Heart Transplantation

Targeting the Innate Immune Response to Improve Cardiac Graft Recovery after Heart Transplantation: Implications for the Donation after Cardiac Death

Heart transplantation (HTx) is the ultimate treatment for end-stage heart failure. The number of patients on waiting lists for heart transplants, however, is much higher than the number of available organs. The shortage of donor hearts is a serious concern since the population affected by heart failure is constantly increasing. Furthermore, the long-term success of HTx poses some challenges despite the improvement in the management of the short-term complications and in the methods to limit graft rejection. Myocardial injury occurs during transplantation. Injury initiated in the donor as result of brain or cardiac death is exacerbated by organ procurement and storage, and is ultimately amplified by reperfusion injury at the time of transplantation. The innate immune system is a mechanism of first-line defense against pathogens and cell injury. Innate immunity is activated during myocardial injury and produces deleterious effects on the heart structure and function. Here, we briefly discuss the role of the innate immunity in the initiation of myocardial injury, with particular focus on the Toll-like receptors and inflammasome, and how to potentially expand the donor population by targeting the innate immune response.

Cardiac Reserve in the Transplanted Heart: Effect of a Graft Polymorphism in the β1-adrenoceptor

BACKGROUND

Polymorphism of the beta1-adrenoceptor (beta1-AR) affects outcome and beta-blocker efficacy in patients with heart failure. We studied the influence of the beta1-AR Ser49Gly polymorphism on cardiac reserve in transplanted hearts.

METHODS

Beta1-AR polymorphism was determined by allelic discrimination analysis. Patients were divided into two groups: either homozygous for Ser49 (n = 15) or with Gly49 in one or both alleles (Gly49; n = 5). Patients underwent a maximal bicycle exercise test and echocardiographic evaluation at rest and during low-dose dobutamine stress.

RESULTS

Patients with Gly49 grafts had better physical endurance (144 +/- 26 vs 112 +/- 31 W, p = 0.03), a trend toward better chronotropic reserve (deltaHR 64 +/- 13 vs 47 +/- 16 bpm, p = 0.056) during exercise, and lower resting heart rate (82 +/- 7 vs 90 +/- 7 bpm, p = 0.04) than those homozygous for Ser49. There were no significant differences in left ventricular ejection fraction (LVEF), with the exception of a decrease in cardiac reserve in patients with the Gly49 variants at the lowest dose of dobutamine (deltaLVEF -4.4 +/- 1.5 vs 2.2 +/- 5.8%, p = 0.04). Doppler myocardial tissue velocities of early relaxation were increased in patients with the Gly49 variants compared with patients homozygous for Ser49, both at rest (14.5 +/- 3.2 vs 10.4 +/- 2.0 cm/s, p = 0.03) and during the lowest dose of dobutamine (15.0 +/- 3.7 vs 10.9 +/- 2.5 cm/s, p = 0.04).

CONCLUSIONS

Heart transplant patients with the beta1-AR Gly49 variants had a lower heart rate, and better stress endurance and diastolic function compared with patients homozygous for Ser49. They also showed a trend toward better chronotropic reserve. These results provide a possible explanation for differences in cardiac reserve among patients with heart transplants.

Cardiac Transplantation Using Extended-Donor Criteria Organs for Systemic Amyloidosis Complicated by Heart Failure

BACKGROUND

Systemic amyloidosis complicated by heart failure is associated with high cardiovascular morbidity and mortality. Heart transplantation for patients with systemic amyloidosis is controversial due to recurrence of disease in the transplanted organ or progression of disease in other organs.

METHODS

All patients with systemic amyloidosis and heart failure referred for heart transplant evaluation from 1997 to 2004 were included in this retrospective cohort analysis. An interdisciplinary protocol for cardiac transplantation using extended-donor criteria organs, followed in 6 months by either high-dose chemotherapy and stem cell transplantation for patients with primary (AL) or by orthotopic liver transplantation for familial (ATTR) amyloidosis, was developed. Survival of the transplanted amyloid cohort was compared to survival of those amyloid patients not transplanted and to patients transplanted for other indications.

RESULTS

A total of 25 patients with systemic amyloidosis and heart failure were included in the study; 12 patients received heart transplants. Amyloid heart transplant recipients were more likely female (58% vs. 8%, P=0.02) and had lower serum creatinine (1.3+/-0.5 vs. 2.0+/-0.7 mg/dL, P=0.01) than nontransplanted amyloid patients. Survival at 1-year after heart transplant evaluation was higher among transplanted patients (75% vs. 23%) compared to patients not transplanted (P=0.001). Short-term survival posttransplant did not differ between transplanted amyloid patients and contemporaneous standard and extended-donor criteria heart transplant patients (P=0.65).

CONCLUSIONS

Cardiac transplantation for amyloid patients with extended-donor criteria organs followed by either stem cell or liver transplantation is associated with improved survival compared to patients not transplanted. Short- to intermediate-term survival is similar to patients receiving heart transplantation for other indications. This clinical management strategy provides cardiac amyloid patients a novel therapeutic option.

Nesiritide in cardiovascular anesthesia

PURPOSE OF REVIEW

Acute heart failure has become a major medical issue in the western population. Because mortality is still as high as 50%, the treatment of these patients has been the focus of many studies. A new approach has recently been proposed, including B-type natriuretic peptide as a medication. The purpose of this review is to discuss these new developments.

RECENT FINDINGS

Recent studies have shown that plasma levels of B-type natriuretic peptide may serve as a marker for the severity of acute decompensated heart failure. Nesiritide, which is the recombinant equivalent of B-type natriuretic peptide, is a vasodilator, acting by increasing cyclic guanosine 3', 5'-monophosphate in the vascular smooth muscle cells. It is mainly considered to be an alternative for nitroglycerin, because it has fewer side-effects, and its activity is more prolonged. Treatment with nesiritide has shown fewer arrhythmias and a lower mortality rate compared with dobutamine and milrinone. In cardiac surgery, nesiritide is mainly administered to patients awaiting heart transplantation, but intraoperatively the doses of nesiritide and anesthetics must be adjusted because of a potential interaction. A few anecdotal reports have shown the advantageous effects of nesiritide in the early post-bypass period.

SUMMARY

Anesthesiologists will be confronted with increasing numbers of patients with heart failure, who require new forms of medication. Nesiritide is a promising new tool, and its application, which is still mainly restricted to the preoperative period, will probably soon be extended to the early post-bypass period.

Suppression of (5R)-5-hydroxytriptolide (LLDT-8) on Allograft Rejection in Full MHC-Mismatched Mouse Cardiac Transplantation

BACKGROUND

(5R)-5-hydroxytriptolide (LLDT-8) is a new compound derived from triptolide, which is the major immunosuppressive fraction of Tripterygium wilfordii Hook. F (TWHF). Studies in vitro and in vivo have demonstrated that LLDT-8 had potent immunosuppressive activities. Here we tested LLDT-8 in major histocompatibility complex (MHC)-mismatched cardiac transplantation and investigated the mechanisms underlying the prevention of transplant rejection.

METHODS

LLDT-8 was administered orally to recipients in Balb/c to C57BL/6 murine cardiac transplantation model. Allograft survival after transplantation was recorded in recipients. The T cell immunity and cytokine production were observed. Histological analysis was performed. The chemokine and its receptor were analyzed by reverse transcriptase-polymerase chain reaction on cardiac graft RNA.

RESULTS

LLDT-8 administered orally significantly induced the survival prolongation of allogeneic cardiac graft. Histological results showed that LLDT-8 well preserved myocardium and significantly reduced infiltration of the graft with inflammatory cells. LLDT-8 decreased IL-2 production in recipient splenocytes stimulated by concanavalin A (ConA) ex vivo. LLDT-8 significantly inhibited the immunoreactivity of recipient to specific donor alloantigens, but preserved immunity to third-party alloantigens and mitogen. However, the flow cytometry analysis of the proportion of CD4+, CD8+ T cell subgroup in recipient spleens showed LLDT-8 had a normalizing effect on the splenic lymphocytes population. LLDT-8 decreased CC chemokine receptor 5 (CCR5) and their ligands macrophage inflammatory protein 1 alpha (MIP-1alpha) and beta (MIP-1beta) mRNA expressions in allografts.

CONCLUSION

The results outline the great potential of LLDT-8 as a therapeutic tool in transplant rejection.

High level of cerebral microembolization in patients supported with the DeBakey left ventricular assist device

OBJECTIVE

Microembolic signals detected by transcranial Doppler ultrasonography have been demonstrated to be clinically relevant in patients supported with pulsatile left ventricular assist devices. We prospectively investigated the quantity of microembolic signals in patients supported with the continuous-flow DeBakey left ventricular assist device (MicroMed DeBakey VAD; MicroMed Technology, Inc, Houston, Tex) including the refined Carmeda BioActive Surface system (Carmeda AB, Stockholm, Sweden).

METHODS

Twenty-three patients (20 male) aged 14 to 62 years supported with DeBakey left ventricular assist devices (n = 6 with Carmeda) were enrolled in this study. Microembolic signal monitorings were performed twice weekly by insonating the middle cerebral artery for 20 minutes without and 20 minutes with oronasal application of oxygen (6 L/min). Evidence of clinically manifest thromboembolic events was based on regular questionnaires, clinical examinations, and results of diagnostic procedures.

RESULTS

Despite a low incidence of thromboembolic complications (0.24 per 100 left ventricular assist device days), 20 patients (87%) showed circulating microemboli. Overall, microembolic signals were found in 175 of 499 transcranial Doppler ultrasonographic examinations (35.1%), with mean counts of 81.2 +/- 443 (range 0-5042 signals/h). Both microembolic signal prevalence (25% vs 34%, P = .01) and absolute signal counts (46.5 vs 104, P < .01) significantly declined with oxygen delivery. There was no significant correlation between the individual microembolic signal activity and the incidence of clinical thromboembolism or the intensity of antihemostatic treatment. Patients supported with the Carmeda device did not show reduced rates of clinical thromboembolization or cerebral microemboli.

CONCLUSION

In patients with DeBakey left ventricular assist devices, a high load of clinically silent microemboli can be detected within the cerebral arteries despite a low incidence of embolic complications. It needs to be investigated whether such continuous, presumably gaseous microembolization causes cognitive or neuropsychologic deficits.

Outcomes and Complications After Heart Transplantation

In more than 35 years of experience with heart transplantation, improvements in patient selection, surgical techniques, organ preservation, and postoperative management have increased survival rates and reduced complications. However, a number of significant complications continue, limiting the benefit of heart transplantation as the long-term solution for patients. Current survival rates are 83% at 1 year and 72% at 5 years, with 50% of patients surviving 9.4 years or more. Recipient and donor characteristics influence survival outcome. Primary graft dysfunction is the most frequent cause of death during the first 30 days. The function of the transplanted heart allows return to pre-illness activities, though denervation limits peak exercise capacity. Advances in immunosuppressive medications have decreased the incidence and severity of rejection, though only recently have shown promise in attenuating the incidence of cardiac graft vasculopathy, the major complication limiting long-term graft function. This review addresses current outcomes and the short- and long-term complications of heart transplantation.