Rapid Blood Flow Research Articles

Prediction method for decreases in blood pressure during hemocatharsis therapy by arteriolar blood flow measurement

In clinical practice, the prediction of changes in blood pressure during hemocatharsis therapy depends on invasive monitoring, the physician's experience, or blood pressure measurement when patients ask for it. It is extremely difficult to predict blood pressure variation in patients under general anesthesia or with disturbance of consciousness. Therefore, the prediction of blood pressure variation during hemocatharsis therapy is an important issue. To address this issue, we invented a new noninvasive continuous blood flow monitor using arteriolar blood flow measurement by laser Doppler flowmetry. Then we examined and determined some extremely important phenomena, including the relationship between rapid blood pressure change and arteriolar blood flow, and failures of the cerebral blood flow autoregulatory mechanism, through measurements in clinical practice of hemodialysis, specific hemocatharsis therapy, and drug monitoring. The results suggest that blood pressure variation during hemocatharsis therapy is highly predictable by arteriolar blood flow measurement. Therefore, this new method for arteriolar blood flow measurement might be widely useful for patients under anesthesia, anesthesia monitoring in neonatal infants and animals (no conversation ability), as well as for hemocatharsis therapy.

Neointimal Cracks (Plaque Rupture?) and Thrombosis in Wrapped Arteries Without Flow

In Response: Falk and colleagues raise a number of important issues regarding lesion formation and the modeling of plaque rupture in mice.1 The first of these concerns the question of whether the processes that lead to neointima breakdown in the model of Sasaki et al2 are congruent with those occurring during the breakdown of a fibrous cap overlying a lipid-rich necrotic core. Falk et al consider that there is no obvious reason to suppose that there is any such congruence. The second deals with the genesis of thrombi in the model of Sasaki et al compared with over a ruptured atherosclerotic plaque. Falk et al argue that the processes of thrombogenesis in conditions of rapid blood flow are likely to be different to those in stagnant blood in a ligated artery, a point well supported by a plethora of experimental evidence that has accrued over many years.3 Falk et al conclude on these bases that the relevance of the model of Sasaki et al …

POTÊNCIA MÁXIMA - COMPREENDENDO A SEXUALIDADE MASCULINA

Poucas coisas proporcionam tanto orgulho e satisfação ao homem adulto - sobretudo se está excitado e diante da mulher amada - que sentir seu pênis flácido tornar-se enorme, rígido, poderoso. Resultado de rápido e eficiente remanejamento de fluxo sanguíneo, a ereção altera de maneira impressionante a anatomia de seu órgão sexual, que se torna o maior dentre as 193 espécies de primatas até hoje conhecidas. Contemplar este órgão em sua máxima potência é, seguramente, evento que a maioria dos homens gostaria de ver repetido muitas vezes em suas vidas, seja para expressar amor, gerar filhos ou por puro prazer. Mas, Homo Sapiens , que também se vangloria de possuir o maior e mais eficiente cérebro dentre todos os primatas, tem o hábito de se entreter com complexas cogitações sobre seu próprio comportamento. Talvez por isso, muitos homens despendem tempo enorme se debatendo num angustiante conflito: por um lado, contemplam o próprio pênis como se fosse a fonte dos momentos mais prazerosos de suas vidas, e por outro, o culpam como se fosse a causa de seus vexames e frustrações. Observações clínicas revelam que os sentimentos ambivalentes que os homens experimentam em relação ao seu desempenho sexual podem comprometer, em grande medida, sua autoconfiança, seu ajustamento social e sua eficiência profissional.

Selectin Ligands Promote Ultrasound Contrast Agent Adhesion under Shear Flow

Contrast-enhanced ultrasound imaging has shown promise in the field of molecular imaging. This technique relies upon the adhesion of ultrasound contrast agent (UCA) to targeted molecular markers of disease. This is accomplished by coating the surface of the contrast agent with a ligand that specifically binds to the intended molecular marker. Most UCA particles remain in the blood space, and their retention is influenced by the forces imposed by blood flow. For a UCA bound to a molecular target on the vascular endothelium, blood flow imposes a dislodging force that counteracts retention. Additionally, contrast agent adhesion to the molecular marker requires rapid binding kinetics, especially in rapid blood flow. The ability of a ligand:target bond complex to mediate fast adhesion and withstand dislodging force is necessary for efficient ultrasound-based molecular imaging. In the current study, we describe a flow-based adhesion assay which, combined with a novel automated tracking algorithm, enables quick determination of the ability of a targeting ligand to mediate effective contrast agent adhesion. This system was used to explore the adhesion of UCA targeted to the proinflammatory endothelial protein P-selectin via four targeting ligands, which revealed several interesting adhesive behaviors. Contrast agents targeted with glycoconjugate ligands modeled on P-selectin glycoprotein ligand 1 exhibited primarily unstable or transient adhesion, while UCA targeted with an anti-P-selectin monoclonal antibody exhibited primarily firm adhesion, although the efficiency with which these agents were recruited to the target surface was relatively low.

Rapid Whole Blood Flow Cytometric Test to Detect ICOS Deficiency in Patients with Common Variable Immunodeficiency

Background/Aims: Common variable immunodeficiency (CVID) is the most common primary immunodeficiency. With respect to underlying defects it comprises a heterogeneous group of deficiencies. For some patients, distinct phenotypical abnormalities have been described, e.g. partial CD40L deficiency or complete ICOS deficiency. For the diagnosis of CD40L deficiency, a rapid whole blood flow cytometric method has been described several years ago. We aimed to determine if the same method can be used to diagnose ICOS deficiency. Methods: Whole blood from 8 healthy volunteers was stimulated for 4 and 20 h with phorbol 12-myristate 13-acetate (PMA) and ionomycin. Induction of ICOS expression was analyzed on CD8–CD3+ lymphocytes using three-color flow cytometry. Blood from a patient with diagnosed ICOS deficiency was also analyzed. Results: Whole-blood stimulation with PMA and ionomycin for 20 h resulted in a significant induction of ICOS expression on CD8–CD3+ lymphocytes in healthy volunteers. Four-hour incubation also demonstrated ICOS upregulation but to a much lower extent. In CD8–CD3+ lymphocytes from an ICOS-deficient patient, no ICOS expression could be induced following 20 h of stimulation. Conclusion: ICOS expression can be analyzed using a rapid whole blood flow cytometric test.

In vivo synergy combining oxaliplatin with AVE8062, a vascular-disrupting agent

13074 Background: AVE8062 is a synthetic, water-soluble compound, analog of Combretastatin A4, currently in Phase I clinical trials. It inhibits tubulin polymerization through binding to the colchicine site of tubulin. In vivo, it induces rapid tumor blood flow shutdown and necrosis, leading to tumor regressions (Proc AACR, 2002). Previously (Proc AACR, 2003), we reported a high synergy resulting from the combination of AVE8062 with either cisplatin or carboplatin in a preclinical in vivo model. We report here the combination data of AVE8062 with oxaliplatin. Methods: A 3-arm dose-response study was performed comparing the single agents and their combination. Synergy was defined as a log cell kill (lck) of at least 1 log superior to the lck of the best single agent. The AVE8062 / oxaliplatin simultaneous combination was evaluated in female BALB/c mice bearing advanced stage (250mg) SC murine colon C51 adenocarcinoma. Drugs were administered IV with 2 intermittent injections, 4 days apart. The combination arm was evaluated over 7 dose levels. Results: At the Highest nontoxic dose (HNTD - 58 mg/kg/inj), AVE8062 was found active: 0.9 lck, 1/5 partial regression (PR) and no complete regression (CR). At the HNTD (7 mg/kg/inj), oxaliplatin was found highly active [5.8 lck, 5/5 CR, no tumor free survivors (TFS)]. The HNTD for the combination (58 mg/kg/inj of AVE8062 with 7 mg/kg/inj of oxaliplatin) was well tolerated with 11.7% body weight loss at nadir. The combination was highly active over the 2 highest dose levels with TFS on day 148 post tumor implantation (4/6 TFS at combination HNTD and 6/6 TFS at 80% HNTD). A high antitumor activity was maintained at 60% HNTD (5.9 lck, 6/6 CR and no TFS). The lowest dose tested, corresponding to 1/10 of the HNTD fractions, was found active with a lck of 1.0 and no regression. Conclusions: The combination of AVE8062 with oxaliplatin was found highly synergistic (superior activity than either of the single agents alone). The combination was well tolerated with a combination toxicity index of 2, indicating that there was no overlap in host toxicity. These data provide a good rationale to perform Phase I combination trials combining AVE8062 with oxaliplatin. [Table: see text]

Time-resolved contrast-enhanced magnetic resonance angiography of the hand with parallel imaging and view sharing: initial experience

We sought to compare a three-dimensional, contrast-enhanced, magnetic resonance angiogram (3D CE MRA) sequence combining parallel-imaging (generalised autocalibrating partially parallel acquisitions (GRAPPA)) with a time-resolved echo-shared angiographic technique (TREAT) in an intraindividual comparison to a standard 3D MRA sequence. Four healthy volunteers (27-32 years), and 11 patients (11-82 years) with vascular pathologies of the hand were examined on a 1.5-Tesla (T) MR system (Magnetom Avanto, Siemens, Erlangen, Germany) using two multichannel receiver coils. Following automatic injection (flow rate 2.5 cc/s) of 0.1 mmol/kg gadoterate (Dotarem, Guerbet, Roissy, France), 32 consecutive 3D data sets were collected with the TREAT sequence (TR/TE: 4.02/1.31 ms, FA: 10 degrees, GRAPPA acceleration factor: R=2, TREAT factor: 5, voxel size: 1.0 x 0.7 x 1.3 mm(3)) and a T1-wwighted 3D gradient-echo sequence (TR/TE: 5.3/1.57 ms, FA: 30 degrees, GRAPPA acceleration factor: 2, voxel size: 0.71 x 0.71 x 0.71 mm(3,)). MR data sets were evaluated and compared for image quality and visualisation of vascular details. In the volunteer group, all MR imaging was successful while technical problems prevented acquisition of the standard protocol in two patients. For the corresponding segments, the number of visible segments was equal on both sequences. Overall image quality was significantly better on the standard protocol than on the TREAT protocol. TREAT MRA provided functional information in lesions with rapid blood flow, e.g. detection of feeding and draining vessels in an haemangioma. TREAT-MRA is a robust technique that combines morphological and functional information of the hand vasculature and deals with the very special physiological demands of vascular lesions, such as quick arteriovenous transit time.

Spatial and Temporal Changes in Gene Expression and Blood Flow Recovery after Chronic and Acute Hindlimb Ischemia in the Mouse

Background Current mechanistic studies of critical limb ischemia are performed in mouse models of acute hindlimb ischemia that are not clinically relevant to most cases of human chronic critical limb ischemia. To overcome this limitation, we have developed the first mouse model of chronic hindlimb ischemia and compared the spatial and temporal change in gene expression and blood flow recovery to that seen in a model of acute hindlimb ischemia. Methods and Results Chronic hindlimb ischemia was induced by placing ameroid constrictors on the proximal and distal left femoral artery and ligation of the femoral artery branches. Blood perfusion and gene expression levels were measured in the thigh muscle and calf muscle of both models by laser Doppler and Q-RT-PCR. Hypoxia related genes increased significantly in the calf, but not in the thigh. Shear stress related genes and inflammatory genes were upregulated immediately in the thigh after induction of acute, but not chronic ischemia. This is consistent with the less blood flow recovery in chronic versus acute ischemia. Conclusion Spatial and temporal changes of gene expression and blood flow recovery are different in models of acute and chronic limb ischemia. After acute ischemia, up regulation of shear stress and inflammatory genes in the thigh muscle appear to contribute to collateral artery enlargement and may be responsible for the more rapid and complete blood flow recovery after induction of acute versus chronic ischemia. The molecular mechanisms that regulate collateral artery enlargement and blood flow recovery are distinct after chronic and acute ischemia.

Blood Coagulation and Propagation of Autowaves in Flow

This study analyses the effect of flow and boundary reactions on spatial propagation of waves of blood coagulation. A simple model of coagulation in plasma consisting of three differential reaction-diffusion equations was used for numerical simulations. The vessel was simulated as a two-dimensional channel of constant width, and the anticoagulant influence of thrombomodulin present on the undamaged vessel wall was taken into account. The results of the simulations showed that this inhibition could stop the coagulation process in the absence of flow in narrow channels. For the used mathematical model of coagulation this was the case if the width was below 0.2 mm. In wider vessels, the process could be stopped by the rapid blood flow. The required flow rate increased with the increase of the damage region size. For example, in a 0.5-mm wide channel with 1-mm long damage region, the propagation of coagulation may be terminated at the flow rate of more than 20 mm/min.

Ruptured high flow gastric varices with an intratumoral arterioportal shunt treated with balloon-occluded retrograde transvenous obliteration during temporary balloon occlusion of a hepatic artery

A patient presented with hematemesis due to gastric variceal bleeding with an intratumoral arterioportal shunt. Contrast-enhanced CT revealed gastric varices and hepatocellular carcinoma with tumor thrombi in the right portal vein. Angiography and angio-CT revealed a marked intratumoral arterioportal shunt accompanied with reflux into the main portal vein and gastric varices. Balloon-occluded retrograde venography from the gastro-renal shunt showed no visualization of gastric varices due to rapid blood flow through the intratumoral arterioportal shunt. The hepatic artery was temporarily occluded with a balloon catheter to reduce the blood flow through the arterioportal shunt, and then concurrent balloon-occluded retrograde transvenous obliteration (BRTO) was achieved. Vital signs stabilized immediately thereafter, and contrast-enhanced CT revealed thrombosed gastric varices. Worsening of hepatic function was not recognized. BRTO combined with temporary occlusion of the hepatic artery is a feasible interventional procedure for ruptured high flow gastric varices with an intratumoral arterioportal shunt.

Effect of Continuous Application of Shear Stress on Liver Tissue: Continuous Application of Appropriate Shear Stress Has Advantage in Protection of Liver Tissue

Rapid blood flow changes occur in the liver following a massive resection or in the grafted liver following transplantation, under which shear stress (SS) change induced by the flow change may determine the postoperative results. We observed changes in liver tissue structure and liver-specific function, and consequently assessed SS effect. The cultured liver tissue exposed to continuous application of moderate SS was shown to express and maintain a long-term liver-specific function. There was also evidence showing that destruction of the liver structure was inhibited. However, the cultured liver tissue not exposed to SS or exposed to high SS was shown to lose liver-specific function soon after expression. The liver structure was destroyed in the early stage of incubation. These results suggested that continuous application of appropriate SS has advantages over other types of stresses to protect liver tissue.

Reduction in flow artifacts by using interleaved data acquisition in segmented balanced steady-state free precession cardiac MRI

Balanced steady-state free precession (SSFP) magnetic resonance (MR) imaging is feasible for cine cardiac images because of the high contrast between myocardium and blood pool and robustness to rapid blood flow. Nonetheless, the flow artifacts are often observed because of off-resonance effects and to in-flow effects of the blood flow. Although reshimming the gradients or readjusting the center frequency reduces the artifacts, the technique can be susceptible for respiratory and cardiac motion and operator-dependent. The purpose of this study is to use another MR imaging technique for the reduction in the flow artifacts in the heart: odd–even interleaved data acquisition in segmented balanced SSFP imaging. The flow artifacts in the ventricle, ghost outside the heart, and visualization of the myocardial border were visually compared between sequential and odd–even interleaved k-space data acquisitions in cine balanced SSFP cardiac MR imaging. The odd–even interleaved k-space data acquisition significantly reduced dark flow artifacts in the left ventricle, improved the visualization of the myocardial border, and was easily installed. This imaging technique should be applied to cine segmented balanced SSFP cardiac MR imaging.

Identification of a unique filamin A binding region within the cytoplasmic domain of glycoprotein Ibalpha.

Binding of the platelet GPIb/V/IX (glycoprotein Ib/V/IX) receptor to von Willebrand factor is critical for platelet adhesion and aggregation under conditions of rapid blood flow. The adhesive function of GPIbalpha is regulated by its anchorage to the membrane skeleton through a specific interaction with filamin A. In the present study, we examined the amino acid residues within the cytoplasmic tail of GPIbalpha, which are critical for association with filamin A, using a series of 25-mer synthetic peptides that mimic the cytoplasmic tail sequences of wild-type and mutant forms of GPIbalpha. Peptide binding studies of purified human filamin A have demonstrated a major role for the conserved hydrophobic stretch L567FLWV571 in mediating this interaction. Progressive alanine substitutions of triple, double and single amino acid residues within the Pro561-Arg572 region suggested an important role for Trp570 and Phe568 in promoting GPIbalpha binding to filamin A. The importance of these two residues in promoting filamin A binding to GPIbalpha in vivo was confirmed from the study of Chinese-hamster ovary cells expressing GPIbalpha Trp570-->Ala and Phe568-->Ala substitutions. Phenotypic analysis of these cell lines in flow-based adhesion studies revealed a critical role for these residues in maintaining receptor anchorage to the membrane skeleton and in maintaining cell adhesion to a von Willebrand factor matrix under high-shear conditions. These studies demonstrate a novel filamin A binding motif in the cytoplasmic tail of GPIbalpha, which is critically dependent on both Trp570 and Phe568.

Shear stress and the role of high molecular weight von Willebrand factor multimers in thrombus formation

High molecular weight von Willebrand factor (VWF) multimers have an important role in the formation of platelet thrombi under conditions of high shear stress resulting from rapid blood flow. Laboratory studies conducted using an endothelial cell system have shown that ultra-large VWF multimers (ULVWF) attach to the surface of histamine-stimulated endothelial cells and form large string-like structures to which platelets adhere. Platelet attachment is mediated through the interaction of the glycoprotein (Gp) Ibalpha subunit of the platelet GpIb-IX-V complex with the A1 domain of VWF. These platelet-ULVWF strings are rapidly cleaved by the addition of normal human plasma or the purified plasma metalloprotease ADAMTS-13 (a disintegrin and metalloprotease with thrombospondin type I motifs domains). Cleaving activity is absent from the plasma of patients with the congenital or acquired forms of thrombotic thrombocytopenic purpura (TTP) and from mixtures of normal plasma with plasma from patients with acquired TTP. The interaction of VWF with P-selectin is at least partially responsible for the attachment of the VWF strings to the endothelium. Increased tensile stress on ULVWF multimers resulting from the tethering of ULVWF strings to the endothelial surface by P-selectin in flowing blood may expose the cleavage site on the A2 domain of VWF, facilitating multimer degradation by ADAMTS-13. These studies have important implications in bleeding and thrombotic disorders, including von Willebrand disease and TTP.

The von Willebrand factor self-association is modulated by a multiple domain interaction

Platelet adhesion and aggregation at sites of vascular injury exposed to rapid blood flow require von Willebrand factor (VWF). VWF becomes immobilized by binding to subendothelial components or by a self-association at the interface of soluble and surface-bound VWF. As this self-association has been demonstrated only under shear conditions, our first goal was to determine whether the same interaction could be observed under static conditions. Furthermore, we wanted to identify VWF domain(s) important for this self-association. Biotinylated VWF (b-VWF) interacted dose-dependently and specifically with immobilized VWF in an enzyme-linked immunosorbent assay (ELISA) assay, showing that shear is not necessary to induce the VWF self-association. Whereas anti-VWF monoclonal antibodies (mAbs) had no effect on the self-association, the proteolytic VWF-fragments SpII(1366-2050) and SpIII(1-1365) inhibited the b-VWF-VWF interaction by 70 and 80%, respectively. Moreover, a specific binding of b-VWF to immobilized Sp-fragments was demonstrated. Finally, both biotinylated SpII and SpIII were able to bind specifically to both immobilized SpII and SpIII. Similar results were observed under flow conditions, which confirmed the functional relevance of our ELISA system. We have developed an ELISA binding assay in which a specific VWF self-association under static conditions can be demonstrated. Our results suggest a multiple domain interaction between immobilized and soluble VWF.

Reduced CD40L Expression on ex vivo Activated CD4+ T-Lymphocytes from Patients with Excellent Renal Allograft Function Measured with a Rapid Whole Blood Flow Cytometry Procedure

Background: The CD40-CD40L (CD154) costimulatory pathway plays a critical role in the pathogenesis of kidney allograft rejection. In renal transplant biopsies, CD4+CD40L+ graft-infiltrating cells were detected during chronic rejection in contrast to acute rejection episodes. Using a rapid noninvasive FACS procedure, we were able to demonstrate CD40L upregulation in peripheral blood of patients with chronic renal allograft dysfunction. Materials and Methods: Whole blood from recipients of renal allografts was stimulated with PMA and ionomycin and measured by flow cytometry. Patients were assigned to three groups based on transplant function. Group 1: 26 patients with excellent renal transplant function; group 2: 28 patients with impaired transplant function; group 3: 14 patients with chronic allograft dysfunction and group 4: 8 healthy controls. Results: The median percentage ±SEM of CD4+/CD40L+cells stimulated ex vivo at 10 ng/ml PMA was as follows: group 1: 28.3 ± 4.1%; group 2: 18.4 ± 2.4%; group 3: 50.1 ± 5.0% and group 4: 40.4 ± 3.4%. Subdivisions of groups 2 and 3 resulted in different CD40L expression patterns. Patients with increased serum creatinine since the initial phase after transplantation (groups 2a and 3a) revealed a higher percentage of CD4+CD40L+ cells than patients showing a gradual increase over time (groups 2b and 3b). Consequently, patients of group 3a exhibited a significantly reduced transplant function compared with those of group 3b. Conclusion: After PMA + ionomycin stimulation, patients with excellent kidney graft function displayed significantly reduced expression of CD40L surface molecules on CD4+ cells early after transplantation. Those with a chronic dysfunction of the renal graft showed significantly more CD4+ cells expressing CD40L compared to the other transplanted groups. These results demonstrate that the percentage of CD4+CD40L+ cells stimulated ex vivo in peripheral blood may be a valuable marker for chronic allograft nephropathy.

Drug Based Approaches for Targeting Tumor Vasculature: Development of Combretastatin A4 Phosphate

Head R&D, Oxigene Inc 321 Arsenal St., Watertown, MA 02472 (USA) Tel. 1 617 673 7811, Fax 1 617 924 9229 E-Mail dchaplin@oxigene.com Tumor vasculature represents an appealing target for the development of new cancer treatments. Most of the research effort has been focused on antiangiogenic therapy. However, recently there has been an increased interest in developing agents, which irreversibly damage the already formed neovasculature in tumors so called vascular targeting agents (VTAs). VTAs differ from antiangiogenic agents in that, rather than preventing new blood vessel formation, they are designed to cause a rapid and selective vascular shutdown in tumors, which occurs over a period of minutes to hours. Moreover such agents are expected to be used in intermittent doses, to synergise with conventional treatments, rather than chronically over months or years. VTAs divide into two main classes (1) the biologics, which utilize antibodies and peptides to deliver toxins, procoagulant and proapoptotic effectors to tumor endothelium and (2) the small molecules, which do not specifically localize to tumor endothelium but exploit the known differences between tumor and normal endothelial cells to induce selective vascular dysfunction. The approach has several advantages • Each vessel provides the nutrition for and facilitates removal of waste products of metabolism from many thousands of tumor cells • Since a vessel is much like any channel involved in transportation, it only has to be damaged at one point to block both upstream and downstream function • It is not necessary to kill endothelial cells, a change of shape or function could also be effective • The endothelial cell is adjacent to the blood stream therefore delivery problems of any therapeutic are minimized • The target cell is a normal diploid cell, therefore drug resistant mutants are more unlikely to emerge • A surrogate marker of biological activity i.e. blood flow, is readily measurable in the clinic One of the most effective group of small molecule VTAs identified to date are certain tubulin depolymerizing agents the most studied compound being Combretastatin A4 phosphate (CA4P) which has completed Phase I trials and moved into Phase II trials. CA4P has been demonstrated to induce rapid, selective and extensive blood flow reductions in a large number of experimental tumor systems. These effects have been observed in spontaneous as well as transplanted tumor models. More recently clinical studies have demonstrated that tumor blood flow reductions are also seen in humans following administration of CA4P. Although the mechanisms responsible for these effects have not been completely defined it has been shown that CA4P induces rapid shape changes in proliferating Drug Based Approaches for Targeting Tumor Vasculature: Development of Combretastatin A4 Phosphate

The Trellis Thrombectomy System in the treatment of acute limb ischemia.

To report the use of a new percutaneous mechanical thrombectomy device in the treatment of acute limb-threatening ischemia. The Trellis Thrombectomy System is a 7-F drug dispersion catheter that features a treatment segment isolated by proximal and distal occlusion balloons, which help prevent distal embolization and systemic release of the infused thrombolytic agent. After inflating the distal balloon, the thrombolytic agent is infused and held at the target site by inflation of the proximal balloon. An oscillating dispersion wire optimizes dispersal of the thrombolytic agent as the thrombus is mechanically fragmented. The liquefied thrombus is then aspirated. Four consecutive patients with acute lower extremity ischemia secondary to bypass graft thrombosis were treated with the Trellis thrombectomy catheter. Overall, 95% of thrombus was successfully removed from the treatment zone, with no device-related complications. Only one patient required adjunctive thrombolytic therapy after thrombectomy with the Trellis device. The Trellis thrombectomy device is a safe and effective technique to isolate the infused thrombolytic agent in association with mechanical fragmentation for rapid blood flow restoration.

Distinct and concerted functions of von Willebrand factor and fibrinogen in mural thrombus growth under high shear flow

Using a perfusion chamber and confocal laser scanning microscopy, we analyzed the interplay of von Willebrand factor (VWF) and fibrinogen during thrombus growth on a collagen surface under physiologic high shear rate conditions. During initial thrombogenesis, platelet thrombi were constructed totally by VWF, not by fibrinogen. Fibrinogen accumulated predominantly inside the growing thrombi as a function of time, whereas the thrombus surfaces directly exposed to flow were occupied constantly by VWF throughout the observation period. In perfusion of afibrinogenemia (AF) blood lacking both plasma and platelet fibrinogen, the final height and volume of thrombi were significantly reduced compared with controls, albeit the area of surface coverage was normal. The impaired thrombus growth in AF was only partially corrected by the addition of purified fibrinogen to AF blood, whereas the addition of purified VWF to blood of severe von Willebrand disease (VWD) completely normalized the defective thrombus growth in this disease. Thus, the initial 2-dimensional thrombus expansion involves only VWF, whereas the time-dependent accumulation of fibrinogen, released from activated platelets, acts as a core adhesive ligand, increasing thrombus strength and height and resulting in 3-dimensional thrombus development against rapid blood flow.

Platelet shape changes and adhesion under high shear flow.

Recent studies have revealed that the platelet adhesive process under flow is tightly regulated by multiple ligand-receptor interactions. However, platelet morphological changes during this process, particularly its physiological relevance, remain unknown under blood flow conditions. Using epifluorescence and scanning electron microscopy, we evaluated the real-time changes in platelet morphology during a platelet adhesive process on a von Willebrand factor-coated surface under physiological high shear flow in a perfusion chamber. Here, we show that dynamic platelet shape changes occurring during distinct phases of the adhesive process are precisely regulated by "inside-out" and "outside-in" integrin signals and are also a key regulatory element in successful platelet thrombogenesis opposing rapid blood flow in vivo.