Fibrinopeptide A and beta thromboglobulin in patients with angina pectoris and acute myocardial infarction

Platelet activity and cardiovascular risk in apparently healthy individuals: a review of the data

Cardiovascular disease is a major cause of morbidity and mortality. Numerous risk scores exist to identify healthy individuals at increased risk of developing cardiovascular disease. Although platelets are a key mediator in the pathogenesis of cardiovascular disease, the role of platelet activity measurements and the incidence of cardiovascular disease are uncertain. Platelet aggregometry-the most well studied method of platelet function testing-is associated with risk factors for cardiovascular disease. However, data supporting platelet aggregation and incident cardiovascular disease is conflicting. Plasma markers of platelet activation are promising candidates. Soluble CD40L and P-selectin are easily measured with a standardized ELISA, and there is some data to suggest an association with cardiovascular disease, but further studies are required. While mean platelet volume is a promising candidate, platelet count and bleeding time are not specific for platelet activity nor are they associated with cardiovascular disease in a healthy population. For this field to progress, we recommend large-scale, prospective studies that measure a battery of these platelet function tests in individuals without cardiovascular disease to better understand the associations, if any, between platelet activity and cardiovascular disease.

High platelet reactivity is associated with myocardial infarction in premenopausal women: a population-based case-control study

SUMMARY BACKGROUND

Platelets are involved in the occlusion of coronary arteries after rupture of an atherosclerotic plaque. Furthermore, activated platelets release large quantities of growth factors, chemokines and interleukins that regulate inflammatory reactions. Therefore, we hypothesized that high basal platelet reactivity may contribute to an increased risk of myocardial infarction (MI) in premenopausal women.

METHODS

We assessed the relation between high platelet reactivity and MI in a population-based case-control study among premenopausal women (aged < 50 years). We used multivariable logistic regression to quantify the effect of high platelet reactivity, adjusted for potential confounders. Platelet reactivity was estimated by plasma levels of neutrophil activating peptide 2 (NAP-2), CXC chemokine ligand (CXCL)4, soluble glycoprotein 1b (sGPIb) and soluble P-selectin.

RESULTS

High platelet reactivity (i.e. levels >or= 90th percentile control subjects) was associated with a 2- to 3-fold increased incidence of MI: the adjusted odds ratios (ORs) were 3.0 [95% confidence interval (CI) 1.4-6.4] for NAP-2, 2.2 (0.9-5.1) for CXCL4, 1.9 (0.7-4.6) for sP-selectin and 2.5 (1.1-5.7) for sGPIb. The incidence of MI dose-dependently increased when more markers were elevated. High platelet reactivity according to both NAP-2 and sGPIb was associated with an up to tenfold increased incidence (9.9, 95% confidence interval 2.0-48.3).

CONCLUSIONS

High basal platelet reactivity was associated with a 2- to 3-fold higher incidence of MI compared with normal platelet reactivity in premenopausal women. Our results suggest that high basal platelet reactivity may contribute to a higher risk of MI.

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.

Platelet-associated and secreted PAF-acetylhydrolase activity in patients with stable angina: sequential changes of the enzyme activity after angioplasty

BACKGROUND

Platelet-activating factor (PAF), the lipid mediator of inflammation and potent platelet agonist, can be hydrolysed and inactivated by PAF-acetylhydrolase (PAF-AH). We investigated the PAF-AH activity in relation to PAF formation in platelets from patients with stable angina undergoing elective percutaneous transluminal coronary angioplasty (PTCA).

DESIGN

Twenty-seven patients with stable angina, undergoing PTCA, and 30 age- and sex-matched controls were studied. The platelet-associated and secreted PAF-AH activity was measured, before PTCA, as well as at 4 h, 48 h and 6 months afterwards. PAF formation by thrombin-stimulated platelets and the platelet aggregation responses to PAF and ADP were also determined.

RESULTS

The PAF-AH activity secreted by thrombin-stimulated platelets before PTCA (in pmol/10(9) cells/h) was significantly higher compared to controls (892 +/- 222 vs. 624 +/- 144, P < 0.001). The enzyme activity was not altered at 4 h after PTCA, but was significantly increased at 48 h (1284 +/- 312, P < 0.005) to return to the levels observed in the control group 6 months afterwards. Detectable levels of PAF in thrombin-stimulated platelets were found only at 6 months after PTCA. Furthermore, the cell-associated enzyme activity in resting platelets before PTCA was significantly lower compared with controls. Unlike in controls, the platelet-associated enzyme activity in the patient group was not increased after stimulation with thrombin and it was associated by a platelet hyperaggregability to PAF. Both the intact cell-associated activity and the platelet hyper-reactivity to PAF were restored at 6 months after PTCA.

CONCLUSIONS

Alterations in the platelet PAF-AH activity, which affect the PAF formation in thrombin-stimulated platelets and are associated by an increased aggregatory response to PAF, are observed in patients with stable angina and are completely restored after PTCA.

Occlusive vascular diseases in oral contraceptive users. Epidemiology, pathology and mechanisms

Despite being an unprecedented departure from normal physiology, the combined oral contraceptive is not only highly effective, but it also has a remarkably good safety record. Concerns over safety persist, though, particularly with regard to venous thromboembolism (VTE), stroke and myocardial infarction (MI). Epidemiological studies consistently show an increase in risk of VTE, but the results are more contentious with regard to arterial diseases. Despite 40 years of research, the mechanisms behind these adverse effects are not understood. In this review, we integrate information from published studies of the epidemiology and pathology of the occlusive vascular diseases and their risk factors to identify likely explanations for pathogenesis in oral contraceptive users. Oral contraceptives induce both prothrombotic and fibrinolytic changes in haemostatic factors and an imbalance in haemostasis is likely to be important in oral contraceptive-induced VTE. The complexity of the changes involved and the difficulty of ascribing clinical significance has meant that uncertainty persists. A seriously under-researched area concerns vascular changes in oral contraceptive users. Histologically, endothelial and intimal proliferation have been identified in women exposed to high plasma estrogen concentrations and these lesions are associated with thrombotic occlusion. Other structural changes may result in increased vascular permeability, loss of vascular tone and venous stasis. With regard to arterial disease risk, epidemiological information relating to dose effects and joint effects with other risk factors, and studies of pathology and changes in risk factors, suggests that oral contraceptive use per se does not cause arterial disease. It can, nevertheless, synergise very powerfully with subclinical endothelial damage to promote arterial occlusion. Accordingly, the prothrombotic effects of the oral contraceptive estrogen intervene in a cycle of endothelial damage and repair which would otherwise remain clinically silent or would ultimately progress - in, for example, the presence of cigarette smoking or hypertension - to atherosclerosis. Future work in this area should focus on modification of the effects of established risk factors by oral contraceptive use rather than modification of the supposed risk of oral contraceptive use by established risk factors. Attempts to understand vascular occlusion in oral contraceptive users in terms of the general features of VTE or with reference to atherosclerosis may be limiting, and future work needs to acknowledge that such occlusions may have unique features. Unequivocal identification of the mechanisms involved would contribute considerably to the alleviation of fears over vascular disease and to the development of even safer formulations.

The pre-procedural platelet state predicts clinical recurrence after coronary angioplasty

Percutaneous transluminal coronary angioplasty is an established therapy for coronary artery disease, but restenosis still occurs at a rate of 25%-40%. The aim of this study was to investigate the acute effect of percutaneous transluminal coronary angioplasty on platelet function and the relationship between platelet function and clinical recurrence. Spontaneous platelet aggregation was assessed before and after successful coronary angioplasty in 155 patients (120 men, 35 women). Patients were followed for a mean time of 20 months; follow-up angiography was performed only in patients with clinical recurrence. In 122 of 155 patients (79%) a significant increase in spontaneous platelet aggregation was observed immediately after coronary angioplasty. Baseline spontaneous platelet aggregation in platelet-rich plasma was significantly lower in patients with clinical recurrence than in those without (P<0.05). Kaplan-Meier event-free survival estimate showed a significant difference in clinical recurrence between patients with spontaneous platelet aggregation in platelet-rich plasma below and above the first quintile (P<0.05) with a relative risk of 2.5. In conclusion. these results indicate that percutaneous transluminal coronary angioplasty enhances spontaneous platelet aggregation and that the platelet state before coronary angioplasty affects the risk of clinical recurrence after the procedure.

Laboratory Measurement of Thrombin Activity--What Every Clinician Scientist Needs to Know

Advances in our knowledge of the biochemistry of coagulation and fibrinolysis have facilitated the development of sensitive and specific assays that detect platelet activation, the generation of coagulation enzymes, and products of intravascular fibrin formation and dissolution. This review focuses on activation markers of blood coagulation and, in particular, on mechanistic information on the pathophysiology of blood coagulation they have provided. The methodological problems faced in employing these moieties in clinical studies are examined. Only the proper use of coagulation activation markers will enable us to establish their real clinical usefulness.

Activation markers of coagulation

Advances in our understanding of the biochemistry of the haemostatic mechanism have led to the development of sensitive methods for measuring peptides, enzyme-inhibitor complexes, and enzymes that are liberated with the activation of the coagulation system in vivo. Studies employing these markers have provided important mechanistic information regarding haemostatic mechanism function both under normal conditions and in response to pathogenic stimuli. While assays for particular components can denote the presence of a 'biochemical' hypercoagulable state prior to the appearance of overt thrombotic phenomena, most of these markers thus far have not been shown to be useful in managing individual patients. Properly designed prospective studies will be required to determine whether these assay techniques will aid in the identification of patients predisposed to thrombotic events or the monitoring of antithrombotic therapy.

Prognostic significance of elevated hemostatic markers in patients with acute myocardial infarction

OBJECTIVES

The purpose of this study was to determine whether the elevated levels of hemostatic markers in the early phase of myocardial infarction may serve as risk factors for subsequent cardiac mortality.

BACKGROUND

Increased plasma hemostatic markers were noted in acute myocardial infarction, indicating that the blood coagulation system is highly activated in those patients. However, there are few clinical data concerning the association between the elevated hemostatic markers and survival in patients with myocardial infarction.

METHODS

Blood samples were obtained from 64 patients (mean age 67 +/- 11 years; 49 male) with acute myocardial infarction within 12 h after the onset of symptoms and before the initiation of any antithrombotic treatment. We measured plasma concentrations of fibrinopeptide A (FPA), prothrombin fragment 1+2 (F1+2) and thrombin-antithrombin complex (TAT) using the enzyme-linked immunosorbent assay method, and examined the associations between the level of these markers and survival with Cox proportional hazards models.

RESULTS

The follow-up time was 27 +/- 17 months, and 19 patients died of cardiac causes during the follow-up. Univariate survival analysis identified Killip class IV (hazard ratio 4.86; 95% confidence interval [CI] 1.55-15.19), left ventricular ejection fraction (hazard ratio 0.94; 95% CI 0.90-0.99), FPA (hazard ratio 1.54; 95% CI 1.13-2.10), F1+2 (hazard ratio 2.03; 95% CI 1.17-3.53) and TAT (hazard ratio 1.88; 95% CI 1.27-2.79) as significant factors associated with cardiac mortality. In multivariate analyses, only FPA level (hazard ratio 1.84; 95% CI 1.03-3.30) and left ventricular ejection fraction (hazard ratio 0.93; 95% CI 0.88-0.98) were independent predictors of cardiac mortality.

CONCLUSIONS

Elevated FPA in the early phase of myocardial infarction identifies patients with increased risk for subsequent cardiac death. This association appears to be independent of residual left ventricular function after infarction.

Prothrombin fragments F1+2, thrombin-antithrombin III complexes, fibrin monomers and fibrinogen in patients with coronary atherosclerosis

We determined the plasma levels of prothrombin fragment F1+2, thrombin-antithrombin III complexes (TAT), fibrin monomers (FM), D-dimers (DD) and fibrinogen in 57 patients with angiographically verified graded coronary artery disease (CAD) free of concomitant peripheral atherosclerosis, cerebrovascular disease or diabetes mellitus and a group of 21 apparently healthy controls. Blood was collected from the antecubital vein through atraumatic venipuncture prior to the angiographic procedure. Plasma levels of hemostatic markers were related to the presence and graded severity of CAD. The levels of prothrombin fragment F1+2 (1.74+/-0.11 vs. 1.0+/-0.07 nmol/l, P<0.001), FM (41.6+/-5.5 vs. 7.42+/-3.05 nmol/l, P<0.001), TAT (15.6+/-2.7 vs. 2.96+/-0.32 microg/l, P<0.001) and fibrinogen (3.64+/-1.3 vs. 3.08+/-0.33 g/l, P<0.01) were significantly higher in patients with CAD compared to controls, while there was no difference regarding the fibrinolytic system represented by DD (441.6+/-58.9 vs. 337.4+/-42.05 microg/l, n.s.). Within the CAD group, patients with extensive coronary atherosclerosis (> or =2 vessel disease) had significantly higher values for prothrombin fragment F1+2 (1.89 vs. 1.57 nmol/l, P = 0.04), FM (50.7 vs. 29.8 nmol/l, P = 0.03), and a trend to significance was noted for fibrinogen (3.9 vs. 3.3 g/l, P = 0.07) suggesting that blood coagulability was related to the severity of the disease and that hemostatic markers of thrombin activity represent a useful tool to identify patients with a latent hypercoagulable state with a higher susceptibility to sustain coronary thrombosis.

Altered platelet function detected by flow cytometry. Effects of coronary artery disease and age

Platelet activation state and responsiveness to physiological agonists were measured in 65 patients with documented coronary artery disease (54 male and 11 female; mean age, 58 years). Twelve patients (mean age, 52 years), selected at random from the male cohort, were compared with 12 age-matched male control subjects (mean age, 52 years) and with 10 normal, young male subjects (mean age, 25 years). Whole-blood flow cytometry was used to measure platelet activation status ex vivo and platelet responsiveness to physiological agonists in vitro. Peripheral blood samples were analyzed for bound fibrinogen and expression of P-selectin, GPIb, and GPIIb-IIIa at rest and in response to ADP (0.1 to 10 mumol/L) and thrombin (0.02 to 0.32 mu/mL). No significant differences were seen in the basal levels of fibrinogen binding between any of the groups, but P-selectin expression was significantly lower in patients compared with age-matched control subjects (P = .0005). When stimulated with agonists, patients' platelets had significantly decreased fibrinogen binding (P < .03) but no difference in P-selectin expression compared with the age-matched group. Both agonist-induced fibrinogen binding and P-selectin expression were, however, higher in the young subjects compared with either the older control group or the patients (P < .05). GPIb and GPIIb-IIIa expression were lowest in the patients with angina and highest in the young control subjects, with levels in the age-matched control subjects falling between these values. Data from the total patient cohort (n = 65) were identical to those in the smaller cohort (n = 12). In conclusion, atherosclerosis impairs platelet aggregatory responses (fibrinogen binding) over and above the decreased response seen with age. Platelet degranulation (P-selectin expression) is also impaired in patients with coronary artery disease, but only in comparison with younger subjects, not age-matched controls.

Prethrombotic state due to hypercoagulability in patients with permanent transvenous pacemakers

Venous thrombosis is a relatively usual but serious complication of permanent transvenous pacing. However, the pathogenesis has not been defined. To clarify underlying abnormalities in the coagulation-fibrinolysis system in patients with permanent transvenous pacemakers, we measured serum levels of fibrinopeptide A (FPA), thrombin-antithrombin III complexes (TATs), plasmin-alpha 2 plasmin inhibitor complexes (PICs), D-dimer (D-D), beta-thromboglobulin (beta-TG), and platelet factor 4 (PF4) in 53 patients with permanent transvenous pacemakers and 10 control subjects. The patients were divided into two groups, as follows, according to the presence of mural thrombus documented along the pacing lead(s) by digital subtraction angiography and transesophageal echocardiography: Group Th (-), patients without venous route thrombus; and Group Th (+), patients with venous route thrombus. FPA and TAT levels increased significantly even in Group Th (-), and further increased in Group Th (+) compared with control subjects (FPA: 7.5 +/- 4.9, 15.3 +/- 8.8 vs 3.0 +/- 1.4 ng/mL, respectively, P < 0.05; TAT: 2.9 +/- 1.3, 4.8 +/- 2.3 vs 1.7 +/- 0.6 ng/mL, respectively, P < 0.05). There were no differences in levels of D-D, PIG, beta-TG, and PF4 among control subjects, Group Th (-), and Group Th (+). These findings suggest that the hypercoagulable state appears in patients with permanent transvenous pacemakers, even without apparent venous thrombosis. The patients with permanent transvenous pacemakers are thought to be in the prethrombotic state even if they have no venous route thrombosis.

Platelet-dependent thrombin generation in patients with hyperlipidemia

OBJECTIVES

We evaluated coagulability as determined by platelet-dependent thrombin generation in hypercholesterolemic patients before and after treatment with pravastatin and in hypertriglyceridemic patients to investigate the usefulness of coagulability as an index of atherosclerosis and to determine the importance of treating hyperlipidemia.

BACKGROUND

An understanding of the interaction between platelets and the plasma coagulation system is important for clarifying the mechanism of the procoagulant process.

METHODS

We assessed coagulability in 58 patients with hypercholesterolemia (serum total cholesterol level > or = 220 mg/dl, age 56.5 +/- 1.5 years [mean +/- SEM]), 37 patients with hypertriglyceridemia (serum triglyceride level > or = 200 mg/dl, age 59.5 +/- 1.7 years), 13 patients with hypercholesterolemia plus hypertriglyceridemia (age 51.4 +/- 3.1 years) and 75 normal subjects (age 52.2 +/- 1.7 years). We also studied platelet-dependent thrombin generation in patients with hypercholesterolemia before and after treatment with pravastatin. Calcium chloride was added to 0.5 ml of platelet-rich plasma (150 x 10(9)/liter) to initiate coagulation. Ten microliters of the sample was transferred into 90 microliters of 3.8% sodium citrate at 10-min intervals for 30 min. A chromogenic substrate, S-2238, was added to each sample, and absorbance was measured spectrophotometrically at a wavelength of 405 nm to determine thrombin generation.

RESULTS

Platelet-dependent thrombin generation was increased in patients with hypercholesterolemia and patients with hypercholesterolemia plus hypertriglyceridemia (p < 0.01) compared with patients with hypertriglyceridemia and control subjects. Treatment with pravastatin normalized thrombin generation.

CONCLUSIONS

Hypercholesterolemia, but not hypertriglyceridemia, was associated with increased platelet-dependent thrombin generation. Pravastatin normalized the generation of thrombin.

Hormone replacement therapy and hemostasis: principles of a complex interaction

Postmenopausal women on hormone replacement therapy (HRT) have been shown to be at reduced risk of arterial thrombotic disease. The risk of venous thrombosis appears not to be increased in HRT users in the absence of specific risk factors. However, while these data refer predominantly to women using conjugated equine estrogens, it is less clear whether the favourable impact on cardiovascular diseases may also be achieved by other preparations. Dose, as well as route of application and, particularly, the combination of steroids have been shown to affect both the clinical and the metabolic profile. With regard to cardiovascular diseases, differential effects on the hemostatic system are of particular interest. The principles of the interaction of steroids with the hemostatic system are reviewed. Also, the principal limitations of the assessment of the hemostatic system, as well as its interpretation, with regard to cardiovascular diseases are discussed. It is proposed to view the hemostatic system predominantly as a monitor of endothelial function rather than as a mediator of potential harmful effects on the cardiovascular system.

Activated clotting times in acute coronary syndromes and percutaneous transluminal coronary angioplasty

A discrete fall in the ACT (activated coagulation time) has been observed in patients with known activation of the coagulation cascade. Injury to the coronary artery resulting in thrombin activation, whether spontaneous as in the case of acute myocardial infarction or planned as with percutaneous transluminal coronary angioplasty (PTCA), may therefore be reflected in a change in ACT values. We reviewed the records of patients undergoing PTCA at St. Luke's Episcopal Hospital/Texas Heart Institute from January 1990 through December 1992 for information regarding ACT values and clinical events. A total of 469 patients, whose record contained adequate information for study inclusion, were divided into four separate groups: acute myocardial infarction (group I, n = 62), unstable angina with heparin therapy that was withdrawn at least 4 hr prior to PTCA (group II, n = 102), unstable angina with heparin therapy continued until the time of PTCA (group III, n = 154), and stable angina undergoing elective PTCA (group IV, n = 151). Heparin was discontinued 12-15 hr after the procedure in all but group I where anticoagulation was often maintained up to 72 hr. ACT values were measured prior to the PTCA procedure (baseline), after the initial heparin bolus of 10,000 U (postheparin) and approximately 12-18 hr after the procedure (heparin withdrawal).(ABSTRACT TRUNCATED AT 250 WORDS)

Increased heparin-releasable platelet factor 4 and D dimer in patients one month after the onset of acute myocardial infarction: persistent activation of platelets and the coagulation/fibrinolytic system

To evaluate the activity of platelets and the coagulation/fibrinolytic system 1 month after the onset of acute myocardial infarction, we measured the plasma levels of molecular markers, i.e. beta-thromboglobulin, platelet factor 4, thrombin-antithrombin III complex and D dimer, in 16 patients with acute myocardial infarction and in 11 normal subjects. Blood was drawn through a catheter placed in the pulmonary artery before heparin injection. The heparin-releasable platelet factor 4 was calculated by subtracting the level before the injection of 5000 U of heparin, from the level 5 min after injection. The plasma beta-thromboglobulin, thrombin-antithrombin III complex and the D dimer levels in the acute phase of myocardial infarction were 134.9 +/- 121.2, 11.2 +/- 7.1 and 164.4 +/- 115.3 ng/ml, respectively. These values were significantly higher than those in the normal subjects. The plasma levels of beta-thromboglobulin and thrombin-antithrombin III complex, 1 month after the onset (36.6 +/- 16.4 and 4.6 +/- 2.3 ng/ml, respectively) were not significantly different from those of the normal subjects. In contrast, D dimer and heparin-releasable platelet factor 4 were 216.9 +/- 176.9 and 80.5 +/- 29.3 ng/ml, respectively, and significantly higher than in the normal subjects. These findings suggest a latent but persistent activation of the platelets and the coagulation/fibrinolytic system 1 month after the onset of acute myocardial infarction.

Activation markers of coagulation

Advances in our understanding of the biochemistry of the haemostatic mechanism have led to the development of sensitive methods for measuring peptides, enzyme-inhibitor complexes or enzymes that are liberated with the activation of the coagulation system in vivo. Studies employing these markers indicate that a biochemical imbalance between procoagulant and anticoagulant mechanisms can be detected in the blood of humans prior to the appearance of thrombotic phenomena. Properly designed prospective studies will be required to determine whether these assay techniques will enable us to identify individuals who are entering a clinically relevant hypercoagulable state, and intervene with appropriate therapy prior to the onset of overt thrombotic disease.

Persistent activation of coagulation mechanism in unstable angina and myocardial infarction

BACKGROUND

The blood coagulation system is activated in the acute phase of unstable angina and acute myocardial infarction. However, it remains unclear whether augmented function of the hemostatic mechanism serves only as a marker of the acute thrombotic episode or whether a hypercoagulable state persists for a prolonged period after clinical stabilization.

METHODS AND RESULTS

We prospectively measured the plasma concentrations of prothrombin fragment 1 + 2 (F1 + 2) and fibrinopeptide A (FPA) in consecutive patients presenting with unstable angina (n = 81) or acute myocardial infarction (n = 32), respectively. At 6 months, plasma determinations were repeated in patients experiencing an uneventful clinical course (unstable angina, n = 57; myocardial infarction, n = 23). We quantitated the plasma levels of F1 + 2 and FPA in control patients with stable angina (n = 37) or healthy individuals (n = 32) who were matched for age and sex. The median plasma concentrations of F1 + 2 and FPA are significantly higher in patients presenting with unstable angina (F1 + 2, 1.08 nmol/L; FPA, 2.4 nmol/L) or acute myocardial infarction (F1 + 2, 1.27 nmol/L; FPA, 3.55 nmol/L) compared with patients with stable angina (F1 + 2, 0.74 nmol/L; FPA, 1.3 nmol/L; P < .0001) or healthy individuals (F1 + 2, 0.71 nmol/L; FPA, 0.80 nmol/L; P < .0001). At 6 months, the median plasma levels of F1 + 2 in patients exhibiting an uneventful clinical course did not differ from values obtained at admission (unstable angina, 1.26 versus 1.07 nmol/L, P = NS; myocardial infarction, 1.22 versus 1.29 nmol/L, P = NS), whereas the median plasma levels of FPA in the same two subpopulations were significantly reduced (unstable angina, 1.1 versus 2.9 nmol/L, P = .0003; myocardial infarction, 1.1 versus 3.0 nmol/L; P = .0028).

CONCLUSIONS

During the acute phase of unstable angina and myocardial infarction, patients exhibit increased coagulation system activity. Over the next 6 months, patients with unstable angina or myocardial infarction experiencing an uneventful clinical course manifest a persistent hypercoagulable state with minimal generation of fibrin.

Activation of the hemostatic system during thrombolytic therapy

Activation of the hemostatic mechanism has been described during thrombolytic therapy. This phenomenon has been detected by new methods of assessing hemostatic system function, based on immunoenzymatic or radioimmunoassays. However, these methods are extremely sensitive and, unless they are performed in expert laboratories, carefully following the recommended procedures, they generate in vitro artifacts. A description of these methods is provided, as well as a critical review of the available studies. The correct use of these methods will provide us with an understanding of the complex response of the hemostatic system to pharmacologic thrombolysis.

Intracoronary artery thrombus formation in unstable angina: a clinical, biochemical and angiographic correlation

OBJECTIVES

We examined the relation between the level of urinary fibrinopeptide A and the presence of angiographic intracoronary thrombus in patients with unstable angina to determine whether this marker predicts active thrombus formation.

BACKGROUND

Although it is known that thrombus plays a role in acute ischemic syndromes, a noninvasive method to predict its presence in individual patients with unstable angina has not been determined. Fibrinopeptide A is a polypeptide cleaved from fibrinogen by thrombin and thus is a sensitive marker of thrombin activity and fibrin generation.

METHODS

Angiographic thrombus, graded 0 to 4, and the presence of ST segment depression or T wave inversions, or both, on the electrocardiogram (ECG) were related to fibrinopeptide A levels in 24 patients with rest angina of new onset, 18 with crescendo angina, 19 with stable angina and 9 with chest pain but without coronary artery disease. All patients had chest pain within the 24 h of sample acquisition.

RESULTS

The angiographic incidence of thrombus was significantly higher in patients with new onset of rest angina (67%, p < 0.001) and crescendo angina (50%, p < 0.001) as were fibrinopeptide A levels (p = 0.002). Fibrinopeptide A levels correlated significantly (p < 0.001) with the presence of a filling defect (grade 4 intracoronary thrombus) or contrast staining (grade 3). All patients with fibrinopeptide A > or = 8 ng/mg creatinine showed grade 3 to 4 thrombus and 15 of 16 patients with levels > or = 6.0 ng/mg creatinine exhibited angiographic evidence of thrombus (13 with grades 3 to 4). Patients with reversible ST changes on the ECG had significantly higher levels of fibrinopeptide A (p < 0.001), and ST changes correlated significantly with the presence of angiographic thrombus (p < 0.001). Nonetheless, a significant minority of patients with unstable angina had neither angiographic nor biochemical evidence of thrombus.

CONCLUSIONS

Elevated fibrinopeptide A levels in unstable angina reflected active intracoronary thrombus formation and were present in patients with angina of new onset as well as crescendo angina. Reversible ST changes are accompanied by thrombin activity and angiographic thrombus formation. However, a sizable percentage of patients with unstable angina had no evidence of thrombus and these patients may have had transient platelet aggregation without fibrin thrombus formation.

Plaque disruption and the acute coronary syndromes of unstable angina and myocardial infarction: if the substrate is similar, why is the clinical presentation different?

In a majority of instances, both unstable angina and acute myocardial infarction occur secondary to plaque disruption and thrombus formation. Although the pathogenetic substrates are similar the clinical presentations are quite different. It is hypothesized in this editorial review that the amount of acute thrombus formation and specifically fibrin deposition is greater in myocardial infarction than in unstable angina. Both angiographic studies and studies analyzing the response to thrombolytic agents suggest more thrombus in myocardial infarction than in unstable angina. These data have recently been substantiated by angioscopic observations in these acute syndromes suggesting that more platelet-rich (whitish) thrombus occurs in unstable angina and more red thrombus in myocardial infarction. The red thrombus presumably would be more responsive to thrombolytic agents. Furthermore, it is proposed that these differences between syndromes in acute thrombus formation can be explained by the interplay of vessel wall injury, coagulation variables or stasis of blood flow occurring at or after the time of presentation. Therefore, acute myocardial infarction is associated with occlusive, fibrin-rich thrombus, whereas in unstable angina, the thrombus is nonocclusive, mural and possibly more platelet-rich. However, the clinical syndrome that ultimately develops after plaque disruption is dependent not only on the amount of acute thrombus formation but on the net result of all factors that influence the balance between coronary blood supply and myocardial oxygen demand.

Effects of two dosages of subcutaneous low molecular weight heparin (Parnaparin) and of unfractionated heparin on fibrin formation and lipolysis in acute myocardial infarction

Although low molecular weight heparins (LMWH) have been extensively investigated for the prophylaxis and treatment of venous thromboembolism in surgical environments, few data in acute myocardial infarction are available in the literature. In this study two dosages of a new LMWH, Parnaparin, and unfractionated heparin (UF) were investigated in 50 pts with acute myocardial infarction. 20 pts received UF (15.000 units, three subcutaneous injections, Group 1), 20 pts received Parnaparin (6.400 units, single injection, Group 2) and 10 pts received a higher dose of Parnaparin (12.800 units, single injection, Group 3). Similar fibrinopeptide A (FpA) levels were observed in Group 1 and Group 2. In Group 3 the dosage of Parnaparin resulted in a significant prolongation of the APTT and in lower FpA levels. Fibrin formation was decreased by Parnaparin in a concentration-dependent way, according to both the anti-Xa activity and the APTT ratio. Parnaparin did not result in a significant increase in free fatty acid concentration, in comparison with UF. Thus, Parnaparin may offer the advantage of a single subcutaneous injection in patients with acute myocardial infarction.

Effects of long-term treatment with warfarin on fibrinogen, FPA, TAT, and D-dimer in patients with coronary artery disease

Sixty-four patients undergoing aorto-coronary bypass surgery were randomized to receive antithrombotic treatment with acetylsalicylic acid (ASA), 300 mg/d (n = 30) or warfarin, INR = 2.5 - 4.2 (n = 34). The levels of fibrinogen, thrombin-antithrombin III complexes (TAT), fibrinopeptide A (FPA) and D-dimer were assessed before surgery and 9 months postoperatively. In the warfarin treated group the fibrinogen levels were increased after 9 months, while the levels of TAT, FPA and D-dimer were decreased. In the ASA group TAT levels were increased at 9 months, whereas no significant changes in fibrinogen, FPA or D-dimer from baseline were noted. Thus, a reduced activation of the coagulation system has been demonstrated during long-term treatment with warfarin in patients with coronary artery disease.

Biological risk factors for sudden death in patients with coronary artery disease and without heart failure

In a study of biological risk factors for sudden death in patients with coronary artery disease, 320 patients were, prospectively, recruited and followed-up over two years. None of the patients had heart failure or recent myocardial infarction. The following variables were recorded: previous acute myocardial infarction, hypertension, smoking habits, ventricular arrhythmia; the angiographic variables included: left ventricular ejection fraction, Jenkins' and mean atherosclerotic scores; lipid profile: cholesterol, triglycerides, high density lipoprotein cholesterol, low density lipoprotein cholesterol, apolipoproteins Al and B; hemostatic profile: fibrinogen, fibrinopeptide A, antithrombin III, factor VIII antigen, factor VIII coagulant, protein C, plasminogen, alpha 2-antiplasmin, euglobulin clot lysis time and tissue plasminogen activator before and after venous occlusion, tissue plasminogen activator inhibitor, platelet factor 4, beta-thromboglobulin. During the follow-up period, 12 of the patients died suddenly. In these patients, ejection fraction was lower: 49 +/- 16% versus 61 +/- 14% for the other patients (P less than 0.02), fibrinogen higher: 3.9 +/- 0.8 g/l versus 3.5 +/- 0.8 for the living patients (P less than 0.05) and protein C lower: 89 +/- 39% versus 111 +/- 39% (P = 0.06) for the other patients. In multivariate analysis: lower ejection fraction (P less than 0.008), older age (P less than 0.03) and lower protein C (P less than 0.01) were correlated with sudden death. Among the patients with coronary artery disease, the raised fibrinogen and the decreased protein C appeared to be risk factors for sudden cardiac death. These alterations reflected a prothrombotic state which might increase the ischemic risk, due to an acute thrombosis, leading to the fatal ventricular arrhythmia. Determination of these hemostatic variables might be a useful adjunct for assessment of the vital prognosis of patients with coronary artery disease, especially the risk of sudden death in addition to other known clinical, electrocardiographic, hemodynamic risk factors. This would also guide both the instigation of complementary investigations and appropriate therapy in such high risk group of patients.

Plasma fibrinopeptide A levels in patients with acute myocardial infarction treated with alteplase. Correlation with concomitant heparin, coronary artery patency, and recurrent ischemia. The European Cooperative Study Group

BACKGROUND

Fibrin generation during and after therapy with alteplase may depend on the level of concomitant anticoagulation. The hypothesis that fibrinopeptide A (FPA) levels, as markers of ongoing in vivo fibrin formation, correlate with the angiographic and clinical outcome of thrombolysis is tested.

METHODS AND RESULTS

Serial plasma FPA levels were determined in 334 patients of the randomized European Cooperative Study Group trial comparing heparin versus placebo plus alteplase and aspirin in patients with acute myocardial infarction. Median FPA levels (with the 10th to 90th percentiles) were 21 ng/ml (2-390 ng/ml) before treatment in placebo-allocated patients (n = 166) and increased to 49 (15-580), 34 (4-320), 27 (2-240), 29 (2-430), and 30 (3-390) ng/ml after 0.75, 3, 12, 24, and 36 hours, respectively. In heparin-allocated patients (n = 168), median baseline FPA values were 18 ng/ml (2-210 ng/ml) and decreased to 6 (1-110), 5 (1-75), 5 (1-60), 7 (1-100), and 10 (1-170) ng/ml at corresponding time points (p less than 0.0001 for the difference at each time point). Adequate anticoagulation, defined as no activated partial thromboplastin time value below twice the pretreatment value at 3, 12, 24, and 36 hours after initiation of treatment, was obtained in 48 patients assigned to heparin. It was associated with normal median FPA levels (less than or equal to 4 ng/ml) at all time points compared with 12 (2-80), 16 (2-240), and 15 (2-240) ng/ml at 12, 24, and 36 hours, respectively, in heparin-assigned but inadequately anticoagulated patients (n = 102, p less than 0.001 for each time point). In the heparin-treated group, median FPA values tended to be lower at all time points in patients with patent vessels than in patients with occluded arteries, but the difference was significant only at 24 hours (p = 0.04). FPA levels did not correlate with clinically apparent recurrent ischemia or with left ventricular thrombosis on two-dimensional echocardiography.

CONCLUSIONS

During and after thrombolytic therapy with alteplase, the enhanced fibrin generation is suppressed by sustained concomitant anticoagulation with intravenous heparin. Adequate anticoagulation warrants individual titration of the heparin dose. High plasma FPA levels 24 hours after alteplase therapy are specific but insensitive markers of vessel occlusion in anticoagulated patients. They do not correlate with clinical outcome.

Possible role of vascular intima for generation of coagulant activity in patients undergoing coronary thrombolysis with recombinant tissue-type plasminogen activator. A randomized, placebo-controlled study

In our present placebo-controlled study on recombinant tissue-type plasminogen activator (rt-PA) and heparin treatment of patients with acute ischaemic heart disease (IHD), we studied the extent of fibrin resolution and generation of coagulant activity. In rt-PA treated patients the lysis of fibrin in vivo (median 60 nmol of fibrin--estimated as fibrinogen equivalents) was significantly higher (p less than 0.02) than can be accounted for solely by lysis of a coronary thrombus (approximately 2 nmol) and circulating soluble fibrin (median 15 nmol). We observed a 200% increase of plasma concentrations of both prothrombin fragment 1 + 2 (p less than 0.001) and thrombin-antithrombin III complexes (p less than 0.001) as a consequence of rt-PA treatment, indicating that the coagulant activity is primarily caused by a physiological activation of the coagulation system. We conclude that an important contribution to the activation of coagulation in patients undergoing coronary thrombolysis is lysis of fibrin deposited widespread on the vascular intima, and that this process causes an intimal-dependent activation of the coagulation system.

Increased thrombin levels during thrombolytic therapy in acute myocardial infarction. Relevance for the success of therapy

BACKGROUND

It has been suggested that thrombolysis in a feedback reaction may generate pro-coagulant activities.

METHODS AND RESULTS

Fifty-five patients were treated with urokinase-preactivated prourokinase (n = 35) or tissue-type plasminogen activator (n = 20) for acute myocardial infarction and underwent coronary angiography at 90 minutes and at 24-36 hours into thrombolysis, and fibrinogen (Ratnoff-Menzie), D-dimer (ELISA) and thrombin-antithrombin III complex levels (ELISA) were measured. Primary patency was achieved in 39 patients (70.9%), 13 of whom (33.3%) suffered early reocclusion. Nonsignificant decreases in fibrinogen levels were observed while D-dimer levels increased +3,008 +/- 4,047 micrograms/l (p less than 0.01), differences not being significant in respect to the thrombolytic agents or to the clinical course. In contrast, while thrombin-antithrombin III complex levels decreased -4.4 +/- 13.0 micrograms/l in patients with persistent patency, they increased +7.5 +/- 13.6 micrograms/l in case of nonsuccessful thrombolysis (p less than 0.02) and +11.9 +/- 23.8 micrograms/l in case of early reocclusion (p less than 0.001). For patients with thrombin-antithrombin III complex levels greater than 6 ng/l 120 minutes into thrombolysis, the unfavorable clinical course was predicted with 96.2% sensitivity and 93.1% specificity.

CONCLUSION

Generation of thrombin, occurring during thrombolysis, is a major determinant for the success of therapy and thrombin-antithrombin III levels may serve as predictors for the short-term prognosis.

Increased arterial adrenaline is related to pain in uncomplicated myocardial infarction

Plasma levels of catecholamines, beta-thromboglobulin (BTG) and arginine vasopressin (AVP), and degree of pain were examined in 22 patients with suspected uncomplicated myocardial infarction within 24 h following onset of chest pain. Sixteen patients developed infarction with peak creatine phosphokinase at 1280 Ul-1 (range 293-3770 Ul-1). Fifteen healthy men served as controls (C). Arterial adrenaline levels were significantly higher in patients with pain (1.15 +/- 0.23 nmol l-1, n = 8, mean value +/- SEM) than in those without pain (0.60 +/- 0.10 nmol l-1, n = 14, P less than 0.05). Plasma catecholamines were moderately but significantly elevated in myocardial infarction; the concentration of arterial adrenaline was 0.83 +/- 0.14 nmol l-1 and that of arterial noradrenaline was 2.70 +/- 0.28 nmol l-1 compared with 0.44 +/- 0.04 nmol l-1 (P less than 0.025) and 1.47 +/- 0.05 nmol l-1 (P less than 0.0005), respectively, in C. One week later, plasma catecholamines had returned to baseline levels. Plasma BTG showed borderline elevation (1.0 +/- 0.1 pmol l-1) compared with C (0.6 +/- 0.1 pmol l-1, P = 0.04), and remained unchanged 1 week later. Plasma AVP was at baseline level. Uncomplicated myocardial infarction, regardless of size, was associated with only moderately increased sympathetic tone. Plasma adrenaline was related more to the degree of pain than to the presence of acute myocardial infarction. Arterial adrenaline may be a sensitive marker of sympatho-adrenal activity related to pain.

Increased plasma beta-thromboglobulin in patients with coronary artery vein graft occlusion: response to low dose aspirin

The therapeutic effect of aspirin on vein graft patency was studied in patients undergoing coronary artery bypass graft surgery. The study design enabled the prospective evaluation of the relation of platelet activation, as measured by plasma beta-thromboglobulin concentration, to subsequent coronary vein graft occlusion. Serial beta-thromboglobulin levels were measured in 105 patients randomized to receive aspirin (324 mg/day) or placebo beginning within 1 h after surgery. Graft patency was assessed angiographically at 1 week and 1 year after surgery. Of 49 patients receiving placebo, 17 (34.7%) had one or more graft occlusions, 6 early, 10 late and 1 with both early and late occlusion. Of 56 patients receiving aspirin, 7 (12.5%) had one or more occlusions, 3 early and 4 late (p less than 0.01). Preoperatively, the beta-thromboglobulin level in surgical patients (29 +/- 13.5 ng/ml) was significantly higher than that of 51 control subjects (22.6 +/- 11.1 ng/ml) (p less than 0.004). Plasma beta-thromboglobulin levels remained comparatively constant at 3 and 12 months after surgery in the 43 patients who had both samples available (p less than 0.001, r = 0.65). The reduction in beta-thromboglobulin concentration from the preoperative level to 12 months postoperatively was greater in the aspirin-treated group (p less than 0.001). Multivariate logistic regression analysis demonstrated a significant association between preoperative beta-thromboglobulin concentration and graft occlusion (p less than 0.02), and aspirin treatment was effective in preventing occlusion when adjusted for the preoperative beta-thromboglobulin level (p less than 0.005). Plasma beta-thromboglobulin concentrations are elevated in patients with coronary artery disease, suggesting ongoing platelet activation.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypercoagulable state after thrombolytic therapy in patients with acute myocardial infarction (AMI) treated with streptokinase

Fibrinogen activity was studied in 70 patients with AMI who were treated with an intravenous infusion of SK (800,000 U/30 min or 1.5 mill U/60 min). Patients received a continuous infusion of heparin after thrombolytic therapy was completed. 800,000 U and 1.5 mill U SK recanalized infarct-related arteries at a rate of 78%. Early re-infarction occurred in 6% in each group. Upon admission to the hospital patients showed a hypercoagulable state that may be related to an elevated level of fibrinogen and HMW fibrinogen (70.5 +/- 2 vs 65 +/- 2% in patient and normal plasmas, respectively) that changed to a transitory hypercoagulable state indicated by decreased fibrinogen levels after SK treatment. Forty-eight hours after SK, a new fibrinogen hyperfunction, related to an increase in fibrinogen level and especially HMW synthesized fibrinogen (82 +/- 1 or 81 +/- 1%, 800,000 and 1.5 mill U SK, respectively) was observed, which was neutralized by heparin therapy (1,660 U/h with continuous infusion). The elevated levels of fibrinogen (363 +/- 21 vs 240 +/- 8 mg/dl in patient and normal plasmas, respectively) and HMW fibrinogen (70 +/- 3% with both SK hypercoagulable state that is not neutralized by the heparin dose were compared with those whose arteries recanalized. The former group had a higher concentration of fibrinogen (197 +/- 31 vs 147 +/- 18 mg/dl), HMW fibrinogen (78 +/- 0.5 vs 74 +/- 0.3%, respectively), and FPA (130 +/- 3 vs 6 +/- 4 pmol/ml) and more extensive fibrin gel formation kinetics (gelation rate 3.3 +/- 1.4 vs 1.1 +/- 0.2 OD/s x 10(-4), respectively) than the second group. The hypercoagulable state found in patients with acute myocardial infarction undergoing thrombolytic therapy may be related mainly to the progression of HMW fibrinogen and fibrinogen levels.

Circadian variation of plasma fibrinopeptide A level in patients with variant angina

Plasma levels of fibrinopeptide A (FPA), beta-thromboglobulin (BTG), and platelet factor 4 (PF4) were examined on venous plasma samples taken every 4 hours for 24 hours in 20 patients with variant angina and 20 patients with stable exertional angina together with 24-hour Holter recordings. The mean plasma FPA levels (ng/ml) at 2:00 PM, 6:00 PM, 10:00 PM, 2:00 AM, 6:00 AM, and 10:00 AM were 4.6 +/- 1.0, 3.1 +/- 0.5, 6.1 +/- 1.6, 9.9 +/- 2.4, 8.7 +/- 1.4, and 4.2 +/- 0.8 in patients with variant angina (p less than 0.01) and 1.8 +/- 0.2, 2.3 +/- 0.3, 1.9 +/- 0.3, and 2.3 +/- 0.2 in those with stable exertional angina. In seven patients with variant angina, we also examined the effects of heparin (3,000 units), given subcutaneously at 6:00 PM, 10:00 PM, and 2:00 AM, on the plasma FPA levels and the anginal attacks. Although heparin suppressed the elevation and circadian variation of plasma FPA levels, it did not suppress the attacks and their circadian variation in these patients. Plasma FPA levels increased significantly from 3.7 +/- 0.5 to 12.5 +/- 2.7 ng/ml during or immediately after an attack in the seven patients with no heparin. On the other hand, the plasma levels of BTG and PF4 were increased in patients with variant angina as compared with those with stable exertional angina but did not show a significant circadian variation in both groups. We conclude that 1) plasma levels of FPA, BTG, and PF4 were increased in patients with variant angina as compared with those with stable exertional angina; 2) there was a significant circadian variation in the plasma levels of FPA in parallel with that of the frequency of the attacks with the peak level occurring from midnight to early morning in patients with variant angina; and 3) elevated levels of plasma FPA are the result and not the cause of coronary spasm.

Urinary fibrinopeptide A levels in ischemic heart disease

Because acute coronary thrombosis can cause unstable coronary artery disease, fibrinopeptide A, a reliable marker of coagulation activity, may play a role in the evaluation of unstable ischemic syndromes. A new method of fibrinopeptide A sampling, spot urine normalized to urinary creatinine, was evaluated in patients with stable and unstable angina pectoris and acute myocardial infarction. Serial samples were obtained to characterize the changes in urinary fibrinopeptide A levels over time in patients with ischemic heart disease. Admission values (mean +/- SD) were similar in the control group (3.3 +/- 1.4 ng/mg creatinine) and the stable angina group (3.2 +/- 1.1 ng/mg creatinine) (p = NS). Values in the unstable angina group (5.7 +/- 2.6 ng/mg creatinine) were higher than those in the control (p = 0.008) and stable angina (p less than 0.001) groups. Myocardial infarction admission values (8.4 +/- 10.0 ng/mg creatinine) were higher than those in the control (p = 0.005) and stable angina (p less than 0.001) groups, but not higher than those in the unstable angina group. Peak values (the highest of multiple samples) were higher in the unstable angina group (7.6 +/- 5.9 ng/mg creatinine) than in the stable angina group (4.0 +/- 1.0 ng/mg creatinine) (p = 0.04), but not in the control group (4.5 +/- 1.9 ng/mg creatinine) (p = 0.056). The two patients with unstable angina with the highest peak values subsequently exhibited infarction. Peak values in patients with infarction (44.5 +/- 60.0 ng/mg creatinine) were significantly higher than those in patients with unstable (p = 0.03) or stable (p = 0.002) angina and control patients (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Increased plasma fibrinopeptide A levels during attacks induced by hyperventilation in patients with coronary vasospastic angina

Plasma fibrinopeptide A levels, beta-thromboglobulin levels and platelet factor 4 levels were estimated by enzyme-linked immunosorbent assay before and after hyperventilation in 12 patients with coronary vasospastic angina and in 12 control subjects matched for age and gender. In all 12 study patients, anginal attacks accompanied by electrocardiographic (ECG) changes (ST elevation in 11 patients and ST depression in 1 patient) were induced by hyperventilation. Coronary angiography was performed on 11 of the 12 patients, and coronary artery spasm with the same ECG changes was induced by intracoronary injection of acetylcholine in all 11. The plasma fibrinopeptide A levels increased significantly from 2.0 +/- 0.4 to 10.0 +/- 2.4 ng/ml during the attack (p less than 0.001) in the study patients, but remained unchanged before and after hyperventilation in the control subjects. The plasma levels of beta-thromboglobulin and platelet factor 4 remained unchanged after hyperventilation in both groups. Our data indicate that coronary artery spasm may induce thrombin generation and trigger thrombus formation in the coronary artery.

Monitoring of fibrin generation during thrombolytic therapy of acute myocardial infarction with recombinant tissue-type plasminogen activator

Fibrinopeptide A (FPA) is a very sensitive marker of fibrin generation in vivo. Because an imbalance between thrombogenic and thrombolytic forces may be responsible for the failure to recanalize and for reocclusion of coronary arteries, such a marker could be of eminent value during thrombolytic treatment of acute myocardial infarction. Thirty-four consecutive patients with acute myocardial infarction (peak creatine kinase level, 1,869 +/- 1,543 IU/l) were treated with 100 mg recombinant tissue-type plasminogen activator (rt-PA) 3.1 +/- 1.1 hours after onset of chest pain. Angiography 12.5 +/- 6.1 days later revealed an 81% patency rate of the infarct-related vessel. FPA plasma levels (normal, 1.9 +/- 0.5 ng/ml) were 34 +/- 46 ng/ml on admission and 93 +/- 86 ng/ml (538 +/- 674% with respect to each patient's admission level) after 90 minutes of rt-PA infusion (p less than 0.01). In patients without evidence of reocclusion (including three primary failures), FPA levels fell under continuous heparin infusion to 6.7 +/- 9.7 ng/ml (24 +/- 33%, p less than 0.01) within 30 minutes and were 3.1 +/- 2.2 ng/ml (15 +/- 15%, p less than 0.01), 1.6 +/- 1.1 ng/ml (8 +/- 10%, p less than 0.01), and 2.5 +/- 3.0 ng/ml (12 +/- 16%, p less than 0.01) 30 minutes, 9 hours, and 21 hours, respectively, after completion of rt-PA therapy. Five patients sustained intermittent or permanent coronary reocclusion after primary thrombolytic success. Their early postlytic FPA levels (13-51 ng/ml) remained high or increased again despite adequate anticoagulation. FPA allows the monitoring of fibrin generation during acute myocardial infarction and thrombolytic therapy. Despite successful recanalization, fibrin generation is increased under rt-PA administration before anticoagulation. Patients under anticoagulation with postlytic FPA levels less than 5 ng/ml or below their admission value seem to be at low risk of reocclusion for several days. FPA levels that are persistently high or that increase again despite adequate anticoagulation indicate ongoing fibrin generation. However, whether FPA can indeed be considered a useful marker of reocclusion remains to be confirmed in a larger population of patients with acute myocardial infarction.

Effect of short-term treatment with bezafibrate on plasma fibrinogen, fibrinopeptide A, platelet activation and blood filterability in atherosclerotic hyperfibrinogenemic patients

The effect of bezafibrate (BZF) on plasma fibrinogen levels has been studied in 62 patients with atherosclerotic vasculopathy and hyperfibrinogenemia (643 +/- 15 (SEM) mg/dl). In a preliminary study, 15-30 days of BZF therapy (400-600 mg/day) normalized fibrinogen values in 16 subjects were compared to 16 controls. The effect was rapid and dose-dependent, and discontinuation in 6 patients who could not complete the study was followed by a rebound increase. A controlled study with 400 mg/day in the other 24 patients for 15 days showed that BZF lowered fibrinogen, PF4, blood filterability and platelet aggregating thresholds to the normal range. BTG and FpA decreased significantly compared to the placebo group (12 and 12 patients randomly distributed) without any variation in potentially biassing hematologic values (WBC, PLTS, Ht, lipids and plasma glucose). BZF may be of value in chronic treatment of hyperfibrinogenemia in atherosclerotic patients with a view to improving the haemorheologic pattern and, hence, reducing activation of the coagulation pathway.

Raised concentrations of glucose and adrenaline and increased in vivo platelet activation after myocardial infarction

Plasma concentration of beta thromboglobulin was used as an index of in vivo platelet activation in 36 patients after acute myocardial infarction. Twelve patients had diabetes, seven had pulmonary oedema or cardiogenic shock (pump failure) or both, and 17 had uncomplicated infarcts. On the first day of admission, concentrations of beta thromboglobulin were higher in the patients with diabetes and those with pump failure than in those with uncomplicated infarcts. Concentrations of beta thromboglobulin in the non-diabetic patients were studied by multiple regression analysis and were significantly associated with plasma concentrations of adrenaline, pump failure, and glucose but not with noradrenaline or infarct size. When all subjects were considered together, glucose, adrenaline, and pump failure were associated with the beta thromboglobulin concentration but diabetes was without significant effect. Hyperglycaemia and raised plasma adrenaline concentration after myocardial infarction may activate platelets, and this could contribute to poor outcome in such patients.

Lack of association between haemostatic variables and the presence or the extent of coronary atherosclerosis

Blood samples were taken for haemostatic analysis from 225 patients with angina pectoris who were admitted to hospital for coronary angiography. beta thromboglobulin, platelet factor 3, platelet factor 4, factor VII:C, factor VIII:C, von Willebrand factor antigen, activated partial thromboplastin time, fibrinogen, antithrombin III, protein C:Ag, plasminogen, and antiplasmin were measured before angiography. Patients who had had a myocardial infarction in the two months before the investigation were excluded from the study. Multiple linear regression analysis showed that none of the haemostatic variables contributed independently to the prediction of an angiographic score that indicated the extent of coronary atherosclerosis. History of myocardial infarction, male sex, worsening of angina pectoris, serum triglycerides, and ejection fraction were independently associated with the angiographic score. There were some significant correlations between haemostatic variables and conventional risk factors for coronary heart disease. Thus data obtained from haemostatic analyses of peripheral venous blood do not permit the presence or the extent of atherosclerosis in coronary arteries to be predicted.

Association between time of increased fibrinopeptide A levels in plasma and episodes of spontaneous angina: a controlled prospective study

Thirty-seven patients affected by spontaneous angina and 15 comparable control subjects were enrolled in a 12-month prospective study to evaluate the relationship between blood clotting activation (assessed by fibrinopeptide A [FPA] plasma concentration) and the occurrence of myocardial ischemic attacks. FPA measurements and clinical examinations in patients were performed every 2 weeks. In control subjects blood sampling was performed every 4 weeks. Data from 28 patients who completed the study and from the 15 control subjects were analyzed. The clinical activity of angina was divided into three classes (asymptomatic, mildly symptomatic, and severely symptomatic) on the basis of the number and time-concentration of the ischemic attacks and ECG changes during the 15 days preceding each clinical examination. In all but one patient, a cyclic pattern of activity of coronary artery disease was observed. During follow-up studies, 624 FPA measurements were performed in patients and 173 in control subjects. Mean values were 4.68 +/- 4.53 and 1.32 +/- 0.60 ng/ml, respectively (p less than 0.001). FPA levels differed markedly in relation to the activity of angina. A relationship between FPA levels and activity of disease (r = 0.54, p less than 0.01) was found in time course. Bolus heparin administration (100 IU/kg) during the active phase of angina sharply but incompletely lowered FPA plasma levels, indicating thrombin formation both intravascularly and extravascularly. Present results indicate that a marked blood clotting activation occurs simultaneously with the outbursts of clinical activity of spontaneous angina.

Fibrinopeptide A and platelet factor levels in unstable angina pectoris

Fibrinopeptide A, platelet factor 4, beta-thromboglobulin, thromboxane B2, and 6-keto-prostaglandin F1 alpha were estimated by radioimmunoassay on venous plasma samples taken within 48 hr of admission from 16 consecutive patients with unstable angina and 15 patients with stable angina matched for clinical variables. The ratio of circulating platelet aggregates, platelet aggregation to increasing concentrations of ADP (0.455 to 1.82 micrograms/ml), and platelet thromboxane B2 production in vitro were also tested. The two groups of patients were statistically similar in terms of sex distribution, age, presence of risk factors, use of medication, extent of coronary artery disease and history of previous myocardial infarction. Mean plasma levels of fibrinopeptide A were 2.7 +/- 0.4 ng/ml (geometric means +/- SEM, range 1.5 to 5.5) in patients with stable angina vs 5.5 +/- 1.8 ng/ml (range 2.4 to 32; p less than .001) in those with unstable angina. In the latter group, after 6 to 8 days, fibrinopeptide A levels decreased to 3.6 +/- 0.5 ng/ml (range 1.5 to 9.3; p less than .04 vs admission). All other variables measured were statistically identical in the two groups. We conclude that plasma fibrinopeptide A levels, as opposed to platelet factors, discriminate between patients with unstable and stable angina, indicating an activation of the coagulation system in unstable angina.

Fibrin formation and platelet aggregation in patients with acute myocardial infarction: effects of intravenous and subcutaneous low-dose heparin

Fibrinopeptide A (FPA) and beta thromboglobulin (BTG) were measured in 42 patients with acute myocardial infarction (AMI) allocated on admission to one of three groups: 14 patients received a heparin bolus injection of 5000 IU intravenously followed by a 2-hour intravenous infusion (830 IU/hr) (group 1), 14 patients received a heparin bolus of 5000 IU subcutaneously (group 2), and the remaining 14 patients received no anticoagulant treatment (group 3). In group 1 the initially elevated FPA level of 5.8 +/- 1.8 ng/ml dropped to 2.0 +/- 1.5 ng/ml 30 minutes after the intravenous heparin bolus injection of 5000 IU (p less than 0.001) and returned to normal (1.9 +/- 0.8 ng/ml) in 8 of 14 patients. The initially elevated BTG level of 64 +/- 21 ng/ml did not change significantly during intravenous heparin treatment, whereas there was a rapid but only transitory increase in platelet factor 4, (PF4) from 25 +/- 9 to 74 +/- 16 ng/ml (p less than 0.01) after the intravenous heparin bolus. In group 2 the initial FPA of 5.0 +/- 2.3 ng/ml was similarly elevated as in group 1 and dropped to 2.7 +/- 1.7 and 3.3 +/- 1.5 ng/ml 2 and 4 hours after 5000 IU subcutaneously (p less than 0.05), whereas 6 and 8 hours after subcutaneous heparin bolus the mean FPA levels were 4.2 +/- 1.7 and 5.5 +/- 2.0 ng/ml and no more significantly different from the initial FPA values. BTG and PF4 did not change significantly after the subcutaneous heparin bolus. In group 3 the initially elevated mean FPA level of 4.9 +/- 2.4 ng/ml did not change significantly during the first 8 hours after admission, whereas the FPA level 24 hours after admission was 8.4 +/- 3.9 ng/ml and higher than the initial value (p less than 0.01). We conclude that heparin may reduce the elevated FPA level in plasma found in patients with AMI; however, neither subcutaneous nor intravenous heparin in a dosage frequently used is sufficient to consistently normalize the elevated rate of fibrin formation found in these patients.

Soluble fibrinogen derivatives generated by thrombin: affinity for elastin

When human citrated plasma is dialysed against a phosphate buffer containing Ca++, citrate anions are removed, thrombin is generated and soluble fibrinogen derivatives (fibrin monomers and/or soluble fibrin polymers) are formed. These derivatives are able to combine with human or bovine elastin to form a very stable addition product or adduct. The formation of the adduct is dependent on time, Ca++ and thrombin concentrations.

Platelet hyperaggregability in patients with chest pain and angiographically normal coronary arteries

Forty-one patients with chest pain and angiographically normal coronary arteries were studied for platelet abnormalities. Patients with conditions known or suspected to be associated with chest pain or platelet dysfunction were excluded. After coronary angiography and 2-week withdrawal from all medications, platelet aggregometry was performed using peripheral venous plasma samples and 3 concentrations of adenosine diphosphate, 2.34, 1.17 and 0.58 microM, and epinephrine, 11, 1.1 and 0.55 microM, as stimuli. Platelet morphology in response to surface contact (adhesion) was evaluated by transmission electron microscopy to determine the percentage of platelets in the round/abortive (inactive), dendritic (intermediate) and spread (activated) forms. Plasma specimens obtained from healthy volunteers of similar age and sex were analyzed in parallel and served as control subjects. Compared with control subjects, patients had increased aggregation at all concentrations of both adenosine diphosphate and epinephrine (p less than 0.001). Patients also had fewer platelets in the dendritic form and more in the round/abortive and spread forms. Thus, patients with chest pain and normal coronary arteries have platelet hyperaggregability in vitro, although the clinical relevance of this finding is unclear.

Plasma levels of platelet secretory proteins

Platelets contain three types of secretory organelles: the dense granules, the alpha granules, and the lysosomes. Most of the proteins secreted from platelets are stored in the alpha granules, whereas the dense granules contain substances such as adenine nucleotides, serotonin, Ca++, and inorganic pyrophosphate types as well as a heparatinase. Three of the secreted alpha granule proteins have been measured by radioimmunoassay and it has been suggested that levels of these proteins in patient plasmas provide an index of in vivo platelet activation and secretion. These three are beta-thromboglobulin, platelet factor 4, and thrombospondin. In this chapter the chemistry of these proteins will be considered briefly, as will their clearance from the circulation, and then the clinical studies will be reviewed critically. Since radioimmunoassays were developed for these proteins (the first was reported in 1975), there has been a profusion of reports on levels of one or another of these proteins in a wide range of disease states, and these reports have indicated secreted platelet protein levels ranging from normal to grossly elevated in a given disease state. Possible reasons for such variability will be discussed.

Fibrinopeptide A excretion in urine in patients with atherosclerotic artery disease

Urinary fpA excretion and fpA in plasma were studied in patients with peripheral artery disease, aortic aneurysm, severe coronary artery disease, acute myocardial infarction and in normal controls. Mean urinary fpA was significantly higher in all groups of patients than in normal controls whose excretion was 1.9 +/- 1.2 micrograms/24 hours (mean +/- SD). We found a good correlation between urinary fpA excretion and plasma fpA (r = 0.68, p less than 0.01, n = 81). The highest levels of urinary fpA were found in 9 patients with aortic aneurysm (11.9 +/- 6.1 micrograms/24 hours). The 10 patients with acute myocardial infarction had also abnormally elevated values (4.3 +/- 1.8 micrograms/24 hours) which were only slightly higher than the levels found in another 10 patients with myocardial infarction receiving subcutaneous heparin in a dosage of 2 X 5000 IU daily (2.9 +/- 1.7 micrograms/24 hours). The 13 patients with peripheral artery disease showed an increase in urinary fpA excretion from 4.0 +/- 1.7 to 10.5 +/- 2.3 micrograms/24 hours after percutaneous angioplasty (p less than 0.001). These data demonstrate that urinary fpA excretion may represent a valid means to detect the cumulative effect of thrombin action on fibrinogen in patients with atherosclerotic vascular disease and after therapeutic intervention.