Nizar Yonan

Cytokine gene polymorphism and heart transplant rejection

BACKGROUND Allograft rejection is mediated by cytokines. As polymorphism in cytokine genes can result in interindividual differences in cytokine production, we hypothesize that some patients may have an increased risk of rejection. METHODS We have related polymorphisms that influence cytokine production in the tumor necrosis factor (TNF)-A and interleukin (IL)-10 genes to early graft rejection in 115 heart transplant recipients. RESULTS Certain combinations of TNF-A and IL-10 gene polymorphisms are associated with rejection. Five of 19 patients who had high levels of rejection typed as high TNF-alpha/low IL-10 producers compared with 4 of 96 patients with lower levels of rejection (P<0.005). CONCLUSIONS We have identified a particular cytokine genotype that may confer susceptibility to increased levels of early rejection. Patients with a worse prognosis may be able to be identified pretransplant by DNA analysis of TNF-A, IL-10, and other gene polymorphisms.

Comprehensive Validation of Cardiovascular Magnetic Resonance Techniques for the Assessment of Myocardial Extracellular Volume

Background— Extracellular matrix expansion is a key element of ventricular remodeling and a potential therapeutic target. Cardiovascular magnetic resonance (CMR) T1-mapping techniques are increasingly used to evaluate myocardial extracellular volume (ECV); however, the most widely applied methods are without histological validation. Our aim was to perform comprehensive validation of (1) dynamic-equilibrium CMR (DynEq-CMR), where ECV is quantified using hematocrit-adjusted myocardial and blood T1 values measured before and after gadolinium bolus; and (2) isolated measurement of myocardial T1, used as an ECV surrogate. Methods and Results— Whole-heart histological validation was performed using 96 tissue samples, analyzed for picrosirius red collagen volume fraction, obtained from each of 16 segments of the explanted hearts of 6 patients undergoing heart transplantation who had prospectively undergone CMR before transplantation (median interval between CMR and transplantation, 29 days). DynEq-CMR–derived ECV was calculated from T1 measurements made using a modified Look-Locker inversion recovery sequence before and 10 and 15 minutes post contrast. In addition, ECV was measured 2 to 20 minutes post contrast in 30 healthy volunteers. There was a strong linear relationship between DynEq-CMR–derived ECV and histological collagen volume fraction (P<0.001; within-subject: r=0.745; P<0.001; r 2=0.555 and between-subject: r=0.945; P<0.01; r 2=0.893; for ECV calculated using 15-minute postcontrast T1). Correlation was maintained throughout the entire heart. Isolated postcontrast T1 measurement showed significant within-subject correlation with histological collagen volume fraction (r=−0.741; P<0.001; r 2=0.550 for 15-minute postcontrast T1), but between-subject correlations were not significant. DynEq-CMR–derived ECV varied significantly according to contrast dose, myocardial region, and sex. Conclusions— DynEq-CMR–derived ECV shows a good correlation with histological collagen volume fraction throughout the whole heart. Isolated postcontrast T1 measurement is insufficient for ECV assessment.

Transforming growth factor beta (TGF-β) and obliterative bronchiolitis following pulmonary transplantation

BACKGROUND Obliterative bronchiolitis (OB) characterised by small-airway fibrosis is a major cause of morbidity and mortality after lung transplantation. TGF-beta has been implicated in the pathogenesis of fibrosis. METHODS We immunohistochemically examined 380 transbronchial biopsies (from 91 pulmonary transplants) using TGF-beta polyclonal antibodies. OB and interstitial fibrosis were diagnosed and graded in all biopsies. Other potential histologic and clinical risk factors for OB were analysed. RESULTS Procedures were heart and lung (n = 32), bilateral sequential lung (n = 18), and single lung transplantation (n = 41). The incidence of OB in this group was 28.5%. In all patients with OB, TGF-beta was immunolocalized in the airways and lung parenchyma. TGF-beta expression was greater in OB patients (median score 8, range 5-12) in comparison to patients without OB (median score 4, range 1-13), p < .0001. Positive TGF-beta staining preceded the histologic confirmation of OB by 6 to 18 months. The development of OB was associated with two HLA mismatches at the A locus (p = .02); recurrent acute rejection episodes (p < .0005); lymphocytic bronchiolitis (p = .0001); and tissue eosinophilia, regardless of the rejection grade (p < .0001). CONCLUSIONS Increased expression of TGF-beta is a risk factor for the development of OB. Other risk factors are recurrent acute rejection, lymphocytic bronchiolitis, tissue eosinophilia, and two mismatches at the HLA-A locus. This suggests that the pathogenesis of progressive small airway fibrosis characteristic of OB may be inflammatory damage, followed by an aberrant repair process due to excessive TGF-beta production following allograft injury. Hence, modulation of TGF-beta levels or function by antagonists may represent an important approach to control OB.

Superior prevention of acute rejection by tacrolimus vs. cyclosporine in heart transplant recipients--a large European trial.

We compared efficacy and safety of tacrolimus (Tac)‐based vs. cyclosporine (CyA) microemulsion‐based immunosuppression in combination with azathioprine (Aza) and corticosteroids in heart transplant recipients. During antibody induction, patients were randomized (1:1) to oral treatment with Tac or CyA. Episodes of acute rejection were assessed by protocol biopsies, which underwent local and blinded central evaluation. The full analysis set comprised 157 patients per group. Patient/graft survival was 92.9% for Tac and 89.8% for CyA at 18 months. The primary end point, incidence of first biopsy proven acute rejection (BPAR) of grade ≥ 1B at month 6, was 54.0% for Tac vs. 66.4% for CyA (p = 0.029) according to central assessment. Also, incidence of first BPAR of grade ≥ 3A at month 6 was significantly lower for Tac vs. CyA; 28.0% vs. 42.0%, respectively (p = 0.013). Significant differences (p < 0.05) emerged between groups for these clinically relevant adverse events: new‐onset diabetes mellitus (20.3% vs. 10.5%); post‐transplant arterial hypertension (65.6% vs. 77.7%); and dyslipidemia (28.7% vs. 40.1%) for Tac vs. CyA, respectively. Incidence and pattern of infections over 18 months were comparable between groups, as was renal function. Primary use of Tac during antibody induction resulted in superior prevention of acute rejection without an associated increase in infections.

CA repeat allele polymorphism in the first intron of the human interferon-gamma gene is associated with lung allograft fibrosis.

Interferon-gamma (IFN-gamma) is an inflammatory cytokine that has been implicated in the development of fibrosis in inflamed tissues. In this study we have analysed the association between genetically-determined high IFN-gamma production and development of fibrosis in lung transplants. The human IFN-gamma gene has a variable length CA repeat in the first intron. Our previous study showed that polymorphism of this microsatellite is associated with individual variation in the levels of IFN-gamma production. In vitro production of IFN-gamma showed significant correlation with presence of allele #2 (p < 0.01). In this study allele #2 was found to be associated with allograft fibrosis defined by transbronchial biopsy. An analysis of two groups of lung transplant recipients showed a significant increase in the frequency of allele #2 in the group which developed fibrosis after transplantation compared to the group that did not (p < 0.005). We postulate that the production of IFN-gamma, which is under genetic control, can influence the development of fibrosis in lung allografts.

Transforming growth factor-beta (TGF-β1) genotype and lung allograft fibrosis

BACKGROUND TGF-beta1 is a prosclerotic cytokine implicated in fibrotic processes. Fibrosis of the pulmonary parenchyma and airways is a frequent presentation in lung transplant recipients before and after transplantation. There are two genetic polymorphisms in the DNA sequence encoding the leader sequence of the TGF-beta1 protein, located at codon 10 (either leucine or proline) and at codon 25 (either arginine or proline). The codon 25 arginine allele is associated with higher TGF-beta1 production by cells activated in vitro. We tested the hypothesis that inheritance of alleles of the TGF-beta1 gene conferring higher production of TGF-beta1 may be responsible for over-expression of TGF-beta1 in transplant recipients resulting in lung allograft fibrosis. METHODS We extracted DNA from leukocytes collected from 91 pulmonary transplants performed at our centre and 96 normal healthy volunteers between May 1990 and September 1995. Part of the first exon was amplified by PCR. Samples were genotyped by using sequence specific oligonucleotide probes. RESULT The distribution of codon 10 alleles was similar in a normal healthy control group and in lung transplant recipients, regardless of their pretransplant lung pathology. By contrast, there was a significant difference in the frequency of codon 25 alleles between the control and transplant groups. In the normal control group 81% were codon 25 arginine/arginine (A/A) homozygotes, 19% were arginine/proline (A/P) heterozygotes and none were proline/proline (P/P) homozygotes. The distribution of codon 25 alleles was similar in lung transplant recipients who did not have a significant fibrosis in pretransplant pathology, but in transplant recipients who came to transplantation with lung fibrosis 98% (41 of 42 patients) were homozygous for the codon 25 A/A allele (p < .05). After lung transplantation 39 of 91 patients developed lung allograft fibrosis, and of these 92.3% (36 of 39 recipients) were of homozygous codon 25 A/A high TGF-beta1 producer genotype (p < .001). Lung transplant recipients who were homozygous for both codon 10 L/L and codon 25 A/A showed poor survival compared with all other TGF-beta1 genotypes (p < .03). CONCLUSION Homozygosity for arginine at codon 25 of the leader sequence of TGF-beta1 that correlates with higher TGF-b production in vitro, is associated with fibrotic lung pathology before lung transplantation and with the development of fibrosis in the graft. In combination with the codon 10 leucine allele, homozygosity for the codon 25arginine allele is a marker for poor post-transplant prognosis and recipient survival.

An alternative surgical technique in orthotopic cardiac transplantation.

Abstract Forty patients underwent orthotopic cardiac transplantation at Wythenshawe Hospital between May 1991 and November 1992. Twenty patients had transplantation using an alternative technique that preserves the shape of the left atrium and leaves the right atrium intact (group A). The remaining twenty had conventional transplantation using the technique described by Lower and Shumway (group B). The patients were randomized to either the new or the conventional technique on an alternate basis. There was no mortality in group A, but two patients in group B developed right ventricular failure and died. Two patients in each group developed nodal rhythm and all four recovered sinus rhythm. Echocardiography and Doppler velocimetry at the transvalvular level confirmed normal atrial function in group A with erratic atrial contraction wave in group B. There was also slightly lower incidence of mitral and tricuspid valve regurgitation in group A than in group B. The improved atrial function in group A may play a part in the prevention of right sided failure following cardiac transplantation.

Orthotopic cardiac transplantation: a comparison of standard and bicaval Wythenshawe techniques.

We describe an alternative technique for orthotopic cardiac transplantation (bicaval Wythenshawe technique), which maintains the right and left atrial anatomy. We compared the new bicaval technique with the conventional (Lower and Shumway) technique of orthotopic cardiac transplantation to identify any beneficial physiologic and clinical outcomes resulting from maintaining the normal anatomy. Seventy-five patients were randomized on an alternate basis to two groups: group A (n = 40) had orthotopic cardiac transplantation with the bicaval technique and group B (n = 35) had conventional orthotopic heart transplantation. All patients were studied with transthoracic echocardiogram, endomyocardial biopsies, and measurement of intracardiac pressures 1, 4, and 12 weeks after transplantation. There were no statistically significant differences in the demographic profile, ischemic time, bypass time, implantation time, transpulmonary gradient, or pulmonary vascular resistance between the two groups. The hemodynamic data were collected in the absence of histologic signs of rejection. In group A right atrial pressure (mean 3.6 mm Hg) was significantly lower (p < 0.03) than in group B (mean 8.8 mm Hg). The right atrial a wave was recorded in 38 patients in group A compared with seven patients in group B (p = 0.041). Atrial tachyarrhythmias occurred in two patients in group A compared with 11 in group B (p < 0.016). Temporary pacing was required in 10 patients in group A and 16 patients in group B (p = 0.034). Four cases of mitral regurgitation (all mild) were detected in group A in comparison with 12 cases (10 mild, 2 severe) in group B (p = 0.008). The mean ejection fraction in the first week after transplantation was 58% in group A and 46% in group B (p = 0.5). In the first 3 months the need for diuretics was less in group A (mean dose 80.8 mg furosemide daily) than in group B (mean dose 134 mg furosemide daily in the first week increasing to 160 mg furosemide daily). Hospital stay was shorter in group A (mean 23 days) than in group B (mean 27 days) (p < 0.015). There were no early deaths as a result of right ventricular failure in group A (n = 0/40) compared with four (n = 4/35; 9%) in group B (p < 0.034). This difference suggests that bicaval orthotopic cardiac implantation is associated with a lower right atrial pressure, a lower likelihood of atrial tachyarrhythmias, less need for pacing, less mitral incompetence, a lower diuretic dose, and a shorter hospital stay.(ABSTRACT TRUNCATED AT 400 WORDS)

Treatment of Mediastinitis: Early Modified Robicsek Closure and Pectoralis Major Advancement Flaps

BACKGROUND The treatment of sternal wound complications is controversial. It is our practice to combine early aggressive debridement, a modified Robicsek sternal closure, and bilateral pectoralis major advancement flaps with or without closed irrigation in a single procedure. We reviewed our experience to determine the efficacy of this approach. METHODS Grade II to IV mediastinitis (dehiscence and infection) developed in 47 patients 3 to 14 days after routine open heart operations between 1990 and 1995. Culture-positive infection was identified in 60% (n = 28); 62% (n = 29) had septicemia. Thirty patients underwent incision, drainage, and surgical assessment of the wound. Once systemic signs of infection were under control (no pyrexia, normal white blood cell count), formal single-stage debridement of all infected soft tissues and bones was performed. Sternal stability was achieved using a modified Robicsek closure and bilateral pectoralis major advancement flaps. Seventeen patients were treated with staged procedures. RESULTS Early sternal closure and coverage with pectoralis major advancement flaps can be associated with a low mortality (0%), low morbidity (13%; n = 4: three superficial wound infections, one seroma), and shortened hospital stay (median, 22 days, compared with a median of 82 days in patients managed with conservative staged treatment; p < 0.05). Sternal stability with excellent functional and aesthetic results has been achieved in all patients. CONCLUSIONS The combination of aggressive early surgical debridement, sternal closure, and the placement of bilateral pectoralis major advancement flaps is a simple procedure associated with a low mortality and morbidity and a short hospital stay.

Bicaval and standard techniques in orthotopic heart transplantation: Medium-term experience in cardiac performance and survival

OBJECTIVE The aim of this study was to compare the medium-term results of right heart pressures, tricuspid valve dysfunction, overall cardiac performance, and survival between the bicaval and standard techniques. METHOD Between 1991 and 1997, 201 heart transplantations were performed in our center. Right heart catheterization was performed up to 12 months after transplantation. Echocardiography was used to assess left ventricular and tricuspid valve function. RESULT The standard technique was used in 105 cases, and the bicaval technique was used in 96 cases. There was no difference in the age, preoperative parameters, pulmonary hemodynamics, or ischemic time between the 2 groups. Right atrial pressure (4.3 +/- 4.0 mm Hg for the bicaval vs 10.9 +/- 4.8 mm Hg for standard technique) and mean pulmonary artery pressure (17.5 +/- 5.3 mm Hg and 22.5 +/- 5.2 mm Hg, respectively) were lower for the bicaval recipients up to 12 months after the operation (P =.001 and. 01, respectively). Left ventricular ejection fraction was higher for the recipients of the bicaval technique up to the most recent measurement (P =.005). The prevalence of moderate or severe tricuspid regurgitation was higher in the recipients of the standard technique up to the most recent measurement (28% vs 7%; P =.02). The actuarial survival at 1, 3, and 5 years was 74%, 70%, and 62% for the recipients of the standard technique versus 87%, 82%, and 81% for the recipients of the bicaval technique (P <.03, <.04, and <.02, respectively). CONCLUSION The bicaval technique maintains good left ventricular function, lower incidence and severity of tricuspid valve dysfunction, and improved survival compared with the standard technique.