Tamás Szerafin

Alpha-Gal specific IgG immune response after implantation of bioprostheses.

BACKGROUND We have previously shown that the alpha-Gal (Galalpha1.3-Galbeta1-4GlcNAc-R) epitope is a relevant xenoantigen present on bioprostheses utilized in cardiac surgery and elicits an alpha-Gal specific IgM immune response. We sought to investigate whether that immune response continues after valve implantation. MATERIALS AND METHODS We collected plasma samples from patients who underwent bioprosthesis implantation (n = 19) or mechanical valve replacement (n = 8), respectively, prior to, at 10 days and at 3 months after cardiac surgery. ELISA was utilized to quantify alpha-Gal specific IgG and IgG subclasses. 3 bioprosthetic tissue samples were obtained from patients who had to undergo re-operation within 1 week (n = 1) or at 12-15 months (n = 2) after the initial operation. We utilized confocal laser scanning microscopy (CLSM) to detect the presence of alpha-Gal epitopes (IB4) and cell nuclei (DAPI). RESULTS alpha-Gal specific IgG was significantly increased 3 months after implantation of bioprostheses compared to preoperative values (p < 0.001) and was significantly higher than alpha-Gal specific IgG levels of the control group (p < 0.05). IgG3 was the major subclass directed against alpha-Gal (p < 0.05, pre- vs. postoperative values). In CLSM analysis we demonstrated that bioprostheses explanted 1 week after implantation contained IB4/DAPI positive cells within the collagen matrix. In contrast, in patients who underwent reoperation after 12 months, porcine tissue showed a complete lack of IB4/DAPI. CONCLUSION Our results indicate that the implantation of bioprostheses elicits a specific humoral immune response against alpha-Gal bearing cells compared to controls within 3 months after cardiac surgery. The complete absence of IB4/DAPI positive structures 12 months after implantation indicates a specific degradation of alpha-Gal bearing cells through previous exposure to the human blood circuit.

Adaptation of Vasomotor Function of Human Coronary Arterioles to the Simultaneous Presence of Obesity and Hypertension

Objectives—We hypothesized that simultaneous presence of obesity and hypertension activates adaptive vascular mechanisms affecting dilations of human coronary arterioles. Methods and Results—Agonist-induced dilations were assessed in isolated pressurized coronary arterioles from patients (n=38) who underwent cardiac surgery. Among normotensives we found that dilations to bradykinin (BK) and the NO-donor, sodium-nitroprusside (SNP) were reduced in obese subjects (BK, 10−7 mol/L, lean:90±4%, obese:64±7%; SNP, 10−6 mol/L, lean:89±7%, obese:76±5%). However, among hypertensives, both BK- and SNP-induced dilations were significantly enhanced in obese patients, when compared with lean individuals (BK, lean:71±7%, obese:85±3%; SNP, lean:60±6%, obese:83±2%). Correspondingly, in hypertensive patients, but not in those of normotensives, a positive correlation was found between body mass index (BMI) and BK-induced (P=0.036, r=0.46), and also SNP-evoked (P=0.031, r=0.44) coronary dilations. Moreover, in additional 55 hypertensive patients flow-mediated (FMD) and nitroglycerin (NTG)-induced dilations of the brachial artery were assessed. In obese hypertensive individuals, FMD- and NTG-induced dilations were greater (FMD:6.2±0.7%, NTG:17.2±0.9%), than in lean hypertensive patients (FMD:3.7±0.6%, NTG:13.6±1.1%). Correspondingly, FMD- and NTG-induced dilations were positively correlated with BMI (P=0.020, r=0.31 and P=0.033, r=0.29, respectively). Conclusions—These findings are the first to suggest that obesity may lead to activation of adaptive vascular mechanisms to enhance the dilator function of coronary and peripheral arterial vessels in hypertensive patients.

Secretion of soluble ST2 - possible explanation for systemic immunosuppression after heart surgery.

BACKGROUND Cardiopulmonary bypass is known to affect cytokine release leading to a generalized endogenous immune reaction similar to that described in sepsis, without having been explored in great detail. Therefore we evaluated the anti- and pro-inflammatory cytokine responses after heart surgery. METHODS 16 patients who underwent coronary artery bypass graft (CABG) surgery with extracorporeal circulation were included. ST2, IL-4 and IL-10 served as markers for TH2 cytokine response; IL-6, IL-8 and IFN-gamma as TH1 markers. Furthermore, total immunoglobulin subtype analysis (IgM, IgG, IgE) was performed. RESULTS Serum levels of soluble ST2 started to climb at 60 minutes (from 38 +/- 14 preoperatively to 1 480 +/- 890 pg/ml) and peaked 24 hours after surgery (13 360 +/- 2 840 pg/ml, P < 0.001). IL-10 reached a maximum at 60 minutes and returned to baseline levels 24 hours later. IL-6 and IL-8 levels peaked 60 minutes after surgery. IL-4 and IFN-gamma did not change. Only IgM showed a significant peak on day eight ( P < 0.001). CONCLUSION Our results demonstrate that CABG surgery induces a massive long-lasting secretion of ST2, a protein related to immune suppression.

Five-year experience with a suture annuloplasty for mitral valve repair.

We present five years’ experience with mitral plication annuloplasty, performed with a semicircular buttressed suture around the posterior leaflet in 130 patients (mean age 58 11 years) with primary mitral valve disease ( n = 71) or functional mitral regurgitation ( n = 59). In 65 cases the mitral valve itself was also repaired. Concomitant myocardial revascularization was performed in 40 cases and aortic valve replacement in 43. All but three patients were followed up (97.6%). Postoperative echocardiography showed acceptable mitral area (2.28 0.39 cm) and good valve competence in all cases. Inhospital mortality was 3% and late mortality 4.8%. During the follow-up period (22.8 10.9 months) 8 patients (6.6%) required mitral valve replacement because of progression of native valve disease ( n = 4), technical failure (2) or expansion of the annuloplasty suture (2). Mitral annuloplasty thus can be performed simply and with good results, using a strong, non-stretchable buttressed suture. This procedure can be an inexpensive alternative to ring implantation.

Various clinical scenarios leading to development of the string sign of the internal thoracic artery after coronary bypass surgery: the role of competitive flow, a case series.

BackgroundThe left internal mammary artery (LIMA) is the choice for grafting of the left anterior descending coronary artery (LAD). One possible mechanism of the rare graft failure involve the presence of competitive flow.Method105 patients who had undergone coronary bypass grafting between 1998 and 2000 were included in this observational study. The recatheterizations were performed 28 months after the operations. The rate of patency the LIMA grafts was determined, and the cases with graft failure were analyzed.ResultsThe LIMA graft was patent in 99 patients (94%). Six patients (6%) exhibited diffuse involution of the graft (string sign). The string sign was always associated with competitive flow as the basis of the LIMA graft involution. In one case quantitative re-evaluation of the preoperative coronary angiography revealed merely less than 50% diameter stenosis on the LAD with a nonligated side-branch of the LIMA. At recatheterization in two patients the pressure wire measurements demonstrated only a non-significant decrease of the fractional flow reserve (0.83 and 0.89), despite the 53% and 57% diameter stenosis in the angiogram. Another patient displayeda significant regression of the LAD lesion between the pre- and postoperative coronary angiography (from 76% to 44%) as the cause of the development of the competitive flow. In one instance, a radial artery graft on the LAD during a redo bypass operation resulted in competitive flow in the radial graft due to the greater diameter than that of the LIMA. In a further patient, competitive flow developed from a short sequential part of the LIMA graft between the nonsignificantly stenosed diagonal branch and the LAD, with involution of the main part of the graft to the diagonal branch.ConclusionsThe most common cause of the development of the string sign of a LIMA graft due to competitive flow is overassessment of the lesion of the LAD. Regression of a previous lesion or some other neighboring graft can also cause the phenomenon.

Protein kinase C contributes to the maintenance of contractile force in human ventricular cardiomyocytes

Prolonged Ca2+ stimulations often result in a decrease in contractile force of isolated, demembranated human ventricular cardiomyocytes, whereas intact cells are likely to be protected from this deterioration. We hypothesized that cytosolic protein kinase C (PKC) contributes to this protection. Prolonged contracture (10 min) of demembranated human cardiomyocytes at half-maximal Ca2+ resulted in a 37 ± 5% reduction of active force (p < 0.01), whereas no decrease (2 ± 3% increase) was observed in the presence of the cytosol (reconstituted myocytes). The PKC inhibitors GF 109203X and Gö 6976 (10μmol/liter) partially antagonized the cytosol-mediated protection (15 ± 5 and 9 ± 2% decrease in active force, p < 0.05). Quantitation of PKC isoform expression revealed the dominance of the Ca2+-dependent PKCα over PKCδ and PKCϵ (189 ± 31, 7 ± 3, and 7 ± 2 ng/mg protein, respectively). Ca2+ stimulations of reconstituted human cardiomyocytes resulted in the translocation of endogenous PKCα, but not PKCβ1, δ, and ϵ from the cytosol to the contractile system (PKCα association: control, 5 ± 3 arbitrary units; +Ca2+, 39 ± 8 arbitrary units; p < 0.01, EC50,Ca = 645 nmol/liter). One of the PKCα-binding proteins were identified as the thin filament regulatory protein cardiac troponin I (TnI). Finally, the Ca2+-dependent interaction between PKCα and TnI was confirmed using purified recombinant proteins (binding without Ca2+ was only 28 ± 18% of that with Ca2+). Our data suggest that PKCα translocates to the contractile system and anchors to TnI in a Ca2+-dependent manner in the human heart, contributing to the maintenance of contractile force.

Low Tidal Volume Ventilation during Cardiopulmonary Bypass Reduces Postoperative Chemokine Serum Concentrations

BACKGROUND Open-heart surgery with cardiopulmonary bypass (CPB) is associated with a generalized immune response and postoperative lung dysfunction. Chemokines are involved in the pathogenesis of postoperative lung dysfunction. We investigated whether continued mechanical ventilation during CPB has an impact on chemokine serum concentrations. METHODS A total of 30 patients undergoing coronary artery bypass graft operation were randomized to either continuous ventilated group (n=15) or nonventilated group (n=15). Blood samples were drawn at the beginning and at the end of surgery and on the 5 consecutive days. Serum CCL2, CCL4, and CCL20 concentrations were measured and given as mean ± standard deviation. RESULTS Chemokine concentrations were elevated at the end of surgery in both groups. CCL2 and CCL4 levels returned to baseline on postoperative day (POD)-1 in the ventilation group and stayed elevated in the nonventilation group. CCL4 serum levels were significantly lower in ventilated-group patients on POD-1 (10.9 [39.0] vs. 153.2 [168.1]; p=0.005), POD-2 (16.8 [36.8] vs. 147.9 [165.4]; p=0.019), POD-3 (14.2 [24.0] vs. 97.9 [87.1]; p=0.005), and POD-5 (6.5 [25.0] vs. 33.6 [38.4]; p=0.045). CONCLUSION Continued mechanical ventilation during CPB results in reduced CCL4 concentrations on POD-1 to -5.

Local and Systemic RAGE Axis Changes in Pulmonary Hypertension: CTEPH and iPAH

Objective The molecular determinants of chronic thromboembolic pulmonary hypertension (CTEPH) and idiopathic pulmonary arterial hypertension (iPAH) remain poorly understood. The receptor for advanced glycation endproducts (RAGE) and its ligands: HMGB1 and S100A9 are involved in inflammatory disorders. We sought to investigate the role of the RAGE axis in patients with CTEPH undergoing pulmonary endarterectomy (PEA), iPAH undergoing lung transplantation (LuTX). The high pulmonary vascular resistance in CTEPH/iPAH results in pressure overload of the right ventricle. We compared sRAGE measurements to that of patients with aortic valve stenosis (AVS) – pressure overload of the left ventricle. Methods We enrolled patients with CTEPH(26), iPAH(15), AVS(15) and volunteers(33). Immunohistochemistry with antibodies to RAGE and HMGB1 was performed on PEA specimens and lung tissues. We employed enzyme-linked immunosorbent assays to determine the concentrations of sRAGE, esRAGE, HMGB1 and S100A9 in serum of volunteers and patients with CTEPH, iPAH, AVS before and after PEA, LuTX and aortic valve replacement (AVR). Results In endarterectomised tissues from patients with CTEPH RAGE and HMGB1 were identified in myofibroblasts (α-SMA+vimentin+CD34−), recanalizing vessel-like structures of distal myofibrotic tissues and endothelium of neointima. RAGE was differentially expressed in prototypical Heath Edwards lesions in iPAH. We found significantly increased serum concentrations of sRAGE, esRAGE and HMGB1 in CTEPH. In iPAH, sRAGE and esRAGE were significantly higher than in controls. Serum concentrations of sRAGE were significantly elevated in iPAH(p<0.001) and CTEPH(p = 0.001) compared to AVS. Serum sRAGE was significantly higher in iPAH compared to CTEPH(p = 0.042) and significantly reduced in AVS compared to controls(p = 0.001). There were no significant differences in sRAGE serum concentrations before and after surgical therapy for CTEPH, iPAH or AVS. Conclusions Our data suggest a role for the RAGE pathway in the pathophysiology of CTEPH and iPAH. PEA improves the local control of disease but may not influence the systemic inflammatory mechanisms in CTEPH patients through the RAGE pathway.

New Perspectives in the Renin-Angiotensin-Aldosterone System (RAAS) II: Albumin Suppresses Angiotensin Converting Enzyme (ACE) Activity in Human

About 8% of the adult population is taking angiotensin-converting enzyme (ACE) inhibitors to treat cardiovascular disease including hypertension, myocardial infarction and heart failure. These drugs decrease mortality by up to one-fifth in these patients. We and others have reported previously that endogenous inhibitory substances suppress serum ACE activity, in vivo, similarly to the ACE inhibitor drugs. Here we have made an effort to identify this endogenous ACE inhibitor substance. ACE was crosslinked with interacting proteins in human sera. The crosslinked products were immunoprecipitated and subjected to Western blot. One of the crosslinked products was recognized by both anti-ACE and anti-HSA (human serum albumin) antibodies. Direct ACE-HSA interaction was confirmed by binding assays using purified ACE and HSA. HSA inhibited human purified (circulating) and human recombinant ACE with potencies (IC50) of 5.7±0.7 and 9.5±1.1 mg/mL, respectively. Effects of HSA on the tissue bound native ACE were tested on human saphenous vein samples. Angiotensin I evoked vasoconstriction was inhibited by HSA in this vascular tissue (maximal force with HSA: 6.14±1.34 mN, without HSA: 13.54±2.63 mN), while HSA was without effects on angiotensin II mediated constrictions (maximal force with HSA: 18.73±2.17 mN, without HSA: 19.22±3.50 mN). The main finding of this study is that HSA was identified as a potent physiological inhibitor of the ACE. The enzymatic activity of ACE appears to be almost completely suppressed by HSA when it is present in its physiological concentration. These data suggest that angiotensin I conversion is limited by low physiological ACE activities, in vivo.

GRANULATED SUGAR TREATMENT OF SEVERE MEDIASTINITIS AFTER OPEN-HEART SURGERY

Fifteen cases of mediastinitis developing after 1,164 open-heart operations (incidence 1.3%) were analyzed. Closed mediastinal irrigation was used as primary therapy in ten cases and led to complete healing in five. Granulated sugar treatment was given primarily to four patients and to five others after failure of closed mediastinal irrigation. The sugar treatment was successful in six patients with hospital stay averaging 91.6 +/- 8 days. The three other patients in this group died before discharge from hospital. During 22-month follow-up there was no recurrence of mediastinitis in the granulated sugar group, but reoperation was necessitated by sternal fistula in two of the patients with closed mediastinal irrigation. Granulated sugar treatment is effective in refractory, severe mediastinal infections.