[Show abstract][Hide abstract] ABSTRACT: Voltage-gated sodium channels composed of a pore-forming α subunit and auxiliary β subunits are responsible for the upstroke of the action potential in cardiac muscle. However, their localization and expression patterns in human myocardium have not yet been clearly defined. We used immunohistochemical methods to define the level of expression and the subcellular localization of sodium channel α and β subunits in human atrial myocytes. Nav1.2 channels are located in highest density at intercalated disks where β1 and β3 subunits are also expressed. Nav1.4 and the predominant Nav1.5 channels are located in a striated pattern on the cell surface at the z-lines together with β2 subunits. Nav1.1, Nav1.3, Nav1.6 channels are located in scattered puncta on the cell surface in a pattern similar to β3 and β4 subunits. Nav1.5 comprised approximately 88% of the total sodium channel staining, as assessed by quantitative immunohistochemistry. Functional studies using whole cell patch-clamp recording and measurements of contractility in human atrial cells and tissue showed that TTX-sensitive (non-NaV1.5) α subunit isoforms account for up to 27% of total sodium current in human atrium and are required for maximal contractility. Overall, our results show that multiple sodium channel α and β subunits are differentially localized in subcellular compartments in human atrial myocytes, suggesting that they play distinct roles in initiation and conduction of the action potential and in excitation-contraction coupling. TTX-sensitive sodium channel isoforms, even though expressed at low levels relative to TTX-sensitive NaV1.5, contribute substantially to total cardiac sodium current and are required for normal contractility.
Full-text · Article · May 2013 · Journal of Molecular and Cellular Cardiology
[Show abstract][Hide abstract] ABSTRACT: This prospective cohort study in patients with aortic stenosis (AS) aimed to identify surrogates of myocardial fibrosis that are easy to derive in clinical practice, allow the differentiation of low-gradient severe AS from moderate AS, and have an impact on clinical outcome.
In patients with symptomatic aortic AS, a characteristic subgroup (i.e., up to one-third) exhibits severe AS with a concomitant low mean valve gradient either with preserved or reduced ejection fraction (EF). It is hypothesized that these patients tend to have an advanced stage of myocardial fibrosis and poor clinical outcome.
Eighty-six patients with moderate or severe AS were examined by echocardiography including conventional aortic valve assessment, mitral ring displacement, and strain-rate imaging. Replacement fibrosis was quantified by late-enhancement magnetic resonance imaging. Biopsy samples were taken from patients with severe AS (n = 69) at aortic valve replacement. All patients were followed for 9 months.
Patients were divided into 4 groups according to aortic valve area (<1.0 cm(2)), mean valve gradient ≥40 mm Hg, and EF (<50%): group 1, moderate AS (n = 17); group 2, severe AS/high gradient (n = 49); group 3, severe AS/low gradient/preserved EF (n = 11); and group 4, severe AS/low gradient/decreased EF (n = 9). At baseline, a significant decrease in mitral ring displacement and systolic strain rate was detected in patients with low-gradient AS. In low-gradient groups, a higher degree of interstitial fibrosis in biopsy samples and more late-enhancement magnetic resonance imaging segments were observed. A close inverse correlation was found between interstitial fibrosis and mitral ring displacement (r = -0.79, p < 0.0001). Clinical outcome was best for patients in group 1, whereas mortality risk increased substantially in groups 2 through 4.
In severe AS, a low gradient is associated with a higher degree of fibrosis, decreased longitudinal function, and poorer clinical outcome despite preserved EF. Mitral ring displacement differentiates between moderate AS and low-gradient/severe AS with preserved EF.
Full-text · Article · Jul 2011 · Journal of the American College of Cardiology
[Show abstract][Hide abstract] ABSTRACT: Inhibition of calcineurin (CnA) activity by cyclosporine A (CsA) is the mainstay in immunosuppressive therapy. CsA inhibits the phosphatase activity of the cytosolic phosphatase CnA and, therefore, prevents the dephosphorylation and subsequently nuclear translocation of the transcription factor nuclear factor of activated T cells (NFAT). However, CsA has multiple other targets within the cell and is, therefore, not specific. We developed a new approach to inhibit CnA/NFAT signaling. This synthetic peptide prevented CnA nuclear translocation in vitro. The purpose of this study was to demonstrate that this novel approach could potentially inhibit T-cell function in vitro and in vivo.
T-cell activation (Jurkat T cells, naïve rat T cells, and peripheral human T cells) was assessed by protein synthesis, interleukin (IL)-2 promoter activity, and IL-2 levels after T-cell activation. Immunohistological stainings for CnA were performed to investigate nuclear localization of CnA. The immunosuppressive effects in vivo of the synthetic peptide were investigated in rats with heterotopic transplanted hearts.
The nuclear localization signal peptide significantly decreased alloantigen-specific T-lymphocyte proliferation, IL-2 promoter activity, and IL-2 production (338% ± 27% vs. 149% ± 11%, n=8, P<0.05) in cultured T cells by inhibition of CnA nuclear translocation. The synthetic peptide also significantly decreased the number of graft infiltrating CD8 T lymphocytes. Moreover, treatment with the synthetic inhibitory inhibited acute graft rejection (5 ± 0.6 days vs. 12 ± 2 days, n=10, P<0.05).
Inhibition of nuclear translocation of CnA is a novel approach to inhibit the activation of the CnA/NFAT signaling cascade. Further studies have to demonstrate the long-term use of this principle in vivo.
[Show abstract][Hide abstract] ABSTRACT: Chronic transplant dysfunction, a major impediment to long-term allograft survival, is caused by several factors including an ongoing alloimmune response termed chronic rejection. To define some of these factors further, we selected 107 patients mismatched to their donors from 623 patients transplanted at a single center. Patients were categorized according to their immunosuppressive treatment and further divided into those with stable or chronic allograft dysfunction. Donor human lymphocyte antigen allopeptide-specific T-cell lines were then generated from stable patients and those with biopsy-proven chronic allograft nephropathy. Increased amounts of CD4+CD25+ regulatory T cells (Tregs) and Treg-associated gene expression profiles were found in cell lines derived from the patients with stable compared with those with chronic allograft dysfunction. Furthermore, a higher percentage of Tregs was found in patients with stable graft function on tacrolimus-based compared with cyclosporine-based immunosuppression protocols. Patients with stable graft function had a significantly higher expression of interleukin (IL)-4 and IL-10, whereas the cytokines IL-2, IL-17, and interferon-γ were significantly higher in patients with allograft dysfunction in vitro. Thus, enhancing the operational role of naturally occurring donor-specific Tregs in allograft recipients by adjusting the immunosuppression protocol may be advantageous particularly for patients with ongoing chronic rejection.
No preview · Article · Jan 2011 · Kidney International
[Show abstract][Hide abstract] ABSTRACT: Direct magnetic resonance imaging (MRI) planimetry of the maximal systolic aortic valve area does not consider temporal variations of the opening area during the ejection period. We evaluated an MRI-based methodology for the assessment of valvular dynamics in patients with severe aortic stenosis by measuring the systolic variability of the valvular blood stream, that is, the "vena contracta."
With institutional review board approval, we examined 22 patients (13 male, 9 female; mean age, 68 ±10 years) with severe aortic stenosis using 1.5 T MRI and a standardized scanning protocol consisting of gradient-echo phase-contrast velocity imaging and steady-state free precession-cine MRI before and after valve replacement therapy. Temporal changes of the aortic valve area, represented by systolic variations of the area of poststenotic turbulent flow at its smallest convergence, that is, the proximal vena contracta, were determined by MRI and quantified by a calculated parameter of temporal valve dynamics (T). T was defined as the period which the aortic valve spent over its maximal opening area (>85%) during systole. MRI was also used to determine left ventricular hypertrophy before (LVMI) and its regression (LVMR) after valve replacement. Findings were compared with transthoracic echocardiography and cardiac catheterization.
All patients had an echocardiographic effective orifice area, EOATTE, of <1.0 cm2. The comparison of T to LVMI and LVMR revealed significant correlations (LVMI: r = -0.62; P = 0.002; LVMR: r = 0.62; P = 0.002). Further significant correlations with aortic stenosis severity were observed in the comparison with manual planimetry, invasive measurements, and echocardiographic valve areas, as well as with pressure gradients.
MRI can measure systolic variations of the aortic valve area. Quantitative parameters of the hemodynamic relevance of valve dynamics obtained by this method correlate with established parameters of aortic stenosis severity and LVMR.
No preview · Article · Jan 2011 · Investigative radiology
[Show abstract][Hide abstract] ABSTRACT: Patients with a history of hematologic malignancies (HMs) are considered high-risk candidates for cardiac surgery. Increased perioperative rates of infections, thrombo-embolic complications, and bleeding disorders are reported. However, low patient numbers and lack of control groups limit all published studies.
A total of 56 patients with a history of HM underwent cardiac surgery. As many as 29 patients suffered from non-Hodgkin lymphoma, five from Hodgkin disease, and 12 from myeloproliferative disorders, one from acute lymphatic leukemia, and nine from monoclonal gammopathy. Surgery consisted of coronary artery bypass grafting, valvular surgery or combination procedures. HM patients were matched to 142 controls. Matching criteria applied consisted of sex, age, main diagnosis, and co-morbidities.
In-hospital mortality was elevated in HM patients though not reaching significance (P = 0.7). HM patients demonstrated increased rates of vascular, pulmonary, infectious complications (P > 0.1), and transfusion requirements (P = 0.077). The long-term survival of HM patients was significantly impaired (P = 0.043). A history of irradiation or chemotherapy predisposed to postoperative respiratory insufficiency, acute renal failure, and an impaired long-term survival (P > 0.065).
Cardiac surgery in patients with a history of a malignant hematologic disorder might achieve acceptable results. However, a higher complication and mortality rate have to be anticipated. Patients with hematologic disorders and a history of either irradiation or chemotherapy appear to be at an increased risk to develop postoperative end-organ failure.
Full-text · Article · Dec 2010 · European journal of cardio-thoracic surgery: official journal of the European Association for Cardio-thoracic Surgery
[Show abstract][Hide abstract] ABSTRACT: We investigated the effect of concomitant intracranial meningiomas on perioperative and postoperative complications after cardiac operations. Also studied was the intraoperative and perioperative management and long-term outcome of such patients.
We retrospectively evaluated 16 cardiac surgical patients with intracranial meningiomas between January 1996 and July 2007. Neurologic outcome, incidence of transient neurologic deficits, and long-term follow-up focusing on freedom from any cardiac or neurosurgical intervention were assessed.
Five men and 11 women with a concomitant diagnosis of intracranial meningioma underwent cardiac operations using extracorporeal circulation. One patient received additional edema prophylaxis by intravenous dexamethasone. All patients were discharged home in good physical condition. Data on long-term survival were available on 14 patients, with 12 alive. Postoperatively, 2 patients died from myocardial infarction at 26.8 months and 2 from metastatic colon cancer at 57.9 months. Perioperative neurologic disorders were observed in 2 patients, comprising one stroke after intervention for aortic dissection and one thromboembolic event 2 weeks after biologic mitral valve replacement due to anticoagulation disorders. No meningioma-related adverse event was observed.
The presence of intracranial meningioma does not appear to be a risk factor for patients undergoing cardiac operations. No meningioma-related neurologic sequelae were documented postoperatively. Neurosurgical consultation should be obtained in all patients preoperatively.
Full-text · Article · Oct 2009 · The Annals of thoracic surgery
[Show abstract][Hide abstract] ABSTRACT: In this prospective follow-up study, the effect of myocardial fibrosis on myocardial performance in symptomatic severe aortic stenosis was investigated, and the impact of fibrosis on clinical outcome after aortic valve replacement (AVR) was estimated.
Fifty-eight consecutive patients with isolated symptomatic severe aortic stenosis underwent extensive baseline characterization before AVR. Standard and tissue Doppler echocardiography and cardiac magnetic resonance imaging (late-enhancement imaging for replacement fibrosis) were performed at baseline and 9 months after AVR. Endomyocardial biopsies were obtained intraoperatively to determine the degree of myocardial fibrosis. Patients were analyzed according to the severity of interstitial fibrosis in cardiac biopsies (severe, n=21; mild, n=15; none, n=22). The extent of histologically determined cardiac fibrosis at baseline correlated closely with New York Heart Association functional class and markers of longitudinal systolic function (all P<0.001) but not global ejection fraction or aortic valve area. Nine months after AVR, the degree of late enhancement remained unchanged, implying that AVR failed to reduce the degree of replacement fibrosis. Patients with no fibrosis experienced a marked improvement in New York Heart Association class from 2.8+/-0.4 to 1.4+/-0.5 (P<0.001). Only parameters of longitudinal systolic function predicted this functional improvement. Four patients with severe fibrosis died during follow-up, but no patient from the other groups died.
Myocardial fibrosis is an important morphological substrate of postoperative clinical outcome in patients with severe aortic stenosis and was not reversible after AVR over the 9 months of follow-up examined in this study. Because markers of longitudinal systolic function appear to indicate sensitively both the severity of myocardial fibrosis and the clinical outcome, they may prove valuable for preoperative risk assessment in patients with aortic stenosis.
[Show abstract][Hide abstract] ABSTRACT: True alloantigen-specific tolerance is the ultimate goal of solid organ transplantation, eliminating the need for long-term immunosuppression. Recent evidence suggests that Th1-derived cytokines are associated with rejection and Th2-derived cytokines with long-term allograft survival, but the roles of these subsets in rejection and tolerance are incompletely understood. Here, we analyzed the functional and regulatory capacities of T cell clones derived from tolerant and rejecting rats (Wistar rat donors, Lewis rat recipients). We generated and subcloned T cell lines from lymphocytes derived from either acutely rejecting grafts or from the grafts of CTLA4-Ig-treated tolerant rats. Pretransplantation adoptive transfer of T cell clones generated from rejected grafts (Th1 clones) accelerated acute rejection or promoted development of chronic rejection, whereas transfer of T cell clones generated from tolerized grafts (Th2 clones) protected rats from acute rejection and progressive organ dysfunction. When Th1 and Th2 clones were injected simultaneously, Th2 clones specifically regulated activation of Th1 clones. Rats that received injections of Th2 clones accepted long-term donor-specific skin grafts but acutely rejected third-party skin grafts. Tolerant rats treated with Th2 clones demonstrated an increased number of regulatory CD4+CD25+Foxp3+ cells and strong mononuclear cell staining for IL-10 but negligible IFN-gamma, IL-17, and IL-23 compared with untreated rats or those treated with Th1 clones. In summary, these results demonstrate the regulatory functions of Th2 cells in a clinically relevant allogeneic transplant model and provide new insight into the functional role of Th2 cells in preventing the process of chronic rejection.
No preview · Article · May 2009 · Journal of the American Society of Nephrology
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to explore patients' needs and changes to these needs during a hospital stay for coronary artery bypass graft (CABG) surgery.
70 patients (60 males; mean age = 64.1; SD = 8.9) reported their needs two days before and ten days after CABG surgery using a specifically developed 15-item questionnaire. Student's T-test was used to detect significant differences.
Before CABG, patients rated the need for "preparation for surgery", and after CABG the need for "information about the correct handling of drugs", as the most important. The rating of "information about the correct handling of drugs" showed a significant increase after CABG surgery ( T(69) = - 3.46; P < 0.001) and the need for a "letter with the latest scientific information on heart disease" was significantly reduced during this period ( T(69) = 2.07; P = 0.04).
The results indicate that preparation for surgery should be conducted very carefully without time pressure. Patients should receive more detailed information on prescribed drugs.
No preview · Article · Feb 2009 · The Thoracic and Cardiovascular Surgeon
[Show abstract][Hide abstract] ABSTRACT: Primary graft dysfunction is a still poorly understood complication after cardiac transplantation. Ischemia/reperfusion injury contributes to different disorders resulting in impaired graft function.
In a heterotopic rat heart transplantation model we extended graft ischemic time up to 8 hours.
Using immunohistochemistry we detected an up to 4-fold increase in intracellular adhesion molecule-1 (ICAM-1) expression during 4 hours of reperfusion, independent of ischemic time (30-minute ischemia: 7.65 +/- 2.15 without reperfusion, 19.46 +/- 4.6 after 4-hour reperfusion; 240-minute ischemia: 5.6 +/- 1.99 and 22.3 +/- 3.77; 480-minute ischemia: 3.7 +/- 1.56 and 13.1 +/- 2.2). Eight-hour ischemic allografts had an increase in CD8-positive cells (1.37 +/- 0.5 and 2.3 +/- 0.77) and a significant increase in MHC II expression (11.48 +/- 2.1 and 18.27 +/- 1.34) during 4 hours of reperfusion.
We hypothesize that these findings reflect an early inflammatory reaction in the allograft possibly triggered by oxidative stress. During therapeutic interventions, both of these pathways must be considered.
No preview · Article · Oct 2008 · The Journal of heart and lung transplantation: the official publication of the International Society for Heart Transplantation
[Show abstract][Hide abstract] ABSTRACT: Our 18-year old female patient suffered from microscopic polyangiitis. After invasive diagnostics, a diffuse alveolar hemorrhage occurred, leading to acute lung failure. In spite of differential ventilation, respiratory insufficiency and lactate-acidosis increased quickly. Due to the massive hemorrhage, a pumpless extracorporeal lung assist was implanted and, after six hours, low-dose heparinization was started. In response to this therapy, hypercapnia and acidosis improved quickly and were completely eliminated within 24 hours. Simultaneously, treatment with prednisolon and cyclophosphamid was started. After 7 days, the patient's conditions allowed weaning from the pumpless extracorporeal lung assist and after 9 days she was extubated. In conclusion, the pumpless lung assist was shown to be a very practical option to treat the most serious forms of hypercapnia, especially for patients disposed to diffuse bleeding.
No preview · Article · Apr 2008 · The International journal of artificial organs
[Show abstract][Hide abstract] ABSTRACT: Considerable experimental evidence has accumulated over the past years that proinflammatory cytokines, especially TNF-alpha and IL-1beta, impair myocardial function in different animal species. On the other hand, several prospective clinical trials studying TNF-alpha antagonist in patients with chronic heart failure were not able to demonstrate a benefit. As there might be a relevant species-related discrepancy, we intended to prove our previous results demonstrating impaired myocardial economy after exogenous administration of recombinant TNF-alpha in rat myocardium. In the present study, both TNF-alpha and IL-1beta not only revealed an immediate negative inotropic effect but also increased specific oxygen demand in human right-atrial myocardium. Enhanced oxygen consumption was not caused by an elevated basal metabolism but an impaired economy of contraction. Our results suggest that proinflammatory cytokines have a considerable effect on myocardial mechano-energetic parameters in human myocardium as well.