Cardiac allograft vasculopathy: advances in understanding its pathophysiology, prevention, and treatment

The First Dedicated Comprehensive Heart Failure Program in the United States: The Division of Circulatory Physiology at Columbia Presbyterian (1992-2004)

The first dedicated multidisciplinary heart failure program in the United States was founded as the Division of Circulatory Physiology at the Columbia University College of Physicians & Surgeons in 1992. The Division was administratively and financially independent of the Division of Cardiology and grew to 24 faculty members at its peak. Its administrative innovations included (1) a comprehensive full-integrated service line, with 2 differentiated clinical teams, one devoted to drug therapy and the other to heart transplantation and ventricular assist devices; (2) a nurse specialist/physician assistant-led clinical service; and (3) a financial structure independent of (and not supported by) other cardiovascular medical or surgical services. The division had 3 overarching missions: (1) to promote a unique career development path for each faculty member to be linked to recognition in a specific area of heart failure expertise; (2) to change the trajectory and enhance the richness of intellectual discourse in the discipline of heart failure, so as to foster an understanding of fundamental mechanisms and to develop new therapeutics; and (3) to provide optimal medical care to patients and to promote the ability of other physicians to provide optimal care. The major research achievements of the division included (1) the development of beta-blockers for heart failure, from initial hemodynamic assessments to proof-of-concept studies to large-scale international trials; (2) the development and definitive assessment of flosequinan, amlodipine, and endothelin antagonists; (3) initial clinical trials and concerns with nesiritide; (4) large-scale trials evaluating dosing of angiotensin converting-enzyme inhibitors and the efficacy and safety of neprilysin inhibition; (5) identification of key mechanisms in heart failure, including neurohormonal activation, microcirculatory endothelial dysfunction, deficiencies in peripheral vasodilator pathways, noncardiac factors in driving dyspnea, and the first identification of subphenotypes of heart failure and a preserved ejection fraction; (6) the development of a volumetric approach to the assessment of myocardial shortening; (7) conceptualization and early studies of cardiac contractility modulation as a treatment for heart failure; (8) novel approaches to the identification of cardiac allograft rejection and new therapeutics to prevent allograft vasculopathy; and (9) demonstration of the effect of left ventricular assist devices to induce reverse remodeling, and the first randomized trial showing a survival benefit with ventricular assist devices. Above all, the division served as an exceptional incubator for a generation of leaders in the field of heart failure.

MMP-14 promotes VSMC migration via up-regulating CD44 expression in cardiac allograft vasculopathy

Cardiac allograft vasculopathy (CAV) was the leading cause of late death in heart transplantation recipients. Matrix metalloproteinase-14 (MMP-14), as a member of the MMPs family, has been reported to play a vital role in coronary vascular lesions of allotransplanted hearts. However, concrete mechanism is still unclear. Herein, we showed that the expression of MMP-14 was different between isografts and allografts. Interestingly, we found MMP-14 could interact with CD44 in allografts. Cluster of differentiation 44 (CD44), as a cell adhesion receptor and is involved in cell migration, caused our interest in MMP-14/CD44 complex in allografts. Then we analyzed the effect of MMP-14/CD44 complex on pro-MMP-9 activation and vascular smooth muscle cell (VSMC) migration in rat VSMC TNF-α treated model. Then, we further found intervention of MMP-14/CD44 complex could inhibit VSMC migration. Our results elucidate the molecular mechanism of VSMC migration after cardiac transplantation and provide theoretical basis for seeking new specific drug targets for CAV prevention and treatment.

Erythroblast transformation-specific 2 correlates with vascular smooth muscle cell apoptosis in rat heterotopic heart transplantation model

BACKGROUND

Cardiac allograft vasculopathy (CAV) decreases the long-term survival of heart transplantation recipients. Vascular smooth muscle cell (VSMC) apoptosis is an important pathological feature of CAV. Erythroblast transformation-specific 2 (Ets-2), as a transcription factor, participates in cell apoptosis and plays an important role in organ transplantation.

METHODS

Hearts from Wistar-Furth (WF:RT1u) rats were heterotopically transplanted into Lewis (Lew:RT1(l)) rats without immunosuppression. Additional syngeneic heterotopic cardiac transplantations were performed in Lewis rats. HE staining was used to identify CAV. Ets-2 expression was examined by western blot. Ets-2 tissue location was examined by immunohistochemical assay and double immunostaining. Cleaved caspase 3 expression was detected by western blot. Co-localization of Ets-2 and cleaved caspase 3 was detected by double immunostaining. Ets-2, p53, cleaved caspase 3 and Bcl-xl expression in rat VSMC line A7R5 was examined after Ets-2 siRNA transfection. TUNEL assay was applied to detect A7R5 apoptosis with or without ETS-2 siRNA transfection. Immunoprecipitation was performed to explore the interaction between Ets-2 and p53.

RESULTS

Ets-2 expression decreased in the allograft group but had no obvious change in the isograft group. Meanwhile, the phenomenon of CAV was observed in the allograft group and there is neointima formation in the isograft group which is not obvious compared with allograft group. Additionally, Ets-2 expression was opposite to VSMC apoptosis in the allograft group. In vitro, Ets-2 siRNA transfection in A7R5cells resulted in enhanced cell apoptosis. Finally, Ets-2 interacted with p53.

CONCLUSIONS

Ets-2 might inhibit VSMC apoptosis via p53 pathway. The results further elucidate the molecular mechanism of VSMC apoptosis after heart transplantation during CAV and provide theoretical basis for seeking new specific drug targets for CAV prevention and treatment.

Dose/time-dependent modulation of the endothelial function through induction agents: non-depleting versus depleting agents

BACKGROUND

Polyclonal anti-thymocyte globulins (ATGs) and anti-CD25 antibodies are agents used for induction of immunosuppression in solid-organ transplantation. We aimed to investigate the effect of different regimens of these immunosuppressive induction agents on transendothelial migration of peripheral blood mononuclear cells (PBMC) and evaluated the endothelial apoptosis after treatment.

METHODS

Human microvascular endothelial cells were either activated with tumor necrosis factor-α/interferon-γ or not and further treated with 25 or 125 μg/mL ATG (Thymoglobulin, Sanofi-Aventis, Germany) for 2 hours or 24 hours, or with 5 μg/mL Basiliximab (Simulect, Novartis, Germany) for 2 hours or 24 hours. PBMC were either activated with phytohaemagglutinin (PHA) or not and further treated with 25 or 125 μg/mL ATG or with 5 μg/mL Basiliximab for 2 h and then used for transendothelial migration assays. Apoptosis of endothelial cells was detected by means of Annexin-V staining after 2-hour incubation with either 25 or 125 μg/mL ATG or 5 μg/mL Basiliximab.

RESULTS

Prophylactic 24-hour administration of ATG to naive endothelial cells without PBMC treatment reduced transendothelial migration. Prophylactic 24-hour administration of ATG and Basiliximab to naive endothelial cells after PBMC treatment with the same agents reduced the transendothelial migration after 24 hours. In both cases, no effect could be observed after 2-hour treatment. Basiliximab but not ATG showed a reduction of transmigration after 2-hour treatment of PBMCs without naive EC treatment. Apoptosis of endothelial cells after treatment increased in both cases, being in case of ATG dose-dependent, increasing from 1.2% after either 25 μg/mL ATG to 8.7% after 125 μg/mL ATG.

CONCLUSIONS

Immunosuppressive induction agents modulate the endothelial activity in a dose- and time-dependent manner. Our results suggest that administration of induction agents over longer time periods could provide a potential benefit regarding endothelial immunomodulation. Increased doses may, however, show a deleterious effect on endothelial survival.

Therapeutic potential of HDL in cardioprotection and tissue repair

Epidemiological studies support a strong association between high-density lipoprotein (HDL) cholesterol levels and heart failure incidence. Experimental evidence from different angles supports the view that low HDL is unlikely an innocent bystander in the development of heart failure. HDL exerts direct cardioprotective effects, which are mediated via its interactions with the myocardium and more specifically with cardiomyocytes. HDL may improve cardiac function in several ways. Firstly, HDL may protect the heart against ischaemia/reperfusion injury resulting in a reduction of infarct size and thus in myocardial salvage. Secondly, HDL can improve cardiac function in the absence of ischaemic heart disease as illustrated by beneficial effects conferred by these lipoproteins in diabetic cardiomyopathy. Thirdly, HDL may improve cardiac function by reducing infarct expansion and by attenuating ventricular remodelling post-myocardial infarction. These different mechanisms are substantiated by in vitro, ex vivo, and in vivo intervention studies that applied treatment with native HDL, treatment with reconstituted HDL, or human apo A-I gene transfer. The effect of human apo A-I gene transfer on infarct expansion and ventricular remodelling post-myocardial infarction illustrates the beneficial effects of HDL on tissue repair. The role of HDL in tissue repair is further underpinned by the potent effects of these lipoproteins on endothelial progenitor cell number, function, and incorporation, which may in particular be relevant under conditions of high endothelial cell turnover. Furthermore, topical HDL therapy enhances cutaneous wound healing in different models. In conclusion, the development of HDL-targeted interventions in these strategically chosen therapeutic areas is supported by a strong clinical rationale and significant preclinical data.

Influence of proliferation signal inhibitors on vascular endothelial growth factor production in heart transplant recipients - preliminary report

Proliferation signal inhibitors (PSI) are especially beneficial for heart transplant recipients, but are rarely used due to frequent side effects. As they may be caused by vascular endothelial growth factor (VEGF), we performed a prospective cross-sectional pilot study to assess the influence of PSI and/or calcineurin inhibitors (CNI) presence in immunosuppressive protocols of heart transplant recipients on VEGF secretion. All electively screened heart transplant recipients willing to participate were enrolled in the study. The preliminary report was based on the results of the first 89 serum samples. The study group (n = 84) consisted of the PSI group (n = 14) further divided into the PSI + CNI subgroup (n = 10) and PSIw/oCNI subgroup (n = 4) based on concomitant CNI use, and the CNIw/oPSI group (n = 70) receiving CNI without PSI. The control group (n = 5) consisted of patients not requiring immunosuppression. VEGF was present in serum of 70 (83%) study group patients: median (range) 18 (0-316) pg/mL, mean 35 ± 57 pg/mL; in 13 (93%) PSI group patients: 22 (0-110) pg/mL, 28 ± 28 pg/mL, with 19 (8-20) pg/mL, 16 ± 6 pg/mL in the PSI + CNI subgroup, and 29 (0-110) pg/mL, 32 ± 32 pg/mL in the PSIw/oCNI subgroup. In the CNIw/oPSI group VEGF was present in 57 (81%) patients: 16 (0-316) pg/mL, 37 ± 62 pg/mL, and in the control group in 3 (60%) patients: 4 (0-110) pg/mL, 32 ± 48 pg/mL. None of the differences observed between any compared groups and/or subgroups was significant (χ² and Mann-Whitney U test). In conclusion, differences of VEGF concentration observed among groups imply the influence of PSI and CNI on VEGF production, but further studies involving higher numbers of participants are needed to prove it.

Everolimus in patients with severe pulmonary hypertension: a safety and efficacy pilot trial

Abstract Despite the availability of vasodilating compounds, pulmonary hypertension (PH) of various origins remains a disease with a poor prognosis. In recent years, pulmonary arterial hypertension (PAH) has been recognized as a predominantly proliferative process. Everolimus, an inhibitor of the mammalian target of rapamycin (mTOR), inhibits cellular protein synthesis and growth not only in lymphocytes but also in cells of the vascular wall. Ten patients suffering from PAH ([Formula: see text]) or chronic thromboembolic PH ([Formula: see text]) with progressive disease despite therapy with at least 2 vasodilating drugs were included in a prospective open-label pilot study. All patients were treated with everolimus in addition to their prior medication. Safety and tolerability were observed throughout the study. Pulmonary vascular resistance (PVR) and 6-minute walk distance (6MWD) were considered coprimary end points. In 2 patients, study medication was stopped prematurely because of an adverse event. One patient had acute bronchitis, and the other had right heart decompensation. The remaining 8 patients exhibited a significant 31% decrease in PVR (median [interquartile range], 1,012 [688-1,344] vs. 663 [546-860] dyn s cm(-5); [Formula: see text]) and an increase in 6MWD (median [interquartile range], 236 [139-350] vs. 298 [207-450] m; [Formula: see text]) after 6 months of treatment with everolimus. In conclusion, in this pilot study antiproliferative therapy with everolimus was well tolerated in patients with PH. The observed improvements in PVR and 6MWD may stimulate further consideration of mTOR inhibition with everolimus for the treatment of PH.

Can HLA-G polymorphisms predict the development of cardiac allograft vasculopathy?

A 14 bp insertion/deletion polymorphism in exon 8 of the HLA-G gene is associated with mRNA stability and HLA-G expression. In cardiac transplantation, the 14 bp deletion polymorphism plays an important role in the expression of HLA-G and is associated with fewer episodes of cellular rejection. We investigated the association between the 14 bp insertion/deletion HLA-G polymorphism and cardiac allograft vasculopathy (CAV) post heart transplantation. There were no statistically significant differences in the presence of the three HLA-G genotypes (-14 bp/-14 bp, +14 bp/-14 bp, +14 bp/+14 bp) between patients without CAV and patients with CAV at 1 year (p=0.61) or 5 years (p=0.76) post-transplant. We found no correlation between HLA-G genotypes and CAV progression from baseline to 5 years post-transplant (p=0.55). HLA-G polymorphism appears to play an important role as a genetic indicator for cellular rejection post-transplant; however, it is not a reliable marker to identify patients at risk of CAV.

Heart transplant patient outcomes: 5-year mean follow-up by coronary computed tomography angiography

BACKGROUNDS

We evaluate the feasibility and safety of coronary computed tomography angiography (CCTA) as the first-line investigation in heart transplant patients and the rate of coronary allograft vasculopathy detected using CCTA.

METHODS

From September 2003 to June 2009, we prospectively included 65 heart transplant recipients, retaining 62 who underwent yearly CCTA for coronary allograft vasculopathy detection (261 CCTAs). We used 16-slice, 64-slice, and 2×64-slice CT machines. Patients with coronary artery stenosis by CCTA had a confirmation and a further follow-up exclusively by conventional coronary angiography (CCA).

RESULTS

No major coronary events occurred during the study. Of the 62 baseline CCTAs, 37 (60%) were normal, 18 (29%) showed wall thickening, and 7 (11%) known significant stenosis, confirmed by CCA. The mean follow-up duration was 5 years. At the last follow-up, 26 (70%) patients with normal baseline findings remained normal, 9 (24%) had wall thickening, and 2 (6%) significant stenoses. Time to stenosis was consistently greater than 3 years. Of the 18 patients with initially wall thickening, 14 (78%) had wall thickening and 4 (22%) significant stenosis at last follow-up. The mean interval without any coronary lesion was 9.46±3.98 years. The mean interval without de novo significant stenosis was 10.31±4 years.

CONCLUSIONS

CCTA seems to be a safe noninvasive tool for monitoring heart transplant patients, and thus obviating the need for CCA. In patients with normal baseline CCTA, a 2-year interval between CCTAs may be safe.

Drug eluting versus bare metal stents in cardiac allograft vasculopathy: a systematic review of literature

BACKGROUND

Cardiac allograft vasculopathy (CAV) is a distinct pathological condition characterized by diffuse and progressive arteriopathy and it is an important determinant of long-term graft survival. Definitive CAV treatment is retransplantation but palliation with stenting might temporarily alleviate it. The benefit of drug eluting stents (DES) over bare metal stents (BMS) in the treatment of such lesions is debatable. We therefore sought to do a literature search to review the available evidence comparing DES to BMS.

METHODS

We conducted Pub Med, EMBASE, Cochrane database review, Web of Science search of studies comparing DES with BMS in CAV. Available studies were retrospective in nature with either direct comparison groups (n = 5) or historical controls (n = 1). The main outcomes analyzed were in stent restenosis (ISR) during follow-up and clinical outcomes.

RESULTS

A total of 312 patients from six studies were included in the review (1995-2007). Most commonly used DES were sirolimus eluting stent. DES appeared to reduce the long-term risk of ISR compared with BMS. Three of the five studies showed a statistically significant reduction in ISR at 12 months while the one study assessing ISR at 6 months showed no significant difference. Clinical endpoints such as death and major adverse cardiac events were not statistically different.

CONCLUSION

DES appear to reduce the incidence of ISR in CAV as compared with BMS. Prospective randomized clinical trials are needed to determine the clinical benefit of DES beyond a reduction in ISR.

Gene Expression Signatures of Peripheral Blood Mononuclear Cells during the Early Post-Transplant Period in Patients Developing Cardiac Allograft Vasculopathy

Background. Cardiac allograft vasculopathy (CAV) is a major cause of graft loss and death after heart transplantation. Currently, no diagnostic methods are available during the early post-transplant period to accurately identify patients at risk of CAV. We hypothesized that PBMC gene expression profiles (GEP) can identify patients at risk of CAV. Methods. We retrospectively analyzed a limited set of whole-genome PBMC microarrays from 10 post-transplant patients who did (n = 3) or did not (n = 7) develop advanced grade CAV during their long-term follow-up. We used significance analysis of microarrays to identify differentially expressed genes and High-Throughput GoMiner to assess gene ontology (GO) categories. We corroborated our findings by retrospective analysis of PBMC real-time PCR data from 33 patients. Results. Over 300 genes were differentially expressed (FDR < 5%), and 18 GO-categories including “macrophage activation”, “Interleukin-6 pathway”, “NF-KappaB cascade”, and “response to virus” were enriched by these genes (FDR < 5%). Out of 8 transcripts available for RT-PCR analysis, we confirmed 6 transcripts (75.0%) including FPRL1, S100A9, CXCL10, PRO1073, and MMP9 (P < .05). Conclusion. Our pilot data suggest that GEP of PBMC may become a valuable tool in the evaluation of patients at risk of CAV. Larger prospectively designed studies are needed to corroborate our hypothesis.

Levels of circulating CXCR4-positive cells are decreased and negatively correlated with risk factors in cardiac transplant recipients

The association between levels of circulating endothelial progenitor cells (EPCs) and heart transplant recipients (HTX) with cardiac allograft vasculopathy (CAV) is under debate. The chemokine receptor CXCR4 plays an important role in the mobilization of progenitor cells and is implicated in pathological conditions, including cardiovascular disease. This study aims to evaluate the association between EPCs and CXCR4-positive cells in HTX patients. Peripheral blood mononuclear cells (PBMCs) from 34 HTX patients and 25 control participants were analyzed by flow cytometry for CXCR4-positive cells and EPCs. Endothelial progenitor cells were defined by the expression of a range of hematopoietic and endothelial lineage markers in different combinations. The ability to form endothelial cell colonies in vitro was also assessed by colony-forming unit (CFU) assay. Phenotypic analysis of EPCs by flow cytometry revealed similar levels in HTX patients compared to controls. In addition, no difference was observed between levels of EPCs or CFU number in patients with and without CAV. By contrast, CFU assay revealed a reduced number of CFUs in HTX patients compared to controls (3.3% ± 0.95 and 13.3% ± 4.5%, respectively, P = 0.014). Likewise, levels of CXCR4-positive cells were significantly reduced (15.9 ± 1.4 in patients vs 24.8 ± 3.3% in controls, P < 0.01), negatively correlated with Framingham risk score (rho = -0.4, P = 0.02) and the number of risk factors (rho = -0.3, P = 0.049). Levels of CXCR4-positive cells were also correlated with CFU number (r = 0.65, P = 0.0005). These findings further develop our understanding of the role of EPCs and endothelial CFUs in cardiovascular disease, in addition to highlighting the potential importance of CXCR4 in heart transplantation.

CC chemokine receptor-1 activates intimal smooth muscle-like cells in graft arterial disease

BACKGROUND

Graft arterial disease (GAD) limits long-term solid-organ allograft survival. The thickened intima in GAD contains smooth muscle-like cells (SMLCs), leukocytes, and extracellular matrix. The intimal SMLCs in mouse GAD lesions differ from medial smooth muscle cells in their function and phenotype. Although intimal SMLCs may originate by migration and modulation of donor medial cells or by recruitment of host-derived precursors, the mechanisms that underlie their localization within grafts and the factors that drive these processes remain unclear.

METHODS AND RESULTS

This study of aortic transplantation in mice demonstrated an important function for chemokines beyond their traditional role in leukocyte recruitment and activation. Intimal SMLCs, but not medial smooth muscle cells, express functional CC chemokine receptor-1 (CCR1) and respond to RANTES by increased migration and proliferation. Although RANTES infusion in vivo promoted inflammatory cell accumulation in the adventitia of aortic allografts of wild-type and CCR1-deficient recipients, it increased GAD intimal thickening with SMLC proliferation in only the wild-type hosts. Aortic allografts transplanted into CCR1-deficient mice after wild-type bone marrow transplantation did not develop intimal lesions, which indicates that CCR1-bearing inflammatory cells do not contribute to intimal lesion formation. Moreover, RANTES induced SMLC proliferation in vitro but did not promote medial smooth muscle cell growth. Blockade of CCR5 attenuated RANTES-induced T-cell and monocyte/macrophage proliferation but did not affect RANTES-induced SMLC proliferation, consistent with a larger role of CCR1-binding chemokines in SMLC migration and proliferation and GAD development.

CONCLUSIONS

These studies provide a novel mechanistic insight into the formation of vascular intimal hyperplasia and suggest a novel therapeutic strategy for preventing allograft arteriopathy.

Human leukocyte antigen antibodies in chronic transplant vasculopathy-mechanisms and pathways

Transplant recipients exhibiting posttransplant antibodies are at a higher risk for acute and chronic antibody mediated rejection (AMR). The primary alloantigens recognized by antibodies in recipients with AMR are the highly polymorphic HLA class I and class II molecules expressed on the surface of the endothelial cells (ECs) of the graft. Traditionally, anti-HLA antibodies were thought to mediate graft injury through complement-dependent mechanisms. However, recent studies indicate that antibodies can also contribute to alterations in EC function through complement-independent mechanisms by transducing intracellular signals. Anti-HLA antibodies transduce signals that are both pro-inflammatory and pro-proliferative suggesting mechanistic roles in acute and chronic AMR.

Tea polyphenols regulate key mediators on inflammatory cardiovascular diseases

Tea polyphenols known as catechins are key components with many biological functions, including anti-inflammatory, antioxidative, and anticarcinogenic effects. These effects are induced by the suppression of several inflammatory factors including nuclear factor-kappa B (NF-κB). While these characteristics of catechins have been well documented, actions of catechins as mediators on inflammation-related cardiovascular diseases have not yet been well investigated. In this article, we reviewed recent papers to reveal the anti-inflammatory effects of catechins in cardiovascular diseases. In our laboratory, we performed oral administration of catechins into murine and rat models of cardiac transplantation, myocarditis, myocardial ischemia, and atherosclerosis to reveal the effects of catechins on the inflammation-induced ventricular and arterial remodeling. From our results, catechins are potent agents for the treatment and prevention of inflammation-related cardiovascular diseases because they are critically involved in the suppression of proinflammatory signaling pathways.

Critical role of scavenger receptor-BI–expressing bone marrow–derived endothelial progenitor cells in the attenuation of allograft vasculopathy after human apo A-I transfer

Allograft vasculopathy is the leading cause of death in patients with heart transplantation. Accelerated endothelial regeneration mediated by enhanced endothelial progenitor cell (EPC) incorporation may attenuate the development of allograft vasculopathy. We investigated the hypothesis that modulation of EPC biology and attenuation of allograft vasculopathy by increased high-density lipoprotein cholesterol after human apo A-I (AdA-I) transfer requires scavenger receptor (SR)–BI expression in bone marrow–derived EPCs. After AdA-I transfer, the number of circulating EPCs increased 2.0-fold (P < .001) at different time points in C57BL/6 mice transplanted with SR-BI+/+ bone marrow but remained unaltered in mice with SR-BI−/− bone marrow. The effect of high-density lipoprotein on EPC migration in vitro requires signaling via SR-BI and extracellular signal-regulated kinases and is dependent on increased nitric oxide (NO) production in EPCs. Human apo A-I transfer 2 weeks before paratopic artery transplantation reduced intimal area at day 21 3.7-fold (P < .001) in mice with SR-BI+/+ bone marrow but had no effect in mice with SR-BI−/− bone marrow. AdA-I transfer potently stimulated EPC incorporation and accelerated endothelial regeneration in chimeric SR-BI+/+ mice but not in chimeric SR-BI−/− mice. In conclusion, human apo A-I transfer accelerates endothelial regeneration mediated via SR-BI expressing bone marrow–derived EPCs, thereby preventing allograft vasculopathy.

Complications related to the transplantation of thoracic organs: consensus definitions from the Multi-Societal Database Committee for Pediatric and Congenital Heart Disease

A complication is an event or occurrence associated with a disease or a healthcare intervention, which constitutes a departure from the desired course of events, and may cause, or be associated with, suboptimal outcome. A complication does not necessarily represent a breech in the standard of care that constitutes medical negligence or medical malpractice. An operative or procedural complication is any complication, regardless of cause, occurring (1) within 30 days after an intervention in or out of the hospital, or (2) after 30 days during the same hospitalization subsequent to the operation or intervention. Operative and procedural complications include both intraoperative/intraprocedural complications and postoperative/postprocedural complications in this time interval. The Multi-Societal Database Committee for Pediatric and Congenital Heart Disease has set forth a comprehensive list of complications associated with the treatment of patients with congenital cardiac disease, related to cardiac, pulmonary, renal, haematological, infectious, neurological, gastrointestinal, and endocrinal systems, as well as those related to the management of anaesthesia and perfusion, and the transplantation of thoracic organs. The objective of this manuscript is to examine the definitions of operative morbidity as they relate specifically to patients who have received transplantation of the heart, heart and lung(s) or lung(s). These specific definitions and terms will be used to track morbidity associated with transplantation in a common language across many separate databases. The complications of transplantation are known risks of congenital cardiac surgery. The purpose of this effort is to propose consensus definitions for post-transplant complications following cardiac surgery so that collection of such data can be standardized. Clinicians caring for patients who have had transplantation of thoracic organs will be able to use this list for databases, quality improvement initiatives, reporting of complications, and comparing treatment strategies.

The autoimmune origin of atherosclerosis

Atherosclerosis is a chronic inflammatory disease. Many studies and observations suggest that it could be caused by an immune reaction against autoantigens at the endothelial level, the most relevant of which are oxidized LDL and heat shock proteins (HSP) 60/65. Endothelial dysfunction plays a fundamental role. The first antigen is related to the increased leakage and oxidation of LDL; the second to cellular reaction to stress. Experimental and clinical observations confirm the pathogenetic role of these antigens. Both innate and adaptive immunity and impaired regulatory mechanisms of the autoimmune reaction are involved. Different triggering factors are examined: infectious agents, smoking, air pollution, diabetes and hypercholesterolemia. Analogies and differences between systemic atherosclerosis and transplant-related coronary atherosclerosis help to understand their respective nature. Immune mechanisms might be responsible for the passage from stable plaque to unstable and rupture-prone plaque. Finally, prospects of treatment and prevention are linked to the induction of tolerance to responsible antigens, activation of immune regulatory response and the use of immunomodulatory drugs.

Cardiac retransplantation in children

To discuss the indications for and outcomes of cardiac retransplantation in childhood. The major challenge of pediatric heart transplantation is graft failure. The major causes of graft failure include coronary allograft vasculopathy and chronic rejection. Retransplantation may be considered in children or young adults who develop graft failure following pediatric heart transplantation. Retransplantation now accounts for 7% of all pediatric transplants. Recent studies have demonstrated that cardiac retransplantation has a poorer outcome than primary heart transplantation. However, the interval from primary transplant to retransplantation appears to impact significantly the success of retransplantation. When children undergo retransplantation for early graft failure, the survival is quite poor and the appropriateness of this strategy is questionable. However, children who undergo retransplantation many years after primary transplantation have outcomes that are similar to primary transplantation. The decision to pursue retransplantation depends on the severity of graft failure and recent data suggest that identification of mild graft dysfunction or coronary allograft vasculopathy does not imply impending graft failure. Novel therapies to extend the life of the primary graft and to stratify those at risk of severe graft dysfunction will improve the allocation of scarce organs for pediatric patients who might be candidates for cardiac retransplantation. Retransplantation can extend the lives of children who develop graft failure after primary transplantation. However, not all patients who develop graft dysfunction should necessarily be listed for retransplantation.

Anti-MHC class I antibody activation of proliferation and survival signaling in murine cardiac allografts

Anti-MHC class I alloantibodies have been implicated in the process of acute and chronic rejection because these Abs can bind to endothelial cells and transduce signals leading to the activation of cell survival and proliferation pathways. To characterize the role of the MHC class I-signaling pathway in the pathogenesis of Ab-mediated rejection, we developed a mouse vascularized heterotopic cardiac allograft model in which B6.RAG1 KO hosts (H-2K(b)/D(b)) received a fully MHC-incompatible BALB/c (H-2K(d)/D(d)) heart transplant and were passively transfused with anti-donor MHC class I Ab. We demonstrate that cardiac allografts of mice treated with anti-MHC class I Abs show characteristic features of Ab-mediated rejection including microvascular changes accompanied by C4d deposition. Phosphoproteomic analysis of signaling molecules involved in the MHC class I cell proliferation and survival pathways were elevated in anti-class I-treated mice compared with the isotype control-treated group. Pairwise correlations, hierarchical clustering, and multidimensional scaling algorithms were used to dissect the class I-signaling pathway in vivo. Treatment with anti-H-2K(d) Ab was highly correlated with the activation of Akt and p70S6Kinase (S6K). When measuring distance as a marker of interrelatedness, multidimensional scaling analysis revealed a close association between members of the mammalian target of rapamycin pathway including mammalian target of rapamycin, S6K, and S6 ribosomal protein. These results provide the first analysis of the interrelationships between these signaling molecules in vivo that reflects our knowledge of the signaling pathway derived from in vitro experiments.

A national conference to determine research priorities in pediatric solid organ transplantation

The need for evidence-based practice guidelines requires high quality, carefully controlled clinical research trials. This multidisciplinary conference attempted to: identify urgent clinical and research issues, identify obstacles to performing clinical trials, develop concepts for organ-specific and all-organ research and generate a report that would serve as a blueprint for future research initiatives. A few themes became evident. First, young children present a unique immunologic environment which may lead to tolerance, therefore, including young children in immunosuppression withdrawal and tolerance trials may increase the potential benefits of these studies. Second, adolescence poses significant barriers to successful transplantation. Non-adherence may be insufficient to explain poorer outcomes. More studies focused on identification and prevention of non-adherence, and the potential effects of puberty are required. Third, the relatively naive immune system of the child presents a unique opportunity to study primary infections and alloimmune responses. Finally, relatively small numbers of transplants performed in pediatric centers mandate multicenter collaboration. Investment in registries, tissue and DNA repositories will enhance productivity. The past decade has proven that outcomes after pediatric transplantation can be comparable to adults. The pediatric community now has the opportunity to design and complete studies that enhance outcomes for all transplant recipients.

Thromboaspiration during acute myocardial infarction in a heart transplant patient

Each year, an estimated 10% of heart transplant recipients develop coronary allograft vasculopathy, an aggressive form of coronary artery disease that limits survival after transplantation. The pathologic characteristics of coronary allograft vasculopathy are not uniform and both the clinical importance and pathophysiological significance of thrombosis and vasospasm in this setting are not completely understood. Mechanical reperfusion is a better alternative to systemic thrombolysis in patients with acute myocardial infarction and thrombus removal before standard percutaneous coronary intervention improves coronary epicardial flow. We report the case of a 38-year-old male admitted to the emergency room of our hospital with acute inferior myocardial infarction complicated by cardiogenic shock. He underwent heart transplant because of ischemic cardiomyopathy. Coronary angiography showed acute coronary thrombosis of the circumflex coronary artery. Percutaneous coronary intervention with thrombus extraction was successfully attempted. This case represents an unusual clinical presentation and treatment of cardiac allograft vasculopathy.

Therapeutic applications of bilirubin and biliverdin in transplantation

Bilirubin is the end product of heme catabolism by heme oxygenases. The inducible form of these enzymes is heme oxygenase-1 (HO-1), which is the rate-limiting enzyme that can degrade heme into equimolar quantities of carbon monoxide (CO), biliverdin, and free iron. Biliverdin is very rapidly converted to bilirubin by the enzyme biliverdin reductase, and free iron upregulates the expression of ferritin. HO-1 is a ubiquitous stress protein and is induced in many cell types by various stimuli. Induced HO-1 exerts antiinflammatory effects and modulates apoptosis. Expression of HO-1 in vivo suppresses the inflammatory responses in endotoxic shock, hyperoxia, acute pleurisy, and organ transplantation, as well as ischemia-reperfusion injury, and thereby provides salutary effects in these conditions. Accumulating evidence indicates that biliverdin/bilirubin can mediate the protective effects of HO-1 in many disease models, such as IRI and organ transplantation, via its antiinflammatory, antiapoptotic, antiproliferative, and antioxidant properties, as well as its effects on the immune response. This review attempts to summarize these protective roles as well as the molecular mechanisms by which biliverdin/bilirubin benefit IRI and solid-organ transplantation, including chronic rejection, and islet transplantation.

Ezetimibe in Heart Transplantation: Initial Experience

Dyslipidemia is a common problem among heart transplant (HT) recipients; it is a frequent risk factor in these patients that is exacerbated by immunosuppressive drugs. Statins are effective drugs to treat dyslipidemia in HT recipients, but control is suboptimal in some patients. Ezetimibe acts through inhibition of the enterohepatic recirculation, a mechanism different from but complementary to statins. Our objective was to assess the effect of the addition of ezetimibe to statin therapy among a population of HT patients.

PATIENTS AND METHODS

We included 19 stable patients on statin therapy with suboptimal control of cholesterol. Determinations were performed at baseline on statins and at 6 months (statins + ezetimibe). The analyzed variables were total cholesterol and fractions, triglycerides, cyclosporine levels, CPK, SGOT/SGPT, and bilirubin. The statistics were Student's t test for paired samples.

RESULTS

The overall mean age was 59 +/- 9 years with 95% males and mean BMI 27.5 +/- 3.5. The time since HT was 7 +/- 3 years. The reason for HT included ischemic heart disease in 68%. Pre-HT risk factors included in arterial hypertension in 32% and insulin-dependent diabetes mellitus in 10%, Dyslipidemia occurred in 68%; hypertriglyceridemia in 16% and hyperuricemia in 21%. Immunosuppression was cyclosporine in 100% and steroids in 94%. Type of lipid-lowering agent was simvastatin in 5%; pravastatin, 32%; atorvastatin, 58%; fibrates, 10%. The ezetimibe dose was 10 mg/day in 95% of cases. When ezetimibe was added we observed differences in total cholesterol values (total cholesterol at baseline: 279 +/- 74, total cholesterol with ezetimibe: 198 +/- 47 mg/dL; P = .0001) and LDL-cholesterol values (LDL-cholesterol at baseline: 171 +/- 69, LDL-cholesterol with ezetimibe: 109 +/- 41 mg/dL; P = .001). The remaining variables did not show significant differences.

CONCLUSION

The addition of ezetimibe to statin therapy among heart transplant patients was effective to control dyslipidemia and showed an excellent safety profile.

Update on cardiac transplantation pathology

CONTEXT

The endomyocardial biopsy is the mainstay for monitoring acute allograft rejection in heart transplantation. Objective and accurate assessment of cellular and humoral types of rejection is important to optimize immunosuppressive therapy, avoid therapeutic complications, and improve patient outcome. The grading system for evaluation of heart transplant biopsies published in 1990 was revised in 2004 after more than a decade of implementation.

OBJECTIVE

In this review, we focus on a practical approach to the evaluation of human heart transplant biopsies as diagnostic surgical pathologic specimens. We discuss the revised International Society of Heart and Lung Transplantation working formulation.

DATA SOURCES

We reviewed pertinent literature, incorporating ideas and vast experience of participants in various work groups that led to the revision of the 1990 grading system.

CONCLUSIONS

The grading system for cellular rejection is presented with detailed light microscopic morphology and comparison of the 1990 and 2004 International Society of Heart and Lung Transplantation working formulations. We show how the pathologic recognition of cellular rejection and antibody-mediated rejection has evolved. We emphasize the interpretation of immunostains for complement components C4d and C3d in the diagnosis of antibody-mediated rejection. Evidence of regulation of complement activation in human heart transplant biopsies is presented in this context. We also discuss the pitfalls, caveats, and artifacts in the interpretation of allograft endomyocardial biopsies. Lastly, we discuss the pathology of human cardiac allograft vasculopathy in practical detail.

Can mTOR inhibitors reduce the risk of late kidney allograft failure?

The most frequent causes of late kidney allograft failure are chronic rejection, nonalloimmune injury and death, all of which may depend on the characteristics of the donor and recipient, but may also be influenced by the type of immunosuppression. Combining calcineurin inhibitors (CNIs) and corticosteroids offers potent immunosuppression, but may also cause side effects leading to progressive graft dysfunction or an increased risk of death. New immunosuppressive strategies may come from the availability of inhibitors of mTOR, a downstream effector of phosphatidylinositol-3 kinase that provides the signal for cell proliferation by phosphorylating a cascade of kinases. Recent trials have shown that it is possible to minimize the dose or withdraw CNIs a few weeks after transplantation when they are combined with mTOR inhibitors and their combination may also make it possible to minimize or avoid the use of corticosteroids. Moreover, by inhibiting the signal for cell proliferation, mTOR inhibitors may reduce the replication of cytomegalovirus inside host cells, prevent transplant vasculopathy, and exert anti-oncogenic activity. All of these characteristics offer a ray of hope for reducing the risk of long-term allograft failure.

Elevated uric acid levels predict allograft vasculopathy in cardiac transplant recipients

BACKGROUND

Cardiac allograft vasculopathy (CAV) poses the greatest threat to the long-term survival of cardiac transplant recipients, and these individuals often exhibit elevated levels of uric acid (UA), a stimulator of T cells. We hypothesized that hyperuricemia is associated with CAV in cardiac transplant recipients.

METHODS

UA levels were measured in cardiac transplant recipients between January 2003 and January 2005. Surveillance cardiac catheterizations performed 3 months to 1 year after UA measurement were reviewed. The relationship between UA and CAV was adjusted for possible confounders with propensity scores and confirmed with goodness-of-fit tests.

RESULTS

The 105 patients included in this study were a median 63.3 months post-transplant and their left heart catheterizations were performed a median 5.6 months after UA measurement. Focal stenosis was evident in 25 angiograms and 31 showed distal pruning of the coronary arteries. Compared with the lowest quartile of UA, the highest quartile had an increased risk of CAV: odds ratio (OR) 6.11 (95% CI 1.47 to 25.5; p = 0.013) for focal stenosis and OR 4.60 (95% CI 1.34 to 15.8; p = 0.015) for distal pruning. After adjustment, this relationship persisted for both focal stenosis (OR 5.53, 95% confidence interval [CI] 1.29 to 23.7; p = 0.021) and distal pruning (OR 4.21, 95% CI 1.15 to 15.4; p = 0.029).

CONCLUSIONS

Elevated UA confers an increased risk of CAV. This association may be causal, with pathophysiologic implications for the role of hyperuricemia in allograft failure and, if substantiated, could have clinical implications for the use of xanthine oxidase inhibitors in cardiac transplant recipients.

The Emerging Role of Multi-Detector Computed Tomography in Heart Failure

BACKGROUND

Recent advances in cardiac multi-detector computed tomography (MDCT) technology now permits entire coronary tree evaluation in a single breath hold with submillimeter slice collimation and improved temporal resolution.

METHODS AND RESULTS

Besides excellent correlation with invasive angiogram for the detection of significant coronary occlusion, MDCT also provides reliable and reproducible data regarding various other cardiac anatomic and functional parameters that are pertinent to heart failure patients. These include left ventricular measurement (eg, ejection fraction, regional wall motion, dimensions, volumes), pulmonary vein anatomy and drainage, right ventricular function, and cardiac venous system, among many others. However, there are radiogenic and nonradiogenic risks associated with MDCT that should be considered before scanning the patients.

CONCLUSIONS

This review summarizes the existing literature of the various cardiac MDCT applications pertinent to heart failure patients.

Drug-induced immunomodulation to affect the development and progression of atherosclerosis: a new opportunity?

Inflammation and cytokine pathways are crucial for the development and progression of atherosclerotic lesions. In this review, the hypothesis that immunomodulatory drugs provide a possible therapeutic modality for cardiovascular disease is evaluated. Therefore, after a short overview of the specific inflammatory pathways involved in atherosclerosis, literature on the effect of several immunomodulatory drugs, such as nonsteroidal anti-inflammatory drugs, specific cyclooxygenase inhibitors and immunosuppressive drugs, used currently in the prevention of rejection after organ transplant, on the development and progression of atherosclerosis is reviewed. In addition, the pleiotropic immunomodulatory effect of two established cardiovascular drugs (angiotensin-converting enzyme inhibitors and statins) is discussed.

Vascular Remodeling 1 Year After Cardiac Transplantation

BACKGROUND

The belief that vascular remodeling and intimal hyperplasia are causes of luminal narrowing in cardiac allograft vasculopathy (CAV) is controversial. This study evaluated the relationship of vascular remodeling and intimal hyperplasia to luminal narrowing 1 year after orthotopic heart transplantation.

METHODS

Intravascular ultrasound imaging was performed on 190 cardiac transplant recipients at baseline and again 1 year after transplantation as part of a randomized trial of mycophenolate mofetil (MMF) and azathioprine (Aza). Studies 1 year apart were matched at 625 sites. All sites were classified into positive, non-significant and negative remodeling patterns, depending on a change of +/-10% in external elastic membrane area. Of the 190 patients, 99 were randomized to receive MMF, and 91 to receive Aza.

RESULTS

A total of 625 sites were observed. Of these, 52% had no remodeling, 25% exhibited vessel dilation, and 23% had vessel shrinkage in the presence of variable intimal growth (Delta intimal area: 0.73 +/- 1.70 mm2, p < 0.0001; 1.23 +/- 2.02 mm2, p < 0.0001; and 0.20 +/- 1.40 mm2, p = 0.09, respectively). Sixty percent of the lumen loss was due to a decrease in external elastic membrane area and 40% to an increase in intimal area (p = 0.005). Compared with Aza-treated patients, the MMF-treated patients had a lower incidence of vessel shrinkage (17% vs 28%, p = 0.001), and a trend for smaller maximum intimal thickness (0.21 +/- 0.25 mm vs 0.29 +/- 0.31 mm, p = 0.052).

CONCLUSIONS

Positive remodeling is associated with intimal growth, but negative remodeling does not correlate with any specific change in intimal hyperplasia. Constrictive remodeling is more responsible than intimal hyperplasia for the luminal narrowing that occurs. MMF is more efficacious than azathioprine in preventing the development of CAV at 1 year, by reducing the degree and incidence of vessel shrinkage and the progression of intimal hyperplasia.