Immunological aspects of fresh and cryopreserved aortic valve transplantation in rats.

BACKGROUND: The influence of immune activation on valve allograft degeneration remains unclear. We studied the combined effect of major histocompatibility complex (MHC)-incompatibility and cryopreservation on valve performance, histomorphology, and tissue antigenicity in rats. METHODS: Fresh or cryopreserved allogeneic aortic valves from WAG (RT1u) rats were transplanted to DA (RT1a) recipients and syngenic transplants served as controls. After 7 or 21 days, valves were examined for competence and morphology. Immune reactivity of the recipient was measured by concanavalin A (conA) stimulation and analysis of donor-reactive Helper T-lymphocyte frequencies (HTLf) in peripheral blood and spleen. RESULTS: Syngenic grafts demonstrated normal competence and structure. Allografts lost their competence over time caused by destruction of the leaflets combined with cellular infiltration in the vascular wall. Cryopreservation induces early loss of competence and retrovalvular thrombosis. Cryopreserved allografts were also heavily infiltrated. ConA stimulation indices and HTLf were higher in allogeneic recipients compared to syngenic recipients (p < 0.03). Cryopreserved allografts elicited a lower immune response compared with fresh allografts (p < 0.03). CONCLUSIONS: Aortic valve allografts are able to induce a donor-reactive immune response that is related to early graft destruction and incompetence. Cryopreservation appears to diminish but not eliminate the antigenicity of the allograft.

Right ventricular outflow tract reconstruction with an allograft conduit.

BACKGROUND: Allograft conduits are used for reconstruction of the right ventricular outflow tract in patients with congenital heart disease and in the pulmonary autograft procedure. A retrospective evaluation of our experience with the use of allograft conduits for reconstruction of the right ventricular outflow tract was conducted. METHODS: Between August 1986 and March 1999, 316 allografts (246 pulmonary, 70 aortic) were implanted in 297 patients for reconstruction of the right ventricular outflow tract. Main diagnostic groups were aortic valve pathology (n = 112, 35%), tetralogy of Fallot (n = 71, 22%), and pulmonary atresia with ventricular septal defect (n = 46, 14%). Kaplan-Meier analyses were done for survival, valve-related reoperation, and valve-related events. In addition, Cox regression analysis was used for evaluation of potential risk factors. RESULTS: Mean age at operation was 18 years (range, 7 days to 61 years). Mean follow-up was 4 years (range, 2 days to 12 years). Twelve patients (4%) died within 30 days after operation. Patient survival was 90% (95% confidence interval [CI], 86% to 94%) at 5 years and 88% (95% CI, 83% to 94%) at 8 years. Twenty-four reoperations were required for allograft dysfunction in 23 patients; 21 allografts were replaced. Freedom from valve-related reoperation was 91% (95% CI, 86% to 95) at 5 years and 87% (95% CI, 81% to 93%) at 8 years. Twenty-nine valve-related events were reported (2 deaths, 24 reoperations, 2 balloon dilatations, and 1 endocarditis). Freedom from valve-related events was 90% (95% CI, 85% to 94%) at 5 years after implantation, and 84% (95% CI, 77% to 91%) at 8 years. Risk factors for accelerated allograft failure were extra-anatomic position of the allograft (p = 0.03; hazard ratio, 9.7) and the use of an aortic allograft (p = 0.02; hazard ratio, 2.4). CONCLUSIONS: Right ventricular outflow tract reconstruction with an allograft conduit has good medium-term results, although progression of allograft degeneration is noted. Aortic allografts should preferably not be used for reconstruction of the right ventricular outflow tract.

Laparoscopic transabdominal pericardial window: new standard in the treatment of recurrent pericardial effusion complicated by cardiac tamponade.

Creation of a transabdominal transdiaphragmatic pericardial window for life-threatening recurrent pericardial effusion has proved to be a safe minimally invasive technique. By inducing adequate pericardial sac decompression while avoiding single-lung ventilation and thoracic drainage in severely ill patients, it provides anatomopathologic diagnosis and can direct further therapeutic measures. The transabdominal approach improves postoperative recovery dramatically by limiting postoperative pain and prevents sometimes invalidating intercostal neuralgia. Transabdominal pericardial sac fenestration should be part of the armamentarium used by every minimally invasive surgeon.

Circulating donor-specific cytotoxic T lymphocytes with high avidity for donor human leukocyte antigens in pediatric and adult cardiac allograft valved conduit recipients.

OBJECTIVE: Specific immunological responses may be involved in the process of cryopreserved allograft valved conduit (AVC) degeneration, which is more frequently seen in young recipients. Rejection of heart and corneal allografts is preceded by an increase in the fraction of cytotoxic T lymphocytes (CTL) with high avidity for donor human leukocyte antigens (HLA) circulating in both peripheral blood and the affected graft. These donor-specific high-avidity CTLs are regarded as the destructive cells capable of causing graft damage. To monitor the precursors of these cells (CTLp) in young and adult AVC recipients, in vitro quantitative tests were performed on sequentially taken blood samples to quantitate CTLp frequencies and their avidity for donor antigens. METHOD: Six children and nine adults who received a cryopreserved AVC in the period between 1994 and 1997 were included in the study. From these patients, two to six blood samples were obtained up to 3 years after valve implantation. The number of circulating CTLp present within the peripheral blood mononuclear cell (PBMC) population was determined by limiting dilution analysis (LDA). The fraction of CTLp with high avidity for donor HLA class I was determined by addition of CD8 monoclonal antibodies (mAb) during the cytotoxic phase of the assay. Third-party stimulator cells were used to verify the donor-specificity of the response. RESULTS: The number of donor-specific CTLp increased significantly in the period 6-12 months after AVC implantation, while third-party-specific CTLp frequencies were not affected. Additionally, we found a significant increase of the high-avidity fraction of CTLp directed against donor antigens as early as during the first 6 months after AVC implantation. The fraction of high-avidity CTLp remained significantly higher post- compared with pre-implantation, even after 12 months. We observed no significant difference in the kinetics of CTLp frequencies between pediatric and adult AVC recipients. CONCLUSION: Implantation of cryopreserved human AVC induces an increase in the total number of circulating CTLp directed against donor HLA class I in both adults and children. The shift towards more destructive high-avidity CTLp in the peripheral blood indicates their potential damaging effect towards the heart valve allograft.

Escherichia coli endocarditis of a native mitral valve with paravalvular pseudoaneurysm formation and fatal hemopericardium.

Until recently only few cases have been described of acute infective endocarditis with E. Coli limited to a normal native mitral valve. Furthermore, mechanisms of so called abcess formation and rupture are still uncompletely understood. We report the case of an E. Coli endocarditis developing a rapidly progressive pseudoaneurysm of the mitral annulus. At necropsy diffuse infectious tissue weakening with pseudoaneurysm formation of the mitral ring and dissection into an hemorraghic pericard were seen. The authors further discuss the changing pattern of infectious agents causing acute infective endocarditis of the native mitral valve, transesophageal echocardiographic characteristics of paravalvular cavities and insights in mechanisms of pseudoaneurysm formation and dissection from clinicopathological findings.

Experimental validation of frequently-used echocardiographic right-ventricular impedance parameters.

BACKGROUND: Aim of the study was to validate commonly used bedside right-ventricular (RV) impedance parameters, which are utilized in determining heart-lung interactions during mechanical ventilation. METHODS: Fifteen pigs were equally assigned to either an open or a closed pericardium group. In all animals, an inflatable vascular occluder and a flow probe were placed around the main pulmonary artery, which allowed for a gradual increase in pulmonary vascular impedance with banding of the pulmonary artery. A median sternotomy was performed for the open pericardium group, and a lateral thoracotomy was performed for the closed pericardium group. RESULTS: In the open pericardium group, mean acceleration time (ACmean) and the slope of the pulmonary artery flow correlated significantly with Poiseuille resistance over the banding (r=0.67 and r=0.65, respectively). In the closed pericardium group, the ratio of the right to left ventricular area, eccentricity index, and tricuspid annular plane systolic excursion did not correlate with resistance over the banding, only the ACmean showed a significant correlation with resistance over the banding (r=0.88). CONCLUSION: ACmean is a reliable parameter of RV impedance that can be used to study the heart-lung interactions during mechanical ventilation.

Increased numbers of circulating donor-specific T helper lymphocytes after human heart valve transplantation.

Implantation of cryopreserved human donor heart valves for either congenital or acquired cardiac disease has been performed since the last three decades. Although the clinical outcome is good, long-term valve degeneration resulting in dysfunction has been observed. A specific immunological response of the recipient against the allograft has been proposed as one of the factors involved in this process. Helper T lymphocytes play an important intermediate role in cellular and humoral immune response. Increasing numbers of circulating donor-specific helper T lymphocytes precursors (HTLp) correlate with graft rejection after organ transplantation. To investigate whether cryopreserved human donor heart valves are able to induce a donor-specific T helper response, we monitored the HTLp frequencies (HTLpf) in peripheral blood samples of 13 patients after valve allograft transplantation by use of a limiting dilution assay followed by an interleukin-2 bioassay. Prior to transplantation, HTLpf specific for donor and third-party antigens showed individual baseline levels. After allografting, the antidonor frequencies significantly increased in 11 of the 13 patients (P = 0.02). This was not found for stimulation with third-party spleen cells (P = 0.68), which indicates a donor-specific response. Maximal donor-specific HTLpf were already found at 1--2 months after operation. Valve allograft transplantation induces an increase in the numbers of donor-specific HTLp in peripheral blood of the patients. Analogous to organ transplantation, these HTLp may play a crucial role in events that lead to valve damage. Therefore, monitoring of HTLp in peripheral blood samples might be informative for donor valve degeneration (rejection) and subsequently valve allograft failure.

A size-matching heterotopic aortic valve implantation model in the rat.

BACKGROUND: Structural failure of cardiac valve allografts may be related to technical factors such as size mismatch, resulting in early intimal proliferation and fibrosis or immunological reactions against the transplanted valves, featuring lymphocytic infiltration. OBJECTIVE: To develop a heterotopic aortic valve implantation model in the rat to study the immunological factors leading to graft failure in the setting of a technical adaptation for size mismatch. METHODS: Syngeneic (WAG-WAG or DA-DA) and allogeneic (WAG-BN or WAG-DA) rat strain combinations were used to study the effect of the allogeneic response on valve properties. An end-to-side anastomosis was made between the U-shaped aortic root graft and the recipient's abdominal aorta to resolve the problems of size matching. RESULTS: No animals suffered from ischemic or neurological complications during the study period. One hundred percent survival and patency of the aortic grafts were achieved at the end of a 21-day observation period. In the syngeneic group 9 of 10 valves were still competent when assessed during retrograde injection. In contrast, 2 of 10 allogeneic valve grafts were competent on postoperative Day 21. Microscopic evaluation revealed no fibrosis or intimal thickening in the syngeneic valve grafts while the allogeneic valve grafts demonstrated rejection-like morphology. CONCLUSION: The absence of fibrosis and intimal thickening in the syngeneic transplanted valve grafts indicates that this implantation model is not influenced by nonimmunological-based structural changes. Therefore, this new model enables us to study the association between donor-directed immune responses and allograft degeneration in a technically unbiased manner.

Heart valve dysfunction resulting from cellular rejection in a novel heterotopic transplantation rat model.

Structural failure of heart valve allografts may be related to technical factors or immunological reactions. To circumvent nonimmunological factors a new rat implantation model was developed to study whether alloreactivity results in histopathological changes and valve dysfunction. Syngeneic (WAG-WAG, DA-DA) and allogeneic (WAG-BN, WAG-DA) transplantation was carried out using this new technique, and the function of explanted valves was assessed 21 days later by retrograde competence testing. Additionally, grafts were examined using standard histological and immunohistochemical techniques. There was no leakage during retrograde injection in nine of tem syngeneic and two of ten allogeneic grafts. Microscopically, syngeneic valves appeared normal without fibrosis or intimal thickening, although CD8+ lymphocytes and macrophages were found in necrotic myocardial rim and adventitia. In contrast, allogeneic valves were deformed and noncellular, with extensive infiltration of CD4+, CD8+ and CD68+ cells in adventitia and media. Absence of fibrosis and intimal thickening in syngeneic transplanted valves indicated circumvention of nonimmunological factors. Allogeneic valve transplantation induces cellular infiltration in the graft with subsequent graft failure.

Selective regional myocardial infiltration by the percutaneous coronary venous route: A novel technique for local drug delivery.

Recent advances in the treatment of heart disease, in particular cardiovascular gene therapy and therapeutic angiogenesis, highlight the need for efficient and practical local delivery methods for the heart. We assessed the feasibility of percutaneous selective coronary venous cannulation and injection as a novel approach to local myocardial drug delivery. In anesthetized swine, the coronary sinus was cannulated percutaneously and a balloon-tipped catheter advanced to the anterior interventricular vein (AIV) or middle cardiac vein (MCV). During balloon occlusion, venous injection of radiographic contrast caused regional infiltration of targeted myocardial regions. Complete AIV occlusion had no impact on LAD flow parameters. Videodensitometric analysis following venous injection showed that radiographic contrast persisted for at least 30 min. Selective regional myocardial infiltration is feasible by this approach, targeting selected myocardial beds, including the apex, anterior wall, septum, and inferoposterior wall. This novel technique has potential application for local myocardial drug or growth factor delivery. Cathet. Cardiovasc. Intervent. 51:358-363, 2000.