Human Thrombi Research Articles

Comparison of methods used to measure the thickness of soft tissues and their influence on the evaluation of tensile stress

Measuring the physical dimensions of soft tissue is difficult due to its deformable nature. Such measurements are used to evaluate the tissue's mechanical properties. Imprecise measurements of the tissue's thickness can alter the assessment of tensile stress which may have significant clinical relevance when used as a diagnostic tool. The performance of routinely used measurement methods including a (i) vernier calipers, (ii) micrometer, (iii) thickness gauge, (iv) glass slide technique coupled with (i) and (ii) and a (v) laser displacement sensor were assessed by comparing them to a photogrammetric technique which was considered to be the measurement standard. All measurements were performed on two tissue types: porcine aorta and human intraluminal thrombus from an abdominal aortic aneurysm (AAA) and results were compared against predetermined criteria whose limits represented a 10% change in experimentally derived tensile stress. The inter-rater and retest reliability of the vernier calipers, micrometer and thickness gauge were also investigated. The thickness gauge was shown to be the most reliable and could accurately measure the thickness of aortic tissue. The conditions of the criteria were not met by any instrument used to measure the thickness of the AAA intraluminal thrombus, however, the micrometer, which proved highly reliable, was considered the most suitable (effects on tensile stress: +14.7%). For both tissues the glass slide and laser techniques significantly over estimated the thickness measurement altering the tensile stress by up to −29.6%. This study highlights the effects of inaccurate measurements on the assessment of tensile stress and recommends a thickness gauge be used to measure structured tissue (aorta) and a micrometer for unstructured tissue (AAA intraluminal thrombus).

2:18 PM Abstract No. 98 - Influence of thrombin content and fibrin complexity on in vitro sonothrombolysis rate and efficacy

Purpose Blood clots that cause stroke and other vascular occlusion diseases vary with regard to fibrin complexity, and rigidity. This study sought to establish protocols for producing blood clots with different levels of fibrin content and rigidity for in vitro experiments to determine how to adjust pulsed ultrasound parameters (intensity, frequency, and duty factor), tPA and microbubbles (MBs) to improve STBL efficacy for more fibrin-rich, rigid and aged clots. Materials and Methods Clots were formed by mixing pooled rabbit plasma with fresh rabbit blood cells. Fibrin content and complexity were adjusted by varying thrombin content, calcium concentration, incubation time at 37 o C (3 h to 72 h), and curing time at 5 o C (24 h to 72 h). In vitro STBL of 7.5-12.0 mg pieces of clot was performed in a flow chamber (37.0 o C) through which fresh bovine serum containing tPA and/or MBs was flowed continuously. STBL efficacy was measured as % of clot mass lysed in 15 min. Clot fibrin content was measured using a D-Dimer assay and complexity determined by scanning electron microscopy. Results Increasing thrombin content, 37 o C incubation time, and 5 o C curing time produced more rigid clots that were increasingly resistant to STBL. Resistance to STBL was maximal with a thrombin concentration of 30 U/mL, a 24 h 37 o C incubation time, and a 24 h 5 o C curing time. Using tPA or MBs improved STBL efficacy, but improvement was less pronounced as clot rigidity increased. Combining tPA with MBs improved STBL efficacy additively in the least rigid clots, but this complementation diminished markedly as clot rigidity increased. Conclusion Varying thrombin concentration, 37 o C incubation time and/or 5 o C cure time provided reproducible control for forming clots with different rigidity and resistance to STBL. Such clots can putatively be used to model the STBL response of different clot types found in human thrombi and how well tPA and MBs can potentiate STBL. The degree to which tPA and MBs complement each other to potentiate STBL decreases with increasing clot rigidity. tPA and MB complementation was additive for thrombin concentrations of 1-12 U/mL but became sub-additive when higher concentrations of thrombin were used to form clots.

Targeting Chemokines in Aortic Aneurysm

Aortic aneurysm rupture and aortic dissection are important causes of death. In the last decade, several developments have improved the outlook for patients with aortic diseases, including the introduction of ultrasound screening for abdominal aortic aneurysm (AAA) in some countries; more detailed ways of imaging the aorta and the development and subsequent sophisticated advancement of technology to repair large aortic aneurysms via endovascular means. An important remaining challenge is the development of an effective range of medications, which limit the progression of aortic aneurysms and dissections.1 See accompanying article on page 718 Although the molecular biological characteristics of aortic aneurysms vary depending on the region of the aorta affected and the risk profile of the patient, a key pathological feature is inflammation. Biopsies of human AAA wall and thrombus have been shown to be densely infiltrated by a range of innate and adaptive immune cells, including neutrophils, macrophages, mast cells, lymphocytes, and dendritic cells.2 Studies in rodent models suggest that blocking aortic wall inflammation can limit the development and progression of aortic aneurysm.3 Currently, however, no effective and safe means of limiting aneurysm progression in patients has been developed.1 Chemokines are a group of structurally related cytokines originally defined by their ability to promote cell migration, especially that of inflammatory cells. Previous studies have demonstrated upregulation of a range of different chemokines within animal models of aortic aneurysm and human …

A proteomic portrait of atherosclerosis

We have arranged in this review the main evidence about proteome alterations in different cell and body fluid compartments along the progression of atherosclerosis. With time the description of the molecular phenomena is becoming more and more detailed yet the complex interrelationships among different factors are still elusive and previously neglected aspects (such as size for lipoprotein particles) emerge as not less relevant than the absolute abundance of individual proteins. Physiological limits to the kinetics of protein distribution through the biological fluids seem to hinder the early diagnosis of acute conditions through plasma analysis but suggest urine analysis as a workable alternative for the assessment of chronic conditions. The survey of literature data is complemented with a few unpublished results from our laboratories, featuring 2DE maps of the proteins extracted from human thrombi.

Abnormal Whole Blood Thrombi in Humans with Inherited Platelet Receptor Defects

To delineate the critical features of platelets required for formation and stability of thrombi, thromboelastography and platelet aggregation measurements were employed on whole blood of normal patients and of those with Bernard-Soulier Syndrome (BSS) and Glanzmann’s Thrombasthenia (GT). We found that separation of platelet activation, as assessed by platelet aggregation, from that needed to form viscoelastic stable whole blood thrombi, occurred. In normal human blood, ristocetin and collagen aggregated platelets, but did not induce strong viscoelastic thrombi. However, ADP, arachidonic acid, thrombin, and protease-activated-receptor-1 and -4 agonists, stimulated both processes. During this study, we identified the genetic basis of a very rare double heterozygous GP1b deficiency in a BSS patient, along with a new homozygous GP1b inactivating mutation in another BSS patient. In BSS whole blood, ADP responsiveness, as measured by thrombus strength, was diminished, while ADP-induced platelet aggregation was normal. Further, the platelets of 3 additional GT patients showed very weak whole blood platelet aggregation toward the above agonists and provided whole blood thrombi of very low viscoelastic strength. These results indicate that measurements of platelet counts and platelet aggregability do not necessarily correlate with generation of stable thrombi, a potentially significant feature in patient clinical outcomes.

Detection of Extracellular Genomic DNA Scaffold in Human Thrombus: Implications for the Use of Deoxyribonuclease Enzymes in Thrombolysis

PurposeMechanisms underlying transition of a thrombus susceptible to tissue plasminogen activator (TPA) fibrinolysis to one that is resistant is unclear. Demonstration of a new possible thrombus scaffold may open new avenues of research in thrombolysis and may provide mechanistic insight into thrombus remodeling. Materials and MethodsTen human thrombus samples were collected during cases of thrombectomy and open surgical repair of abdominal aortic aneurysms (five samples < 3 d old and five samples > 1 y old). Additionally, an acute murine hindlimb ischemia model was created to evaluate thrombus samples in mice. Human sections were immunostained for the H2A/H2B/DNA complex, myeloperoxidase, fibrinogen, and von Willebrand factor. Mouse sections were immunostained with the H2A antibody. All samples were further evaluated after hematoxylin and eosin and Masson trichrome staining. ResultsAn extensive network of extracellular histone/DNA complex was demonstrated in the matrix of human ex vivo thrombus. This network is present throughout the highly cellular acute thrombus. However, in chronic thrombi, detection of the histone/DNA network was predominantly in regions of low collagen content and high cell density, which were mostly near the lumen. These regions of high cell density contained neutrophils and monocytes. Similarly, sections from the acute murine hindlimb ischemia model also exhibited extensive immunoreactivity to the histone antibody in the extracellular space within murine thrombi. ConclusionsExtensive detection of genomic DNA associated with histones in the extracellular matrix of human and mouse thrombi suggest the presence of a new thrombus-associated scaffold.

Synthesis of NanoQ, a copper-based contrast agent for high-resolution magnetic resonance imaging characterization of human thrombus.

A new site-targeted molecular imaging contrast agent based on a nanocolloidal suspension of lipid-encapsulated, organically soluble divalent copper has been developed. Concentrating a high payload of divalent copper ions per nanoparticle, this agent provides a high per-particle r1 relaxivity, allowing sensitive detection in T1-weighted magnetic resonance imaging when targeted to fibrin clots in vitro. The particle also exhibits a defined clearance and safety profile in vivo.

레이저 펄스 에너지를 이용한 무통증 마이크로젯 약물전달시스템

We have developed a laser-based needle-free liquid drug-injection device. A laser beam is focused inside the liquid contained in the rubber chamber of a micro-scale. The focused laser beam causes explosive bubble growth, and the sudden volume increase in a sealed chamber drives a microjet of liquid drug through the micronozzle. The exit diameter of a nozzle is less than 100 , and we verify that the injected microjet is fast enough to penetrate soft human tissue. In the experiment, the microjet penetrated a 5% gelatin-water solution that replicates the human thrombus and pork-fat tissue.

The role of PGE2 in human atherosclerotic plaque on platelet EP3 and EP4 receptor activation and platelet function in whole blood

Atherosclerosis has an important inflammatory component. Macrophages accumulating in atherosclerotic arteries produce prostaglandin E(2) (PGE(2)), a main inflammatory mediator. Platelets express inhibitory receptors (EP(2), EP(4)) and a stimulatory receptor (EP(3)) for this prostanoid. Recently, it has been reported in ApoE(-/-) mice that PGE(2) accumulating in inflammatory atherosclerotic lesions might contribute to atherothrombosis after plaque rupture by activating platelet EP(3), and EP(3) blockade has been proposed to be a promising new approach in anti-thrombotic therapy. The aim of our investigation was to study the role of PGE(2) in human atherosclerotic plaques on human platelet function and thrombus formation. Plaque PGE(2) might either activate or inhibit platelets depending on stimulation of either EP(3) or EP(4), respectively. We found that the two EP(3)-antagonists AE5-599 (300nM) and AE3-240 (300nM) specifically and completely inhibited the synergistic effect of the EP(3)-agonist sulprostone on U46619-induced platelet aggregation in blood. However, these two EP(3)-antagonists neither inhibited atherosclerotic plaque-induced platelet aggregation, GPIIb/IIIa exposure, dense and alpha granule secretion in blood nor reduced plaque-induced platelet thrombus formation under arterial flow. The EP(4)-antagonist AE3-208 (1-3μM) potentiated in combination with PGE(2) (1μM) ADP-induced aggregation, demonstrating that PGE(2) enhances platelet aggregation when the inhibitory EP(4)-receptor is inactivated. However, plaque-induced platelet aggregation was not augmented after platelet pre-treatment with AE3-208, indicating that plaque PGE(2) does not stimulate the EP(4)-receptor. We found that PGE(2) was present in plaques only at very low levels (15pg PGE(2)/mg plaque). We conclude that PGE(2) in human atherosclerotic lesions does not modulate (i.e. stimulate or inhibit) atherothrombosis in blood after plaque rupture.

Humanized Mouse Model of Thrombosis Is Predictive of the Clinical Efficacy of Antiplatelet Agents

In vivo testing of novel antiplatelet agents requires informative biomarkers. By genetically modifying mouse von Willebrand factor (VWF(R1326H)), we have developed a small animal model that supports human but not mouse platelet-mediated thrombosis. Here, we evaluate the use of this biological platform as a pharmacodynamic biomarker for antithrombotic therapies. The antithrombotic effects of several αIIbβ3 inhibitors were determined in VWF(R1326H) mutant mice infused with human platelets. Administration of abciximab, eptifibatide, or tirofiban at doses recommended for percutaneous coronary intervention (per 1 kg of body weight) significantly reduced human platelet-mediated thrombus formation in laser-injured arterioles by > 75% (P < 0.001). In contrast, clot size in wild-type control animals remained essentially unchanged (P > 0.05), results consistent with observed species differences in IC₅₀ values obtained by aggregometry. To further demonstrate that our biological platform is unique among standard mouse models, we evaluated the thrombogenic potential of platelets from healthy volunteers before and after clopidogrel therapy. Consistent with the antithrombotic effect of this agent, platelets postdrug administration formed smaller thrombi than cells before therapy and were less responsive to ADP-induced aggregation (P < 0.001). The ability of αIIbβ3 and P2Y₁₂ inhibitors to limit human platelet clot formation at doses recommended by the American College of Cardiology/American Heart Association suggests that VWF(R1326H) mutant mice can serve as both a pharmacodynamic and a functional response biomarker, attributes essential for not only expediting drug development but also designing clinical studies.

P-002 Realistic clot models with different mechanical characteristics for preclinical evaluation of endovascular recanalization devices

IntroductionEfficacy and safety of devices for the endovascular recanalization of acute ischemic stroke (AIS) are mostly validated in experimental vascular models and in vivo animal models. Efforts have been made...

Potentiating role of Gas6 and Tyro3, Axl and Mer (TAM) receptors in human and murine platelet activation and thrombus stabilization.

Interaction of murine Gas6 with the platelet Gas6 receptors Tyro3, Axl and Mer (TAM) plays an important role in arterial thrombus formation. However, a role for Gas6 in human platelet activation has been questioned. To determine the role of Gas6 in human and murine platelet activation and thrombus formation. Gas6 levels appeared to be 20-fold higher in human plasma than in platelets, suggesting a predominant role of plasma-derived Gas6. Human Gas6 synergizes with ADP-P2Y(12) by enhancing and prolonging the phosphorylation of Akt. Removal of Gas6 from plasma impaired ADP-induced platelet aggregation. Under flow conditions, absence of human Gas6 provoked gradual platelet disaggregation and integrin α(IIb) β(3) inactivation. Recombinant human Gas6 reversed the effects of Gas6 removal. In mouse blood, deficiency in Gas6 or in one of the TAM receptors led to reduced thrombus formation and increased disaggregation, which was completely antagonized by external ADP. In contrast, collagen-induced platelet responses were unchanged by the absence of Gas6 in both human and mouse systems. The ADP-P2Y(12) and Gas6-TAM activation pathways synergize to achieve persistent α(IIb) β(3) activation and platelet aggregation. We postulate a model of thrombus stabilization in which plasma Gas6, by signaling via the TAM receptors, extends and enhances the platelet-stabilizing effect of autocrine ADP, particularly when secretion becomes limited.

Carboxypeptidase U (TAFIa): a new drug target for fibrinolytic therapy?

Procarboxypeptidase U (TAFI) is a recently discovered plasma procarboxypeptidase that upon activation by thrombin or thrombin-thrombomodulin turns into a potent antifibrinolytic enzyme. Its prominent bridging function between coagulation and fibrinolysis raised the interest of many research groups and of the pharmaceutical industry. The development of carboxypeptidase U (CPU) inhibitors as profibrinolytic agents is an attractive concept and possibilities for rational drug design will become more readily available in the near future as a result of the recently published crystal structure. Numerous studies have been performed and many of them show beneficial effects of CPU inhibitors for the improvement of endogenous fibrinolysis in different animal sepsis and thrombosis models. CPU inhibitors combined with tissue-type plasminogen activator (t-PA) seem to increase the efficiency of pharmacological thrombolysis allowing lower dosing of t-PA and subsequently fewer bleeding complications. This review will focus on recently obtained in vivo data and the benefits/risks of targeting CPU for the treatment of thrombotic disorders.

In vivo clot lysis of human thrombus with intravenous abciximab immunobubbles and ultrasound

Abciximab immunobubbles have been introduced recently for ultrasonographic molecular imaging of human thrombus. This study investigates the potential of using these novel bubbles for enhancing sonothrombolysis. In particular, it addresses the question of whether ligand targeting of bubbles with abciximab improves the effectiveness of lysis with ultrasound. A partial thrombotic occlusion of the right common carotid artery of 16 rats was produced by insertion of human clot material via an external carotid artery catheter. Rats received abciximab immunobubbles, non-specific control immunobubbles or saline intravenously over 30 minutes in combination with pulsed 2 MHz ultrasound. Blood samples were taken at baseline and 5, 10, 20, 30 and 60 minutes after beginning treatment. Human D-dimer levels for quantification of thrombolysis were analysed by ELISA. Only animals treated with abciximab immunobubbles and ultrasound showed a significant increase of D-dimer levels over time (p = 0.043, linear trend p = 0.037), whereas in the other two groups, no significant increase over time was found. Overall, animals in the abciximab immunobubbles group showed higher plasma D-dimer levels than animals treated with non-specific immunobubbles (p = 0.049) and animals treated with ultrasound alone (p = 0.017). In histological sections, thrombi treated with abciximab immunobubbles and ultrasound showed clear signs of disintegration in contrast to thrombi in both control groups. 2 MHz ultrasound in combination with abciximab immunobubbles induces thrombolysis without lytic agents that is superior to insonation of non-specific immunobubbles.

Phosphatidic Acid Enhances Procoagulant Activity and Thrombosis through Phosphatidylserine Exposure in Human Erythrocytes.

The increased phospholipase D (PLD) activity and phosphatidic acid (PA) level are frequently observed in various disease states including cancers, diabetes, inflammation, sepsis, and thrombosis. While PA has been previously regarded as a precursor for lysophosphatidic acid (LPA) and diacylglycerol (DAG), increasing evidence suggests the biological activities of PA, itself. Here we demonstrated that the PA can enhance procoagulant activities in human erythrocytes and thrombus formation mediated through phosphatidylserine (PS) exposure. Conspicuously, the PS exposure by PA was substantially greater than that of LPA and we examined its mechanism of action in an effort to elucidate the biological significance of PA. In human erythrocytes, PA treatment resulted in PS exposure without microvesicle generation or hemolysis as determined by flow cytometry. These effects were not attenuated by inhibitors of phospholipase A2 and phosphatidate phosphatase, that convert PA to LPA and DAG, respectively, suggesting that PA directly induced PS exposure. PA exposed erythrocytes showed significantly high intracellular calcium level and resultant protein kinase C (PKC) a activation. Consistent with these findings, the activity of scramblase was enhanced by PA treatment, while that of flippase was inhibited. Furthermore, PA-exposed erythrocytes were aggregated, accelerated thrombin generation, and increased adherence to endothelial cells, implying PA treatment enhanced the thrombogenic activities of erythrocytes indeed. Of note, these procoagulant activations by PA were confirmed in rat in vivo venous thrombosis model. These results suggest that PA can contribute to enhanced thrombosis, mediated through PS exposure on erythrocytes. With this study, we believe a novel insight was given into the role of PA in cardiovascular diseases.

4-thio-deoxyuridylate-modified thrombin aptamer and its inhibitory effect on fibrin clot formation, platelet aggregation and thrombus growth on subendothelial matrix.

The consensus thrombin aptamer C15-mer is a single-stranded DNA of 15 nucleotides [d(GGTTGGTGTGGTTGG)] that was identified by the selection of thrombin-binding molecules from a large combinatorial library of oligonucleotides. It is capable of inhibiting thrombin at nanomolar concentrations through binding to a specific region within thrombin exosite 1. As has been shown in our earlier studies, the 4-thio-deoxyuridylate (s4dU)-containing oligonucleotides have high affinity for a number of proteins, due to the reduced hydrophilic character of the modified oligonucleotide. Three different analogs of the original thrombin-inhibiting sequence, in which some of the thymidylate residues were replaced by 4-thio-deoxyuridylates, were synthesized. The inhibitory effect of modified aptamers was tested on thrombin-catalyzed fibrin clot formation and fibrinopeptide A release from fibrinogen, thrombin-induced platelet aggregation/secretion, and the formation of thrombus on coverslips coated with human collagen type III, thrombin-treated fibrinogen or subendothelial matrix of human microvascular endothelial cells. As compared with the C15-mer, the analog with the sequence GG(s4dU)TGG(s4dU)G(s4dU)GGT(s4dU)GG (UC15-mer) showed a 2-fold increased inhibition of thrombin-catalyzed fibrin clot formation, fibrinopeptide A release, platelet aggregation and secretion in human plasma and thrombus formation on thrombin-treated fibrinogen surfaces under flow conditions. Concerning the inhibition of thrombin-induced fibrin formation from purified fibrinogen and activation of washed platelets, UC15-mer was 3-fold and twelve-fold more effective than C15-mer, respectively. The replacement of four thymidylate residues in C15-mer by 4-thio-deoxyuridylate resulted in a new thrombin aptamer with increased anticoagulant and antithrombotic properties.

Fibrin Clot Visualized by Optical Coherence Tomography

Optical coherence tomography (OCT) is a recently developed optical imaging technique that provides high-resolution (≈10 to 20 μm) cross-sectional images of vessels.1 It has been reported that OCT images of white and red thrombus were characterized as backscattering protrusions in the coronary lumen.2 However, OCT characteristics of fibrin clot composed of fibrin material and few blood cells have not been described. The coronary arteries of a 75-year-old man …

The use of the Chandler loop to examine the interaction potential of NXY‐059 on the thrombolytic properties of rtPA on human thrombi in vitro

Recombinant tissue-type plasminogen activator (rtPA) is the only globally approved treatment for acute ischaemic stroke. Other potential treatments might be administered with rtPA, making it important to discover whether compounds interfere with rtPA-induced lysis. We evaluated methods for examining the effect of the neuroprotectant NXY-059 on the lytic property of rtPA. Plasma clot formation and lysis in the presence of rtPA and NXY-059 was measured as the change in plasma turbidity. The effect of NXY-059 on rtPA-induced lysis was similarly assessed on preformed clots. Lysis of the thrombus formed in a Chandler loop measured release of fluorescent-tagged fibrinogen that had been incorporated during thrombus formation. Thrombi were exposed to both rtPA and NXY-059 throughout lysis in the presence of 80% autologous plasma and the release of label during lysis was measured. Data interpretation is limited in the clot lysis experiments because either the rtPA was present during clot formation or the drug was added to a clot formed in static conditions. In contrast, thrombi were formed in dynamic flow conditions in the Chandler loop and the time course of lysis in plasma was examined. rtPA increased thrombolysis and the antifibrinolytic trans-4-(aminomethyl) cyclohexane carboxylic acid (AMCA) inhibited lysis. Lysis induced by rtPA was unaltered by NXY-059. The Chandler loop method provides a reliable technique for examining the effect of compounds on rtPA-induced lysis in vitro and demonstrated that NXY-059 does not alter rtPA-induced lysis at clinically relevant concentrations of either drug.

Molecular Imaging of Human Thrombus With Novel Abciximab Immunobubbles and Ultrasound

Molecular imaging of therapeutic interventions with targeted agents that simultaneously carry drugs or genes for local delivery is appealing. We investigated the ability of a novel microbubble carrier (immunobubble) for abciximab, a glycoprotein IIb/IIIa receptor inhibitor, for ultrasonographic molecular imaging of human clots. Human thrombi were incubated with immunobubbles conjugated with abciximab. Control clots were incubated in either saline or with immunobubbles conjugated with nonspecific antibody. We evaluated immunobubble suspensions with variable concentrations of encapsulated gas and measured mean acoustic intensity of the incubated clots. In vivo molecular imaging of human thrombi with abciximab immunobubbles was evaluated in a rat model of carotid artery occlusion. Mean acoustic intensity was significantly higher for abciximab immunobubbles as compared with control immunobubbles under all conditions tested with maximum difference in intensity at a gas volume of 0.2 microL (P=0.0013 for mechanical index 0.05, P=0.0001 for mechanical index 0.7). Binding of abciximab immunobubbles to clots in vitro led to enhanced echogenicity dependent on bubble concentration. In vivo ultrasonic detectability of carotid thrombi was significantly higher for clots targeted with abciximab immunobubbles (P<0.05). Quantification of in vivo contrast enhancement displayed a highly significant increment for abciximab immunobubble-targeted clots compared with nonspecific immunobubble-targeted clots (P<0.0001) and to native clots (P<0.0001). This study demonstrates the feasibility of using a therapeutic agent for selective targeting in vascular imaging. Abciximab immunobubbles improve visualization of human clots both in vitro and in an in vivo model of acute arterial thrombotic occlusion.

Thrombus Formation at the Surface of Guide-Wire Models: Effects of Heparin-releasing or Heparin-exposing Surface Coatings

This study was conducted to investigate whether thrombus formation at the surface of guide wires occurs, and--if so--whether this can be suppressed or prevented through incorporation of heparin in the surface coating. Five guide wire models were examined; three had a polymeric hydrophilic surface coating (90/10 guide wire), which was either heparin-free, impregnated with sodium-heparin (Na-hep), or impregnated with benzalkonium heparin (BAK-hep). The other two guide wires had a coating of polytetrafluoroethylene (PTFE), either without heparin, or impregnated with BAK-hep. Release of heparin, exposure of heparin at the surface of the guide wires, thrombogenicity (under static and flow conditions) and their propensity to attract blood platelets were investigated. The guide wire 90/10 Na-hep releases approximately 150-200 mU active heparin per cm coil within the first few minutes after incubation in buffer. The PTFE BAK-hep shows a relatively slow release of 60-70 mU active heparin per cm coil. The 90/10 BAK-hep showed no released heparin but the most exposed heparin. In a static experiment with human full blood excessive thrombus formation occurred at the heparin-free models, whereas the others remained essentially clean. In a thrombin-generation assay under flow the authors observed strong retardation of thrombin formation in the case of the 90/10 Na-hep guide wire. The static and dynamic in vitro assays, taken together, show that the 90/10 Na-hep provides a coating with an extremely low level of surface thrombogenicity. Use of a guide wire with a hydrophilic distal coating that releases and exposes sodium heparin may contribute to the safety of diagnostic and therapeutic interventional procedures.