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Platelet inhibition after moderate alcohol consumption in patients with ischaemic heart disease may contribute to reducing the risk for developing acute coronary syndromes. However, the mechanism by which ethanol affects platelets is not clarified. We sought to determine the in vitro effects of alcohol on the surface expression of human platelet receptors using whole blood flow cytometry. Blood samples from 10 healthy volunteers were incubated for 30 min with 25 and 50 mmol l(-1) of phosphate buffered saline diluted grain ethanol, concentrations often used in in vitro studies. The surface expression of platelet receptors was determined by flow cytometry after fixation with 2% paraformaldehyde using the following monoclonal antibodies: CD 41 (GP IIb/IIIa), CD 42b (GP Ib), CD 62p (P-selectin), CD 51/CD 61 (vitronectin receptor), CD 31 (PECAM-1), CD 107a (LAMP-1), CD 107b (LAMP-2), CD 63 (LIMP, LAMP-3) and CD 151 (PETA-3). Dose-dependent inhibition of GP IIb/IIIa, P-selectin, CD 63 and CD 107a receptor expression was observed in the ethanol-treated whole blood samples. This study for the first time establishes a direct effect of ethanol on selective major platelet receptors. Beneficial cardiovascular properties of moderate alcohol consumption may be explained by ethanol's antiplatelet action.

Data from small studies have suggested the presence of platelet abnormalities in patients with congestive heart failure (CHF). We sought to characterize the diagnostic utility of different platelet parameters and platelet-endothelial biomarkers in a random outpatient CHF population investigated in the EPCOT ('Whole Blood Impedance Aggregometry for the Assessment of Platelet Function in Patients with Congestive Heart Failure') Trial. Blood samples were obtained for measurement of platelet contractile force (PCF), whole blood aggregation, shear-induced closure time, expression of glycoprotein (GP) IIb/IIIa, and P-selectin in 100 consecutive patients with CHF. Substantial interindividual variability of platelet characteristics exists in patients with CHF. There were no statistically significant differences when patients were grouped according to incidence of vascular events, emergency revascularization needs, survival, or etiology of heart failure. Aspirin use did not affect instrument readings either. PCF correlates very poorly with whole blood aggregometry (r(2) = 0.023), closure time (r(2) = 0.028), platelet GP IIb/IIIa (r(2) = 0.0028), and P-selectin (r(2) = 0.002) expression. Furthermore, there was no correlation with brain natriuretic peptide concentrations, a marker of severity and prognosis in heart failure reflecting the neurohumoral status. Patients with heart failure enrolled in the EPCOT Trial exhibited a marginal, sometimes oppositely directed change in platelet function, challenging the diagnostic utility of these platelet parameters and biomarkers to serve as useful tools for the identification of platelet abnormalities, for predicting clinical outcomes, or for monitoring antiplatelet strategies in this population. The usefulness of these measurements for assessing platelets in the different clinical settings remains to be explored. Taken together, opposite to our expectations, major clinical characteristics of heart failure did not correlate well with the platelet characteristics investigated in this study., (Copyright 2002 S. Karger AG, Basel)

Background: Platelets play an important role in the natural history of coronary artery disease. Enhanced platelet aggregation and receptor expression unquestionably occur after coronary stent implantation; however, the functional characteristics of platelets before stenting have not been fully elucidated., Methods: Platelets were assessed before intervention by platelet-rich plasma aggregation (PA) with 5 mmol adenosine diphosphate (ADP) and 1 mg/mL collagen; whole blood aggregation (WBA) by 1 mg/mL collagen; shear-induced closure time (CT); contractile force (CF); and expression of 9 surface receptors by flow cytometry in 126 patients undergoing elective coronary artery stent placement. All patients received aspirin for at least 7 days. The data were compared with those from 64 healthy volunteers., Results: Each test revealed sustained platelet activation in patients undergoing coronary stenting compared with control values. These differences were significant for collagen-induced PA (P =.031); CF (P =.0001); expression of glycoprotein (GP) IIb/IIIa (P =.0001); P-selectin (P =.0008); platelet/endothelial cell adhesion molecule (PECAM)-1 (P =.0001); CD107a (P =.0001); CD107b (P =.0004); and CD63 (P =.009)., Conclusion: Platelets are indeed activated before coronary stenting despite antecedent therapy with aspirin.

Recently, clinical depression has been identified as an independent risk factor for increased mortality in patients following acute coronary events. Although the underlying mechanisms of this link remain uncertain, increased platelet activity has been suggested but never proven as the mechanism responsible for this association. Sertraline hydrochloride is a selective serotonin reuptake inhibitor (SSRI), and is an effective antidepressant agent. Its major liver metabolite, N-desmethylsertraline (NDMS), is known to be neurologically inactive. We assessed the in vitro effects of escalating concentrations of sertraline and NDMS on human platelets by aggregometry in plasma and whole blood, by expression of major surface receptors with flow cytometry in washed cells and in the whole blood, and quantitatively by various platelet function analysers in healthy volunteers and patients with coronary artery disease. Pretreatment of blood samples with sertraline and NDMS resulted in a dose-dependent inhibition of platelet-rich plasma aggregation induced by 5 microM ADP (P =, 0.002), by 10 microM ADP (P = 0.0017), by collagen (P = 0.008), and by thrombin (P = 0.026). Whole blood platelet aggregability was also significantly reduced when induced by 20 microM ADP (P = 0.006), and by collagen (P = 0.01). Surface expression of CD9 (P = 0.004), GP Ib (P = 0.0001), GP IIb/IIIa (P = 0.007), VLA-2 (P = 0.01), P-selectin (P = 0.02), and PECAM-1 (P = 0.01), but not the vitronectin receptor, was also reduced in sertraline and NDMS pretreated washed platelets. Whole blood flow cytometry revealed significant inhibition of GP IIb/IIIa (P = 0.008), and P-selectin expression (P = 0.0001) in NDMS treated samples. Closure time was delayed for the collagen-ADP cartridge (P = 0.009), and for the collagen-epinephrin cartridge (P = 0.01), indicating platelet inhibition in whole blood under high shear conditions. Rapid platelet-function assay revealed a decreased (P = 0.002) ability of platelets to agglutinate fibrinogen-coated beads, suggesting GP IIb/IIIa inhibition. Both sertraline, and its neurologically inactive metabolite NDMS, exhibited significant dose-dependent inhibition of human platelets. The documented anti-platelet effects of sertraline and NDMS may be directly related to the mortality benefits of SSRIs after ischemic events including myocardial infarction and stroke., (Copyright 2001 Academic Press.)

Background: Myocardial injury and platelet activation play important roles in the pathogenesis of unstable coronary syndromes. We sought to determine whether the combined measurement of platelet and necrosis markers would improve risk stratification, and yield higher diagnostic utility in patients presenting to the emergency department with chest pain., Methods and Results: Platelet and soluble P-selectin together with myoglobin, creatine kinase, CK-MB fraction, and troponin I were measured from the autologous samples in 122 consecutive patients. Statistical analysis revealed strong Spearman correlation coefficients (0.141--0.412; p<0.001) between platelet expression of P-selectin and plasma levels of necrosis markers. Platelet P-selectin and necrosis markers were independent predictors (c-index>0.7) for acute myocardial infarction, while plasma P-selectin exhibited random distribution. Elevated soluble P-selectin and myoglobin were the most valuable in identifying patients with congestive heart failure. None of the markers were useful for triaging chest pain patients with unstable angina. Analysis of incremental gains (Chi-squares) reveals that with respect to platelet P-selectin, myoglobin adds 50 % to AMI diagnostic value, and creatine kinase yields an additional 20 % in triaging these patients. The diagnostic value of soluble P-selectin is substantially (72 %) increased by myoglobin measurements, and enhanced even further (44 %) by adding cardiac troponin I for identifying heart failure patients among the chest pain population., Conclusion: Simultaneous determination of platelet and necrosis markers improve the early diagnosis of acute myocardial infarction and congestive heart failure among patients with chest pain presenting into the Emergency Department. Well controlled clinical trials are needed to prove the advantage of combining platelet and necrosis data over presently used techniques in emergency medicine.

Background: Data from small studies have shown the presence of platelet abnormalities in patients with congestive heart failure (CHF). We sought to characterize the diagnostic utility of platelet function analyzer (PFA-100) in the CHF population., Methods: Blood samples were obtained for measurement of adenosine diphosphate (ADP)/collagen and epinephrine/collagen shear-induced closure time (CT), whole blood aggregation, platelet contractile force, activity of glycoprotein (GP) IIb/IIIa, and P-selectin receptors in 100 consecutive outpatients with CHF., Results: Substantial interindividual variability of platelet characteristics exists in patients with CHF. There were no statistically significant differences when patients were divided by the incidence of vascular events, emergency revascularization needs, survival, or etiology of heart failure. Aspirin use did not affect instrument readings as well. CT correlates well with whole blood aggregometry (r(2)=.587) and less with GP IIb/IIIa activity (r(2)=.326). No correlation has been observed for the CT with the platelet-bound P-selectin (r(2)=.041) and platelet contractile force measures (r(2)=.028)., Conclusions: PFA-100 is indeed capable to serve as a platelet analyzer and may be successfully used as a screening device. However, patients with heart failure enrolled in the EPCOT trial exhibited a marginal, sometimes oppositely directed changes in the platelet function, challenging the diagnostic utility of PFA-100 to serve as a useful tool for the identification of platelet abnormalities, predicting clinical outcomes, or for the monitoring of antiplatelet strategies in this population.

Pre- and post-treatment platelet and soluble P-selectin were measured in a group of patients enrolled in the GUSTO-III study and were correlated with clinical outcomes. A peak in soluble P-selectin levels at 3 hours after thrombolytic therapy and lower baseline platelet P-selectin were associated with successful thrombolysis.

Fibrinolytic therapy is the established treatment for the management of patients with ST elevation acute myocardial infarction (AMI). Present fibrinolytic regimens have a number of shortcomings, including the failure to produce early and sustained reperfusion, as well as failure to prevent reocclusion in at least some patients. Platelets play an important role in coronary thrombosis responsible for AMI. The effect of coronary fibrinolysis on platelets has been extensively debated in the literature with evidence of both platelet activation and inhibition. Among fibrinolytic agents, tissue plasminogen activator (t-PA) is considered to be the mainstay in the treatment of coronary artery disease. The native t-PA molecule has been modified in an attempt to achieve improved lytic characteristics with less risk of bleeding. The result is a group of mutant t-PA variants considered third-generation plasminogen activators. TNK-t-PA is one bioengineered variant of t-PA. Another third-generation plasminogen activator is reteplase (r-PA). Like TNK-t-PA, it is a variant of t-PA that has been developed to establish a more rapid, complete, and stable coronary artery patency, thus promising reduced mortality. Both r-PA and TNK-t-PA are effective when given as bolus therapy. This feature may facilitate more rapid treatment as well as decrease overall costs of treatment. New fibrinolytic regimens include potent antiplatelet agents that may improve sustained reperfusion. This review summarizes the latest and often confusing data on the interaction between fibrinolytic therapy and platelets in certain in vitro, animal and clinical scenarios., (Copyright 2001 S. Karger AG, Basel)

Major depression is a common comorbidity associated with ischemic heart disease (IHD). There is growing evidence that psychological stress in general and depression in particular predispose to cardiovascular disease. Persons who have mental stress during daily life are at twice the risk of myocardial ischemia, and patients with post-myocardial infarction depression have higher mortality rates than nondepressed controls. These data suggest a psychophysiologic mechanism underlying the vulnerability of depressed patients to IHD. Clinical studies have demonstrated that depression is associated with a much higher risk of both cardiovascular morbidity and mortality, which could be caused by platelet activation. Physicians should maintain a heightened level of clinical suspicion for depression and depressive disorders in persons with IHD, particularly those individuals who are recovering from an acute ischemic event, such as myocardial infarction. Furthermore, depression may complicate the recovery of IHD, but in most cases depression can be effectively treated with antidepressant agents.

In patients with coronary artery disease (CAD), azithromycin therapy is associated with decreased cytokine levels and overall reduction of inflammation. Chlamydia pneumoniae (C.Pn) is a common pathogen that may be an important factor in the development and progression of atherosclerosis. Cell-adhesion molecules have an important role in recruitment of inflammatory cells during plaque development and are expressed by endothelial cells on activation. We sought to define the effect of treatment with azithromycin on circulating levels of soluble vascular cell-adhesion molecule (VCAM-I), intercellular adhesion molecule (ICAM-1), and E-selectin in patients with CAD. Plasma concentrations of VCAM-1, ICAM-1, and E-selectin were measured in 40 patients with documented CAD and a positive (> or = 1:16) immunoglobulin G (IgG) titer against C.Pn, 20 subjects with normal coronary arteries, and 14 healthy volunteers. Patients were assigned randomly to receive either 500 mg/wk of azithromycin or placebo for 3 months. Serum samples were obtained at baseline, at 3 months, and during the follow-up visit at 6 months. Patients with documented CAD exhibited elevation of VCAM-1 (535 +/- 227 ng/ ml; p = 0.0001) and E-selectin (69 +/- 29 ng/ml; p = 0.006), but not ICAM-1 (321 +/- 65 ng/ml) concentrations as compared with the patients with angiographically proven normal coronary arteries (252 +/- 80; 50 +/- 22; and 311 +/- 40 ng/ml) and healthy controls (110 +/- 18; 29 +/- 2; and 238 +/- 47 ng/ml, respectively). Prolonged treatment with azithromycin did not significantly affect the plasma levels of soluble VCAM-1, ICAM-1, and E-selectin. Soluble markers of endothelial activation are markedly increased in patients with documented CAD as compared with those with normal coronary arteries and healthy controls. Despite substantial heterogeneity in plasma E-selectin, ICAM-1, and VCAM-1 levels, long-term azithromycin treatment did not affect plasma levels of these adhesion molecules, indicative of endothelial activation, over a period of 6 months.

Osteonectin is a phosphoglycoprotein exclusively located in bone and platelet alpha-granules. Human platelet-derived osteonectin is released into plasma after thrombin-induced activation. Recognizing the unique distribution of the osteonectin pool, we first sought to investigate whether osteonectin could serve as a sensitive marker of platelet activity, and identify patients with acute myocardial infarction (AMI). The second objective was to define the effects of thrombolytic therapy in these patients on the plasma concentrations of osteonectin at prespecified time points following attempted reperfusion. Osteonectin levels by ELISA were determined in AMI patients before thrombolysis and at 3, 6, 12, and 24 hours thereafter and compared with 12 healthy controls. At baseline, soluble osteonectin plasma levels were similar between controls (447. 7+/-20.6 ng/ml) and AMI patients (425.7+/-43.3 ng/mL; p=NS). A significant increase of the soluble osteonectin was observed at 3 hours after thrombolysis (519.4+/-26.9 ng/mL; p=0.03), and was followed by a decrease to baseline levels at 6 hours after attempted reperfusion. Contrary to expectations, the plasma osteonectin level in our pilot study was not a sensitive marker distinguishing patients with AMI. The early peak of soluble osteonectin at 3 hours after thrombolytic therapy is most likely not related to coronary thrombolysis per se but rather to the phasic changes of platelet activity during myocardial ischemia-reperfusion. The unquestionable platelet origin of this protein and the lack of elevated plasma levels of this alpha-granule constituent, challenge the postulate of uniform platelet activation in AMI patients.

Thrombin plays a central role in thrombogenesis: it activates platelets, converts fibrinogen to fibrin, and activates factor XIII, which then crosslinks and stabilizes the fibrin clot. In addition, thrombin amplifies coagulation by activating factors VIII and V, key cofactors in the generation of activated factor X and thrombin, respectively. Even platelet function is influenced by thrombin. Hence, thrombin generation is most important both in the chronic progression of coronary atherosclerotic disease and in its conversion to acute events. To date, various therapeutic approaches capitalize on this knowledge by targeting specific thrombin-related pathways. Among the successful and carefully documented pharmacologic strategies in acute or chronic coronary heart disease are the use of unfractioned heparin, low-molecular-weight heparin, thrombolysis, hirudin, and/or inhibition of thrombin generation by glycoprotein IIb/IIIa antagonists, most often utilized on top of antiplatelet therapy (e.g., with acetylsalicylic acid) and/or vitamin K antagonism. The present review provides insights into the pathophysiology of thrombin generation in coronary atherosclerosis and gives an overview over the above mentioned therapeutic thrombin modifications.

It has been reported that platelet expression and plasma levels of soluble P-selectin are increased in patients with unstable coronary artery syndromes. However, the origin of soluble P-selectin remains unknown. We sought to determine whether platelet expression of P-selectin correlates with plasma levels in the population of patients presenting to the emergency department with chest pain. In 338 patients presenting with chest pain to the emergency departments of three different hospitals, simultaneous soluble and platelet P-selection levels were determined using enzyme-linked immunosorbent assay (ELISA) and whole blood flow cytometry, respectively. Using regression analysis no correlation (R(2)=0.055) was found between soluble and platelet-bound P-selectin for the study population, including those patients with noncardiac chest pain (R(2)=0.019), unstable angina (R(2)=0.007), acute myocardial infraction (R(2)=0.033), congestive heart failure (R(2)=0.231), and gastrointestinal illness (R(2)=0.020). The platelet expression of P-selectin is unrelated to the level found in plasma in patients with acute chest pain, irrespective of the etiology of chest pain. Dissociation between platelet and soluble P-selectin suggests that the soluble form cannot serve as a surrogate marker to indicate platelet activation in the chest pain population.

Knowledge of the pathogenesis of congestive heart failure (CHF) has improved greatly in recent years. However, this disease continues to cause one of the highest morbidities and mortalities in the Western world. The pathophysiology of heart failure is complex and much of our understanding revolves strictly around the neurohormonal mechanisms involved. Various pharmacologic interventions have significantly improved morbidity and include ACE inhibitors, beta-blockers, diuretics, and inotropic agents. Yet, no consensus has been reached regarding the use of anticoagulants or antiplatelet agents. It has been suggested that CHF is associated with altered hemostasis, but whether this prothrombotic state contributes to the pathogenesis and progression of the disease is unknown. The purpose of this review article is to discuss our current knowledge of platelet activation, thrombin generation, fibrinolysis, and endothelial dysfunction in CHF patients, and the potential role of anticoagulants and/or antiplatelet agents in preventing these hemostatic abnormalities.

Moderate alcohol consumption (MAC) and platelet inhibition have been independently associated with a reduced risk for the development of acute myocardial infarction (AMI). The effects of MAC on the initial platelet status in patients presenting with AMI are not elucidated. Here we sought to define the effects of MAC on platelet characteristics in AMI patients before applying any reperfusion strategies. The study was designed as an analysis within the cohort study in 23 patients with AMI enrolled in the GUSTO-III. Platelets were investigated by different techniques, including aggregometry, flow cytometry, and ELISA. MAC patients exhibited mild, but consistent, inhibition of platelet aggregability, surface receptor expression, and released substances as compared to non-alcohol consuming patients. These differences were significant for 5 microM ADP (p = 0.04), 10 microM ADP-induced aggregation (p = 0.02); P-selectin (p = 0.01), and PECAM-1 (p = 0.02) platelet-bound expression. Our study confirms that moderate alcohol consumption is associated with diminished platelet activation in patients presenting with AMI. The ability of MAC to favorably modulate the pre-reperfusion platelet status in such patients is of clinical importance, and further investigation in large-scale clinical trials seem warranted.

Background: It has been reported that selectins participate in the pathogenesis of acute coronary syndromes by modulating platelet-leukocyte-endothelium interactions. Elevated P-selectin level also has been observed in the clinical setting of myocardial ischemia and reperfusion; however, its utility in differentiating cardiac from noncardiac origins of chest pain is unknown., Methods and Results: Soluble and platelet fractions of P-selectin were measured for 122 patients with chest pain and 14 healthy persons acting as controls. Patients with a cardiac problem (unstable angina, congestive heart failure, acute myocardial infarction) had significantly elevated levels of soluble P-selectin (156.0 +/- 58.8 ng/mL, P =.002) and platelet-bound P-selectin (11.7% +/- 6.4% positive cells, P =.013) compared with the P-selectin profile among controls (102.6 +/- 29.0 ng/mL, 4.1% +/- 1.2% positivity) and among patients with noncardiac chest pain (114.7 +/- 36.6 ng/mL, 5.7% +/- 2.9% positivity). With a cutpoint of 10% positivity for membrane and 120 ng/mL for soluble P-selectin, the sensitivities were 0.442 and 0. 558, and the specificities were 0.915 and 0.553., Conclusions: When a patient arrives in the emergency department, measurement of membrane P-selectin may serve as an additional diagnostic tool to detect heightened platelet activity, which is most prevalent among patients with a cardiac origin of chest pain. However, low sensitivity limits the utility of the P-selectin profile alone in suitably differentiating acute coronary syndromes within the overall population of patients with chest pain.

The early identification of patients with heightened platelet activity for aggressive antiplatelet regimens represents a critical clinical issue in acute myocardial infarction (AMI) therapy. We sought to determine whether the degree of pre-reperfusion platelet function is related to subsequent activity following thrombolysis. Platelets were investigated at baseline and at 24 h following thrombolytic therapy by aggregometry, and flow cytometry in 19 AMI patients enrolled in the GUSTO-III trial. Regression analysis revealed a significant correlation for 5 microM ADP (r2 = 0.529), 10 microM ADP (r2 = 0.445), thrombin (r2 = 0.226), collagen (r2 = 0.568), and ristocetin-induced aggregation (r2 = 0.964). Platelet expression linearly correlated for GPIIb/IIIa (r2 = 0.337), P-selectin (r = 0.817), PECAM-1 (r2 = 0.586), and the vitronectin receptor (r2 = 0.634). The data suggest that the baseline characteristics predict future platelet activity, and may prospectively identify patients who will benefit most from antiplatelet strategies after coronary thrombolysis.

It has been shown that endothelial cell adhesion molecules play an important role in the development of coronary atherosclerosis and inflammatory disease. We sought to test whether soluble vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1) and E-selectin are increased in patients with documented coronary artery disease (CAD). Plasma levels of VCAM-1, ICAM-1 and E-selectin were measured in 40 patients with documented CAD, 20 subjects with angiographically documented normal coronary arteries, and 14 healthy volunteers. Patients with documented CAD exhibited significant elevation of VCAM-1 (535 +/- 227.1 ng/ml, p = 0.0001), E-selectin (69.4 +/- 29.4 ng/ml, p = 0.006), but not ICAM-1 (320.5 +/- 65.1 ng/ml, p = 0.9) concentrations as compared to subjects with normal coronary arteries (252.3 +/- 79.8, 49.7 +/- 22.0 and 311.4 +/- 40.2 ng/ml), and healthy controls (110.0 +/- 17.7, 29.0 +/- 2.0 and 237.5 +/- 46.5 ng/ml), respectively. Soluble markers of endothelial injury are not uniformly increased in patients with documented CAD as compared to those with normal coronary arteries and healthy controls. However, VCAM-1 and E-selectin, but not ICAM-1 could identify endothelial injury in such patients., (Copyright 2000 S. Karger AG, Basel)

Each year, at least 5 million patients in the United States present to hospital emergency departments with the complaint of chest pain, and more than 10% of them will be diagnosed with acute myocardial infarction. One of the foremost tasks of the emergency department physician is to avoid unnecessary admissions and concomitantly to minimize the number of patients discharged home inappropriately. Currently available diagnostic tools, including the electrocardiogram and myocardial markers, have several shortcomings, including low specificity, and delayed sensitivity for the timely detection of myocardial necrosis. Therefore, the search for better methods of rapidly identifying patients with unstable coronary syndromes is one of the utmost priorities of modern emergency medicine. Available biochemical diagnostic tools are discussed in this review, focusing on the potential benefits of combining myocardial necrosis markers with indicators of platelet activation. It is hypothesized that such a combined approach may be more powerful in myocardial infarction risk stratification than separate marker determination., (Copyright 2000 S. Karger AG, Basel)

Surface expression of P-selectin is known to be a marker of platelet activation in patients with acute coronary syndromes. However, direct comparisons of flow cytometer data may be obscured by differences in methodology, artifactual platelet activation during washing procedures, choice of antibodies, absence of control measurements, and possible observer bias due to unblinded data collection. We sought to test the hypothesis that the model of flow cytometer represents another variable affecting P-selectin measurements. Platelet P-selectin in whole blood was measured by FACScan (Becton Dickinson, Inc., San Diego, CA, USA) or EPICS XL (Coulter Corporation, Hialeah, FL, USA) flow cytometry in 338 patients presenting with chest pain to the emergency departments of three community hospitals as part of a multicenter diagnostic trial. Platelet expression of P-selectin (% of cell positivity) was consistently higher for each discharge diagnosis when measured with FACScan flow cytometer (13.2+/-4.1 for myocardial infarction, 10.0+/-3.6 for unstable angina, 9.9+/-3.5 for heart failure, 4.7+/-0.1 for gastrointestinal illness, and 6.3+/-0.7 for patients with noncardiac chest pain) when compared with results obtained from the EPICS XL instrument (2.4+/-0.2, 2.5+/-0.2, 2.5+/-0.1, 1.8+/-0.1, and 2.3+/-0.1 respectively, p=0.0001 for all groups). This study reveals marked discrepancies in the level of platelet P-selectin measurement based exclusively on the model of flow cytometer used. If P-selectin is to become a diagnostic tool for differentiating an etiology of chest pain, standardized measurements must be defined for each model of flow cytometer.

Myocardial stunning is characterized by transient contractile dysfunction occurring subsequent to an episode of ischemia followed by reperfusion. Platelet activation and hemostatic abnormalities have been described in patients with unstable angina and acute myocardial infarction, however, their role in the pathogenesis of myocardial stunning is unknown. The purpose of this study was to determine if platelet aggregation and certain hemostatic factors change during myocardial stunning following brief coronary arterial occlusion. Nine Yorkshire swine underwent left anterior descending coronary artery occlusion for 8 minutes followed by 90 minutes of reperfusion. Blood samples were obtained at baseline, at 4 and 8 minutes of occlusion, and at 60 and 90 minutes of reperfusion. Platelet aggregability and concentrations of antithrombin III, protein C, protein S, fibronectin, endothelin 1, and the stable metabolites of thromboxane (TxB2) and prostacyclin (6-keto-PGF1a) were measured in systemic circulation. The occlusion phase was associated with a decline of endothelin 1 (-13.6%), and TxB2 (-19.6%), and elevation of antithrombin III (+40.2%) and protein C (+22.9%). Mild myocardial stunning was associated with a significant increase in platelet aggregation (+33.7%), endothelin-1 (+24.7%), 6-keto-PGF1a (+41.5%), TxB2 (+11.9%), and protein C (+42.3%) during the reperfusion phase. There were no changes in plasma fibronectin and total protein S. Thus, mild myocardial stunning following brief coronary artery occlusion is associated with substantial dynamic changes in platelet aggregability and certain hemostatic factors. These results may be relevant to understanding the mechanisms determining myocardial stunning and coronary arterial patency following reperfusion.

Background: Platelet-endothelial interactions modulated by adhesion molecules, may play an important role in the pathogenesis of congestive heart failure (CHF). Soluble levels of these molecules and platelet-derived substances are reportedly elevated in patients with CHF. However, no data are available on the plasma levels of Platelet/Endothelial Cell Adhesion Molecule-1 (PECAM-1), and platelet-derived osteonectin in this growing population., Methods and Results: Soluble levels by ELISA were prospectively determined in patients with severe CHF (n = 37) and correlated to etiology and antecedent aspirin use, and compared with 14 healthy control subjects. Left ventricular dysfunction was attributed to idiopathic dilated cardiomyopathy in 18 and coronary artery disease in 19 patients. Twenty-one patients were aspirin-free and 16 patients were using aspirin (81-500 mg daily). Elevated soluble PECAM-1 (51.31+/-2.44 ng/ml, P = 0.0001), and osteonectin (826.27+/-22.37 ng/ml, P = 0.0001) were observed in patients with CHF, as compared to healthy controls (32.56+/-1.21 ng/ml, and 478.02+/-31.32 ng/ml, respectively). Neither etiology of CHF, nor antecedent aspirin therapy significantly affects the levels of PECAM-1 or osteonectin., Conclusions: Despite long-term aspirin therapy and independently of the etiology of the disease, soluble PECAM-1 and osteonectin were elevated in the majority of patients with severe CHF, suggesting platelet-endothelial activation. The present data provide additional evidence that more potent anti-platelet and endothelial preservation regimens deserve further study in the heart failure population.

Ticlopidine has become an established therapy in patients with stroke, and during stenting in patients with coronary artery disease. Clopidogrel, another thienopyridine, is a safe and promising alternative, that irreversibly inhibits ADP-induced platelet aggregation, and reduces formation of both arterial and venous thrombi. In a recent, large, well-controlled trial (CAPRIE), clopidogrel has been shown to be superior to aspirin in terms of prevention of ischaemic stroke, myocardial infarction and death in patients with atherosclerotic vascular disease. Clopidogrel provides a safe opportunity to enhance reperfusion when administered during stent placement, by protecting platelets from excessive activation. However, the ability of clopidogrel to be superior to ticlopidine in terms of its antiplatelet properties in the clinical setting of coronary stenting, is unknown. The effects of clopidogrel versus ticlopidine on platelet and endothelial function are yet to be determined and may strongly affect the outcome, benefits, and complications following coronary stent placement. Further clinical trials, well-designed, and carefully conducted, should elucidate possible benefits of clopidogrel during coronary interventions, especially in conjunction with new and aggressive reperfusion techniques. The benefits of clopidogrel in an expanding array of clinical conditions, including myocardial infarction, may be directly related to platelet inhibition. Moreover, marginal clinical benefits, and recently reported severe bleeding events in some patients after oral platelet glycoprotein IIb/IIIa therapy, may advance clopidogrel as a safe, and efficient alternative during coronary interventions. This review summarises the latest, and often confusing data on the effects of thienopyridines on certain haemostatic characteristics in interventional cardiology. 1999 Academic Press., (Copyright 1999 Academic Press.)

The role of prostanoids in patients with ischemic heart disease including acute myocardial infarction (AMI) has been recognized. However, there is very limited knowledge of the baseline TXB2 and 6-keto-PGF1a plasma levels in patients with AMI before therapy has been administered. We compared plasma levels of TXB2 and 6-keto-PGF1a by enzyme immunoassay in 18 AMI patients before thrombolysis, with those of 13 healthy controls. Plasma levels of TXB2 (319.78+/-16.50 pg/ml) and 6-keto-PGF1a (536.72+/-56.71 pg/ml) were heterogeneous, but significantly higher in the AMI patients than in controls (175.92+/-17.29 pg/ml and 192.08+/-26.11 pg/ml, respectively). In some patients, long-term aspirin therapy mildly inhibits baseline prostanoid levels, however, limited data prevents us from further speculations on this issue. Although, the contributions by prostanoids to the pathogenesis of AMI have been well proposed, their plasma concentrations are not uniformly elevated, and it is still unclear whether the resultant changes are indicative of clinically meaningful effects.

P-selectin is an important marker of platelet activation and may be up-regulated in patients with congestive heart failure (CHF). We sought to prospectively compare simultaneously determined platelet and soluble P-selectin in patients with CHF and in healthy controls. Matched soluble levels by enzyme-linked immmunosorbent assay, and platelet-bound expression by whole blood flow cytometry of P-selectin were measured in 22 patients with CHF and compared with 14 healthy controls. Twelve patients were aspirin free and 10 patients were taking aspirin (81 to 500 mg/day). Patients with CHF had significantly elevated soluble P-selectin (186.6 +/- 82.7 ng/ml, p = 0.017) and more than twofold increased expression of platelet-bound P-selectin (9.58 +/- 7.16% of positive platelets, p = 0.021) compared with the P-selectin profile (102.6 +/- 29.0 ng/ml of plasma, and 4.06 +/- 1.21% of positive platelets, respectively) in controls. Aspirin therapy did not affect the P-selectin profile in patients with CHF. Despite antecedent aspirin therapy and interindividual variability of the P-selectin profile, soluble and platelet P-selectin were elevated in most patients with severe CHF, suggesting persistent platelet activation.

Platelets play an important role in the natural history of idiopathic nephrotic syndrome (NS). Although thromboembolic events are rare, the activation of circulating platelets is generally considered an important factor in the prethrombotic state in children with NS. Platelet-activating factor (PAF), a potent endogenous phospholipid mediator of inflammation, stimulates intracellular free calcium (Ca2+) mobilization, aggregation, and release reactions in platelets obtained from normal donors. Platelet-related effects of PAF in children with NS are unknown. We studied PAF-induced intracellular Ca2+ mobilization in washed platelets and ATP secretion in platelet-rich plasma in 34 children with idiopathic NS and in 7 healthy children. There was a significant decrease in ATP secretion: 0.021+/-0.011 microg/10(7) cells with 20 nM PAF and 0.089+/-0.017 microg/10(7) platelets with 200 nM PAF versus control values (0.195+/-0.004 microg/10(7) and 0.813+/-0.09 microg/10(7), respectively). Moreover, PAF-evoked increase in intracellular free Ca2+ concentration was twofold lower in NS patients than in control subjects (230.1+/-22.4 nM versus 455.6+/-15.3 nM). Also, thrombin-induced intracellular free Ca2+ mobilization was diminished in children with NS compared with the control group. Thus, contrary to expectations, a decrease of platelet reactivity in response to PAF in vitro was observed in children with idiopathic NS. We suggest that this decreased platelet reactivity may reflect a period refractory to PAF and may be considered as platelet desensitization to PAF released in vivo in children with NS.

Animal studies have shown that the administration of antibodies against platelet/endothelial cell adhesion molecule-1 (PECAM-1) before reperfusion can reduce infarct size. The purpose of the present study was to define the effects of thrombolytic therapy in acute myocardial infarction (AMI) patients on the platelet expression and plasma concentrations of PECAM-1 at prespecified time points after attempted reperfusion. The plasma concentration and platelet expression of PECAM-1 were determined in 23 AMI patients enrolled in the Global Use of Strategies to Open Occluded Coronary Arteries (GUSTO-III) trial before thrombolysis and at 3, 6, 12, and 24 hours thereafter and compared with 22 healthy controls. At baseline, PECAM-1 was expressed significantly more on the platelet surface in the AMI patients than in controls (P=0.027) while soluble PECAM-1 plasma levels were almost identical between groups. There were no significant diurnal variations in both plasma and platelet PECAM-1 levels in controls. A significant decrease in platelet PECAM-1 expression was observed 3 hours after thrombolysis (P=0.03) compared with baseline, followed by a significant increase (P=0.004) in fluorescence intensity later at 24 hours after thrombolysis. Conversely, a significant increase in soluble PECAM-1 was observed 3 hours after thrombolysis (P=0.02), followed by a significant decrease later at 24 hours after attempted reperfusion (P=0.03). The expression of platelet-bound PECAM-1 is increased in AMI patients. Discordantly directed changes in soluble and platelet PECAM-1 after the first 24 hours after thrombolytic therapy may represent redistribution of the whole PECAM-1 pool. Further investigation of the possible role of PECAM-1 and the relationship between its soluble and platelet fractions in AMI are warranted.

NPC 15669, a member of the leumedins family, inhibits leukocyte adhesion to the endothelium by blockage of upregulation of a member of beta2 integrin family Mac-1 (CD11b/CD18). Inhibition of neutrophil-endothelial interactions may alter the course of myocardial reperfusion injury. However, the effects of NPC 15669 supplementation on the hemostatic profile during ischemia-reperfusion are unknown. The aim of the present study was to define changes in the certain hemostatic factors in the natural course of preconditioned myocardial infarction. Twelve consecutive Yorkshire swine underwent myocardial stunning (8 min. left anterior descending artery occlusion followed by 90 min. of reperfusion) and then preconditioned myocardial infarction (50 min. occlusion followed by 3 hours of reperfusion) experiments. NPC 15669 (10 mg/kg loading dose followed by constant infusion at 6 mg x kg(-1) x h(-1)) was administered in 6 animals; another 6 swine received saline and served as controls. Blood samples were obtained at baseline, twice during occlusion; and three times during reperfusion. The levels of antithrombin-III, Protein C, total Protein S, fibronectin, endothelin-1, as well as the stable metabolites of thromboxane (TxB2) and prostacyclin (6-keto-PGF1a), were determined. NPC 15669 treatment was associated with diminished endothelin-1, TxB2 levels and increased fibronectin, 6-keto-PGF1a, Protein C and total Protein S concentrations in the setting of preconditioned myocardial infarction. There were no changes in the plasma concentrations of antithrombin-III in NPC 15669 group when compared with controls. The increase in Protein C, total Protein S, and 6-keto-PGF1a (favoring antithrombosis), and decrease in endothelin-1 and TxB2 levels (favoring vasodilatation), following NPC 15669 may explain the reduction in infarct size previously reported with this agent.

Determination of platelet function has become increasingly important as new antiplatelet drugs are being developed. Objective means to monitor the pharmacological effects of these agents, in order to maximize efficacy and minimize toxicity, is needed. The available methods for determination of platelet function at the current time are reviewed, including platelet aggregometry, the PFA-100, flow cytometry, platelet contractile force, the rapid platelet function assay, the clot signature analyzer, Sonoclot, and thromboelastography. The principle, advantages, disadvantages, and clinical utility of each method is presented. The uses of the various methods of determining platelet function reported in the literature are summarized, in an effort to provide information regarding the applicability of those different methods.

We sought to determine plasma levels of platelet/endothelial cell adhesion molecule-1 (PECAM-1), P-selectin, and platelet-derived osteonectin, and prospectively compare these data with the discharge diagnosis in patients presenting with chest pain in a community hospital Emergency Department. Soluble antigens were measured by ELISA in 44 subjects including patients with acute myocardial infarction (AMI) (n = 13), chest pain of noncardiac origin (n = 17), and compared to those of age- and sex-matched healthy controls (n = 14). Elevated soluble PECAM-1 (64.5 +/- 18.3 ng/ml, p = 0.019), but not P-selectin (149.5 +/- 49.8 ng/ml, p = NS), nor osteonectin (549. 5 +/- 159.1 ng/ml, p = NS), occurred in the AMI group as compared to patients with noncardiac chest pain (46.2 +/- 7.5 ng/ml, 118.2 +/- 40.1 ng/ml, and 619.4 +/- 74.4 ng/ml, respectively). Increased plasma PECAM-1 may serve as a useful marker in the early detection of patients with AMI. Larger studies will be necessary to confirm the utility of soluble PECAM-1 in identifying AMI among patients presenting with chest pain.

Thrombin generation (TG) is an important pathogenic factor in acute coronary syndromes including acute myocardial infarction (AMI). Since the diagnostic utility of TG remains uncertain we sought to determine whether markers of TG may triage patients presenting to the Emergency Department with chest pain. Soluble plasma levels of prothrombin fragment 1+2 (F(1+2)), and thrombin/antithrombin III complexes (TAT) were determined by ELISA in 80 patients presenting with chest pain to the Emergency Department and compared with 20 controls. There were no differences in TG markers between patients with non-cardiac chest pain and healthy controls. Patients with unstable angina (UA), and congestive heart failure (CHF) did not differ from controls with respect to F(1+2), and TAT was elevated in UA patients (6.05 +/- 1.15 ng/ml, p = 0.033) when compared with controls (3.34 +/- 0.20 ng/ml). Contrary to expectations, TAT levels at presentation with AMI were well below the concentrations observed in patiens with UA and CHF. Moreover, plasma F(1+2) levels were significantly lower than in healthy controls (0.84 +/- 0.10 ng/ml versus 1.22 +/- 0.11, p = 0.026). At the time of presentation to the Emergency Department, F(1+2) and TAT failed to suitably triage patients with chest pain. The surprisingly low levels of TG markers in AMI patients before applying intensive therapy and reperfusion strategies deserves further investigation., (Copyright 2000 S. Karger AG, Basel)

Cell membrane phospholipids, including platelet-activating factor (PAF), participate in the pathogenesis of acute myocardial infarction (AMI). The plasma level of PAF acetylhydrolase (AH) was determined in 18 patients at presentation with AMI before thrombolysis, and the administration of adjunctive therapy, and compared with 13 healthy controls. Plasma levels of PAF-AH were significantly lower in the AMI patients (23.15 +/- 1.75 nmol/min/ml) than in the controls (30.43 +/- 2.13 nmol/min/ml; p = 0.027). Considering normal plasma levels of PAF and lyso-PAF, and lack of evidence that anti-PAF antibodies are really beneficial in myocardial ischemia-reperfusion, it is reasonable to speculate that an inability of systemic PAF to 'turn on' PAF-AH enzymatic activity could contribute substantially to the observed events. Decreased PAF-AH activity in AMI patients may represent not a consequence, but rather, a risk factor for the development of acute coronary syndromes.

The key role of endothelin-1 (ET-1) has been recognised in patients with ischaemic heart disease. However, the serial changes of ET-1 during both brief and prolonged ischaemia-reperfusion are poorly known. Serial changes of plasma ET-1 were measured during myocardial stunning (MS) and acute myocardial infarction (AMI). The effects of magnesium (Mg), diltiazem and a MAC-1 inhibitor on the plasma ET-1 were elucidated. Forty-nine swine underwent brief (8 min) or prolonged (50 min) coronary artery occlusion followed by reperfusion. ET-1 plasma concentration was measured by ELISA at prespecified time points. The occlusion was associated with a decline of ET-1 followed by a significant increase during the reperfusion. Mg as well as diltiazem similarly affected the plasma ET-1 by reducing ET-1 release during the first hour of the reperfusion period. MAC-1 inhibition was also associated with decreases of ET-1. Ability of Mg, diltiazem and leumedins to decrease the ET-1 plasma level may have direct clinical implications for the use of these agents in patients with coronary artery disease., (Copyright 1998 The Italian Pharmacological Society)