunosuppression increases the risk of acute rejection. A variety of dysrhythmias such as atrial fibrillation and ventricular dysrhythmias may occur. These patients are also at risk of acute coronary syndrome, cardiac allograft vasculopathy, and medication adverse events. Importantly, patients with acute coronary syndrome can have an altered presentation with the so-called "painless" myocardial infarction. Consultation with the transplant physician is recommended, if available, for these patients to assist in evaluation and management.

CONCLUSIONS

An understanding of the presentations and various complications that may affect patients with cardiac transplant will assist emergency clinicians in the care of these patients.

Cardiac Implantable Electronic Devices Following Heart Transplantation

Permanent pacemaker (PPM) implantation is required in a subset of patients (∼10%) for sinus node dysfunction or atrioventricular block both early and late after heart transplantation. The incidence of PPM implantation has decreased to <5% with the advent of bicaval anastamosis transplantation surgery. Pacing dependence upon follow-up has been variably reported. An even smaller percentage of transplantation recipients (1.5% to 3.4%) undergo implantable cardioverter-defibrillator (ICD) placement. Rigorous data are lacking for the use of ICDs in the transplantation population and is largely derived from cohort studies and case series. Sudden cardiac death occurs in approximately 10% of transplantation recipients, but multiple nonarrhythmic factors are believed to be responsible, including acute rejection, late graft failure with electromechanical dissociation, and ischemia due to cardiac allograft vasculopathy. This review provides a comprehensive analysis of the existing data regarding the role for PPMs and ICDs in this population, including leadless PPMs and subcutaneous ICDs, special considerations, and future directions.

Bicaval vs biatrial anastomosis techniques in orthotopic heart transplantation: An updated analysis of the UNOS database

BACKGROUND

Despite the significant increase in the number of orthotopic heart transplants (OHT) performed yearly using the bicaval anastomosis technique, the impact on long-term outcomes remains a topic of debate. We analyzed the United Network for Organ Sharing (UNOS) database in search of the latest insight.

METHODS

We performed a retrospective analysis of the UNOS database from 2006 to 2016 to identify first-time OHT recipients. Patients were primarily stratified according to anastomosis technique: bicaval vs biatrial. Baseline characteristics and clinical status were recorded. The primary endpoint was all-cause mortality. Secondary outcomes included need for permanent pacemaker (PPM), and length of hospital stay (LOS). The Kaplan-Meier method was used to compare survival between the two groups. The Cox proportional hazards regression model was used to conduct multivariable analysis. Statistical significance established at P < .0001.

RESULTS

A total of 26 990 patients were identified. Of those who met the inclusion criteria (21 597), 16 573 (77%) underwent bicaval anastomosis. There were no major differences in baseline characteristics between the two groups. The bicaval anastomosis technique was not associated with increased survival during the study period (hazard ratio: 0.97; P = .3557), but the bicaval group required postoperative PPM less often (2.51% vs 5.79%, P < .0001) and was associated with shorter LOS on multivariable analysis.

CONCLUSIONS

The use of either bicaval or biatrial anastomosis during OHT offers comparable survival advantage. Nonetheless, bicaval anastomosis is associated with less need for postoperative PPM and slightly shorter LOS.

Clinical and procedural characteristics predicting need for chronotropic support and permanent pacing post-heart transplantation

BACKGROUND

Postoperative bradycardia can complicate orthotopic heart transplantation (OHT). Previous studies suggested donor age and surgical technique as possible risk factors. However, risk factors in the era of bicaval anastomosis have not been elucidated.

OBJECTIVE

We sought to examine the association between donor/recipient characteristics with need for chronotropic support and permanent pacemaker (PPM) implantation in patients with OHT.

METHODS

All patients treated with OHT between January 2003 and January 2018 at the Hospital of the University of Pennsylvania were retrospectively evaluated until June 2018. Chronotropic support was given upon postoperative inability to increase the heart rate to patient's demands and included disproportionate bradycardia and junctional rhythm.

RESULTS

A total of 820 patients (mean age 51.3 ± 12.6 years; 607, 74% men) underwent 826 OHT procedures (787 patients, 95.3% bicaval anastomosis). Patients who were exposed to amiodarone (odds ratio [OR] 2.30; 95% confidence interval [CI] 1.58-3.34; P < .001) and have older donor (OR 1.02; 95% CI 1.01-1.04; P = .001) were more likely to develop need for chronotropic support. In multivariable analysis, recipient age (OR 1.03; 95% CI 1.00-1.06; P = .04) and biatrial anastomosis (OR 6.12; 95% CI 2.48-15.09) were significantly associated with PPM implantation within 6 months of OHT. No association was found between pre-OHT amiodarone use and PPM implantation. No risk factors assessed were associated with PPM implantation 6 months post-OHT.

CONCLUSION

Surgical technique and donor age were the main risk factors for the need for chronotropic support post-OHT, whereas surgical technique and recipient age were risk factors for early PPM implantation.

Risk factors and survival of patients with permanent pacemaker implantation after heart transplantation

Background

Permanent pacemaker (PPM) implantation after heart transplantation (HTX) may be required due to severe bradycardia. The aim of this study was to investigate the risk factors, indications, perioperative outcomes and complications of PPM implantation after HTX as well as the underlying effect on post-transplant mortality including causes of death.

Methods

This registry study included 621 patients receiving HTX at Heidelberg Heart Center between 1989 and 2018. Patients were stratified by PPM implantation after HTX. Data analysis of risk factors for PPM implantation included donor and recipient demographics, post-transplant medication, mortality, and causes of death.

Results

Thirty-six patients (5.8%) received PPM implantation after HTX, 12 (33.3%) with early PPM and 24 (66.7%) with late PPM. Indications for PPM implantation after HTX included sinus node dysfunction (SND) (n=15; 41.7%) and atrioventricular block (AVB) (n=21; 58.3%). Multivariate analysis revealed recipient body mass index (BMI) [hazard ratio (HR): 1.10; confidence interval (CI): 1.01-1.21; P=0.03], donor age (HR: 1.07; CI: 1.03-1.10; P<0.01), and biatrial HTX (HR: 2.63; CI: 1.22-5.68; P=0.01) as significant risk factors for PPM implantation after HTX. Kaplan-Meier estimator displayed a statistically significant inferior 5-year post-transplant survival among patients with early PPM after HTX in comparison to patients with late PPM or no PPM after HTX (P<0.01) along with a higher percentage of death due to infection (P<0.01).

Conclusions

Multivariate risk factors for PPM implantation after HTX include recipient BMI, donor age, and biatrial HTX. Early PPM implantation after HTX is associated with increased 5-year post-transplant mortality due to infection.

Postoperative management of heart transplantation patients

Heart transplant recipients are at risk for a number of post-transplantation complications such as graft dysfunction, rejection, and infection. The rates of many complications are decreasing over time, and prognosis is improving. However, these patients continue to experience significant morbidity and mortality. This review focuses on the optimal management of heart transplant recipients in the postoperative period, based on current knowledge. More information is needed about the best ways to predict, prevent, and treat primary graft dysfunction, right ventricular failure, and cellular and antibody-mediated rejection.