Evidence for reduced fibrinolytic activity in unstable angina at rest. Clinical, biochemical, and angiographic correlates

Predictors for layered coronary plaques: an optical coherence tomography study

Healed coronary plaques, morphologically characterized by a layered pattern, are signatures of previous plaque disruption and healing. Recent optical coherence tomography (OCT) studies showed that layered plaque is associated with vascular vulnerability. However, factors associated with layered plaques have not been studied. The aim of this study was to investigate predictors for layered plaque at the culprit plaques and at non-culprit plaques. Patients with coronary artery disease who underwent pre-intervention OCT imaging of the culprit lesion were included. Layered plaques were defined as plaques with one or more layers of different optical density and a clear demarcation from underlying components. Among 313 patients, layered plaque at the culprit lesion was observed in 18.8% of ST-segment elevation myocardial infarction patients, 36.3% of non-ST-segment elevation acute coronary syndrome patients, and 53.4% of stable angina pectoris (SAP) patients (p < 0.001). In the multivariable model, SAP, multivessel disease, type B2/C lesion, and diameter stenosis > 70% were independent predictors for layered plaque at the culprit lesion. In addition, 394 non-culprit plaques in 190 patients were assessed to explore predictors for layered plaques at non-culprit lesions. SAP, and thin-cap fibroatheroma and layered plaque at the culprit lesion were independent predictors for layered plaques at non-culprit lesions. In conclusion, clinical presentation of SAP was a strong predictor for layered plaque at both culprit plaques and non-culprit plaques. Development and biologic significance of layered plaques may be related to a balance between pan-vascular vulnerability and endogenous anti-thrombotic protective mechanism.

Effects of Recombinant Human Erythropoietin on Functional and Injury Endothelial Markers in Peritoneal Dialysis Patients

Clinical effects of recombinant human erythropoietin (rHuEPO) such as thrombosis, convulsions, hyperviscosity, hypertension, and angiogenic effect in culture cells have been described. We studied the rHuEPO effect on endothelial damage markers and endothelial function markers: tissue-type plasminogen activator (t-PA), nitrate (NO3), thrombomodulin (TM), and von Willebrand factor (vWF). Twenty-six peritoneal dialysis patients treated with rHuEPO and 19 controls were included.

The study design for rHuEPO patients consisted of four periods: long-term treatment (rHuEPO-1); 2 months of withdrawal (rHuEPO-2); and 4 months on 5000 IU/week rHuEPO subcutaneously, with markers being measured after 2 months (rHuEPO-3) and after 4 months (rHuEPO-4).

After 2 months of rHuEPO withdrawal, a decrease in hemoglobin level appeared (11 ± 1.8 g/dL to 9.2 ± 1.5 g/dL, p < 0.01). After rHuEPO reintroduction, this value reached 10.6 ± 1.5 g/dL at two months, and 11.1 ± 1.4 g/dL at four months. A significant increase in t-PA ratio was observed from two months without rHuEPO to two months on rHuEPO, returning to previous values after four months. Similarly, TM increased for patients with creatinine clearances (CrC) < 5 mL/min. No changes in the higher-thannormal plasma vWF levels were found during the various periods. A statistically significant lower value was found in controls compared with rHuEPO-4 patients. A statistically significant increase in NO3 levels was observed in the pre-venous occlusion (VO) test immediately after the re-introduction of rHuEPO. This increment returned to prior values four months after rHuEPO was reintroduced.

Our results show that rHuEPO treatment causes an increase in some endothelial damage markers (TM, t-PA) and modifies endothelial function markers (t-PA ratio, NO3). These changes might favor thrombosis and atherosclerosis.

Impact of cilazapril on fibrinolytic system in hypertensive patients

Impaired fibrinolysis is associated with thromboembolic complications in hypertensive patients. Cardiovascular morbidity/mortality rates have been reported high even after lowering the elevated blood pressure with antihypertensive drugs. We investigated the effects of clinically used dosages of cilazapril on the fibrinolytic system in hypertensive patients. The present study was performed among 30 hypertensive patients (22 women, eight men), who received 2.5-5.0 mg cilazapril daily for 1 month. Before and after the cilazapril treatment, patients' venous blood was drawn for fibrinolytic tests. The fibrinolytic activity was examined utilizing the euglobulin clot lysis time and fibrin plate methods. Using the fibrin plate method, as compared with the pretreatment group, we observed a 57% increased activity in the hypertensive patients receiving cilazapril (P < 0.001). When assessed by the euglobulin clot lysis time method, the activity due to cilazapril treatment was found to be relatively low, although highly significant (approximately 20%, P < 0.001). Changes in fibrinolytic activity were observed in 23 (77%) hypertensive patients after cilazapril treatment; however, their blood pressure remained normal. The remaining seven patients' (23%) blood pressures and fibrinolytic activity did not change significantly after cilazapril treatment. In conclusion, we suggest that the observed differential fibrinolytic activity between the pre and post cilazapril treatment values is due to the plasminogen activators released from the vascular endothelium, which may have been stimulated by cilazapril. It appears that cilazapril is not only an angiotensin-converting enzyme inhibitor but also a stimulator for fibrinolytic activity, which may be an added component in reducing thromboembolic complications in hypertensive patients.

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.

Relationship between minor myocardial damage and inflammatory acute-phase reaction in acute coronary syndromes

BACKGROUND

In severe acute coronary syndromes (ACS) elevation of markers of inflammation and acute phase reaction (APR) like C-reactive protein (CRP) as well as a release of troponin have been reported. Using a high sensitivity troponin T (TnT) test we investigated whether an APR occurs in ACS only in the presence of ischemic myocardial damage.

METHODS

In 85 patients with ACS C-reactive protein (CRP), serum amyloid A (SAA), fibrinogen, thrombin antithrombin III complexes (TAT) and kallikrein were determined vs. high sensitive TnT (> or =0.02 ng/ml) initially and 2 d later vs. 45 patients with stable angina pectoris and 42 controls.

RESULTS

In stable angina pectoris, markers of inflammation and coagulation were slightly elevated (p < 0.05). Initially in ACS elevations of CRP to 1.2 +/- 0.3 mg/dl, SAA to 4.8 +/- 2.6 mg/dl and fibrinogen to 448 +/- 21 mg/dl (all p < 0.01 vs. controls) were found followed by a significant APR (p < 0.01). In the subgroup of TnT positive ACS patients, an APR with increased CRP (4.1 +/- 1.3 mg/dl), SAA (20.4 +/- 8.3 mg/dl), and fibrinogen (641 +/- 45 mg/dl) was detectable (all p < 0.05 vs. TnT negative patients). In contrast, patients without TnT release showed APR markers comparable to patients with stable angina pectoris.

CONCLUSION

Our findings demonstrate an association between myocardial injury in ACS and acute phase reaction as evidenced by several molecular markers. A highly sensitive TnT-test identified myocardial injury in about all patients with APR while a standard TnT cut-off (0.1 ng/ml) missed 32% of these patients. Thus, the APR in patients with ACS is strongly associated with at least minor ischemic myocardial damage and prior findings of an APR independent from myocardial injury are probably based on less sensitive troponin tests.

Platelet-dependent thrombin generation in patients with unstable angina pectoris

Platelet-dependent thrombin generation was assessed during both unstable and stable periods in 59 patients with unstable angina and at rest in 31 healthy controls. Thrombin generation during the unstable period was significantly greater than that at rest in the healthy control group (p < 0.0001) and that during the stable period (p < 0.0001). Changes in thrombin generation were related to the time after onset of unstable angina, not to degree of improvement in the severity of coronary stenosis.

Maximal endothelial tissue plasminogen activator release is not impaired in patients with acute coronary syndromes before heparin treatment

Procoagulant and fibrinolytic disturbances are described in patients with acute coronary syndromes (ACS), but whether defective maximal tissue plasminogen activator (t-PA) release from the endothelium is also present is still controversial. Previous studies did not take into consideration the contribution of heparin, which strongly affects fibrinolysis. Accordingly, in this study, we measured maximal t-PA release in patients with ACS before, during, and after heparin treatment. Maximal t-PA release was measured by the venous occlusion test in 38 hospitalized patients with confirmed ACS (18 acute myocardial infarctions and 20 unstable anginas) before starting heparin, during heparin treatment, and 4 and 12 h after discontinuation. Plasma plasminogen activator inhibitor type 1 (PAI-1), D-dimer and prothrombin fragment F1 + 2 were also measured. Eighteen age-matched subjects with no evidence of coronary disease were used as controls. At admission, patients showed significantly higher plasma levels of t-PA, PAI-1, and F1 + 2 than controls. Before heparin, maximal t-PA release was similar in patients and controls. Heparin treatment was associated with a significant increase of plasma t-PA, while it did not affect maximal t-PA release. Coagulative and fibrinolytic disturbances are present in patients with ACS, but these do not include maximal t-PA release. Among our patients, maximal t-PA release appears stable over time and is not affected by heparin treatment.

Surface 12-Lead Electrocardiographic Findings and Plasma Markers of Thrombin Activity and Generation in Patients with Myocardial Ischemia at Rest

Background: Myocardial ischemia at rest is typically associated with atherosclerotic coronary artery disease, atherommous plaque rupture, and intracoronary thrombosis. In areas of advanced disease and vascular injury, the extent of thrombus is influenced largely by a delicate balance of procoagulant factors, favoring thrombus initiation, growth, and development, and anticoagulant factors, attempting to limit potentially flow-limiting coronary thrombosis. Thrombin, a 308 amino acid serine pretense, is considered the most patent procoagulant factor in the setting of acute vessel wall injury, playing an essential role in the conversion of fibrinogen to fibrin, accelerating the prothrombinase complex, activating platelets, and stabilizing fibrin polymers. The purpose of this study was to determine the relationship between electrocardiographic abnormalities and markers of thrombin activity and generation among patients with unstable angina and non-Q.wave myocardial infarction. Mehtods and Results: In a study of 36 patients (59.1+/- 11.0 years) with myocardial ischemia at rest participating in the Thrombolysis in Myocardial Ischemia (TIMI) IIIB trial, thrombin activity in plasma, as determined by fibrinopeptide A (FPA), prothrombin fragment 1.2 (F 1.2), and thrombin-antithrombin III complexes (TAT) concentrations, were found to be increased significantly when compared with healthy volunteers (p < 0.004). Thrombin generation was also increased modestly compared with age-matched patients with stable coronary artery disease undergoing elective cardiac catheterization. Given that,he surface 12-lead electrocardiogram (ECG) is frequently abnormal in patients with ischemic chest pain at rest and represents a readily available, first-line diagnostic test for assessing disease activity and treatment response, we investigated whether ECG abnormalities and thrombin activity/generation in plasma were correlated. Twenty-six patients (72%) had ECG changes compatible with myocardial ischemia at the time of study entry, including 18 (50%) with newly inverted T waves (or pseudonormalization), 14 (39%) with reversible ST-segment depression, and 4 (11%) with transient (<30 minutes) ST-segment elevation. Within the predefined ECG groups there were no differences in plasma thrombin activity between patients with and those without confirmed abnormalities. Similarly, there were no differences in either plasma thrombin activity or generation between the predefined ECG groups. Conclusion: Although ECG abnormalities supporting the presence of myocardial ischemia occur commonly in patients with chest pain at rest, they do not correlate closely with markers of thrombin activity and generation in plasma. The diagnostic and prognostic capabilities of these diagnostic tools, considered either alone or together, require further investigation.

Differential effects of enalapril and nitrendipine on the fibrinolytic system in essential hypertension

BACKGROUND

Impaired fibrinolysis is associated with thromboembolic complications in hypertensive patients. It has been reported that cardiovascular morbidity and mortality rates are high even after lowering the elevated blood pressure with antihypertensive drugs. The aim of this study was to assess the effect of clinically used dosages of enalapril and nitrendipine on the fibrinolytic system.

METHODS

Tissue plasminogen activator antigen (tPA) and tissue plasminogen activator inhibitor-1 (PAI-1) activity were measured in 20 normotensive male subjects and 46 male patients with mild essential hypertension divided into 2 groups (22 patients treated with 5 to 10 mg enalapril once a day and 24 treated with 5 to 10 mg nitrendipine once a day) before and 3 months after drug administration. Plasma renin activity and norepinephrine concentration were also measured.

RESULTS

There were no significant differences in basal characteristics between the 2 hypertensive groups. In both hypertensive groups, blood pressure was significantly reduced to a similar level after drug treatment. In the 2 hypertensive groups, plasma renin activity significantly increased after drug treatment; however, there were no significant changes in norepinephrine concentration. Before drug treatment, the 2 hypertensive groups had significantly higher tPA and higher PAI-1 activity than the normotensive subjects. In the enalapril group, there was no significant change in tPA although PAI-1 activity significantly decreased after drug treatment. In the nitrendipine group, there was no significant change in tPA although PAI-1 activity significantly increased after drug treatment.

CONCLUSION

Thus enalapril improved impaired fibrinolysis but nitrendipine further aggravated fibrinolysis in essential hypertension. Considering the effect of antihypertensive drugs on the fibrinolytic system, more effective and beneficial treatment of hypertensives, especially at a high risk for thrombus formation might be selected.

Postmenopausal hormone replacement, risk estimators for coronary artery disease and cardiovascular protection

Menopause, regardless of age at onset, is associated with a marked increase in coronary artery disease (CAD) risk. A large body of observational clinical studies repeatedly demonstrated favorable associations between postmenopausal hormone replacement therapy (HRT) and cardiovascular morbidity, mortality, and risk factors. Estrogens may act in a gender-specific way on vascular endothelial cells and other components of the vessel wall, enhancing the synthesis and release of nitric oxide (NO) and other vasodilators, and by inhibiting the synthesis and release of vasoconstricting agents, thus favoring vasodilation. Menopause-related changes in metabolic cardiovascular risk factors are identifiable, as are HRT-related changes in these factors. The metabolic effects include changes in lipoprotein (a), coagulation and fibrinolysis as well as homocysteine metabolism. The various actions of estrogen alone and combined with progestogen on the vascular system are reviewed. Furthermore, the outcome of the recently published Heart and estrogen/progestin replacement study (HERS) data are put in perspective. In addition, we outline the present data on the effects of raloxifene, a new second generation selective estrogen receptor modulator (SERM), which has been shown to favorably alter several markers of cardiovascular risk in postmenopausal women.

Systemic and translesional activation of coagulation, fibrinolytic, and inhibitory systems in candidates for coronary angioplasty: basal state and effect of successful dilation

OBJECTIVES

Thrombosis is a major contributor to complications associated with coronary interventions. It is unclear whether patients who have undergone angioplasty are predisposed to thrombus formation because of underlying perturbations in their hemostatic equilibrium.

METHODS

Concentration or activity was measured for 14 plasma proteins involved in the coagulation, fibrinolytic, and inhibitory systems. Baseline systemic measurements were compared between patients undergoing balloon angioplasty (n = 15) and normal subjects (n = 32), with sampling repeated at the end of the procedure. To better assess the local hemostatic environment near the site of dilation, intracoronary arterial samples were also obtained just proximal and distal to the dilated stenosis.

RESULTS

Multiple differences in measured coagulation proteins were found at baseline between the angioplasty candidates and control subjects, including higher mean concentration of plasma fibrinogen (P <.001) and lower high-molecular-weight kininogen concentration (P <.01) and factor XII activity (P <.01). Concentrations of the inhibitory proteins antithrombin III and protein S also differed significantly (P <.001 and P <.01, respectively), with a trend toward lower protein C concentration as well (P <.05). Finally, heightened fibrinolysis was suggested by a marked increase in mean plasma d-dimer concentration in the angioplasty candidates (293 +/- 191 ng/mL vs 116 +/- 31 ng/mL, P <.01), with a more modest increase in tissue plasminogen activator (P <.05) and decrease in alpha2-antiplasmin (P <.001). Importantly, none of the parameters obtained during the procedure differed significantly from samples obtained before and after angioplasty, and no translesional gradients were observed.

CONCLUSIONS

Patients with active ischemic syndromes who are considered candidates for coronary angioplasty demonstrate significant and multiple alterations in their coagulation, inhibitory, and fibrinolytic systems. However, no further changes were observed during coronary dilation, either systemically or locally, after pretreatment with typical doses of heparin and aspirin.

Streptokinase-induced activation of the kallikrein-kinin system and of the contact phase in patients with acute myocardial infarction

Thrombolytic therapy in acute myocardial infarction (AMI) is hampered by a considerable reocclusion rate. Thrombin activity is enhanced, and contact-system activation via plasminemia might be possible. Prospectively we examined the contact phase and the kallikrein-kinin system and additional molecular markers of hemostasis and fibrinolysis in AMI. In 22 patients with AMI, blood sampling was performed at admission and < or =10 days afterward. Eleven patients received 1.5 Mio U streptokinase (group A) and were compared with 11 AMI patients without thrombolytic therapy (group B). All patients had systemic heparinization (5,000 IU bolus, i.v.; 1,000 IU/h, i.v.). In group A (vs. group B), the kallikrein-factor XII system was significantly activated (3 h after start of therapy): kallikrein activity 140 +/- 41 (vs. 43 +/- 8) U/L (p < 0.05); kallikrein inhibition 87 +/- 9 (vs. 113 +/- 7%; p < 0.05), and factor XII 70 +/- 14 (vs. 94 +/- 6%). C1 inhibitor and factor XII inhibition were decreased. High-molecular-weight kininogen consumption indicating bradykinin generation was enhanced (p < 0.01). In group A, thrombin activity (TAT) was increased, and a hypercoagulative state with increased fibrin degradation products (d-dimer) was found. Plasmin activation in group A was reflected by decreased plasminogen and antiplasmin levels (p < 0.01). The findings indicate that streptokinase induces activation of the contact phase-kinin system in vivo associated with a consecutive increase of thrombin and bradykinin generation. Activation of this pathway might substantially contribute to reocclusion after initially successful thrombolytic therapy and to hypotensive reactions observed after streptokinase.

Endothelial tissue-type plasminogen activator release in coronary heart disease: Transient reduction in endothelial fibrinolytic reserve in patients with unstable angina pectoris or acute myocardial infarction

OBJECTIVES

We sought to examine whether the disturbed fibrinolytic system in patients with an acute coronary syndrome is associated with a reduced endothelial fibrinolytic capacity.

BACKGROUND

Intracoronary thrombus formation is a frequent finding in acute coronary syndromes. Systemic alterations of coagulation and fibrinolysis are known to occur, but possible disturbances of endothelial fibrinolytic function have not been investigated.

METHODS

We compared 42 patients with an acute coronary syndrome (acute myocardial infarction in 11 and unstable angina pectoris in 31) with 25 patients with stable angina. Venous blood was sampled serially for determination of markers of the fibrinolytic system and of hypercoagulability from admission to day 10. An occlusion test to determine the maximal endothelial tissue-type plasminogen activator (t-PA) release was also performed.

RESULTS

Both on day 0 and day 10, patients with an acute coronary syndrome had a marked elevation of t-PA mass concentration (mean value +/- SEM 14.4 +/- 1.6 [day 0], 18.9 +/- 2.5 ng/ml [day 10]) and of plasminogen activator inhibitor (PAI) (9.4 +/- 2.2 [day 0], 11.3 +/- 2.6 AU/liter [day 10], p < 0.05 vs. patients with stable angina). There was also a hypercoagulative state with elevated thrombin activity and increased D-dimers (p < 0.05 vs. patients with stable angina). Maximal endothelial t-PA release was initially reduced (p < 0.05 vs. patients with stable angina) to 2.3 +/- 0.9 ng/ml, but levels recovered during follow-up to 4.4 +/- 1.4 ng/ml (vs. 5.7 +/- 1.5 ng/ml in patients with stable angina).

CONCLUSIONS

Despite the known prolonged systemic alteration of fibrinolysis in acute coronary syndromes, endothelial fibrinolytic capacity is reduced only during the acute phase and becomes normalized during follow-up, and thus is linked more to intravascular thrombus formation than to steady state levels of markers of the fibrinolytic system.

Enhanced coagulation activation in troponin T-positive unstable angina pectoris

Intracoronary thrombus formation and systemic activation of coagulation have been demonstrated in unstable angina pectoris. Circulating troponin T as a marker of minor myocardial cell injury is associated with adverse outcome in this condition. Little information exists about the interrelation of coagulation activation and myocardial cell injury in unstable angina. We quantitatively assessed systemic activation of coagulation and myocardial cell injury in serial blood samples obtained up to 10 days from 22 patients with angiographically documented coronary heart disease and unstable angina pectoris at rest. In the nine patients with increased maximal levels of serum troponin T, maximal concentrations of fibrin monomers during the first 48 hours were higher than those in patients with persistently normal troponin T concentrations (6.3+/-4.8 vs. 2.9+/-2.3 mg/L; p = 0.04). The proportion of patients with at least one blood sample showing an increased concentration of plasma fibrin monomer was also higher in the group with increased troponin T (67% vs. 15%; p = 0.04). Plasma prothrombin fragment F1+2 levels showed a nonsignificant trend toward higher values in troponin T-positive patients. Enhanced activation of coagulation in patients with troponin T-positive unstable angina may contribute to the adverse outcome associated with this condition.

Percutaneous interventions alter the hemostatic profile of patients with unstable versus stable angina

OBJECTIVES

The objectives of this study were to define the hemostatic profiles of patients with unstable angina compared with patients with stable angina and to investigate the effect of percutaneous interventions on the follow-up hemostatic profiles of these patients.

BACKGROUND

Disturbances in hemostatic factors have been shown to be present in various clinical syndromes involving coronary artery disease. However, their role in stable angina versus unstable angina is less well defined.

METHODS

We studied 61 patients with either stable or unstable angina undergoing percutaneous coronary interventions. Blood samples were drawn immediately before the intervention and at 1-month follow-up. Plasma levels of tissue-type plasminogen activator (t-PA), plasminogen activator inhibitor-1 (PAI-1) and von Willebrand factor (vWF) were measured by enzyme-linked immunosorbent assays.

RESULTS

Patients with unstable angina had significantly higher t-PA levels (mean [+/-SE] 23.7 +/- 3.4 vs. 14.3 +/- 1.4 ng/ml, respectively, p = 0.02) and vWF antigen concentrations (2,231 +/- 157 vs. 1,792 +/- 108 mU/ml, respectively, p = 0.03) than patients with stable angina. No statistically significant differences were observed in the PAI-1 levels between the two groups (27.9 +/- 5.5 vs. 21.4 +/- 2.5 ng/ml, respectively, p = 0.25). At 1-month follow-up, there were no longer any significant differences in the t-PA or vWF levels between the two groups (15.7 +/- 1.2 vs. 13.6 +/- 0.6 ng/ml, p = 0.13; 1,962 +/- 170 vs. 1,809 +/- 88 mU/ml, p = 0.39, respectively). There were no significant differences between the hemostatic profiles of patients undergoing percutaneous transluminal coronary angioplasty or coronary stenting initially and at 1-month follow-up.

CONCLUSIONS

These data suggest that elevated plasma levels of t-PA and vWF may correlate with instability of atheromatous plaques, and that their decrease after coronary interventions may reflect plaque reendothelialization and stabilization.

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.

The effects of cardiopulmonary bypass on fibrin formation and lysis: is a normal fibrinolytic response essential?

Fibrinolytic activity in blood is regulated by a dynamic process that includes control of production, secretion, inhibition, and clearance of fibrinolytic proteins. The concentration of active tissue plasminogen activator (tPA) in the region of the thrombus controls the rate of fibrinolytic activation. We have developed a first-generation kinetic model that can be used to simulate the effects of secretion, inhibition, and clearance reactions on the concentrations of active tPA, active plasminogen activator inhibitor type 1 (PAI-1), and tPA/PAI-1 complex in the circulation. This model was used to estimate the rate and pattern of secretion of tPA and PAI-1 in individual subjects. We also undertook a laboratory evaluation of fibrinolysis in patients with a history of myocardial infarction. Elevated PAI-1 activity in the absence of elevations in other acute-phase proteins suggested an intrinsic increase in PAI-1 secretion in patients post-myocardial infarction. Cardiopulmonary bypass (CPB) results in a major increase in fibrinolytic activity that has been associated with an increased risk for hemorrhage. Fibrinolytic proteins were sampled from patients both during surgery and for 2 days postoperatively. Total tPA antigen rose throughout CPB and returned to baseline in the post-operative period. PAI-1 activity fell during the initial bypass and by the end of bypass had returned to baseline. On the first to second postoperative day there was a large increase in PAI-1 activity and a significant decrease in tPA activity. These data suggest that during this period there is a window of risk for a thromboembolic event. There was, however, a large individual variability in patient response to CPB.

Risk factors for restenosis after percutaneous transluminal coronary angioplasty: role of lipoprotein (a)

To evaluate serum levels of lipoprotein (a) (Lp[a]) as a predictor of restenosis after percutaneous transluminal coronary angioplasty (PTCA), we evaluated 71 patients who underwent elective single-vessel angioplasty. Patients were divided into two groups according to the presence (n = 24 [34%]; group R) or absence (n = 47 [66%]; group N) of restenosis. Serum insulin levels were similar before and after the glucose challenge test in both groups. The median level of serum Lp(a) was 34.9 mg/dl in group R compared with 19.4 mg/dl in group N (p < 0.01). The frequency of the apo E4 allele was 4 (17%) in group R and 4 (9%) in group N (p = NS). The incidence of restenosis was significantly higher in patients with Lp(a) levels > or = 30 mg/dl than in those with Lp(a) levels < 30 mg/dl (65% vs 26%; p < 0.01). Our results indicate that a serum Lp(a) level > or = 30 mg/dl is a risk factor for restenosis.

Time significance of acute thrombotic reactant markers in patients with and without silent myocardial ischemia and overt unstable angina pectoris

Ischemic electrocardiographic changes were recorded within 2 hours of admission using a 12-lead electrocardiographic continuous monitor with a 20-second scanning interval and an alarm mode for asymptomatic events. Blood samples were obtained at admission and at the moment of asymptomatic events (group A). In the other patients who did not develop ischemia, a second blood sample was taken 12 hours later (group B). We determined prothrombin time, activated partial thromboplastin time, clotting factor VIII activity, tissue plasminogen activator activity, tissue plasminogen activator inhibitor-1, cross-linked fibrin degradation product, and thrombin-antithrombin III complexes. There was a statistically significant difference between group A and B patients when the basal samples were analyzed for thrombin-antithrombin III (p = 0.046) and d-Dimer (p = 0.005). Prothrombin fragment 1 + 2 were significantly reduced, and d-Dimer was elevated when basal blood samples were compared with the second sample in patients who developed silent events (p = 0.008 and 0.055, respectively). A plasma concentration of thrombin-antithrombin III complex was also significantly decreased when sample 2 was compared with the basal blood sample (p = 0.039). Five recurrent episodes of angina and 2 nonfatal infarctions occurred, and 4 urgent revascularization procedures were performed in group A. In group B, there was only 1 nonfatal infarction (p = 0.01). The results of the present study suggest that a time-dependent thrombotic process is detectable in the blood stream as a cyclic movement. Further studies are needed to determine if some other factors, such as intensive shear stress in the vessel wall, may activate plaque instability during asymptomatic episodes.

Hemostatic factors and the risk of myocardial infarction or sudden death in patients with angina pectoris. European Concerted Action on Thrombosis and Disabilities Angina Pectoris Study Group

BACKGROUND

Increased levels of certain hemostatic factors may play a part in the development of acute coronary syndromes and may be associated with an increased risk of coronary events in patients with angina pectoris.

METHODS

We conducted a prospective multicenter study of 3043 patients with angina pectoris who underwent coronary angiography and were followed for two years. Base-line measurements included the concentrations of selected hemostatic factors indicative of a thrombophilic state or endothelial injury. The results were analyzed in relation to the subsequent incidence of myocardial infarction or sudden coronary death.

RESULTS

After adjustment for the extent of coronary artery disease and other risk factors, an increased incidence of myocardial infarction or sudden death was associated with higher base-line concentrations of fibrinogen (mean +/- SD, 3.28 +/- 0.74 g per liter in patients who subsequently had coronary events, as compared with 3.00 +/- 0.71 g per liter in those who did not; P = 0.01), von Willebrand factor antigen (138 +/- 49 percent vs. 125 +/- 49 percent, P = 0.05), and tissue plasminogen activator (t-PA) antigen (11.9 +/- 4.7 ng per milliliter vs. 10.0 +/- 4.2 ng per milliliter, P = 0.02). The concentration of C-reactive protein was also directly correlated with the incidence of coronary events (P = 0.05), except when we adjusted for the fibrinogen concentration. In patients with high serum cholesterol levels, the risk of coronary events rose with increasing levels of fibrinogen and C-reactive protein, but the risk remained low even given high serum cholesterol levels in the presence of low fibrinogen concentrations.

CONCLUSIONS

In patients with angina pectoris, the levels of fibrinogen, von Willebrand factor antigen, and t-PA antigen are independent predictors of subsequent acute coronary syndromes. In addition, low fibrinogen concentrations characterize patients at low risk for coronary events despite increased serum cholesterol levels. Our data are consistent with a pathogenetic role of impaired fibrinolysis, endothelial-cell injury, and inflammatory activity in the progression of coronary artery disease.

Tissue-type plasminogen activator and plasminogen activator inhibitor activities as predictors of adverse events in unstable angina

Among patients with recent-onset unstable angina and evidence of ischemia or coronary artery disease, the incidence of subsequent cardiovascular events is high. The aim of this study was to investigate, in this high-risk population, whether unstable angina was associated with abnormalities of tissue-type plasminogen activator (t-PA) or plasminogen activator inhibitor (PAI) activities and whether, in a prospective study, any of these parameters would identify patients with an adverse cardiovascular prognosis. A group of 22 high-risk patients with unstable angina (64% event rate at 3 months) was studied prospectively for 12 weeks, and the fibrinolytic parameters measured at presentation were related to subsequent cardiovascular progress. A group of 20 age- and sex-matched healthy subjects acted as control subjects. Patients who had subsequent cardiovascular events (acute myocardial infarction or severe recurrent angina +/- intervention) had significantly elevated PAI activity at presentation compared with both those who remained event-free (p < 0.05) or with control subjects (p < 0.02). In addition, basal activation of fibrinolysis was demonstrated in unstable angina at presentation; this persisted at 9 weeks in patients with a favorable outcome (p < 0.02 vs control subjects), whereas it was no longer evident in those who developed cardiac events. These findings suggest that measurements of t-PA/PAI activity may reflect the underlying pathophysiologic state and relate to subsequent cardiovascular events in unstable angina.

Myocardial ischemia after orthotopic liver transplantation

A hypercoagulable state exists after orthotopic liver transplantation. This hematologic abnormality may predispose patients to coronary thrombosis and unstable angina. The incidence of postoperative myocardial ischemia in such patients is unknown. Suitable electrocardiograms and clinical events of consecutive patients undergoing orthotopic liver transplantation (n = 45) and major intraabdominal surgery (n = 28) during a 3-month period at a major university teaching hospital and transplant center were examined retrospectively. Clinical myocardial ischemia or ischemic electrocardiographic changes, or both, occurred in 6 transplant patients compared with no patient in the nontransplant or comparison group. In 4 of the 6 patients with dramatic electrocardiographic changes and ischemic events, coronary arteriography failed to demonstrate significant obstructive disease. It is concluded that severe myocardial ischemia may occur in patients after orthotopic liver transplantation in the absence of significant coronary disease. A hypercoagulable state may predispose to coronary thrombosis in this setting, providing insight (and a future model for study) into the development of unstable angina.

Importance of thrombosis and thrombolysis in silent ischaemia: comparison of patients with acute myocardial infarction and unstable angina

OBJECTIVE

To investigate whether plaque rupture and thrombosis have a role in silent ischaemia as well as in unstable angina.

DESIGN

Prospective analysis of the results of haemostatic diagnostic tests at the moment of developing silent ischaemia at rest.

SETTING

Coronary care unit.

PATIENTS

22 patients with acute myocardial infarction, 12 patients with symptomatic angina (unstable angina), and 10 normal volunteers (control group).

INTERVENTIONS

Continuous cardiac monitoring detected 15 asymptomatic episodes (silent ischaemia) in 6 patients with unstable angina. Blood samples were obtained at admission and when an asymptomatic alteration was detected and 10 minutes later.

MAIN OUTCOME MEASURES

Comparisons of concentrations of tissue plasminogen activator, urokinase type plasminogen activator, tissue plasminogen activator inhibitor-1, cross-linked fibrin degradation products, von Willebrand factor, and thrombin-antithrombin III complexes in patients and controls at admission; same comparisons in patients with silent ischaemia at the start of an episode and 10 minutes later.

RESULTS

Tissue plasminogen activator concentrations were raised at admission in patients with acute myocardial infarction (mean (SD) 14.2 (6) ng/ml) and in patients with unstable angina (10.1 (2.5) ng/ml) in comparison with controls (5.1 (2.7) ng/ml, p < 0.01 and < 0.05 respectively). There was no differences between the two groups of patients, however. Similar results were observed at the start of a silent ischaemic episode (9.8 (1.9) ng/ml) and 10 minutes later (10.5 (2.9) ng/ml) compared with controls (p < 0.05). Tissue plasminogen activator inhibitor-1 concentrations were raised in patients with acute myocardial infarction (45.1 (15) ng/ml) compared with volunteers (20.6 (16) ng/ml, p < 0.01). In patients with silent ischaemia tissue plasminogen activator inhibitor-1 concentrations were slightly but not significantly increased. Concentrations of cross-linked fibrin degradation products (D dimer) increased during unstable angina (2150 (350) ng/ml) and silent ischaemia (2270 (450) ng/ml) compared with the concentrations in volunteers (340 (80) ng/ml) and patients with acute myocardial infarction (310 (120) ng/ml; p < 0.01).

CONCLUSIONS

The results suggest that thrombosis mediates the pathophysiological mechanisms of silent ischaemia and unstable angina.

Circadian variation in fibrinolytic activity in patients with variant angina

BACKGROUND

Coronary artery spasm induces activation of the coagulation system. Turnover and maintenance of thrombus depend not only on formation but also on lysis. The relation between coronary spasm and fibrinolytic system has not been elucidated.

OBJECTIVE

To examine whether there is impairment of or a circadian variation in fibrinolytic activity in patients with variant angina.

METHODS

Plasminogen activator inhibitor (PAI) activity and concentrations of tissue plasminogen activator (t-PA) antigen were measured in venous plasma samples taken at 2200, 0600, and 1400 and 24 h Holter tapes were recorded in 15 patients with variant angina, 12 patients with stable exertional angina, and 12 controls.

RESULTS

There were significant circadian variations in PAI activity and t-PA antigen with peak values at 0600 in all three groups. Mean (SEM) PAI activity (IU/ml) at 2200, 0600, and 1400 was 6.1 (1.1), 11.0 (1.3), and 4.4 (0.6) in the variant angina group; 1.8 (0.7), 5.6 (1.1), and 1.2 (0.3) in the stable exertional angina group; and 1.1 (0.5), 4.5 (0.8), and 0.7 (0.3) in the control group. Furthermore, both plasma PAI activity and t-PA antigen concentrations were significantly higher in the variant angina group than in the stable exertional angina group and the control group at each sampling time.

CONCLUSIONS

In patients with variant angina there was a circadian variation in fibrinolytic activity, which was lowest in the early morning, and impaired fibrinolytic activity particularly in the early morning, when attacks of angina occur most frequently.

Activation of leukocytes and of the kallikrein-kinin system in patients with unstable angina pectoris

We investigated the leucocyte-elastase and the activity of the kallikrein system including kinin precursors and plasma inhibition levels in 14 patients with unstable angina pectoris (normal or only slightly elevated creatinine kinase levels; no transmural myocardial infarction) and compared them with 10 controls. Leucocyte-elastase levels and activity of the kallikrein system were significantly elevated in unstable angina pectoris. The bradykinin precursor high-molecular-weight kininogen was markedly decreased to 79 +/- 16% indicating kinin generation. Except for a slight decrease in the beta factor XIIa inhibition, we observed no abnormalities in the plasma kallikrein inhibition or in the antithrombin III levels in patients with unstable angina pectoris. The findings indicate a significant activation of the plasma kallikrein-kinin system, which is not associated with a considerable reduction in the plasma inhibitor levels. Kinin generation might influence vascular tone and leucocyte function and thus be involved in the pathophysiologic alterations occurring in patients with recurrent angina at rest.

Plasmin and thrombin inhibitors in essentially untreated patients with coronary artery spasm

We examined activities or levels of plasmin and thrombin inhibitors in essentially untreated patients with angiographically documented coronary artery spasm. The patients received the ergonovine malate provocation test and were classified into two groups: (a) those with significant coronary artery spasm that produced reduction of the internal luminal diameter of 50% or greater with chest pain and change of electrocardiography (n = 18), and (b) those without coronary artery spasm (n = 17). There was no significant differences in alpha 1-antitrypsin and alpha 2-macroglobulin levels, and C1-inactivator activity between the control and patients with coronary artery spasm. On the other hand, the lower antithrombin III and alpha 2-plasmin inhibitor activities were noted in patients with coronary artery spasm than the control. Thrombin/antithrombin III complex and alpha 2-plasmin inhibitor/plasmin complex levels were significantly higher in coronary artery spasm patients. These results suggest that the coagulation and fibrinolytic systems may maintain their equilibrium in untreated patients with coronary artery spasm.

Predictive value for thrombotic disease of plasminogen activator inhibitor-1 plasma levels

Plasminogen activator inhibitor-1 plays a major role in the fibrinolytic system as the main physiological inhibitor of both tissue-type and urinary-type plasminogen activators. The inhibitor is present in plasma in small amounts and derives mainly from endothelial cells. Positive correlations have been reported between plasma levels and different parameters, such as serum triglycerides, insulin plasma levels and body mass index. Moreover, high plasma inhibitor concentrations have been observed in different disease states, but it must be stressed that plasminogen activator inhibitor-1 behaves as an acute-phase reactant and measurement of plasma levels is not significant in the acute phase of the disease. A possible predictive value of inhibitor levels for thrombotic events such as deep vein thrombosis and ischemic heart disease has been studied. On the basis of available studies, the predictive value is not clear for venous thrombosis, whereas plasminogen activator inhibitor-1 levels can predict some coronary events, at least in subgroups of young patients with a first myocardial infarction. It remains to be established if treatments able to reduce plasma inhibitor levels lead to a decrease in the risk of thromboembolic events.

High PAI activity with correlation to triglyceride and HDL cholesterol values in patients with coronary artery disease with no difference in survivors of myocardial infarction

The fibrinolytic capacity of blood depends mainly on the amount of tissue-type plasminogen activator (t-PA) activity and plasminogen activator inhibitor type-1 (PAI-1) activity. Previous studies linked high PAI activity or low t-PA activity with the development of atherosclerosis and thromboembolic diseases. Yet, there are conflicting reports in the literature as to whether there is higher PAI activity in patients with myocardial infarction (MI) than in patients with coronary artery disease (CAD) without previous MI. In this retrospective study, t-PA activity, t-PA antigen, and PAI activity before and after a venous occlusion test (VOT) of 10 min were assessed in 109 patients with angiographically documented CAD, in two subgroups of CAD patients with (n = 66) or without (n = 43) previous MI, and in subgroups of CAD patients according to their triglyceride levels and other risk factors. The mean values of t-PA activity in the whole patient group showed a 100-fold increase and a 3.1-fold increase in t-PA antigen after VOT (0.03 +/- 0.03 to 3.0 +/- 6.8 U/ml and 16.5 +/- 6.9 to 51.0 +/- 25.4 ng/ml, p < 0.05). PAI activity was 24.4 +/- 11.0 before and 19.6 +/- 13.2 U/ml after VOT. Within the CAD group, no difference was found between patients without MI and survivors of previous MI in PAI activity before VOT (24.6 +/- 10.7 vs. 24.3 +/- 11.3 U/ml) and after VOT (19.0 +/- 12.1 vs 20.0 +/- 14.0 U/ml), or t-PA activity before (0.03 +/- 0.01 vs. 0.04 +/- 0.04 U/ml) and after VOT (2.8 +/- 7.0 vs. 3.2 +/- 6.7 U/ml). In 39.4% of CAD patients elevated plasma PAI activity before VOT (> 25 U/ml) was found. This subgroup of patients represented the highest PAI activity after VOT (p < 0.05), the lowest t-PA activity after VOT (p < 0.001), and the highest triglyceride levels (p < 0.05). In 11% of the patients, a small increase in t-PA activity (less than 0.5 U/ml) after VOT was seen. This group showed the lowest t-PA antigen after VOT (p < 0.001) and the highest fibrinogen level (p < 0.05). Both subgroups showed the same distribution among patients with and without MI. CAD patients with triglyceride levels over 200 mg/dl had the highest PAI activity values before VOT (28.3 +/- 11.8 U/ml; p < 0.01) and after VOT (24.9 +/- 13.2 U/ml; p < 0.01), resulting in low t-PA activity after VOT (p < 0.01).(ABSTRACT TRUNCATED AT 400 WORDS)

Difference in plasminogen activator inhibitor activity between non-Q-wave infarction and Q-wave infarction

We examined the plasma levels of tissue plasminogen activator antigen and plasminogen activator inhibitor activity in 14 patients with non-Q-wave infarction and in 27 patients with Q-wave infarction before the start of thrombolytic therapy and in 34 control subjects. The mean level of plasma tissue plasminogen activator antigen (ng/ml) was higher (P < 0.01) both in the patients with non-Q-wave infarction and in those with Q-wave infarction than in the control subjects (10.3 +/- 1.9, 9.5 +/- 0.8 vs. 5.8 +/- 0.3), and there was no difference in the level between the patients with non-Q-wave infarction and those with Q-wave infarction. The mean level of plasma plasminogen activator inhibitor activity (IU/ml) was lower (P < 0.01) in the patients with non-Q-wave infarction than in those with Q-wave infarction (7.3 +/- 2.0 vs. 17.1 +/- 2.2), and there was no difference in the level between the patients with non-Q-wave infarction and the control subjects (7.3 +/- 2.0 vs. 4.1 +/- 2.6). The patency rate of infarct-related coronary artery before thrombolytic therapy was higher (P < 0.01) in the patients with non-Q-wave infarction than in those with Q-wave infarction (54% vs. 15%). We conclude that plasminogen activator inhibitor activity was lower in non-Q-wave infarction than in Q-wave infarction and this may be related to the higher patency rate of infarct-related coronary artery in non-Q-wave infarction.

Plasminogen activator inhibitor: a risk factor for myocardial infarction in diabetic patients

OBJECTIVE

To determine whether diabetic patients admitted with acute myocardial infarction have impaired fibrinolytic activity due to raised plasminogen activator inhibitor compared with non-diabetic patients.

SETTING

A district general hospital.

PATIENTS

90 non-diabetic and 38 diabetic patients admitted with acute myocardial infarction.

RESULTS

Both plasminogen activator inhibitor activity and antigen were significantly higher in diabetic than in non-diabetic patients (24.7 (6.8) v 18.5 (6.8) AU/ml; p = 0.0001 and 64.2 (range 13.1 to 328.8) v 38.5 (range 10.9 to 173.7 ng/ml; z = 3.3; p = 0.0008) with a positive correlation between activity and antigen (rs = 0.51; p = 0.0001). In both groups, activity and antigen concentrations were significantly higher than in diabetic and non-diabetic subjects without coronary artery disease (p = 0.002 to 0.0001 for each comparison). Plasminogen activator inhibitor activity correlated significantly with admission plasma glucose (r = 0.32; p = 0.0001), glycated haemoglobin (r = 0.32; p = 0.0001), admission plasma insulin (rs = 0.48; p = 0.001), and Killip grade of heart failure both on admission (rs = 0.27; p = 0.001) and on discharge (rs = 0.22; p = 0.006), but not with cumulative creatine kinase MB isoenzyme release (rs = -0.08). There were similar but weaker correlations between tissue plasminogen activator antigen and admission plasma glucose, glycated haemoglobin, and insulin. In 18 patients (12 non-diabetic and six diabetic) plasminogen activator inhibitor activity was measured between six and 12 months (8.3 (1.6)) after the acute infarct and remained similar to activity on admission (24.8 (1.9) AU/ml (NS) for diabetic and 17.9 (6.9) AU/ml (NS) for non-diabetic patients) and was still significantly higher in diabetic than in non-diabetic patients (p = 0.007).

CONCLUSION

These results show that diabetic patients have higher plasminogen activator inhibitor activity than non-diabetic patients both on admission with acute myocardial infarction and at follow up six to 12 months later. Raised plasminogen activator inhibitor activity may predispose diabetic patients to myocardial infarction and may also impair pharmacological and spontaneous reperfusion after acute myocardial infarction thus contributing to the poor outcome in these subjects.

Treatment of unstable angina pectoris

Unstable angina pectoris may be manifested as new-onset angina, a change in the anginal pattern, pain at rest with associated electrocardiographic (ECG) changes, or postinfarction angina. Of these, pain at rest with ischemic ECG changes is known to be associated with the poorest prognosis. The pathogenesis of unstable angina pectoris involves a combination of a fixed atherosclerotic obstruction and a dynamic component related to coronary vasoconstriction, thrombus formation, or both. Long-acting nitrates, inhibitors of platelet aggregation, beta blockers, and calcium antagonists are among the agents that have been shown to be effective in the medical management of unstable angina. A study now in progress is evaluating the routine use of thrombolytic therapy for this indication. Although alleviation of symptoms and prevention of death and myocardial infarction are important therapeutic goals, the overall efficacy of a particular medical therapy can best be assessed by objective evaluation of its ability to control ischemia, using such techniques as exercise scintigraphy and ambulatory ECG monitoring. Cardiac catheterization and revascularization are indicated for patients with unstable angina who continue to experience symptoms or who show evidence of silent ischemia despite medical therapy. A study is under way to determine the advisability of routine revascularization of such patients. Revascularization will provide symptomatic relief in most patients with unstable angina and may prolong survival and improve left ventricular function in certain subsets.

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.

Fibrinolytic activity after vessel wall injury

The goal of this study was to assess fibrinolytic activity after vessel wall injury and to correlate changes in fibrinolytic activity with angiographic and histologic findings. Accordingly, in 18 atherosclerotic rabbits, vessel wall injury was produced by means of iliac artery balloon angioplasty (the injury group), whereas 8 atherosclerotic rabbits served as a control group. In all rabbits from the injury group, deep vessel wall injury was documented by either angiography or histologic study. Plasminogen activator inhibitor-1 activity in plasma increased significantly, from 21.79 +/- 1.29 arbitrary units/ml (AU/ml) at baseline study to 32.05 +/- 1.47 AU/ml at 6 h after vessel wall injury (p less than 0.01), whereas activity remained unchanged throughout the 24-h period in the control group. Plasma levels of tissue plasminogen activator activity were similar in both groups. Intravascular thrombus was found in five of six additional rabbits 6 h after vessel wall injury, that is, at the time of impaired fibrinolytic activity, whereas no thrombus was found in the control group (p less than 0.05). It is concluded that deep vessel wall injury is associated with reduced fibrinolytic activity. In addition to other procoagulant factors, elevated plasminogen activator inhibitor-1 activity may lead to intravascular thrombosis and impaired resolution of thrombus.