Biomedical subjects

Mark I Furman

Publications and source records attributed to Mark I Furman.

16 recordsLinked to original sources

PubMed2006

Current options in platelet function testing.

The variable response to antiplatelet therapy has led to the use of platelet function tests to monitor the effects of antiplatelet drugs in cardiovascular diseases. The goal is to guide antiplatelet therapy to the optimal dose for the prevention or treatment of thrombosis while minimizing hemorrhagic side effects. The bleeding time is no longer recommended for use because of its nonspecificity and lack of clinical correlations. The current de facto "gold standard" test of platelet function is turbidometric platelet aggregometry. Although this method has been successful in measuring the aggregation of platelets in a glycoprotein (GP) IIb/IIIa (integrin alpha(IIb)beta(3))-dependent manner, it has several limitations, including poor reproducibility, high sample volume, requirement for sample preparation, length of assay time, requirement for a skilled technician, and cost. Therefore, new options for platelet function testing have been developed to address these disadvantages and to meet the need for point-of-care testing that can be performed at or near a patient's bedside without requiring a high degree of technical expertise. The new tests include VerifyNow (Accumetrics, San Diego, CA); Plateletworks (Helena Laboratories, Beaumont, TX); Thrombelastograph PlateletMapping System (Haemoscope Corporation, Niles, IL); Impact cone and plate(let) analyzer (DiaMed, Cressier, Switzerland); and Platelet Function Analyzer 100 (PFA-100; Dade Behring, Newark, DE). In patients treated with antiplatelet drugs, the degree of platelet inhibition, as determined by several of these new platelet function assays, has been shown to predict major adverse cardiac events.

Cardiovascular Diseases↗

PubMed2006

Residual arachidonic acid-induced platelet activation via an adenosine diphosphate-dependent but cyclooxygenase-1- and cyclooxygenase-2-independent pathway: a 700-patient study of aspirin resistance.

BACKGROUND: Thrombotic events still occur in aspirin-treated patients with coronary artery disease. METHODS AND RESULTS: To better understand aspirin "resistance," serum thromboxane B2 (TXB2) and flow cytometric measures of arachidonic acid-induced platelet activation (before and after the ex vivo addition of aspirin and indomethacin) were analyzed in 700 consecutive aspirin-treated patients undergoing cardiac catheterization. In 680 of 682 evaluable patients, serum TXB2 concentrations were reduced compared with nonaspirinated healthy donors. Twelve patients had serum TXB2 that was lower than nonaspirinated healthy donors but >10 ng/mL. Arachidonic acid stimulated greater platelet activation in patients with high serum TXB2 (>10 ng/mL) than in patients with low serum TXB2. Addition of ex vivo aspirin reduced arachidonic acid-induced platelet activation to similar levels regardless of serum TXB2 concentrations, which suggests that patients with high residual serum TXB2 concentrations were either noncompliant or underdosed with aspirin. Among the remaining 98% of patients, ex vivo administration of either aspirin or indomethacin failed to prevent platelet activation across all degrees of arachidonic acid-induced platelet activation and aspirin doses. Although the patients were not randomized with respect to clopidogrel treatment, multivariate analysis showed that arachidonic acid-induced platelet activation was less in patients receiving clopidogrel. CONCLUSIONS: There is a residual arachidonic acid-induced platelet activation in aspirin-treated patients that (1) is caused by underdosing and/or noncompliance in only approximately 2% of patients and (2) in the remaining patients, occurs via a cyclooxygenase-1 and cyclooxygenase-2 independent pathway, in direct proportion to the degree of baseline platelet activation, and is mediated in part by adenosine diphosphate-induced platelet activation.

Adenosine Diphosphate↗

PubMed2004

Release of soluble CD40L from platelets is regulated by glycoprotein IIb/IIIa and actin polymerization.

OBJECTIVES: The purpose of this study was to examine the effects of glycoprotein (GP) IIb/IIIa antagonists (abciximab, eptifibatide, and tirofiban) and other inhibitors on translocation of CD40L from intraplatelet stores to the platelet surface and on the release of soluble CD40L (sCD40L) from platelets. BACKGROUND: CD40L is a proinflammatory and prothrombotic ligand in the tumor necrosis factor family. METHODS: Platelet surface CD40L was measured by flow cytometry, and sCD40L was measured by enzyme-linked immunosorbent assay. RESULTS: Translocation of CD40L from intraplatelet stores to the platelet surface was not inhibited by GP IIb/IIIa antagonists. However, release of sCD40L from the surface of activated platelets was inhibited by GP IIb/IIIa antagonists in a dose-dependent manner, in concert with inhibition of PAC1 binding to platelets (a surrogate marker for fibrinogen binding). Release of sCD40L from activated platelets was also markedly reduced in Glanzmann platelets (deficient in GP IIb/IIIa). Ethylenediaminetetraacetic acid was an effective inhibitor of sCD40L release, but only when added before platelet activation. Both cytochalasin D (an inhibitor of actin polymerization) and GM6001 (an inhibitor of matrix metalloproteinases [MMPs]) inhibited the release of sCD40L from platelets when added before, as well as 3 min after, platelet activation. However, neither cytochalasin D nor GM6001 affected translocation of CD40L to the platelet surface. CONCLUSIONS: The GP IIb/IIIa antagonists inhibit release of sCD40L from activated platelets. Release of sCD40L from platelets is regulated, at least in part, by GP IIb/IIIa, actin polymerization, and an MMP inhibitor-sensitive pathway. In addition to their well-characterized inhibition of platelet aggregation, GP IIb/IIIa antagonists may obviate the proinflammatory and prothrombotic effects of sCD40L.

Actin Depolymerizing Factors↗

PubMed2004

GPIIb/IIIa inhibitor-induced dethrombosis.

GPIIb/IIIa inhibitors have demonstrated clinical benefit in patients with acute coronary syndromes and in those undergoing percutaneous coronary intervention. As opposed to the well documented prevention of platelet aggregation by GPIIb/IIIa inhibitors, we here discuss the less well appreciated reversal of platelet aggregation by, and dethrombotic effects of, GPIIb/IIIa inhibitors. In vivo evidence for GPIIb/IIIa inhibitor-induced dethrombosis includes animal models of arterial thrombosis and human studies (both observational and randomized clinical trials) in the setting of acute myocardial infarction. These human studies demonstrated increased coronary perfusion prior to percutaneous coronary intervention in patients receiving GPIIb/IIIa inhibitors as compared to those patients receiving placebo. Mechanisms of GPIIb/IIIa inhibitor-induced dethrombosis include alterations in thrombus size and structure, reduced capacity for subsequent thrombus growth, inhibition of soluble CD40L release from platelets, and a direct platelet disaggregatory effect that parallels fibrinogen's interactions with GPIIb/IIIa. In summary, mechanistic studies, animal models, human observational studies and randomized clinical trials all strongly suggest that GPIIb/IIIa inhibitors have a direct dethrombotic effect in addition to their well-described preventative effects on platelet aggregation.

Animals↗

PubMed2004

Elevated leukocyte count and adverse hospital events in patients with acute coronary syndromes: findings from the Global Registry of Acute Coronary Events (GRACE).

OBJECTIVE: To examine the association between elevated leukocyte count and hospital mortality and heart failure in patients enrolled in the multinational, observational Global Registry of Acute Coronary Events (GRACE). BACKGROUND: Elevated leukocyte count is associated with adverse hospital outcomes in patients presenting with acute myocardial infarction (AMI). The association of this prognostic factor with hospital mortality and heart failure in patients with other acute coronary syndromes (ACS) is unclear. METHODS: We examined the association between admission leukocyte count and hospital mortality and heart failure in 8269 patients presenting with an ACS. This association was examined separately in patients with ST-segment elevation AMI, non-ST-segment elevation AMI, and unstable angina. Leukocyte count was divided into 4 mutually exclusive groups (Q): Q1 <6000, Q2 = 6000-9999, Q3 = 10,000-11,999, Q4 >12,000. Multiple logistic regression analysis was performed to examine the association between elevated leukocyte count and hospital events while accounting for the simultaneous effect of several potentially confounding variables. RESULTS: Increasing leukocyte count was significantly associated with hospital death (adjusted odds ratio [OR] 2.8, 95% CI 2.1-3.6 for Q4 compared to Q2 [normal range]) and heart failure (OR 2.7, 95% CI 2.2-3.4) for patients presenting with ACS. This association was seen in patients with ST-segment elevation AMI (OR for hospital death 3.2, 95% CI 2.1-4.7; OR for heart failure 2.4, 95% CI 1.8-3.3), non-ST-segment elevation AMI (OR for hospital death 1.9, 95% CI 1.2-3.0; OR for heart failure 1.7, 95% CI 1.1-2.5), or unstable angina (OR for hospital death 2.8, 95% CI 1.4-5.5; OR for heart failure 2.0, 95% CI 0.9-4.4). CONCLUSION: In men and women of all ages with the spectrum of ACS, initial leukocyte count is an independent predictor of hospital death and the development of heart failure.

Adult↗

PubMed2004

Application of flow cytometry to platelet disorders.

Flow cytometry is a powerful and versatile tool that can be used to yield definitive information regarding the phenotypic status of platelets. The method provides a quantitative assessment of the physical and antigenic properties of platelets (e.g., surface expression of receptors, bound ligands, components of granules, or interactions of platelets with other platelets, other blood cells, or components of the plasma coagulation system), thereby facilitating the diagnosis of inherited or acquired platelet disorders (e.g., Bernard-Soulier syndrome, Glanzmann thrombasthenia, storage pool disease), the pathological activation of platelets (e.g., in the setting of acute coronary syndromes, cerebrovascular ischemia, peripheral vascular disease, cardiopulmonary bypass), and changes in the ability of platelets to activate via specific stimuli (e.g., efficacy of antiplatelet therapies). Accordingly, this review summarizes the key technical and methodologic components of flow cytometric analysis of platelets, as well as specific examples of its application to diagnosis and patient care.

Blood Platelet Disorders↗

PubMed2004

The role of platelet inhibition in the drug-eluting stent era.

The use of antiplatelet agents in the management of patients undergoing percutaneous coronary interventions involves the administration of aspirin, thienopyridines, and in high-risk patients, GPIIb-IIIa antagonists. Drug-eluting stents now account for greater than 50% of stenting procedures. This review focuses on the limited available data describing the use of antiplatelet agents in patients undergoing drug-eluting stent implantation.

Aspirin↗

PubMed2003

Combined effects of mild hypothermia and glycoprotein IIb/IIIa antagonists on platelet-platelet and leukocyte-platelet aggregation.

Endovascular cooling was assessed as a potential treatment for percutaneous coronary intervention in patients with acute myocardial infarction. Here we show that mild hypothermia: (1) inhibits platelet aggregation; (2) augments eptifibatide- and tirofiban- but not abciximab-induced inhibition of platelet aggregation; (3) increases the formation of adenosine diphosphate-induced leukocyte-platelet aggregates; and (4) diminishes the glycoprotein IIb/IIIa antagonist-induced decrease in leukocyte-platelet aggregates.

Abciximab↗

PubMed2003

A novel point-of-care enoxaparin monitor for use during percutaneous coronary intervention. Results of the Evaluating Enoxaparin Clotting Times (ELECT) Study.

OBJECTIVES: The aim of this study was to discern a target range of anticoagulation for enoxaparin during percutaneous coronary intervention (PCI) as measured by the Rapidpoint ENOX (Pharmanetics Inc., Morrisville, North Carolina), a new point-of-care test. BACKGROUND: In the U.S., enoxaparin has been used in only a small proportion of PCI procedures, partly because a rapid enoxaparin-specific assay was unavailable. METHODS: We analyzed data from 445 enrolled patients receiving subcutaneous or intravenous enoxaparin in a prospective, multicenter study. Serial anticoagulation measurements and clinical outcomes were recorded. RESULTS: The in-hospital composite occurrence of death, myocardial infarction, and urgent target vessel revascularization was 5.4%, and Thrombolysis In Myocardial Infarction (TIMI) major bleeding, minor bleeding, and any reported bleeding occurred in 0.2%, 1.3%, and 7.9% of patients, respectively. No significant association between procedural ENOX times and ischemic events was observed (p = 0.222), although the event rate was 4.0% among those with ENOX times between 250 to 450 s versus 7.2% for those outside this range (p = 0.134). Increasing ENOX time at sheath removal was correlated with any bleeding (p = 0.010) with a 1% increase for every approximately 30-s rise. CONCLUSIONS: Ischemic events were infrequent, and the rate appeared lowest in the mid-range of ENOX times. Bleeding events increased with increasing ENOX times. These observations, combined with a suggested procedural anti-Xa level of 0.8 to 1.8 IU/ml, translate into a recommended ENOX time range of 250 to 450 s for PCI and <200 to 250 s for sheath removal.

Angioplasty, Balloon, Coronary↗

PubMed2003

Leukocytosis and adverse hospital outcomes after acute myocardial infarction.

An elevated white blood cell (WBC) count at the time of hospital presentation is associated with increased mortality after acute myocardial infarction (AMI). The association between WBC count and the development of clinically significant complications of AMI and death during hospitalization for AMI is, however, less clear. The objectives of this observational study were to examine the association between baseline WBC count, the development of heart failure, cardiogenic shock, and death during hospitalization for AMI from a more generalizable community-wide perspective. The study sample consisted of adult residents of all ages from the Worcester, Massachusetts, metropolitan area (1990 census estimate 437,000) hospitalized with confirmed AMI at all greater Worcester medical centers. The study population consisted of 3,796 men and 2,734 women of all ages hospitalized with validated AMI, in 12 annual periods between 1986 and 1999, aggregated into quintiles based on WBC count obtained at the time of hospital admission. In multivariable-adjusted regression analyses controlling for potentially confounding demographic and clinical factors, patients in the uppermost quintiles of WBC count were at increased risk for heart failure (odds ratio [OR] 2.77, 95% confidence interval [CI] 2.33 to 3.31), cardiogenic shock (OR 2.82, 95% CI 2.05 to 3.87), and hospital death (OR 2.14, 95% CI 1.66 to 2.76). The results of our large observational study suggest that the peripheral total leukocyte count is strongly associated with the development of heart failure, cardiogenic shock, and death during hospitalization for AMI. These findings suggest that the WBC count should be considered an important prognostic factor associated with adverse hospital outcomes in patients with AMI.

Aged↗

PubMed2003

Quantification of abciximab-induced platelet inhibition is assay dependent: a comparative study in patients undergoing percutaneous coronary intervention.

BACKGROUND: The best method for measuring the degree of platelet inhibition with glycoprotein (GP) IIb-IIIa antagonists during percutaneous coronary intervention (PCI) and the optimal degree of periprocedural inhibition is uncertain. Low molecular weight heparins have been reported to cause less platelet activation than unfractionated heparin. Therefore, compared with unfractionated heparin (UHF), a low molecular weight heparin could enhance measured platelet inhibition. In this study, we compared 3 methods of measuring platelet inhibition and investigated the effects of half doses of abciximab in combination with either UFH or the low molecular weight heparin dalteparin in patients undergoing PCI with planned abciximab administration. METHODS: Abciximab-induced platelet inhibition was measured serially by means of 3 assays: 1) GP IIb-IIIa receptor occupancy, 2) binding of the activated GP IIb-IIIa-specific monoclonal antibody PAC1, and 3) agglutination of platelets with fibrinogen-coated beads (RPFA). Forty patients were randomly allocated to receive either UFH (70 U/kg) or dalteparin (60 IU/kg), followed by a half dose of abciximab (0.125 mg/kg) administered twice at 10-minute intervals. Assays were obtained 10 minutes after each half dose of abciximab and 8 to 10 and 24 hours after abciximab administration. RESULTS: No differences between UFH and dalteparin were observed. At each time-point measured, the mean percent platelet inhibition as determined by means of the receptor occupancy assay and PAC1 binding assay was less than the degree of inhibition determined by means of the RPFA. CONCLUSIONS: The results of targeted levels of platelet inhibition cannot be extrapolated between different clinical trials of GP IIb-IIIa antagonists unless the same assay is used. Dalteparin, compared with UFH, does not enhance platelet inhibition or receptor occupancy by abciximab, as demonstrated by means of 3 separate assays.

Abciximab↗

PubMed2003

The cleaved peptide of PAR1 is a more potent stimulant of platelet-endothelial cell adhesion than is thrombin.

PURPOSE: Platelet-endothelial cell adhesion is an important pathologic response to vessel injury or inflammation. On binding to its endothelial or platelet G protein-linked seven-transmembrane domain receptor, protease-activated receptor-1 (PAR1), thrombin releases a 41-amino acid peptide (TR(1-41)). We examined the effect of TR(1-41) on platelet activation and on platelet-endothelial cell adhesion. METHODS: A monolayer of confluent human saphenous vein endothelial cells was incubated with washed human platelets. Platelets were stimulated with either TR(1-41), TR(21-41), scrambled TR(1-41), adenosine diphosphate (ADP)-epinephrine (EPI), thrombin, or thrombin receptor activating peptide (TRAP). Platelet activation was identified with flow cytometry. The magnitude of platelet-endothelial cell adhesion was determined with a laser scanning cytometer that scanned the monolayer of endothelial cells and identified fluorescently bound platelets. RESULTS: Maximal thrombin stimulation (0.1 U/mL) induced a threefold increase in platelets bound to endothelial cells compared with buffer alone. Stimulation with TR(1-41) (20 mmol/L) tripled the number of platelets bound to endothelial cells compared with thrombin. Scrambled sequence of TR(1-41) (20 mmol/L) and TR(21-41) (20 mmol/L), neither of which induces platelet activation, had minimal effect on platelet adhesion. Both TRAP (20 mmol/L) and ADP-EPI (20 mmol/L) induced less platelet-endothelial cell adhesion than did thrombin. TR(1-41)-induced platelet-endothelial cell adhesion was partially blocked by glycoprotein (GP)IIb-IIIa-specific monoclonal antibody, 10E5 (10 mg/mL). CONCLUSIONS: TR(1-41), the cleaved peptide of PAR1, is a more potent stimulant of platelet-endothelial cell adhesion than is thrombin, TRAP, or ADP-EPI, and this adhesion is at least in part mediated by the platelet GPIIb-IIIa receptor.

Cell Adhesion↗

PubMed2002

Activated clotting times in the setting of eptifibatide use during percutaneous coronary intervention.

BACKGROUND: Previous studies have demonstrated a prolongation of activated clotting times (ACT) with abciximab administration during percutaneous coronary interventions (PCI). The impact of the short acting glycoprotein (GP) IIb-IIIa inhibitor, eptifibatide, on ACT measurements has not been studied. METHODS: Seventy consecutive patients undergoing PCI in the setting of eptifibatide administration were prospectively enrolled in a single center study. Eptifibatide was administered as two 180 microg/kg boluses 10 minutes apart followed by a continuous infusion of 2.0 microg/kg/min. In 15 patients (Group I), the initial eptifibatide and heparin boluses were separated by 5 minutes, and ACT's were assessed after each bolus as well as at 3 subsequent time points. In 55 patients (Group II), an ACT level was drawn 10 minutes after the initial heparin/eptifibatide bolus and 20 minutes following the second eptifibatide bolus. Two different ACT measuring devices--CoaguChek Pro DM and Hemochron 801--were used to examine the impact of eptifibatide on ACT values. RESULTS: The devices differed in the reproducibility of their measurements, but the overall trends were consistent with both devices. The ACT value was unchanged after the initial eptifibatide bolus (with a delta of 0.6 seconds by CoaguChek Pro DM and 4.2 seconds by Hemochron). While the ACT value rose significantly after the heparin bolus, the second eptifibatide bolus did not result in any further rise in ACT values. CONCLUSIONS: Unlike abciximab, eptifibatide does not significantly prolong the ACT in patients undergoing PCI. This may have implications regarding the need for separate heparin dosing algorithms for patients undergoing PCI in the setting of different GPIIb-IIIa inhibitors.

Angioplasty, Balloon, Coronary↗

PubMed2002

The Ultegra rapid platelet-function assay: comparison to standard platelet function assays in patients undergoing percutaneous coronary intervention with abciximab therapy.

BACKGROUND: Despite the proven benefit of glycoprotein IIb/IIIa inhibitors during percutaneous coronary intervention, significant interpatient variability exists in antiplatelet response. Furthermore, a diminished degree of platelet inhibition is an independent predictor of adverse cardiac events, highlighting the need for accurate and precise monitoring of platelet function. METHODS: Patients (n = 192) who underwent elective percutaneous coronary intervention at 4 centers were enrolled. The following 3 time points were studied: 1, baseline, before abciximab bolus administration; 2, during, within 1 hour of abciximab bolus administration; and 3, post, 24 hours after abciximab bolus administration or at the time of patient discharge, whichever occurred first. The following 3 assays were compared at all time points: Ultegra rapid platelet-function assay (Ultegra RPFA), conventional turbidometric platelet aggregometry, and receptor binding assay with [125I]-abciximab. Variability in Ultegra RPFA measurements between operators was determined with performance of the assays at the point of care and in the laboratory. A sub-study of 22 patients at 1 center was performed in which the laboratory scientist performed all 3 assays in duplicate at each time point. RESULTS: Comparison with the receptor binding assay and conventional platelet aggregometry in 120 patients showed that the Ultegra RPFA correlated with aggregometry (r = 0.89) and with the receptor binding assay (r = 0.89). There was good agreement (r = 0.80) between values obtained by intended users and those obtained by laboratory scientists. Furthermore, Ultegra RPFA values had equivalent precision to the standard assays. CONCLUSION: The Ultegra RPFA has equivalent accuracy and precision when compared with the 2 reference assays studied. Ultegra RPFA measurements are not operator-dependent and are not influenced by concomitant medications, hematologic parameters, or demographics.

Abciximab↗

PubMed2002

An additional mechanism of action of abciximab: dispersal of newly formed platelet aggregates.

BACKGROUND: The ability of abciximab to prevent fibrinogen binding to activated platelets indicates it may also promote dissolution of platelet-rich thrombi. The present study examined the capacity of abciximab to reverse platelet aggregation in vitro. METHODS AND RESULTS: Experiments were performed on blood from healthy non-medicated donors. Platelet aggregate formation and disaggregation were monitored turbidimetrically. Platelet-bound fibrinogen was measured by flow cytometry. For disaggregation studies, platelets were first stimulated with either ADP or the 11-mer thrombin receptor activating peptide (TRAP), then varying amounts of abciximab were added at periodic intervals after agonist addition. Platelet disaggregation was detected by comparing the extent of light transmittance at 4 min after addition of either abciximab or saline to PRP. ATP release was simultaneously monitored by chemi-luminescence. When added 1 min after low concentrations of ADP, abciximab rapidly (< 1 min) dispersed platelet aggregates in a dose-dependent manner, with complete disaggregation observed with 6.25 microg/mL of the beta3 antagonist. In contrast, equivalent concentrations of abciximab did not induce appreciable disaggregation to platelets stimulated with TRAP (10 microM). Platelet counts of samples that had undergone complete disaggregation, as assessed by aggregometry, were equivalent to baseline, indicating dispersal of aggregates to single cells. Concentrations of abciximab that produced complete disaggregation induced partial displacement of platelet-bound fibrinogen (52 +/- 8% inhibition of fibrinogen binding at 12.5 microg/ml abciximab). The disaggregation effectiveness of abciximab decreased as the time between ADP and subsequent abciximab addition widened, and as the amount of both dense granule release and agonist stimulation increased. However, pre-treatment of platelets with acetylsalicylic acid (ASA) did not potentiate platelet disaggregation induced by abciximab. CONCLUSIONS: These data indicate that abciximab facilitates the dispersal of newly formed platelet aggregates in vitro, by partially displacing fibrinogen from activated GPIIb/IIIa receptors. In vivo, abciximab may destabilize coronary thrombi by preventing aggregate formation and dispersing mural thrombi.

Abciximab↗

PubMed2002

Platelet-monocyte aggregates in patients with chronic venous insufficiency remain elevated following correction of reflux.

INTRODUCTION: An increased number of circulating platelet-monocyte aggregates (PMAs) is present in patients with all clinical classes of chronic venous insufficiency (CVI). The purpose of this study was to determine whether patients with CVI maintain elevated levels of PMAs following complete surgical correction of chronic venous insufficiency. METHODS: Patients with superficial venous insufficiency and a normal deep venous system documented by duplex scan were included in the study. Venous blood was drawn from a superficial vein in the leg and an antecubital vein prior to vein stripping and again six weeks postoperatively. Control subjects without evidence of venous disease had blood drawn from an antecubital vein. Whole blood flow cytometry was used to analyze the samples for the presence of platelet-monocyte aggregates following incubation with buffer or 0.5 microM adenosine diphosphate (ADP). RESULTS: Postoperative duplex scanning demonstrated elimination of venous reflux in the superficial venous system and normal deep vein physiology in all nine patients. Preoperatively, patients with CVI had significantly elevated levels of circulating PMAs in both arm and leg samples without stimulation by an agonist compared to controls (15.2+/-1.1 and 14.3+/-1.3 vs 7.4+/-0.3 for controls, p<0.02 for each), and after stimulation by 0.5 microM ADP (33.7+/-4.7 and 34.3+/-5.2 vs 12.5+/-3.8 for controls, p<0.04 for each). There was no significant change in the number of PMAs in either patient arm or leg blood samples six weeks following correction of venous reflux by removal of the diseased veins. CONCLUSIONS: Complete correction of chronic venous insufficiency did not diminish the elevated circulating levels of platelet-monocyte aggregates. We conclude that the presence of an increased number of PMAs identified in patients with CVI is not secondary to the presence of venous reflux, but may be involved with the primary etiology of chronic venous insufficiency. This finding also suggests that a stimulus other than venous hypertension may be important in triggering the leukocyte activation seen in patients with chronic venous disease.

Adult↗