Suzanne Fateh-Moghadam

Platelet function in septic multiple organ dysfunction syndrome

AbstractObjective: Altered platelet function plays a role in the pathophysiology of multiple organ failure in sepsis. The purpose of the present study was to evaluate various aspects of platelet adhesive function in septic patients and its putative relevance for prognosis. Design: Prospective clinical study. Setting: Intensive Care Unit of the University Hospital. Patients and methods: A total of 41 patients admitted to the medical Intensive Care Unit were studied. On the day of admission, patients were evaluated by intensive care scoring systems (Elebute, APACHE II) to assess the severity of sepsis and multiple organ dysfunction syndrome (MODS), and platelet function tests were performed. All patients were observed for 28 days to assess their clinical outcomes. Eleven patients revealed septicemia without MODS (Elebute ≥12, APACHE II <20) and 20 septic patients suffered from MODS (Elebute ≥12, APACHE II ≥20). Ten non-septic patients without MODS served as a control group (Elebute <12, APACHE II <20). Flow cytometric determination of the activated fibrinogen (fg) receptor GPIIb-IIIa and as well as thrombospondin (TSP) on platelets and platelet-neutrophil adhesion (CD41 immunofluorescence) ex vivo was performed using monoclonal antibodies. The effect of plasma obtained from patients on normal platelet aggregation in vitro, and adhesion to cultured endothelial cells was evaluated. Results: The surface expression of TSP on platelets was increased in septic patients with MODS compared to controls (p<0.03). Platelet-neutrophil adhesion was not significantly altered in septicemia (p<0.09) but decreased significantly in the presence of MODS (p<0.05) when compared to controls. Logistic regression analysis showed that platelet-neutrophil adhesion was an independent predictor for poor clinical outcome (p<0.01). Plasma from septic patients sensitized normal platelets to hyperaggregate and to adhere to cultured endothelium (p<0.01). Conclusion: In septic patients platelets become activated and are hyperadhesive to other vascular cells including neutrophils and endothelium. This may induce sequestration of platelets and microcirculatory arrest, thus the development of MODS.

Cytomegalovirus infection status predicts progression of heart-transplant vasculopathy

Background. Transplant vasculopathy (TVP) is the most common cause of death and retransplantation after heart transplantation. Human cytomegalovirus (HCMV) infection has been linked to atherosclerosis and to the development of TVP. A prospective study evaluating the relation between CMV infection and progression of TVP is lacking thus far. The purpose of the present study was to investigate the influence of CMV infection status on the progression of TVP within 1 year. Methods. We enrolled 103 consecutive heart-transplant recipients who underwent routine cardiac catheterization and intracoronary ultrasound examination at study entry and after 1 year. Plaque progression determined by quantitative intracoronary ultrasound was used to define the severity of disease at baseline and at 1-year follow-up. At study entry, HCMV infection status was evaluated by immunological assays and reverse-transcriptase polymerase chain reaction (RT-PCR). Results. HCMV immunoglobulin (Ig)G/IgM seropositivity was found in 34 (33%) of transplant recipients, 11 of whom were HCMV PCR positive. The HCMV-positive group showed more advanced, calcified lesions (64.7% vs. 27.5%, P =0.002), and the maximal plaque thickness was significantly different from the HCMV IgG/IgM-negative group (median [quartile] 1.36 [0.85, 1.88] vs. 1.05 [0.58, 1.34], P =0.02). In a logistic regression model, we demonstrate that HCMV IgG/IgM positivity is a predictor for the progression of TVP independent of cardiovascular risk factors, inflammatory markers, and platelet activation (P =0.038). In addition, HCMV PCR positivity even increases the risk for accelerated TVP (P =0.017) and, consecutively, transplant failure. Conclusions. HCMV infection status in transplant patients detects patients with increased risk for transplant failure caused by TVP.

Course of Platelet Activation and Platelet-Leukocyte Interaction in Cerebrovascular Ischemia

Background and Purpose— Platelet activation plays a crucial role in the pathophysiology of cerebral ischemia. The aim of this study was to investigate the contribution of platelet activation and leukocyte-platelet interactions to the disease. Methods— One hundred thirty-five patients with transient ischemic attack (TIA) or stroke were enrolled in this single-center study. They underwent cranial computer tomography within 24 hours of clinical onset and after 3 months, and systemic venous blood samples were drawn. Platelet activation (CD62P expression), leukocyte activation (L-selectin expression), and the appearance of platelet-specific antigens on leukocytes as an index of platelet-leukocyte aggregation were measured by flow cytometric techniques in the acute state and at 3-month follow-up. Results— Patients with a completed stroke or TIA had significantly increased circulating platelet-leukocyte aggregates, increased P-selectin expression on platelets, and decreased L-selectin expression in the acute state compared with the control group (healthy volunteers). No differences in regard to the tested activation markers could be detected between patients with stroke or TIA in the acute phase of the disease. However, platelet and leukocyte activations were normalized after 3 months in patients with TIA, whereas leukocyte activation (reduced L-selectin expression) remained in stroke patients. Conclusions— In patients with TIA and completed stroke, platelet and leukocyte activation is substantially enhanced in the acute phase of the disease. The sustained leukocyte activation observed in stroke but not in TIA patients at 3-month follow up might play a pathophysiological role in the course of the disease.

Changes in surface expression of platelet membrane glycoproteins and progression of heart transplant vasculopathy.

BACKGROUND Transplant vasculopathy is the main limiting factor of the long-term success of heart transplantation. We sought to establish the role of platelets in the development and progression of transplant vasculopathy. METHODS AND RESULTS Platelet analysis and intracoronary ultrasound examination were performed in 78 heart transplant recipients. Quantitative intracoronary ultrasound was used to define the severity of disease at baseline (48.8+/-4.5 months after transplantation) and at 1-year follow-up. Platelet activation was assessed with the use of immunological surface markers of activation (ligand-induced binding site 1 [LIBS-1], P-selectin, GPIIb-IIIa) and flow cytometry. We found that LIBS-1 immunoreactivity was significantly increased in patients with diffuse disease when compared with focal transplant disease (median [quartile], 27[14, 64] versus 18[7.9, 47], P=0.04). In a logistic regression model, we found that LIBS-1 was an independent predictor for the presence and progression of diffuse transplant vasculopathy (P=0.04). Patients with enhanced LIBS-1 levels (>75% quartile) had a 3.3-fold increased relative risk (95% CI 1.8 and 18.9, P=0.002) for the presence of diffuse transplant vasculopathy. When a cutoff value of 16.5 for the level of LIBS-1 was used, patients had a 4.8-fold increased relative risk (95% CI 1.9 and 12.5, P<0.01) for the progression of transplant vasculopathy. CONCLUSIONS Enhanced platelet activation is strongly associated with the development and progression of transplant vasculopathy. Understanding the underlying pathophysiological mechanisms might contribute to the development of treatment strategies to prevent transplant vasculopathy.

Oxidized LDL-Activated Platelets Induce Vascular Inflammation

Platelets are involved in the initiation of atherosclerosis by adherence to inflamed endothelium. Monocytes bind to these platelets and transmigrate into the vessel wall, transforming into macrophages and foam cells. We have previously shown that lipid-laden platelets are phagocytosed by macrophages. In this study we investigated the functional consequences of oxidized low-density lipoprotein (oxLDL) uptake on platelet function and interaction with the endothelium. Human platelets were isolated from healthy donors and activated by adenosine diphosphate. Immunofluorescence microscopy and flow cytometry revealed that oxLDL is located intracellularly in vesicles. With mepacrine costaining and confocal microtomography, we were able to identify dense granules as the vesicles that contain oxLDL. OxLDL-laden platelets induced intercellular adhesion molecule 1 expression in endothelial cells more than exogenous native LDL, oxLDL, and oxLDL-negative platelets. Furthermore, oxLDL-laden platelets induced foam cell development from CD34(+) progenitor cells. On endothelial regeneration, oxLDL-laden platelets had the opposite effect: The number of CD34(+) progenitor cells (colony-forming units) able to transform into endothelial cells was significantly reduced in the presence of oxLDL-platelets, whereas native LDL had no effect. Our results demonstrate that activated platelets internalize oxLDL and that oxLDL-laden platelets activate endothelium, inhibit endothelial regeneration, and promote foam cell development. Platelet oxLDL contributes significantly to vascular inflammation and is able to promote atherosclerosis.

Hyperresponsiveness of platelets in ischemic stroke

Platelet activation and aggregation are critical in the pathogenesis of acute ischemic cerebrovascular diseases. The aim of our study was to characterize platelet function in patients with acute ischemic stroke or transient ischemic attack (TIA), and to evaluate the effect of platelet activation on clinical outcome. One hundred thirty-eight consecutive patients with TIA (n = 74) or stroke (n = 64) were enrolled in this study. Platelet aggregation in response to ADP, epinephrine, arachidonic acid, or collagen, and expression of platelet activation receptors (CD62P, CD63, LIBS-1 and PAC-1) in the acute phase and at three months follow-up were evaluated. Platelets derived from stroke patients were more hyperaggregable in response to agonists in the acute phase compared to TIA patients (p[ADP] = 0.002, p[arachidonic acid] = 0.047, p[epinephrine] = 0.020). Platelet activation was enhanced in the acute phase irrespective of the severity of the disease (stroke or TIA) and returned to baseline levels three months later. Persistent elevated platelet activation at three months follow-up (PAC-1) was associated with increased incidence of recurrent stroke (median, [interquartile range] 3.4, [3.0-5.2] versus 2.9, [2.3-4.0], p = 0.048). In conclusion, platelets are hyperactive in acute stroke compared with TIA. A more intensified dual antiplatelet therapy may be of benefit for stroke patients.

Interaction of Platelets and Inflammatory Endothelium in the Development and Progression of Coronary Artery Disease

An expanding body of evidence emphasizes the role of platelets as initial actors in inflammatory diseases such as atherosclerosis. Platelets interact with leukocytes and endothelial cells and enforce monocyte transformation into macrophages. Platelets not only mediate the recruitment of leukocytes. They also bind oxidized phospholipids and may promote foam cell formation. Platelets furthermore recruit progenitor cells to the scene, which are able to differentiate into foam cells or endothelial cells, presumably depending on the local microenvironment. Furthermore, platelets are capable of promoting the recruitment of circulating dendritic cells and influencing their functions, thereby presumably modulating immune reactions in atherogenesis. Taken together, platelets may participate in the initiation, development, and total extent of atherosclerotic lesions.

Severity of multiple organ failure (MOF) but not of sepsis correlates with irreversible platelet degranulation

SummaryMultiple hemostatic changes occur in sepsis and multiple organ failure (MOF). To evaluate the role of platelets in patients with sepsis and MOF, we examined changes in surface glycoproteins on circulating platelets of 14 patients with suspected sepsis and MOF. The severity of sepsis and MOF was assessed by the Elebute and APACHE II scoring systems, respectively. Using flow cytometric techniques and platelet specific monoclonal antibodies, platelet surface expression of fibrinogen receptor on GPIIb-IIIa, of von Willebrand Factor receptor GPIb, and of granule glycoproteins (thrombospondin (TSP), GMP-140, GP53) was measured. Plasma membrane expression of GPIIb-IIIa and GPIb on circulating platelets was not affected by sepsis or MOF. Septic patients, however, showed a significantly elevated fibrinogen receptor activity (LIBS1 expression) (p<0.05) that correlated with severity of disease (r=0.597, p=0.043). No significant change in surface expression of granule glycoproteins (TSP, GMP-140, GP53) was noted in septic patients. In contrast, degranulation of granule glycoproteins was significantly elevated in MOF (p<0.05) which correlated well with severity of MOF (GMP-140, r=0.611, p=0.013; TSP, r=0.643, p=0.026). We speculate that platelets in sepsis circulate in a hyperaggregable but still reversible state that results in increased risk of microthrombotic events. In the course of the disease, irreversible platelet degranulation of adhesion molecules occurs that may play an important role in the development of MOF.ZusammenfassungZiel der vorliegenden Pilotstudie war es, die Thrombozytenfunktion von 14 Intensivpatienten mit unterschiedlicher Ausprägung von Sepsis und Multiorganversagen (MOV) zu untersuchen. Schweregrad der Sepsis und des MOV wurde anhand intensivmedizinischer Scoresysteme (APACHE II, Elebute) beurteilt. Die Thrombozytenfunktion wurde durch durchflußzytometrische Bestimmung von membranständigen Glykoproteinen (GPIIb-IIIa, GPIb, Thrombospondin (TSP), GMP-140, GP53) untersucht. Weder Sepsis noch MOV beeinflußten die Oberflächen-expression von GPIIb-IIIa oder GPIb. Die Aktivierung des Fibrinogenrezeptors war jedoch bei Sepsis deutlich erhöht (p<0.05) und korrelierte signifikant mit dem Schweregrad der Erkrankung (r=0,597, p=0,043). Eine signifikant gesteigerte Degranulation der Thrombozyten bei Sepsis konnte jedoch nicht beobachtet werden. Im Gegensatz dazu war die thrombozytäre Freisetzung von Granula-Glykoproteinen (TSP, GMP-140, GP53) bei MOV deutlich erhöht (p<0,05) und korrelierte mit dem Schweregrad der Erkrankung (GMP-140, r=0,611, p=0,013; TSP, r=0,643, p=0,026). Die Ergebnisse dieser Arbeit zeigen, daß Blutplättchen in Patienten mit Sepsis in einem aktivierten jedoch noch reversiblen Aggregationszustand zirkulieren (Aktivierung des Fibrinogenrezeptors), einhergehend mit einem erhöhten Risiko von Mikrothrombosen. Im Laufe der Erkrankung kann es zur gesteigerten Freisetzung und Oberflächenexpression von thrombozytären Glykoproteinen kommen, die eine entscheidende pathophysiologische Rolle in der Entwicklung von Mikrozirkulationsstörungen und MOV spielen könnten.

Student tutors for hands-on training in focused emergency echocardiography – a randomized controlled trial

BackgroundFocused emergency echocardiography performed by non-cardiologists has been shown to be feasible and effective in emergency situations. During resuscitation a short focused emergency echocardiography has been shown to narrow down potential differential diagnoses and to improve patient survival. Quite a large proportion of physicians are eligible to learn focused emergency echocardiography. Training in focused emergency echocardiography usually comprises a lecture, hands-on trainings in very small groups, and a practice phase. There is a shortage of experienced echocardiographers who can supervise the second step, the hands-on training. We thus investigated whether student tutors can perform the hands-on training for focused emergency echocardiography.MethodsA total of 30 volunteer 4th and 5th year students were randomly assigned to a twelve-hour basic echocardiography course comprising a lecture followed by a hands-on training in small groups taught either by an expert cardiographer (EC) or by a student tutor (ST). Using a pre-post-design, the students were evaluated by an OSCE. The students had to generate two still frames with the apical five-chamber view and the parasternal long axis in five minutes and to correctly mark twelve anatomical cardiac structures. Two blinded expert cardiographers rated the students’ performance using a standardized checklist. Students could achieve a maximum of 25 points.ResultsBoth groups showed significant improvement after the training (p < .0001). In the group taught by EC the average increased from 2.3±3.4 to 17.1±3.0 points, and in the group taught by ST from 2.7±3.0 to 13.9±2.7 points. The difference in improvement between the groups was also significant (p = .03).ConclusionsHands-on training by student tutors led to a significant gain in echocardiography skills, although inferior to teaching by an expert cardiographer.

Diagnostic and therapeutic potentials of platelet glycoprotein VI.

Platelets respond immediately to vascular injury by adhesion, aggregation, and thrombus formation. Disruption of the endothelial cell layer exposes extracellular matrix to the bloodstream. Collagen binding to platelet glycoprotein VI (GPVI) mediates the initial adhesion of the rolling platelet to the vascular wound. Signaling by GPVI leads to the onset of the platelet activation cascade that is finally crowned by a firm and shear-resistant integrin-based adhesive clot. Blockade of collagen binding to GPVI would prevent initial adhesion and further activation of the platelet and would have an enormous impact in antithrombotic therapy. Besides the therapeutical implication, radiolabeled GPVI gives us a valuable diagnostic means that may be used clinically for plaque imaging in the near future.