Temporal relation between ischemic episodes and activation of the coagulation system in unstable angina

Reduced Rivaroxaban Dose Versus Dual Antiplatelet Therapy After Left Atrial Appendage Closure

Background:

Percutaneous left atrial appendage closure (LAAC) exposes to the risk of device thrombosis in patients with atrial fibrillation who frequently have a contraindication to full anticoagulation. Thereby, dual antiplatelet therapy (DAPT) is usually preferred. No randomized study has evaluated nonvitamin K antagonist oral anticoagulant after LAAC, and we decided to evaluate the efficacy and safety of reduced doses of rivaroxaban after LAAC.

Methods:

ADRIFT (Assessment of Dual Antiplatelet Therapy Versus Rivaroxaban in Atrial Fibrillation Patients Treated With Left Atrial Appendage Closure) is a multicenter, phase IIb study, which randomized 105 patients after successful LAAC to either rivaroxaban 10 mg (R 10 , n=37), rivaroxaban 15 mg (R 15 , n=35), or DAPT with aspirin 75 mg and clopidogrel 75 mg (n=33). The primary end point was thrombin generation (prothrombin fragments 1+2) measured 2 to 4 hours after drug intake, 10 days after treatment initiation. Thrombin-antithrombin complex, D-dimers, rivaroxaban concentrations were also measured at 10 days and 3 months. Clinical end points were evaluated at 3-month follow-up.

Results:

The primary end point was reduced with R 10 (179 pmol/L [interquartile range (IQR), 129–273], P <0.0001) and R 15 (163 pmol/L [IQR, 112–231], P <0.0001) as compared with DAPT (322 pmol/L [IQR, 218–528]). We observed no significant reduction of the primary end point between R 10 and R 15 while rivaroxaban concentrations increased significantly from 184 ng/mL (IQR, 127–290) with R 10 to 274 ng/mL (IQR, 192–377) with R 15 , P <0.0001. Thrombin-antithrombin complex and D-dimers were numerically lower with both rivaroxaban doses than with DAPT. These findings were all confirmed at 3 months. The clinical end points were not different between groups. A device thrombosis was noted in 2 patients assigned to DAPT.

Conclusions:

Thrombin generation measured after LAAC was lower in patients treated by reduced rivaroxaban doses than DAPT, supporting an alternative to the antithrombotic regimens currently used after LAAC and deserves further evaluation in larger studies.

Registration:

URL: https://www.clinicaltrials.gov . Unique identifier: NCT03273322.

Biomarkers of Thrombosis in ST-Segment Elevation Myocardial Infarction: A Substudy of the ATOLL Trial Comparing Enoxaparin Versus Unfractionated Heparin

BACKGROUND

The aim was to compare the peri-procedural biomarkers of coagulation and platelet activation in patients randomly allocated to intravenous enoxaparin or unfractionated heparin (UFH) in the ATOLL randomized trial (NCT00718471).

METHODS AND RESULTS

A total of 129 patients (n = 58 enoxaparin and n = 71 UFH) admitted for ST-segment elevation myocardial infarction (STEMI) treated by percutaneous coronary intervention (PCI) were included in this substudy of the ATOLL trial. Activated partial thromboplastin time ratio, anti-Xa activity, von Willebrand factor antigen, prothrombin fragment 1 + 2 (F1 + 2), thrombin-antithrombin complex (TAT), tissue factor pathway inhibitor and soluble CD40 ligand were measured at sheath insertion (T1) and at the end of the PCI (T2) and correlated with 1-month clinical outcomes. Target anticoagulation levels at T2 were more readily achieved in patients receiving enoxaparin compared to those receiving UFH (80.3 vs 18.2%, p < 0.0001). Increased levels of F1 + 2 and TAT measured at T2 were associated with the incidence of the composite ischemic endpoint (p = 0.04 and p = 0.03) and all-cause mortality (p < 0.0001 and p = 0.002). Release of F1 + 2 between T1 and T2 also predicted the composite ischemic endpoint (312 ± 513 vs 37 ± 292, p = 0.04) and net clinical outcome (185 ± 405 vs 3.2 ± 278, p = 0.03).

CONCLUSIONS

During primary PCI, enoxaparin achieved therapeutic levels more frequently than UFH. Higher level of thrombin generation measured at the end of the PCI procedure was associated with more frequent ischemic events.

Prothrombin fragments in cardiovascular disease

Prothrombin fragment 1+2 (F1+2), which comes from in vivo cleavage of prothrombin by factor Xa, is considered to be useful for diagnosis of thrombosis. Recognition of the central role of thrombosis in the pathogenesis ofcardiovascular disease has prompted growing interest in the association o F1+2 with cardiovascular clinical syndromes. Increased F1+2 levels have reported in venous thromboembolism, inflammation, cancer, sepsis, acute coronary syndromes, stroke, peripheral arterial disease, atrial fibrillation and during the postoperative period. However, a clear relationship with the appearance of thrombosis has not always been consistently demonstrated. Besides its potential prognostic and diagnostic value, it could also be usefu in assessing the impact of various therapies. However, it should be kept in mind that measurement of hemostasis activation markers has several important biological and methodological disadvantages. Activation markers reflect the presence of thrombosis in any vascular bed, so they are not specific. Furthermore, elevations occur not only in the presence of overt thrombosis but also during the hypercoagulable state. The cutoff level to be used for the definition of elevations is still largely unknown due to the use of different analytical methods, none of which have been standardized until know. Finally, the prognostic value of F1+2 and other markers of coagulation activation remains to be fully defined in future studies.

Association of aortic valve sclerosis with thrombin generation in hypertensive patients

Aortic valve sclerosis (AVS) may predispose to a prothrombotic state, as AVS is predictor of cardiovascular events in hypertensive populations. Thrombin exerts non-thrombotic effects such as vessel tone regulation, progression of atherosclerosis and stimulation of atrial natriuretic peptide (ANP) secretion. We hypothesized that hypertensive patients with AVS may have a persistently activated thrombin generation. We studied 234 asymptomatic never-treated hypertensive patients (73 of them with AVS). Prothrombin F1+2 (F1+2), as a marker of thrombin generation and fibrin D-dimer, as a marker of thrombus formation, ANP and brain natriuretic peptide (BNP) were measured. Presence of AVS, aortic jet velocity and left ventricular diameter at diastole were determined by echocardiography. Glomerular filtration rate was estimated using the Modification of Diet in Renal Disease formula. F1+2 (median and interquartile range (IQR) = 1.05, 0.87-1.38 nM vs. 0.93, 0.72-1.16) and ANP (22, 14-37 pg ml(-1) vs. 17, 11-25) levels were greater, and glomerular filtration rate values (65+/-9 ml min(-1)/1.73 m2 vs. 68+/-11) were lower in hypertensive patients with AVS than in those without AVS. F1+2 (odds ratio, 95% CI = 2.94, 1.07-8.6) was independently associated with AVS after being adjusted for age, gender and the variables of cardiorenal functions measured. After 6 months of treatment using valsartan, F1+2 levels remained elevated in hypertensive patients with AVS (1.14, 0.83-1.42 nM vs. 1.07, 0.84-1.5, n=19), but decreased in those without AVS (1.01, 0.85-1.31 vs. 0.8, 0.84-1.78, n=27). Thrombin generation was associated with AVS in untreated hypertensive patients, and this association was persistent after blood-pressure-lowering treatment using valsartan.

Instability mechanisms in unstable angina according to baseline serum levels of C-reactive protein: the role of thrombosis, fibrinolysis and atherosclerotic burden

BACKGROUND

Mechanisms of instability in patients affected by unstable angina and who exhibit low levels of C-reactive protein (CRP) on admission are unclear. We compared levels of markers of thrombin generation [thrombin-antithrombin complexes (TAT), of fibrinolysis [plasmin-antiplasmin complexes (PAP)], and angiographic severity and extent of coronary atherosclerosis in patients with severe unstable angina and high or low systemic levels of CRP.

METHODS

Forty consecutive patients (age 59.7+/-8.7, 76% males) admitted to our coronary care unit with severe unstable angina (Braunwald class IIIB) were included in the present study. We assayed TAT and PAP using commercially available ELISA assays and CRP with high sensitivity nephelometry. The evaluation of atherosclerotic disease severity and extent was performed. Patients were divided in two groups according to CRP levels: G1=CRP>3 mg/L and G2=CRP<3 mg/L.

RESULTS

Number of diseased vessels and number of stenoses plus occlusion were similar between the two groups (1.8+/-0.9 in G1 vs 2.2+/-0.9 in G2, p=NS and 2.6+/-1.9 in G1 vs 2.7+/-1.3 in G2, p=NS, respectively), as well as extent score and index (8.4+/-4.5 in G1 vs 9.2+/-3.1 in G2, p=NS and 0.6+/-0.3 in G1 vs 0.6+/-0.27 in G2, p=NS, respectively). Episodic activation of thrombin generation, as assessed by TAT was more frequent in G1 than in G2 (85% vs 47%, p=0.03). Episodic activation of the fibrinolysis was more frequent in G1 than in G2 (80% vs 40%, p=0.01).

CONCLUSION

Patients with coronary instability and systemic evidence of inflammation exhibit more frequent activation of the thrombin/fibrinolysis system than patients with a similar clinical presentation but no evidence of systemic inflammation, whereas the coronary atherosclerotic burden is similar. The mechanisms of coronary instability in the absence of systemic evidence of inflammation need to be elucidated by future studies.

Activated platelets contribute importantly to myocardial reperfusion injury

Platelets become activated during myocardial infarction (MI), but the direct contribution of activated platelets to myocardial reperfusion injury in vivo has yet to be reported. We tested the hypothesis that activated platelets contribute importantly to reperfusion injury during MI in mice. After 30 min of ischemia and 60 min of reperfusion, P-selectin knockout mice had a significantly smaller infarct size than that of wild-type mice (P < 0.05). Platelets were detected by P-selectin antibody in the previously ischemic region of wild-type mice as early as 2 min postreperfusion after 45 min, but not 20 min, of ischemia. The appearance of neutrophils in the heart was delayed when compared with platelets. Flow cytometry showed that the number of activated platelets more than doubled after 45 min of ischemia when compared with 20 min of ischemia or sham treatment (P < 0.05). Platelet-rich or platelet-poor plasma was then transfused from either sham-operated or infarcted mice after 45 and 10 min of ischemia-reperfusion to mice undergoing 20 and 60 min of ischemia-reperfusion. Infarct size was increased by threefold and platelet accumulation was remarkably enhanced in mice treated with wild-type, MI-activated platelet-rich plasma but not in mice receiving either platelet-poor plasma from wild types or MI-activated platelet-rich plasma from P-selectin knockout mice. In conclusion, circulating platelets become activated early during reperfusion and their activation depends on the duration of the preceding coronary occlusion and is proportional to the extent of myocardial injury. Activated platelets play an important role in the process of myocardial ischemia-reperfusion injury, and platelet-derived P-selectin is a critical mediator.

Do Haemostasis Activation Markers that Predict Cardiovascular Disease Exist?

Recognition of the central role of thrombosis in the pathogenesis of cardiovascular disease has prompted growing interest in the association of haemostatic variables with cardiovascular disease. In investigating the predictive value of haemostasis markers, a promising type of measurement is that of the activation products of coagulation and fibrinolysis: prothrombin fragment 1+2 (F1+2), fibrinopeptide A (FPA), soluble fibrin,thrombin-antithrombin (TAT), plasmin-antiplasmin(PAP) complexes and D-dimer. D-dimer was most extensively studied and there is substantial evidence that D-dimer is a strong, consistent predictor of cardiovascular events in the general population and inpatients with cardiovascular disease. Data on other markers are considerably less abundant and more controversial. The prognostic value of these markers remains to be fully defined in future epidemiological and clinical studies.

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.

Increased thrombin generation and circulating levels of tumour necrosis factor-alpha in patients with chronic Helicobacter pylori-positive gastritis

BACKGROUND

Conflicting data have been reported concerning the relationship between Helicobacter pylori infection and coronary heart disease.

AIM

To evaluate clotting system activation and plasma levels of tumour necrosis factor-alpha, a procoagulant cytokine, in patients with H. pylori-positive and -negative gastritis.

METHODS

Three groups of patients were identified: 38 with H. pylori-positive gastritis, 18 with H. pylori-negative gastritis, and 40 H. pylori-negative controls with normal gastric mucosa. Plasma levels of prothrombin fragment 1 + 2 (F1 + 2) and tumour necrosis factor-alpha were assayed. Patients were also controlled after 2 and 6 months following standard H. pylori eradication treatment.

RESULTS

At baseline, fragment 1 + 2 and tumour necrosis factor-alpha levels in H. pylori-positive patients were significantly higher than those in H. pylori-negative patients with gastritis (P < 0.05 and P < 0.01, respectively). After H. pylori eradication, fragment 1 + 2 and tumour necrosis factor-alpha levels showed a significant decrease at 2 months (P = 0.03 and P = 0.02, respectively) and a further reduction at 6 months, reaching levels observed in H. pylori-negative patients and controls.

CONCLUSIONS

The increase thrombin generation rate and the correlation of plasma fragment 1 + 2 and tumour necrosis factor-alpha levels in H. pylori-positive patients suggest a role for inflammation in mediating the relationship between H. pylori infection and activation of the clotting system.

Prothrombin activation in eastern tiger snake bite

AIMS

To perform ex vivo studies in eastern tiger snake envenomation which define the haemostatic events associated with prothrombin activation.

METHOD

Serial studies were performed on plasma from six individuals with evidence of eastern tiger snake envenomation. These analyses were particularly directed to fibrinogen levels, F1 + 2, TAT and evidence of fibrinolysis.

RESULTS

There was a substantial rise in F1 + 2 and thrombin-antithrombin (TAT) complexes in all cases, even with minimal evenomation. In some cases the molar ratio of F1 + 2 and TAT was reduced from the relationship normally seen in vitro and ex vivo in clinical thrombosis. There was a dramatic fall in factor V and VIII levels which occurred 4-6 hours before the decline in prothrombin and AT3. This related in time to a fall in alpha2AP and plasminogen. Protein C levels also declined dramatically but many hours after presentation.

CONCLUSIONS

F1 + 2 and TAT are sensitive markers of tiger snake evenomation. In some patients with massive prothrombin activation, the common mechanism for TAT clearance may be altered or overwhelmed. Conversely, the renal clearance of the smaller F1 + 2 may be enhanced. In the absence of thrombocytopaenia, which is a very sensitive marker of DIC, the fall in labile factors with tiger snake envenomation is significantly contributed to by proteolytic digestion of clotting factors.

Coagulation system activity before coronary artery bypass surgery for unstable angina

OBJECTIVE

To measure coagulation activity immediately prior to coronary artery bypass surgery. Previous reports have shown that a hypercoagulable state and reduced fibrinolytic activity increase the risk of postoperative graft failure.

DESIGN

Fifty patients with unstable angina and ongoing low-molecular-weight heparin antithrombotic treatment for a median of 4 days and 25 stable patients undergoing elective surgery were included.

RESULTS

Antithrombin levels were significantly lower whereas fibrinogen and plasminogen activator inhibitor-1 levels were higher in the unstable patients than in the stable patients. Median preoperative levels of thrombin-antithrombin complex (TAT), prothrombin fragment1+2 (F1+2), fibrin D-dimers and beta-thromboglobulin did not differ significantly in unstable and stable patients. There were signs of activated coagulation with elevated levels of TAT and F1+2 before the operation in half of the unstable patients, who had had chest pain at rest within 48 h preceding the operation and also in one-third of patients undergoing elective surgery.

CONCLUSION

A hypercoagulable state may be present in unstable as well as in stable angina pectoris patients accepted for coronary artery bypass surgery.

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

OBJECTIVES

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Thrombin generation after the abrupt cessation of intravenous unfractionated heparin among patients with acute coronary syndromes: potential mechanisms for heightened prothrombotic potential

OBJECTIVES

The purpose of this study was to determine the mechanistic basis for thrombin generation and increased prothrombotic potential after the abrupt cessation of intravenous (i.v.) unfractionated heparin among patients with acute coronary syndromes.

BACKGROUND

A "rebound" increase in prothrombotic potential has been observed biochemically and clinically after the abrupt cessation of unfractionated heparin (UFH) among patients with acute coronary syndromes. Although the mechanism is unknown, tissue factor and the extrinsic coagulation cascade, both operative in atherosclerotic vascular disease and arterial thrombosis, are thought to be centrally involved.

METHODS

In a single-center, pilot study, 30 patients with either unstable angina or non-ST segment elevation myocardial infarction who had received a continuous i.v. infusion of UFH for 48 h were randomly assigned to: 1) abrupt cessation, 2) i.v. weaning over 12 h or 3) subcutaneous weaning over 12 h.

RESULTS

Thrombin generation (prothrombin fragment 1.2) was evident within 1 h of UFH cessation, increased progressively (by nearly two-fold) at 24 h (p = 0.002) and correlated inversely with tissue factor pathway inhibitor concentration (r = -0.61). Thrombin generation was greatest among patients randomized to abrupt cessation (1.6-fold increase at 24 h) and least in those with i.v. weaning.

CONCLUSIONS

Thrombin generation after the abrupt cessation of UFH may represent a drug-induced impairment of physiologic vascular thromboresistance in response to locally generated tissue factor. A dosing strategy of abbreviated i.v. weaning attenuates but does not prevent heparin rebound among patients with acute coronary syndromes.

Thrombotic reactant markers in non-ST segment elevation acute coronary syndromes treated with either enoxaparin (low molecular weight heparin) or unfractionated heparin

BACKGROUND

This study was designed to analyze the impact of treatment with either unfractionated heparin or enoxaparin (low molecular weight heparin) on plasma markers of thrombotic and endogenous thrombolytic activity in patients with non-ST segment elevation acute coronary syndromes.

METHODS

A subset of 174 patients derived from the 3,171 patients of the ESSENCE study was evaluated. Eighty-seven patients were assigned to intravenous unfractionated heparin (target aPTT: 55-85 sec) (group UH), and 87 assigned to subcutaneous enoxaparin (1 mg/kg/q12hr) (group ENOX) for a minimum of 48 hours of treatment (average duration of treatment 88+/-45 hours). The thrombin time, and plasma levels of anti-factor Xa activity, prothrombin fragment F 1+2, thrombin-antithrombin complex (TAT), and D-dimer, were assayed at baseline, and at or close to peak activity 24-36 hrs, and at 72-90 hrs for those remaining on treatment with antithrombotic therapy. Major ischemic and hemorrhagic events were assessed throughout hospitalization. The levels of the thrombotic markers measured at or close to peak activity at 36 hours are presented below, and compared to clinical outcome at 30 days.

RESULTS

In UH patients, the thrombin time increased 7 fold while the mean value for anti-Xa activity was 0.27 IU/ml; in ENOX patients the thrombin time increased 2.3 fold, and the mean value for anti-Xa activity was 0.83 IU/ml. In UH pts, basal levels of F 1+2, TAT, and D-dimer declined by (deltapaired) -0.8, -3. 3, and -66, respectively. In ENOX pts, basal levels of F 1+2, TAT, and D-dimer declined by (deltapaired) -0.3, -4.7, and -23, respectively. No significant differences were observed between the paired differences in thrombotic markers (UH vs ENOX), nor in the rate of recurrent ischemic events or major hemorrhage.

CONCLUSIONS

In this subset of patients enrolled in the ESSENCE study, enoxaparin 1 mg/kg ql2hr significantly increased anti-Xa activity above that seen with unfractionated heparin, and reduced thrombin production without prolonging the thrombin time. The high anti-Xa activity achieved with enoxaparin was not associated with a loss of safety.

Effect of intravenous heparin infusion on thrombin-antithrombin complex and fibrinopeptide A in unstable angina

BACKGROUND

In unstable angina, the clinical efficacy of heparin is limited in time, and recurrence of adverse events has been reported after discontinuation of the anticoagulant.

METHODS

In 21 episodes of unstable angina, we used the plasma level of fibrinopeptide A (FPA) and of thrombin-antithrombin complex (TAT) to evaluate the pattern of thrombin inhibition by heparin and the effect of stopping heparin and initiating aspirin.

RESULTS

At admission, the plasma level of FPA was increased: median value 3.7 ng/mL compared with 5.5 ng/mL in a control group of 20 patients with early myocardial infarction (not significant). The following findings were observed during a 4-day course of intravenous heparin infusion: (1) FPA decreased significantly 6 hours after the start of therapy; (2) FPA was lower when activated partial thromboplastic time (aPTT) was >1.5 times baseline; (3) there was a significant negative correlation between aPTT and FPA. Twenty-four hours after heparin was discontinued and aspirin initiated, a significant increase in TAT and FPA in plasma was observed.

CONCLUSIONS

The results confirm ongoing fibrin formation in the active phase of unstable angina, indicate incomplete and variable inhibition of thrombin by heparin during continuous infusion, and suggest a risk of re-emergence of thrombosis (in spite of initiating aspirin) 24 hours after withdrawal of heparin. Data demonstrate a better control of thrombin activity when heparin is infused at rates that maintain aPTT at >1.5 times baseline, as currently recommended in unstable angina.

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.

Reactivation of the coagulation system: rationale for long-term antithrombotic treatment

Coronary artery thrombosis superimposed on a disrupted atherosclerotic plaque has emerged as the pivotal pathophysiologic event in acute coronary syndromes (i.e., unstable angina, myocardial infarction, and sudden death). The various clinical manifestations depend on the extent and duration of thrombus deposition, which are determined by several local and systemic thrombogenic risk factors. The thrombotic response to plaque disruption involves both platelet activation and thrombin generation. Accordingly, combined treatment with aspirin and heparin has proved more efficacious than either treatment alone in the risk reduction of serious cardiac events in patients with unstable angina or non-Q-wave infarction. However, withdrawal of heparin is, even after prolonged treatment, associated with an increased short-term risk of serious cardiac events relative to the risk in patients given only aspirin. Furthermore, the long-term relative event rate seems not to be influenced by administration of heparin or direct antithrombins in the acute phase. Both transient hypercoagulability associated with heparin withdrawal and continuous thrombin generation over a longer term related to the underlying disease may explain the rebound in clinical events. Longer duration of combined antiplatelet and anticoagulant treatments, e.g., until healing of the culprit lesion or even until stabilization of vulnerable, yet nondisrupted plaques, may improve long-term clinical outcome.