Large Vessel Thrombosis Research Articles

Oxidation of Key Methionine Residues in the N-Terminal Domains of ADAMTS13 Correlates with Loss of Its Proteolytic Activity,

Abstract 3276Deficiency of ADAMTS13 is associated with a life-threatening thrombotic microangiopathic disease—thrombotic thrombocytopenic purpura (TTP), which is characterized by the accumulation of aggregates of hyper-reactive ultra-large von Willebrand factor (VWF) and platelets in the microvasculature. In addition to TTP, systemic inflammatory syndromes such as acute systemic inflammation caused by endotoxin, acute pancreatitis, and severe sepsis demonstrate reduced ADAMTS13 activity. The cause of low ADAMTS13 activity is not known. One possible cause is oxidative inactivation of the enzyme by hypochlorous acid (HOCl), a potent oxidant released from activated neutrophils that is known to damage proteins. In this study, we exposed ADAMTS13 to HOCl produced by a myeloperoxidase (MPO)-H2O2-Cl− system and measured the proteolytic activity of oxidized ADAMTS13 using a small VWF A2 peptide and plasma VWFas substrates. ADAMTS13 activity decreased as a function of oxidant concentration. Treatment with 25 nM MPO plus 50 μM H2O2 reduced ADAMTS13 activity by over 85%. Such concentrations of MPO and H2O2 are routinely found in vivo at sites of inflammation.ADAMTS13 contains a series of structural domains: a metalloprotease domain (M), a disintegrin-like domain (D), a thrombospondin type 1 repeat (TSP1,T), a Cys-rich domain (C), a spacer domain (S), 7 additional TSP1 repeats, and 2 CUB domains. The MDTCS domains are essential for its proteolytic activity, while the C-terminal TSP1 and CUB domains may act as modulators. The MDTCS region contains 10 Met residues, Met being the amino acid residue most vulnerable to oxidation by HOCl. Using mass spectrometry, we identified 7 Met-containing peptides in this region after proteolytic digestion of ADAMTS13. Three of these 7 methionines are highly sensitive to oxidation by HOCl, including M249, M331 and M496. M249 is situated in the ”Met-turn” at the catalytic center of the metalloprotease domain. M331 and M496 are located in the disintegrin-like domain and the Cys-rich domain, respectively. The extent of oxidation of these Met residues was proportional to the HOCl concentration, and strongly correlated with loss of enzymatic activity. The same three Met residues were also oxidized after exposure of ADAMTS13 to activated human neutrophils. These observations suggest an oxidative mechanism for ADAMTS13 inactivation in systemic inflammatory syndromes and that the oxidation-sensitive Mets may serve as biomarkers for this effect. Coupled with our earlier observation that HOCl oxidation of von Willebrand factor enhances its adhesive function and renders it resistant to cleavage by ADAMTS13, these findings indicate that pathological situations during which neutrophils are activated produce extremely prothrombotic conditions, perhaps explaining why many inflammatory syndromes are associated with thrombosis in small and large blood vessels. Disclosures:No relevant conflicts of interest to declare.

In Vivo Fluorescence Imaging of Large-Vessel Thrombosis in Mice

Experimental studies of large-vessel thrombosis have been adapted for applications in mice, but they proffer limited quantifiable information in outcome measures. This study presents a novel approach for evaluating large-vessel thrombogenesis with temporally/spatially quantifiable measures and normalization methods for interanimal comparisons. Shuttered, beam-expanded lasers provided uniform narrow-wavelength illumination of a ×100 microsurgical field with a large depth of focus. Thrombosis was generated in murine carotid arteries and femoral veins by brief vascular surface electrolytic injury. Thrombus-targeting fluorophores were injected systemically and subsequently localized at the site of thrombus induction. A low-light digital video camera with filter wheel provided target-specific image acquisition over a 60-minute interval. Platelets accumulated with a subsequent fibrin border emerging to stabilize the clot in both arteries and veins. Coagulation enzyme complexes colocalized with fibrin deposition. Large arteries underwent cyclic massive thromboembolization, whereas veins showed gradual shedding of microemboli and clot contraction. Systemic administration of fibrin- and platelet-inhibiting compounds reduced their respective targets but also often inhibited their clotting counterparts (platelets and fibrin, respectively) in both arteries and veins. Intermediate-level magnified image capture represents a novel approach for analysis of fluorescence-based in vivo imaging, with quantitative application to the study of large-vessel thrombosis.

Glomerular fibrin thrombi in ABO and crossmatch compatible renal allograft biopsies

Glomerular fibrin thrombi may be an early indication of antibody-mediated rejection in renal allograft biopsies. However, fibrin thrombi have a broad differential; thus, we sought to evaluate the etiology and implications of glomerular fibrin thrombi in allograft biopsies of blood group and cytotoxic crossmatch compatible renal allografts. Biopsies were identified from the pathology files of Oregon Health & Science University. Detailed histopathologic findings were retrospectively correlated with clinical data, treatment, and outcome. Sixteen early posttransplant biopsies had glomerular fibrin thrombi, including three surveillance biopsies. Six of 16 biopsies had no other histopathologic findings; 5/16 had glomerulitis and peritubular capillaritis; 4/16 had concomitant cellular vascular rejection; one had parenchymal infarction. C4d staining was positive in 4/16 cases. Most patients were treated with IVIg and plasmapheresis, others with rapamycin, thymoglobulin, or rituximab. At an average follow-up of 62 months, 8 patients with functioning grafts had a mean serum creatinine of 1.4 mg/dL (122 μmol/L). Antibody-mediated rejection is an important consideration in blood group compatible allograft biopsies with glomerular fibrin thrombi, even with C4d-negative biopsies. However, multidisciplinary evaluation is necessary, given other etiologies, including drug toxicity, hemolytic-uremia syndrome, and large vessel thrombosis. Despite aggressive treatment, both short and long-term graft survival may be compromised.

Plasminogen activators in ischemic stroke: introduction.

A number of plasminogen activators (PAs), enzymes capable of converting the zymogen plasminogen to the active agent plasmin, have been studied as potential therapeutic agents in the settings of ischemic stroke, intracerebral parenchymal hemorrhage, and large vessel thrombosis. Several have found purpose in the acute management of focal cerebral ischemia under strictly limited conditions. All derive from naturally occurring PAs that can generate plasmin in the circulation or in fibrin clots, and all are known to lyse thrombi. This session examines potential modifications to accepted strategies for the treatment of ischemic stroke acutely. The principles for the acute use of PAs in ischemic stroke derive from the common understanding of plasminogen activation in the circulation and in thrombi known to target in situ thrombotic occlusions. Physiologically, the intrinsic (endogenous) thrombolytic system entails the secretion of single-chain urokinase (sc u-PA) and of single-chain tissue type plasminogen activator (sc t-PA) from endothelial cells.1–3 These precursor PAs are converted to urokinase (u-PA) and t-PA by locally derived plasmin. Plasmin is itself generated from the inactive zymogen plasminogen by u-PA and/or t-PA ( Figure ) . The formation of plasmin from plasminogen is the central reaction necessary for thrombus lysis. This conversion is highly regulated under ordinary circumstances. For instance, plasminogen activator inhibitor-1 and -2 directly inhibit the actions of u-PA and t-PA to convert plasminogen to plasmin.4,5 When t-PA is bound to fibrin and plasminogen (fibrin-bound plasminogen) in a ternary complex, both …

Ischemic Stroke in Young Asian Women: Risk Factors, Subtypes and Outcome

Background and Objective: The objective of our study was to describe risk factors, mechanisms and outcome of young Asian women with ischemic stroke. Methods: Twelve tertiary-care centers in 8 Asian countries participated. Women aged 15–45 years were included if they had an ischemic stroke supported by neuroimaging. Data on age, risk factor history, stroke mechanism and discharge status were collected. Results: A total of 958 subjects were included, their mean age was 34 years. Large-vessel thrombosis comprised 24%, cerebral venous thrombosis 21%, cardioembolism 19% and small-vessel thrombosis 15%. The stroke risk factors included hypertension (29%), diabetes (14%), pregnancy (11%), valvular heart disease (10%) and cigarette smoking (3%). Anemia was found in 42%, and mortality was 4%; at discharge, 17% had modified Rankin score (mRS) >4 and 83% mRS 0–3. Conclusion: Unlike among Caucasians, large-vessel thrombosis, cerebral venous thrombosis and cardioembolism are common among young Asian women with stroke. A high proportion are pregnancy-related. More studies are needed.

Reciprocal coupling of coagulation and innate immunity via neutrophil serine proteases

Blood neutrophils provide the first line of defense against pathogens but have also been implicated in thrombotic processes. This dual function of neutrophils could reflect an evolutionarily conserved association between blood coagulation and antimicrobial defense, although the molecular determinants and in vivo significance of this association remain unclear. Here we show that major microbicidal effectors of neutrophils, the serine proteases neutrophil elastase and cathepsin G, together with externalized nucleosomes, promote coagulation and intravascular thrombus growth in vivo. The serine proteases and extracellular nucleosomes enhance tissue factor- and factor XII-dependent coagulation in a process involving local proteolysis of the coagulation suppressor tissue factor pathway inhibitor. During systemic infection, activation of coagulation fosters compartmentalization of bacteria in liver microvessels and reduces bacterial invasion into tissue. In the absence of a pathogen challenge, neutrophil-derived serine proteases and nucleosomes can contribute to large-vessel thrombosis, the main trigger of myocardial infarction and stroke. The ability of coagulation to suppress pathogen dissemination indicates that microvessel thrombosis represents a physiological tool of host defense.

Ischémie aiguë du membre inférieur révélant une leucémie aiguë. À propos d’un cas et revue de la littérature

Large vessel thrombosis is a very rare clinical presentation of acute leukemia which is usually revealed by hemorrhagic complications or thrombosis of small vessels. We present here the case of a patient with previously undiagnosed acute myeloid leukemia who was referred to our hospital with symptoms of acute ischemia of the left lower limb. Occlusion of the left popliteal artery due to a leucostasis was noted and successfully treated with emergency surgical thromboembolectomy and chemotherapy.

Acute Myeloid Leukemia with Mutated NPM1 Presenting with Life-Threatening, Either Arterial or Venous, Thromboembolism: a Report of 4 Cases.

Abstract 4135Acute myeloid leukemia (AML) expressing mutated NPM1 gene and cytoplasmic nucleophosmin (NPMc+ AML) [Falini B et al, NEJM 2005;352:254-266] is a new entity of WHO classification that shows distinctive biological and clinical features. AML with mutated NPM1 usually presents with a high white blood cell count; the bone marrow biopsy is usually markedly hypercellular and leukemic cells frequently show myelomonocytic or monocytic features, with dysplasia and involvement of two or more cell lineages in about 25% of cases. Lack, or low expression, of CD34 in over 90% of cases is the most distinctive immunophenotypic feature of NPM1-mutated AML and is independent of leukemic cell maturation. NPM1 gene mutation without concomitant FLT3-ITD identify a subgroup of AML patients with a favorable prognosis and has been associated with an approximately 50-60% probability of survival at 5 years in younger patients. Here we report 4 out of 41 (10%) patients, admitted at our Hospital in the last year, with new-diagnosed AML with mutated NPM1 presenting with life-threatening thromboembolic (either arterial or venous) events. The main characteristics of these patients are summarized in Table 1. The patients had neither personal nor family history concerning thromboembolism. Hyperleukocytosis was a common feature of the vast majority of NPM1-mutated AML patients at diagnosis. Immunophenotypic analysis did not show a peculiar phenotype in these patients.Table 1Characteristics of patients with NPM1-mutated AML and thrombosis.Case report noAgeSex (M/F)FAB subtypeWBC/mmcType of thrombosisSite of thrombosis141FM114970arterialAnterior interventricular branch of left coronary artery256MM493990arterialexternal iliac and femoral (right limb)363MM2113000deep venousgreat saphenous veins (bilateral)473FM4190000deep venousiliac and femoralIn two patients (cases 1 and 2), the arterial thromboembolic event (acute myocardial infarction and acute ischemia of right lower limb, respectively) presented about one month before diagnosis of leukemia. In the other 2 patients (cases 3 and 4), deep venous thromboembolism was concomitant with the diagnosis of leukemia. One patient (case 4), who could not initiate chemotherapy for severe concomitant renal failure, died few days after diagnosis. The other patients recovered from the acute event and upon diagnosis of leukemia were promptly treated with standard polychemotherapy which allowed to obtain complete hematological remission associated with complete resolution of the thromboembolic event. The clinical course after chemotherapeutic treatment of the patients outlines the importance and life saving role of early chemotherapy even under adverse circumstances. The pathogenesis of thromboembolic disease in hematological malignancies is complex and multifactorial: tumor cell-derived procoagulant, fibrinolytic or proteolytic factors and inflammatory cytokines affect clotting activation. Other important factors include infectious complications and hyperleukocytosis. However, large vessel thrombosis is a very rare clinical presentation. Our report of severe thromboembolic events at presentation in AML with mutated NPM1 suggests some still unidentified biological features of this leukemia which we are currently investigating. Disclosures:No relevant conflicts of interest to declare.

Is Familial Mediterranean Fever a Possible Cofactor for Budd‐Chiari Syndrome?

Budd-Chiari syndrome (BCS) is characterized by obstruction of hepatic venous outflow at any level of the hepatic veins or the inferior vena cava (IVC). Clinical presentation ranges from asymptomatic cases to fulminant hepatic failure or end-stage liver disease (1). Primary endophlebitis or congenital malformations may be responsible for BCS (1). Although several hypercoagulable states such as antithrombin III, protein C and S deficiency, factor V Leiden (FVL), and prothrombin gene 20210A mutations have been linked to BCS, recent data show that primary BCS is a multifactorial disease and the combination of several prothrombotic factors play a role in the development of thrombosis (1). Familial Mediterranean fever (FMF) is an autoinflammatory disorder characterized by episodic fever and polyserositis. Hypercoagulability has been recently reported in patients with FMF, yet thrombotic events were rarely reported in the literature. Although large vessel thrombosis in patients with FMF without amyloidosis is an unexpected event, an occurrence of superior vena cava thrombosis in a patient with FMF has also been reported (2-4). Our report is one of the few articles in the literature in which a major thrombotic event has occurred in the setting of FMF without amyloidosis.

Usefulness of 16-Row Multidetector Computed Tomography With Volume Rendering and Maximum Intensity Projection Reconstruction as a Monitor Pancreatic Graft Vessel Patency During the Early Postoperative Period

Thrombosis of the pancreatic graft vessels is the most common complication after transplantation. It leads to loss of 5% to 8% of grafts during the early postoperative period. The aims of this study were to evaluate the usefulness of 16-row multidetector computed tomography (16-MDCT) with volume rendering (VR) and maximum intensity projection (MIP) reconstruction to monitor pancreatic graft vessel patency during the early postoperative period and the efficacy of a heparin infusion as a treatment for graft thrombosis. Among 40 consecutive simultaneous pancreas-kidney transplant recipients, 16-MDCT was performed at 6 to 8 days after the operation. Secondary reconstructions were obtained with VR and MIP algorithms to evaluate the morphology and patency of the extra- and intrapancreatic arteries and veins. In cases of thrombosis, every patient was treated with an infusion of unfractionated heparin. In 15 recipients, thrombosis of the large vessels was detected by 16-MDCT. Heparin infusions saved five pancreatic grafts (5/15; 33.3%), but the other 10 pancreatic grafts were removed. In another four recipients (4/40; 10%) the thrombi were localized only in small intrapancreatic vessels. Treatment with heparin infusion was successful in 3/4 (75%) cases with patent vessels upon control computed tomography examination. We compared the efficacy of heparin treatment depending on the diameter of the thrombosed vessel, observing a significant difference (5/15 vs 3/4; P < .01; chi-square). 16-MDCT with secondary reconstruction by application of VR and MIP algorithms was an efficient method to visualize not only large pancreatic graft arteries and veins but also intrapancreatic parenchymal vessels. In cases of thrombosis of small intrapancreatic vessels, unfractionated heparin infusion significantly decreased graft loss.

Aortic Valve Vegetation Without Endocarditis

We present a 30-year-old man with an acute middle cerebral artery territory infarction. A transesophageal echocardiogram showed a large, highly mobile mass attached to the patient's aortic valve. We discuss the differential diagnosis of a cardiac mass that includes infection, tumor, and thrombus. A complete workup showed no evidence of systemic infection but did reveal the presence of antiphospholipid antibodies. The patient also had a history of a right lower extremity deep venous thrombosis. Anticoagulation therapy was started, and follow-up showed complete resolution of the aortic valve lesion. This case highlights that when a valvular vegetation is encountered in a clinical setting that does not suggest infectious endocarditis, the diagnosis of antiphospholipid antibody syndrome should be considered. This case and our review of the literature suggest that vegetations in antiphospholipid antibody syndrome, no matter how large and ominous in appearance, can be treated successfully with anticoagulation and vigilant observation.

In Vivo Imaging of Large-Vessel Thrombosis

In vivo thrombosis imaging systems have been developed that show localized smallscale and short-acting thrombotic events in arterioles and venules; however, these microvascular models may not accurately simulate thrombogenesis in large vessels. A new quantitative imaging system was developed for evaluation of electrolytic-injury models of thrombus induction in large vessels of mice (carotid arteries and femoral veins). Laser-induced fluorophore emissions of membrane-labeled platelets and labeled fibrin-specific monoclonal antibodies were captured with time-lapse video recordings. Platelets were seen to accrue slowly after thrombus induction in both arteries and veins, peaking at approximately 15–45 minutes. In arteries, platelets accumulated more rapidly and to a greater extent than fibrin. Surprisingly, platelet accumulation in veins was substantial, occurring diffusely throughout the thrombus. Arterial thrombus dissolution occurred most often via large embolic events, sometimes occurring cyclically every 5–20 minutes by regrowth and re-embolization. In contrast, the rate of thrombus dissolution in veins was more gradual and appeared as micro-embolic events. Standard heparin anticoagulation inhibited venous thrombus growth by reducing fibrin development by 75% without affecting platelet accumulation. In contrast, blocking platelet aggregation at the αIIb/β3 receptor (with RGD-based mimetics) resulted in a 43% reduction in platelets and a surprising 5-fold increase in fibrin accumulation, suggesting the possibility of temporal competition between platelets and fibrin under venous conditions of thrombus formation. In established thrombi, newly activated platelets, identified by exposure of the active site of the αIIb/β3 receptor (using JON/A, a fluorophore-labeled antibody specific to activated αIIb/β3), were seen to roll in small aggregates across the outer margin of the thrombus mass in both arteries and veins for over 30 minutes, indicating continual dynamic platelet aggregation in both vessel types. Fibrin accrual was most intense at the margins of acute thrombotic stimuli and co-localized with fluorophore-labeled anti-Factor Xa and with Factor Va/VIIIa (identified using labeled activated protein C), which suggests that fibrin polymerization predominates adjacent to sites of these assembled coagulation complexes. In summary, the time-lapse nature of this video imaging system provides a unique and quantifiable method for determining how coagulation and platelet aggregation develop and are modulated in vivo within the same thrombus. Its use for the study of large vessel thrombosis often corroborated long-held tenets of platelet activity and coagulation, while revealing several novel findings:platelets are major contributors to venous thrombosis;arteries and veins have profound differences in thrombus dissolution/embolization patterns;inhibiting platelet aggregation may augment fibrin clot formation;platelet aggregation is a dynamic process in both arteries and veins, continually in flux on the thrombus surface for at least 30 minutes; andfibrin forms local to sites of coagulation complex assembly. [Display omitted] Graph illustrating single traces for representative electrolytically-induced, free-radical-mediated thrombi in mouse carotid arteries (EAT) and femoral veins (EVT) over 60 minutes, for anti-fibrin (FBN) and platelet (Plt) labels. The y-axis displays arbitrary units for the product of total thrombus area and average fluorophore intensity within the thrombus.

Recurrent Intestinal Perforation Associated with Thrombosis of Inferior Vena Cava: Uncommon Presentation of Antiphospholipid Syndrome

To the Editor: Antiphospholipid syndrome (APS) is characterized by a state of hypercoagulability potentially resulting in thrombosis of all segments of the vascular bed1,2, fetal loss, and moderate thrombocytopenia3,4. APS is associated with elevated titers of antiphospholipid antibodies (aPL) and/or lupus anticoagulant (LAC)5,6. Gastrointestinal manifestations are rarely observed (about 1.5% of patients) and intestinal infarction, resulting from mesenteric vessel thrombosis, has been infrequently reported3. The presentation may be acute (acute abdomen), often preceded by intestinal angina1. Rarely, thrombosis of large vessels (aorta and inferior vena cava) has also been reported in association with aPL7. We describe a case of recurrent ...

Bilateral, Hyperdense Middle Cerebral Arteries Predict Bihemispheric Stroke

The hyperdense vessel sign is a debated topic in terms of its sensitivity and specificity for acute cerebral ischemia. Bilateral, hyperdense middle cerebral artery signs are rare presentations of bilateral cerebral infarction. We describe a 17-year-old boy with a history of cerebral palsy and a repaired atrial septal defect, presenting with lethargy and respiratory failure. Noncontrast computed tomography of the brain revealed bilateral, hyperdense middle cerebral artery signs, and he subsequently demonstrated bilateral cerebral infarctions in the distributions of the middle cerebral arteries. Hyperdense artery signs must alert physicians to evaluate patients for stroke, with an especially high index of suspicion for pediatric patients with hyperdense vessels, who are less likely to present with atherosclerotic disease causing vascular calcifications; rather, hyperdense artery signs could be an early sign of large-vessel thrombosis and cerebral infarction.

Thromboses veineuses récidivantes et télangiectasies arborescentes généralisées révélatrices d’un lymphome intravasculaire

Intravascular lymphoma is a rare form of non-Hodgkin's lymphoma characterized by proliferation of lymphoid cells within the lumen of small veins, small arteries and capillaries. A 79-year-old man presented with repeated superficial venous thrombosis of the lower limbs associated with diffuse telangiectasia of the trunk, upper arms and thighs but with normal epidermis. Screening for thrombophilia and neoplasm were negative. The patient subsequently developed abdominal pain, lower-limb oedema, deterioration in performance status and rapidly increasing telangiectasia with the appearance of generalized oedematous cutaneous induration. Increased LDH and anaemia were observed without other blood count anomalies. Intravascular lymphoma was diagnosed on a skin biopsy with telangiectasia and oedema. After eight courses of treatment with rituximab-CHOP the outcome was good. A few telangiectasias associated with nodules or infiltrated plaques are often a clinical manifestation of intravascular lymphoma. The dermatological presentation described here is interesting for two reasons: on the one hand, telangiectasias were initially isolated in normal epidermis without any infiltration for more than one year and, on the other hand, the skin infiltration seen subsequently was very extensive and marked. Moreover, although microthrombi are frequent in small and medium-sized blood vessels, thrombosis of large vessels is rarely described in intravascular lymphoma.

Síndrome do anticorpo antifosfolípide causando oclusão bilateral de artérias e veias centrais da retina: relato de caso

The antiphospholipid syndrome (APS) has been related to venous and arterial thrombosis of large and small vessels. Ocular vessels can also be involved causing transient visual loss, diplopia, ischemic optic neuropathy and central artery and venous occlusion. We describe here a case of antiphospholipid syndrome with occlusion of central retinal artery and vein to call the attention to this diagnosis.

Acute lower limb ischemia as the initial symptom of acute myeloid leukemia

Although coagulatory system disorders are well recognized in patients with acute leukemia, these usually present with either hemorrhagic complications or thrombosis of small vessels. Large vessel thrombosis is a very rare clinical presentation. We present a patient with previously undiagnosed acute myeloid leukemia (M5), who was referred to our hospital with symptoms of acute ischemia of his right lower limb. Occlusion of the right external iliac artery due to a combination of leucostasis and coagulation disorders was noted and successfully treated with urgent leukapheresis, immediate chemotherapy and surgical thromboembolectomy.

Catastrophic aortic thrombosis due to Toxocara infection

Toxocariasis, a common helminthozoonosis with a worldwide prevalence, usually manifests as 'visceral larva migrans' (VLM). Among its wide range of clinical presentations, large vessel thrombosis has never been described before. We report a case of aortic thrombosis caused by Toxocara canis infection in a young male who was successfully treated with albendazole.

Platelet Activation Is Linked to the Severity of Pulmonary Hypertension in Sickle Cell Disease and Normalizes on Sildenafil Therapy.

Pulmonary hypertension (PHT) is a severe complication of sickle cell disease (SCD) characterized by abnormal vascular tone, vascular proliferation and thrombosis, associated with chronic hemolysis, and nitric oxide (NO) consumption by cell-free hemoglobin. Since platelets are central to the development of large-vessel thrombosis, and increased platelet activation has been described independently in patients with primary PHT and in patients with SCD, we sought to define the degree of platelet activation in SCD patients with secondary PHT. We hypothesized that the degree of platelet activation may be linked to the severity of PHT, hemolytic rate and NO bioavailability; conversely, platelet activation may decrease with therapy directed to PHT by increasing NO-dependent signaling. We obtained blood samples from SCD patients with PHT (n=16) and without PHT (n=17) during steady state (not in pain crisis). PHT was defined by a tricuspid regurgitant jet (TRjet) velocity >= 2.5 m/sec by Doppler echocardiography. Platelet activation was measured by the flow cytometry detection of activated fibrinogen receptors (activated GPIIb/IIIa) and surface expression of P-Selectin. The mean percentage of platelets with activated GPIIb/IIIa was 10.3 ± 1.8%( mean ± SEM) for non-PHT SCD patients vs. 27.2 ± 4.7% for PHT SCD patients (p = 0.001). The percentage of platelets positive for P-Selectin was 2.0 ± 0.8% for non-PHT SCD patients vs. 5.1 ± 2.5% for PHT SCD patients (p = 0.02). The percentage of activated platelets strongly correlated with TR jet velocities (r = 0.63 and p = 0.0006). (Figure 1) In addition, the percentage of activated platelet correlated to surrogate markers of hemolysis LDH and reticulocyte count. This link may not prove causation but it suggests a common pathophysiology. Nitric oxide plays a central role in vascular homeostasis by regulating vascular tone and platelet activation through the generation of cyclic guanosine 5′-monophosphate (cGMP). It is possible that decreased NO bioavailability is responsible for both pulmonary vasculopathy and platelet activation. Our pilot studies indicate sildenafil, which enhances NO responsiveness by promoting the accumulation of its downstream mediator cGMP, may be useful in treating PHT.To verify the effect of this therapy on the degree of platelet activation, we studied a group of 12 SCD patients receiving sildenafil. Platelet activation was determined from blood samples obtained before and after (120–150 minutes) a single dose of 100 mg. of sildenafil. The mean percentage of activated platelets was higher before than after sildenafil; for activated GPIIb/IIIa 31.2 ± 4.7% vs. 17.1 ±3.9% (p = 0.001); for P-Selectin 6.3 ± 1.6% vs. 3.2 ±0.6% (p = 0.11).Our findings show for the first time the association of platelet activation and pulmonary hypertension in SCD. Furthermore, by demonstrating that platelet activation of SCD patients with PHT is decreased by sildenafil, a drug that potentiates the effects of NO, this work suggests a common pathophysiology. Additional research is needed to define whether platelet activation plays a role in the thrombo-vascular events that characterize PHT.

Undifferentiated Intimal Sarcoma of Large Systemic Blood Vessels

Intimal sarcoma (IS) is defined as a malignant tumor arising in the tunica intima of large blood vessels. In systemic circulation, the majority of IS develop in the aorta, where close to three fourths of published cases lack specific differentiation and are called undifferentiated intimal sarcomas (UIS). The remaining cases are intima-associated sarcomas of recognized types, also called differentiated intimal sarcomas (DIS). In this report, we further characterize UIS, including its immunohistochemical profile and results of comparative genomic hybridization. A total of 14 cases of UIS were collected from 17 medical institutions, including slides, blocks, electron photomicrographs, clinical abstracts, and reports of surgical pathology specimens and autopsies. The patients, 7 women and 7 men, were 41 to 85 years of age (median, 65.6 years). Twelve tumors arose from the aorta, one from the left external iliac and femoral arteries, and one in a large systemic vein (the venous tumor was included due to histologic similarity with the arterial lesions). Tumors ranged from 1 cm to over 10 cm in diameter. Histopathology was that of a largely necrotic, poorly differentiated epithelioid and pleomorphic malignant neoplasm relating to the tunica intima. Usually there was only a thin layer of viable tumor cells overlying a large thrombus. All tumors stained at least focally with the endothelial markers CD31 and Fli-1; however, there was otherwise considerable variability in immunophenotype. The distinctive histopathologic appearance of the primary luminal lesion was lost whenever tumor invaded outside the vessel wall (into adventitia and beyond) or in metastatic sites. Such extravascular tumors assumed a variety of patterns reminiscent of undifferentiated pleomorphic sarcoma (UPS; in older literature also known as pleomorphic malignant fibrous histiocytoma, MFH) or other distinct types of sarcomas, including osteosarcoma, angiosarcoma, and rhabdomyosarcoma. The results of comparative genomic hybridization were nonspecific. Eleven patients died of the disease, in an average of 11 months after diagnosis. Three patients are still alive and free of disease at 4, 16, and 27 years. UIS of large systemic vessels represents a distinct clinical entity where intraluminal sarcoma presents with thrombosis and occlusion of large vessels. It is associated with a highly characteristic, although not entirely specific, histology and immunohistochemical phenotype. The histogenesis of UIS is not certain; however, it seems that the cell of origin must leave the confines of the vessel wall to show altered morphology. Although there are rare long-term survivors, UIS behaves as a fully malignant neoplasm that is almost uniformly associated with metastases and tumor-related death.