Haemostatic variables in patients with unstable angina

Xa inhibition and coagulation activity--the influence of prolonged dalteparin treatment and gender in patients with acute coronary syndrome and healthy individuals

BACKGROUND

We evaluated coagulation activity in relation to gender in patients with acute coronary syndromes and in healthy individuals of similar age, and related coagulation activity to levels of Xa inhibition during dalteparin treatment.

METHODS

Serial blood samples were obtained from 555 (172 women) of 2267 patients in the Scandinavian FRISC II study, and a single sample in 457 (151 women) apparently healthy age- and sex-matched individuals. After randomization, all patients received dalteparin 120 IU/kg s.c. (maximum 10,000 IU) twice daily for 5 to 7 days inhospital and thereafter placebo (n = 285) or sex- and weight-adjusted doses of dalteparin (5000 or 7500 IU) twice daily (n = 270) for 3 months.

RESULTS

Before randomization, 96% of the patients had open-label anticoagulation with unfractionated heparin or dalteparin. Therapeutic anti-Xa levels (> 0.5 IU/mL) were found in 74%, 55%, 58%, and 33% of the dalteparin-treated patients at randomization, 2 days, 4 to 7 weeks, and 3 months, respectively, and were significantly related to lower levels of coagulation activity, ie, factor VIIa, prothrombin fragment 1+2, and D-dimer, during prolonged treatment. Female patients had higher anti-Xa levels than men at randomization (median 0.69 vs 0.60 IU/mL, P = .01) and at 2 days (0.65 vs 0.59 IU/mL, P < .001). Female patients had also significantly higher levels of all 3 coagulation markers at randomization, 2 days, 4 to 7 weeks, and 3 and 6 months. Similarly, healthy women had higher prothrombin fragment 1+2 levels (median 1.19 vs 0.94 nmol/L) and D-dimer levels than men (26 vs 21 microg/L) (both P < .001).

CONCLUSIONS

Despite weight-adjusted dosing, female patients reached higher anti-Xa levels, suggesting increased sensitivity to dalteparin treatment. Healthy women and female patients also had higher coagulation activity, which might increase the risk of thrombus formation. The large proportion of patients with subtherapeutic anti-Xa during prolonged dalteparin treatment may reflect poor compliance and could thus contribute to the gradual loss of clinical efficacy.

Increase of classic and nonclassic cardiovascular risk factors in patients with acromegaly

OBJECTIVE

To evaluate the prevalence of classic and nonclassic cardiovascular risk factors in patients with acromegaly.

METHODS

Sixty-two patients with acromegaly (50 with active disease and 12 with controlled acromegaly) and 36 healthy persons (the control group) underwent measurement of lipids, fasting plasma glucose, homeostasis model assessment of insulin resistance (HOMA-IR) index, Lp(a), high-sensitivity C-reactive protein (hsCRP), homocysteine, and variables primarily related to thrombogenesis (fibrinogen, antithrombin III, protein C, and protein S).

RESULTS

In comparison with control subjects, patients with active acromegaly had significantly higher mean values of fasting plasma glucose, total cholesterol, low-density lipoprotein cholesterol, very-low-density lipoprotein (VLDL) cholesterol, triglycerides, Lp(a), HOMA-IR, and fibrinogen as well as lower mean levels of high-density lipoprotein cholesterol and protein S. In both groups, homocysteine, antithrombin III, protein C, and hsCRP levels were similar. Moreover, patients with active acromegaly, in comparison with those who had controlled acromegaly, presented with significantly higher values of fasting plasma glucose, HOMA-IR, triglycerides, VLDL cholesterol, Lp(a), and fibrinogen, whereas hsCRP and protein S were significantly lower. Finally, low levels of high-density lipoprotein cholesterol and protein S as well as elevated values of VLDL cholesterol, triglycerides, HOMA-IR, and fasting plasma glucose were more prevalent in patients with active acromegaly than in the other groups.

CONCLUSION

Our findings demonstrate that, in comparison with control subjects and patients with controlled acromegaly, patients with active acromegaly had a higher frequency of classic and nonclassic cardiovascular risk factors. These findings are potentially very important because acromegaly is associated with a 2- to 3-fold increase in mortality rate, predominantly related to cardiovascular disease.

Plasma markers of activated hemostasis in the early diagnosis of acute coronary syndromes

BACKGROUND

Because acute coronary syndromes (ACS) are caused by intracoronary thrombosis, plasma markers of coagulation have relevance for early diagnosis.

AIMS AND OBJECTIVES

To provide a critical review of these studies and specific attempts to close the diagnostic time gap left by traditional plasma markers of heart injury.

METHODS

Studies of ACS patients, with at least one control group, were included when blood samples were taken within 24 h after first symptoms prior to medication or intervention. Special attention was paid to studies reporting diagnostic performance, or combination of several markers into a single diagnostic index.

RESULTS

Markers with short plasma half-life (FPA, TAT, etc.) reflect ongoing thrombosis and may identify patients at increased risk. Markers with longer half-life (F1+2, D-Dimer, etc.) may be more useful to indicate a single acute thrombotic event. However, results are highly variable and depend on sampling time, clot property, degree of coronary obstruction and physiological condition. Early diagnostic performance of hemostatic markers was poor even when combined with heart injury markers.

CONCLUSIONS

Early measurement of hemostatic plasma markers in ACS patients provides pathophysiological information and may be helpful in risk stratification or to monitor anticoagulant therapy, but does not seem useful in routine clinical diagnosis of ACS.

Influence of prolonged dalteparin treatment on coagulation, fibrinolysis and inflammation in unstable coronary artery disease

BACKGROUND

Unstable coronary artery disease (CAD) is a multi-factorial disease involving thrombotic and inflammatory processes. Short-term low molecular weight (LMW) heparin treatment reduces coagulation activity and clinical events. We investigated the influence of prolonged treatment on coagulation, fibrinolysis and inflammation.

METHODS AND RESULTS

Serial blood samples were obtained from 555 of 2,267 unstable CAD patients in the FRISC II study. Patients were treated with the LMW heparin dalteparin 120 IU kg(-1) s.c. twice daily for 5-7 days and randomized to placebo (n=285) or gender and weight-adjusted doses of dalteparin (5,000 or 7,500 IU) twice daily (n=270) for 3 months. Dalteparin persistently depressed coagulation activity with, when compared with placebo, lower median levels of factor VIIa (63 IU mL(-1) vs. 84 IU mL(-1)), prothrombin fragment 1 + 2 (0.86 nmol L(-1) vs. 1.09 nmol L(-1)) and D-dimer (21 microg L(-1) vs. 43 microug L(-1)) after 3 months, all P<0.01. Reactivation of coagulation activity was observed after cessation of both short-term and prolonged dalteparin treatment. Higher levels of tPA/PAI-1 complex (11.7 microg L(-1) vs. 6.5 microg L(-1), P<0.001) and von Willebrand factor (162% vs. 136%, P<0.001) were found during prolonged dalteparin treatment. Interleukin-6, C-reactive protein and fibrinogen levels were unaffected by dalteparin treatment.

CONCLUSIONS

Three months dalteparin treatment resulted in a sustained and pronounced reduction of coagulation activity, which corresponds to the observed reduction in death and myocardial infarction during the initial 6 weeks in the FRISC II study. The persistently elevated levels of tPA/PAI-1 complex and von Willebrand factor might reflect effects on platelets and endothelial cells and thus contribute to the gradually decreased efficacy by prolonged dalteparin treatment in unstable CAD.

Low normal level of protein C or of antithrombin increases risk for recurrent cardiovascular events

The relationship between haemostatic factors and recurrent cardiovascular events was investigated in patients enrolled with acute coronary syndrome (acute non-Q myocardial infarction or unstable angina pectoris). One hundred and fifteen patients, aged 64 +/- 10 years, were included in the study. Haemostatic parameters [prothrombin time, activities of factor VII, factor VIII, factor X, antithrombin (AT) and protein C (PC), and concentrations of free protein S, fibrinogen, D-dimer, prothrombin fragment 1+2, and thrombin-antithrombin complex] were measured four times: within 48 h of hospitalization, at discharge (days 5-8), at 3 months and after 1 year. Screening for factor V Leiden mutation was also performed. Patients were followed for cardiovascular endpoints (new or refractory unstable angina pectoris, non-fatal myocardial infarction, stroke, or death) for an average of 555 days. Of all patients, 35 had an endpoint during the follow-up ("endpoint" group) and 80 patients did not ("no endpoint" group). Analysing the whole follow-up period, PC (P < 0.01) and AT (P < 0.01) were lower in the "endpoint" than in the "no endpoint" group. With 50% percentiles at enrollment, the odds ratio for getting an endpoint in the low (cut-off value < 100%) versus high PC group was 2.72 (95% confidence interval, 1.18-6.29; P < 0.05). Lower levels of AT (P < 0.05) and PC (P < 0.05) during the whole follow-up were associated with a shorter event-free time. In conclusion, lower PC and AT values, even within the normal range, seem to be associated with elevated risk for recurrent cardiovascular events and shorter event-free time in acute coronary syndrome patients.

Activation of the inflammation, coagulation, and fibrinolysis systems, without influence of abciximab infusion in patients with non-ST-elevation acute coronary syndromes treated with dalteparin: a GUSTO IV substudy

BACKGROUND

In acute coronary syndromes, the inflammation and the coagulation systems are activated, implying an impaired outcome. In addition to platelet inhibition, recent evidence suggests that the glycoprotein IIb/IIIa receptor inhibitor abciximab attenuates inflammation and coagulation activity.

METHODS

The Swedish Global Utilization of Strategies To open Occluded arteries-IV (GUSTO-IV) substudy included 404 patients with non-ST-elevation acute coronary syndromes. In addition to aspirin and dalteparin, all patients were randomized to receive abciximab infusion for 24 hours or 48 hours or corresponding placebo without early coronary revascularization. Plasma samples were obtained at baseline and 24, 48, and 72 hours.

RESULTS

The median levels of the coagulation markers thrombin/antithrombin complex and soluble fibrin increased significantly from 3.1 to 3.7 ug/L (baseline to peak; P <.001) and from 20 to 23 nmol/L (P <.001), respectively. The fibrinolysis marker, tissue plasminogen-activator, also increased its median levels, from 11.7 to 17.5 ug/L (P <.001), whereas the median level of plasminogen-activator-inhibitor was unchanged. The inflammatory markers interleukin-6, C-reactive protein, and fibrinogen also increased their median levels (5.4-7.8 ng/L, P <.001; 4.4-8.7 mg/L, P <.001; 3.3-3.9 g/L, P <.001). However, there were no differences in median levels or in changes of median levels of any marker at any point between the placebo group and any of the abciximab groups.

CONCLUSIONS

In non-ST-elevation acute coronary syndrome, there was a simultaneous activation of the inflammation, coagulation, and fibrinolysis systems, despite aspirin and dalteparin treatment. Prolonged treatment with abciximab had no influence of the activation of these systems.

The importance of von Willebrand factor level and heart rate changes in acute coronary syndromes: a comparison with chronic ischemic conditions

The pathogenesis of acute coronary syndrome (ACS) and transient myocardial ischemia (TMI) is not completely understood. Therefore, the authors studied the biological indicators of thrombogenesis and sympathetic activity. The study was conducted on 50 patients with acute coronary syndrome and 30 patients with stable angina pectoris. Treatment was standardized with low-molecular-weight heparin and 300 mg aspirin/day but with no IIb/IIIa inhibitors, an oral beta-blocker, diltiazem 60 mg tid, glyceryl trinitrate i.v. in patients with ACS but with mononitrates orally and low-molecular-weight heparin in patients with stable angina. Twenty-four-hour continuous ECG monitoring and ST segment analysis were performed on day 2 of admission and heart rate analysis was performed 10, 5, and 1 minute before and during the myocardial ischemia periods. Blood sampling for von Willebrand factor (vWf) determination was performed through a peripheral vein at 8 AM, noon, 6 PM and 10 PM and half an hour after the description of angina. The patients with ACS were grouped as transient myocardial ischemia positive (n = 20) and negative (n = 30). The patients with stable angina were designated as the control group (n = 30). The detected vWf levels at 4 different daytime periods in patients with ACS were significantly higher than those in patients with stable angina. At the 6 PM to 10 PM period, the vWf level increase was significantly higher in patients with TMI than in the patients without TMI. At the 8 AM to noon period, the detected vWf levels decreased significantly in both TMI groups. During the nocturnal ischemia periods, the increase in vWf levels immediately after angina was significantly more apparent than the detected changes during daytime ischemia. Analysis showed that heart rates before the ischemia during stable angina episodes were significantly higher than those in TMI (-) (silent) angina. The heart rate difference between 10 minutes before and during the ischemia in the angina group was significantly different from that during TMI (-) (silent) ischemia. The heart rates at the times related to ischemia in the nocturnal period were significantly lower than those in the daytime period. The heart rate differences between the ischemia-related times and during the ischemia were significantly higher in daytime ischemic attacks than in nocturnal ischemic attacks. The study confirms that the vWf level, which is an indicator of thrombogenesis, was significantly increased in patients with ACS. Nocturnal ischemia is associated with thrombogenesis. Daytime ischemia is associated with increased sympathetic activity, and symptomatic ischemia is usually associated with increased sympathetic activity.

Coagulation indicators in chronic stable effort angina and unstable angina: relationship with acute phase reactants and clinical outcome

The aim of the study was to evaluate which pattern of coagulation indicators characterizes unstable angina and, particularly, its relationship with short-term prognosis. Forty patients with unstable angina (UA Group) at admission in the intensive care unit, 40 patients with chronic stable effort angina (SEA Group), and 20 age- and sex-matched healthy controls were studied. Blood coagulation indicators were fibrinogen, prothrombin fragment F1 + 2 (F1 + 2), thrombus precursor protein (TpP), and D-dimer. C reactive protein (CRP) and cardiac Troponin I (cTnI) have also been determined and compared. Patients in the UA Group were followed for in-hospital adverse events (sudden death, acute myocardial infarction and angina refractory to medical therapy). CRP, D-dimer and cTnI plasma levels were significantly lower in the SEA Group than in the UA Group; the same trend was found for fibrinogen and F1 + 2 plasma levels, although not statistically significant. The TpP was similar in all groups. The control group showed the lowest levels for all indicators. Within the UA Group, 17 patients developed adverse events during hospitalization; F1 + 2, D-dimer, cTnI and CRP plasma levels were higher in these patients than in those with good outcome. Relative risks for adverse events associated with the highest tertile of D-dimer, cTnI, and CRP plasma levels were 8.4 (95% confidence interval, 1.5-48.9), 6.7 (95% confidence interval, 1.1-38.6) and 5.2 (95% confidence interval, 1.1-25.2), respectively. D-Dimer is significantly increased in patients with unstable angina and, in particular, in those who develop an adverse event.

Coagulation activity and clinical outcome in unstable coronary artery disease

In the current study, we investigated molecular markers of coagulation activity, ie, prothrombin fragment 1+2 (F1+2), thrombin-antithrombin (TAT) complex, soluble fibrin (SF), and D-dimer, and their relation to death, myocardial infarction, and refractory angina during and after anticoagulant treatment in unstable coronary artery disease. Patients with unstable coronary artery disease (N=320) were randomized to a 72-hour infusion with either inogatran, a low-molecular-mass direct thrombin inhibitor, or unfractionated heparin. During the 30-day follow-up, a 40% lower event rate was seen in patients with high compared with low baseline levels of TAT or SF. High baseline levels of coagulation activity were correlated with a larger decrease during treatment. Patients with decreased compared with raised F1+2 or TAT levels after 6 hours of treatment had a 50% lower event rate at 30 days (F1+2, P=0.04; TAT, P=0.02). At the cessation of antithrombin treatment, there was a clustering of cardiac events that tended to be related to a rise in the levels of TAT and the other markers. During long-term follow-up (median, 29 months), there was a relation between higher baseline levels of D-dimer (P=0.003) and increased mortality. High baseline levels of molecular markers of coagulation activity might identify patients with a thrombotic condition (as the major cause of instability) who are good responders to anticoagulant therapy, with a larger decrease in coagulation activity during treatment and a decreased risk of ischemic events. However, this early benefit is lost during long-term follow-up when high baseline levels of coagulation activity are associated with a raised risk of early reactivation and increased mortality.

Thrombin formation and fibrinolytic activity in patients with acute myocardial infarction or unstable angina: in-hospital course and relationship with recurrent angina at rest

OBJECTIVES

The goal of this study was to investigate possible differences in thrombin generation or fibrinolytic capacity in patients with unstable angina (UA) or acute myocardial infarction (AMI) with or without recurrent angina at rest.

BACKGROUND

Angina at rest in patients with AMI or UA is generally produced by a reduction in coronary flow, but it is unclear whether patients with or without this event differ in their thrombin generation or in their fibrinolytic capacities, which might influence the course of the culprit lesion.

METHODS

Thrombin-antithrombin complex (TAT), D-dimer, fibrinogen and plasminogen activator inhibitor (PAI-1) antigen plasma levels were determined in 40 patients with AMI and in 23 with UA on admission, at 10 days and at three months.

RESULTS

First day values for TAT, fibrinogen and D-dimer were comparable in patients with AMI and in those with UA. At 10 days they increased significantly in each group, and at 3 months they decreased to a similar extent. First day PAI-1 levels, however, were highest in both groups and declined in AMI patients at 10 days and at three months, whereas they also decreased at 10 days in UA patients but not any further at three months. Ten patients with AMI (25%) and 12 with UA (52%) developed in-hospital angina at rest. First day values for TAT, fibrinogen and D-dimer were similar in patients with or without angina, but PAI-1 levels were higher in the former subset (p < 0.008). At 10 days, however, TAT (p < 0.013) and D-dimer (p < 0.013) were higher in patients who developed angina than in those who did not.

CONCLUSIONS

The higher inhibition of fibrinolytic activity in the first day in patients with AMI or UA who will develop recurrent angina suggests that maintenance of a prothrombotic status may contribute to its mechanisms, perhaps by preventing passivation of the culprit thrombus/plaque. This is consistent with greater thrombin generation and greater levels of fibrynolitic products at 10 days observed in these patients compared with those who attain early stability.

Low molecular weight heparins

Since its discovery, nearly 90 years, heparin has been used successfully for the treatment of thromboembolic processes. However, therapy with heparin has several important limitations. Most importantly, the poor predictability of its anticoagulant effects has led to the development of the low molecular weight heparins (LMWHs), which are derived from unfractionated heparin and appear to have pharmacologic advantages, require no laboratory monitoring and are more predictable than their parent compounds. LMWHs have been used for several years in the treatment of venous thromboembolic disorders. More recently, the LMWHs have been used to treat patients with acute coronary interventions. As the results of new studies are revealed, we will learn whether the use LMWH can be extended to all disorders where unfractionated heparin is currently the standard therapy.

Serum C-reactive protein and fibrinogen concentrations and self-reported angina pectoris and myocardial infarction: findings from National Health and Nutrition Examination Survey III

C-reactive protein may predict the risk of cardiovascular disease, but its association with angina pectoris in the general population has not been clearly established, however. We used data from National Health and Nutrition Examination Survey III conducted from 1988-1994 to examine the associations between serum C-reactive protein and plasma fibrinogen concentrations and self-reported angina pectoris and myocardial infarction among 7,948 U.S. men and women aged 40 years and older. C-reactive protein and fibrinogen concentrations were moderately correlated (r = 0.43). After adjustment for age, sex, race or ethnicity, education, smoking status, systolic blood pressure, serum cholesterol, high-density lipoprotein cholesterol, history of diabetes mellitus, body mass index, and physical activity, fibrinogen (but not C-reactive protein) concentration was significantly associated with self-reported angina pectoris. Neither fibrinogen or C-reactive protein concentrations were significantly associated with angina pectoris when entered in the model simultaneously. C-reactive protein and fibrinogen concentrations were positively associated with myocardial infarction when entered separately into models, but only C-reactive protein concentration was significantly associated with myocardial infarction when both variables were entered simultaneously. These cross-sectional data showed a significant positive association between C-reactive protein concentration and myocardial infarction but not self-reported angina pectoris in the U.S. population.

No Prognostic Importance of Resistance to Activated Protein C in Unstable Coronary Artery Disease Despite Signs of Thrombin Activation

Resistance to activated protein C (APC resistance) is the single most important hemostatic defect associated with venous thromboembolic disease. However, little is. Known about this defect in arterial disease. The aim of this study was thus to investigate the frequency and prognostic importance of APC resistance and its influence on the coagulation system in one type of arterial thrombosis. In this study, 323 patients admitted to hospital because of unstable coronary artery disease, that is, unstable angina pectoris or non-Q-wave myocardial infarction, were investigated and compared with a reference group of apparently healthy individuals. The patients participated in a prospective, multicenter, randomized, and placebo-controlled investigation evaluating the protective value of low molecular weight heparin (dalteparin) in unstable coronary artery disease. The APC ratio was assayed using a modified activated partial thromboplastin time reaction method to measure the response to activated protein C. APC resistance was defined as an APC ratio </=2.2. Signs of thrombin activation were measured by prothrombin fragment 1+2 levels. The 7.2% (23/318) occurrence of APC resistance found in patients did not differ from the 5.8% (4/69) level in the reference population (P = 0.16). A significant elevation of the prothrombin fragment 1+2 median level of 2.5 nM (interquartile range, 1.9-3.2 nM) was found in the patients with APC resistance compared with 1.7 nM (interquartile range, 1.2-2.4nM) in the group with a normal APC ratio (P < 0.01). During the 150-day follow-up period, there was no increased risk of cardiac events in patients with APC resistance. Although accompanied by signs of increased thrombin formation, APC resistance doesnot seem to be an important risk factor for the development of instability in coronary artery disease.

Early increase of von Willebrand factor predicts adverse outcome in unstable coronary artery disease: beneficial effects of enoxaparin. French Investigators of the ESSENCE Trial

BACKGROUND

The pathogenesis of unstable angina and non-Q-wave myocardial infarction is still poorly understood, and early evaluation of prognosis remains difficult. We therefore studied the predictive value of 5 biological indicators of inflammation, thrombogenesis, vasoconstriction, and myocardial necrosis, and we examined the effects of enoxaparin and unfractionated heparin on these markers after 48 hours of treatment.

METHODS AND RESULTS

Sixty-eight patients with unstable angina or non-Q-wave myocardial infarction randomized in the international ESSENCE trial participated in this French substudy. C-reactive protein, fibrinogen, von Willebrand factor antigen, endothelin-1 and troponin I were measured on admission and 48 hours later. The composite end point of death, myocardial infarction, recurrent angina, or revascularization was significantly lower at 14 and 30 days of follow-up in patients allocated to enoxaparin compared with unfractionated heparin. All acute-phase reactant proteins were elevated on admission and increased further at 48 hours. Multivariate analysis demonstrated that the rise of von Willebrand factor over 48 hours was a significant and independent predictor of the composite end point at both 14 days and 30 days. Moreover the early increase of von Willebrand factor was more frequent and more severe with unfractionated heparin than with enoxaparin (mean change was +8.7+/-8.8% with enoxaparin versus +93.9+/-11.7% with unfractionated heparin, P<0.0001). The other clinical and biological variables did not predict outcome.

CONCLUSIONS

In patients with unstable angina or non-Q-wave myocardial infarction, the acute-phase proteins increase over the first 2 days despite medical treatment. The early rise of von Willebrand factor is an independent predictor of adverse clinical outcome at 14 days and at 30 days. Enoxaparin provides protection as evidenced by the reduced release of von Willebrand factor, which represents a favorable prognostic finding.

Platelet activation with unfractionated heparin at therapeutic concentrations and comparisons with a low-molecular-weight heparin and with a direct thrombin inhibitor

BACKGROUND

The growing use of heparin in acute thrombotic disorders, coupled with the availability of many new antithrombotic agents, emphasizes the need for adequate characterization of the platelet effects of the various anticoagulants. Controversial platelet effects have been reported with heparin (eg, enhanced platelet activation in vitro with high doses and no such effect in vivo at therapeutic doses). This study examined platelet receptor activation and platelet aggregation at therapeutic concentrations of unfractionated heparin (UFH), of enoxaparin, a low-molecular-weight heparin, and of argatroban, a direct thrombin inhibitor.

METHODS AND RESULTS

Platelet P-selectin (CD62) and activated GP IIb/IIIa (PAC-1) expression on platelet membrane was quantified in whole blood as well as platelet aggregation in platelet-rich plasma in 43 patients with unstable angina before and during treatment with UFH or enoxaparin. Studies were also carried out in blood of seven normal volunteers after addition ex vivo of UFH (0.25 U/mL), enoxaparin (0.25 U/mL), argatroban (1 ng/mL), and normal saline. UFH in patients with unstable angina increased the percentage of circulating platelets positive to PAC-1 from 2.7+/-1.7% to 4.4+/-3.4% (P<.05) and to CD62 from 1.6+/-0.9% to 2.7+/-1.5% (P<.01). Platelets were also hyperresponsive to stimulation with ADP and with the thrombin-receptor agonist peptide. Aggregation to ADP increased from 6.8+/-4.6% to 11.2+/-7.0% and to TRAP from 5.2+/-3.5% to 11.1+/-6.0% (P<.001). The addition of UFH to blood of normal volunteers resulted also in activation of GP IIb/IIIa receptors, expression of P-selectin, and enhanced platelet aggregation. Enoxaparin had only minor effects on platelet activation in vivo and ex vivo, and argatroban, evaluated ex vivo, had no detectable effects.

CONCLUSIONS

Therapeutic concentrations of UFH are associated with platelet activation.

Postangioplasty restenosis: platelet activation and the coagulation-fibrinolysis system as possible factors in the pathogenesis of restenosis

We investigated the relationship between changes in hemostatic factors and postangioplasty restenosis by evaluating plasma levels of P-selectin, beta-thromboglobulin (BTG), and other markers of the coagulation-fibrinolysis system. Seventy-three consecutive patients (56 men and 17 women) undergoing elective percutaneous transluminal coronary angioplasty (PTCA) were enrolled in this study. Patients with acute myocardial infarction within the previous month, unstable angina pectoris, chronic total occlusion, target lesions involving saphenous vein grafts, or coronary artery bypass grafting within the previous 6 months were excluded. Fasting blood samples were obtained before elective PTCA and at follow-up coronary angiography. In patients with restenosis, plasminogen activator inhibitor type-1 (PAI-1) levels were significantly higher (88.2 +/- 36.1 vs 118.5 +/- 50.0 ng/dl; p< 0.05) and plasmin-plasmin inhibitor complex (PIC) levels were significantly lower (0.76 +/- 0.26 vs 0.61 +/- 0.26 microg/ml; p < 0.02) than at baseline. P-Selectin levels were also significantly higher (192 +/- 68 vs 239 +/- 99 ng/ dl; p<0.01) and a positive correlation existed between P-selectin and BTG levels (r= 0.43; p< 0.05). The higher PAI-1 and lower PIC levels in patients with postangioplasty restenosis suggest that impaired fibrinolysis may play a role in the pathogenesis of restenosis, whereas the positive correlation between P-selectin and BTG levels implies a role for activated platelets in restenosis.