Early coronary reperfusion blunts the procoagulant response of plasminogen activator inhibitor-1 and von Willebrand factor in acute myocardial infarction

Anti-inflammatory therapy in ischaemic heart disease: from canakinumab to colchicine

Four large trials have recently evaluated the effects of anti-inflammatory drugs in the secondary prevention of major cardiovascular events (MACE) in over 25 000 patients followed for 1.9–3.7 years. CANTOS tested subcutaneous canakinumab [an anti-interleukin (IL) 1β antibody] 300 mg every 3 months against placebo in patients with a history of myocardial infarction (MI) and serum C-reactive protein (CRP) >2 mg/L, demonstrating efficacy in preventing MACE but increased rates of fatal infections. COLCOT (in patients with recent MI) and LoDoCo2 (in patients with chronic coronary syndromes) tested oral colchicine (an NLRP3 inflammasome inhibitor) 0.5 mg daily vs. placebo, demonstrating prevention of MACE with a slightly increased risk of pneumonia in COLCOT (0.9 vs. 0.4%) but not in LoDoCo2. CIRT tested oral methotrexate (an anti-rheumatic anti-nuclear factor-kB) 15–20 mg per week against placebo in ischaemic heart disease patients with diabetes or metabolic syndrome, without significant reduction in MACE rates or in circulating IL6 or CRP levels, and with increased risk of skin cancers. In summary, canakinumab and colchicine have shown efficacy in preventing MACE in ischaemic heart disease patients, but only colchicine has acceptable safety (and cost) for use in secondary cardiovascular prevention. Clinical results are expected with the anti-IL6 ziltivekimab.

Marked von Willebrand factor and factor VIII elevations in severe acute respiratory syndrome coronavirus-2-positive, but not severe acute respiratory syndrome coronavirus-2-negative, pneumonia: a case-control study

Patients with novel coronavirus pneumonia show increased thrombotic risk. Although hemostatic alterations have been described in novel coronavirus pneumonia patients, case-control studies of von Willebrand factor (VWF), factor VIII (FVIII), and a disintegrin-like and metalloprotease with thrombospondin type I motif, member 13 (ADAMTS13) are lacking. VWF, ADAMTS13, FVIII, d-dimer, C-reactive protein, and routine blood cells and chemistry were measured in 10 novel coronavirus pneumonia patients and 10 non-novel coronavirus pneumonia controls. Hemostatic factors were measured less than 48 h of hospital admission in patients without invasive ventilation. d-Dimer, C-reactive protein, and fibrinogen concentrations, high in both groups, did not differ significantly in novel coronavirus pneumonia vs. non-novel coronavirus pneumonia patients. Median VWF-antigen (324 vs. 153 IU/dl, P < 0.0001), VWF-Rco (342 vs. 133 IU/dl, P < 0.001), and FVIII-activity levels (203 vs. 123 IU/dl, P < 0.0001) were significantly higher in novel coronavirus pneumonia cases vs. controls ADAMTS13-activity was normal in both groups. Coronavirus pneumonia cases vs. non-novel coronavirus pneumonia controls showed marked VWF/FVIII elevation, suggesting specific virus-induced endothelial activation causing VWF/FVIII hypersecretion, which may represent a therapeutic target in novel coronavirus pneumonia.

From angiotensin-converting enzyme 2 disruption to thromboinflammatory microvascular disease: A paradigm drawn from COVID-19

We concisely review clinical, autopsy, experimental and molecular data of 2019 coronavirus disease (COVID-19). Angiotensin-converting enzyme 2 disruption and thromboinflammatory microangiopathy emerge as distinctive features. Briefly, entry of the virus into microvessels can profoundly disrupt the local renin-angiotensin system, cause endothelial injury, activate the complement cascade and induce powerful thromboinflammatory reactions, involving, in particular, von Willebrand factor, that, if widespread, may lead to microvascular plugging, ischemia and, ultimately, organ failure. We believe the current COVID-19 data consolidate a widely unrecognised paradigm of potentially fatal thromboinflammatory microvascular disease.

Novel Biomarkers, ST-Elevation Resolution, and Clinical Outcomes Following Primary Percutaneous Coronary Intervention

Background Despite restoration of epicardial flow following primary percutaneous coronary intervention (PPCI), microvascular reperfusion as reflected by ST-elevation resolution (ST-ER) resolution remains variable and its pathophysiology remains unclear. Methods and Results Using principal component analyses, we explored associations between 91 serum biomarkers drawn before PPCI clustered into 14 pathobiologic processes (including NT-proBNP [N-terminal pro-B-type natriuretic peptide] as an independent cluster), and (1) ST-ER resolution ≥50% versus <50%; and (2) 90-day composite of death, shock, and heart failure. Network analyses were performed to understand interbiomarker relationships between the ST-ER groups. Among the 1160 patients studied, 861 (74%) had ST-ER ≥50% at a median 40 (interquartile range, 23-70) minutes following PPCI, yet both groups had comparable post-PPCI TIMI (Thrombolysis in Myocardial Infarction) grade 3 flow (86.6% versus 82.9%; P=0.25). ST-ER ≥50% was associated with significantly lower pre-PPCI concentrations of platelet activation cluster (particularly P-selectin, von Willebrand factor, and platelet-derived growth factor A) and NT-proBNP, including after risk adjustment. Across both ST-ER groups, strong interbiomarker relationships were noted between pathways indicative of myocardial stretch, platelet activation, and inflammation, whereas with ST-ER <50% correlations between iron homeostasis and inflammation were observed. Of all 14 biomarker clusters, only NT-proBNP was significantly associated with the 90-day clinical composite. Conclusions Suboptimal ST-ER is common despite achieving post-PPCI TIMI grade 3 flow. The cluster of platelet activation proteins and NT-proBNP were strongly correlated with suboptimal ST-ER and NT-proBNP was independently associated with 90-day outcomes. This analysis provides insights into the pathophysiology of microvascular reperfusion in ST-segment-elevation myocardial infarction and suggests novel pre-PPCI risk targets potentially amenable to enhancing tissue-level reperfusion following PPCI.

Kinetics of plasma von Willebrand factor in acute myocardial infarction patients: a meta-analysis

Previous studies have shown a variation in plasma level of von Willebrand factor (vWF) in acute myocardial infarction (AMI) patients but with contentious results. In this study, we performed a meta-analysis to evaluate the kinetics of plasma vWF after AMI. A total of 11 qualified studies were obtained through systematical search in PubMed, Web of science, Cochrane Library database and CNKI, followed by search of reference lists, involving 519 AMI patients and 466 non-AMI controls. The standard mean difference (SMD) and 95% confidence intervals (95% CI) were calculated using random-effects model. Results indicated that the plasma vWF was significantly increased in the first several hours after onset of AMI (SMD = 1.94, 95% CI = 1.39-2.48, P < 0.001) and stayed at high level until 24 h (SMD = 1.17, 95% CI = 0.45-1.89, P = 0.001). Elevated level of vWF appeared to persist for one week and reduced to normal until the fourteenth day after AMI (SMD = 0.44, 95% CI = -0.14-1.02, P = 0.14). Subgroup analysis revealed that the high level of vWF lasted just for 1 day in patients with a symptom duration ≤ 6 h before admission. For patients with a symptom duration > 6 h, elevated vWF was found in all 7 days except day 1. Our findings determined the kinetics of plasma vWF after AMI, and might provide a new insight in monitoring AMI progression.

Prospective Evaluation of von Willebrand Factor Release After Multiple and Single Stenting

The hypothesis that von Willebrand factor (vWf) release after multiple coronary stenting may be higher than release after single coronary stenting was tested. Preliminary data suggest that multiple stenting is a predictor of thrombosis, and vWf levels in the coronary sinus reflect coronary endothelial injury. Therefore vWf as an indicator of thrombogenesis and endothelial injury was studied. vWf levels were obtained in the coronary sinus at the prestenting and poststenting period in 50 patients with ischemic heart disease who underwent elective coronary stenting (25 patients in single stent group and 25 patients in multiple stent group). Eight subjects who underwent diagnostic coronary angiography were used as controls. vWf levels increased significantly after multiple stenting and vWf levels were significantly different from vWf levels after single stenting. In single stent group, vWf levels in type C lesions were significantly different from levels detected in type A and B lesions. Multiple coronary stenting induces a rapid increase in vWf expression in the coronary circulation. These changes may contribute to the pathogenesis of acute or subacute stent thrombosis and restenosis after multiple stenting.

von Willebrand factor in cardiovascular disease: focus on acute coronary syndromes

von Willebrand factor (VWF) plays a pivotal role in platelet adhesion and aggregation at sites of high shear rates (eg, in coronary arteries that have stenotic or ruptured atherosclerotic plaque lesions). Numerous studies have investigated the relationship between VWF plasma levels and thromboembolic cardiovascular events. In contrast to the rather weak association in the general population, in patients with preexisting vascular disease, VWF is significantly predictive for adverse cardiac events, including death. Likewise, VWF typically rises during the course of acute coronary syndrome, and the extent of this VWF release is an independent predictor of adverse clinical outcome in these patients. Various lines of evidence indicate that VWF is not only a marker but also actually an important effector in the pathogenesis of myocardial infarction. This central role of VWF in thrombogenesis has made it a promising target for research into new antiplatelet therapies that specifically inhibit VWF. This review focuses on the role of VWF in acute coronary syndrome and further outlines the relevance of therapeutic interventions targeting VWF for acute coronary syndrome patients.

Clinical and biochemical predictors affect the choice and the short-term outcomes of different thrombolytic agents in acute myocardial infarction

BACKGROUND

The presence of plasminogen activator inhibitor-1, angiotensin-converting enzyme and others may play a role in unsuccessful recanalization after thrombolytic therapy.

OBJECTIVES

To find out the clinical and biochemical predictors that may affect the choice and short-term outcomes following different thrombolytic agents in acute myocardial infarction.

METHODOLOGY

Angiotensin-converting enzyme and plasminogen activator inhibitor-1 plasma levels of 184 patients with acute myocardial infarction, treated with streptokinase, metalyze or reteplase, were determined. Failure of thrombolysis was assessed by noninvasive reperfusion criteria. Prolonged hospitalization, impaired left ventricular ejection fraction and reinfarction were considered as short-term outcomes.

RESULTS

Patients who received streptokinase developed higher incidence of >50% resolution of ST-segment elevation (82.5 vs. 64.7%, P-value<0.05, in comparison with metalyze and 82.5 vs. 55.7%, P-value 0.001, in comparison with reteplase) than those who received other thrombolytic agents. High plasma angiotensin-converting enzyme was associated with prolonged hospitalization (55, 63 and 94%, P<0.02) following streptokinase, metalyze and reteplase, respectively. High plasma plasminogen activator inhibitor-1 is associated with impaired left ventricular ejection fraction (55.3, 76.7 and 68.5%, P<0.09), ST resolution<50% (13.2, 36.7 and 37.5%, P=0.03), ST resolution>50% (86.8, 63.3 and 62.5%, P=0.03) following streptokinase, metalyze and reteplase, respectively.

CONCLUSIONS

Rapid determination of pretreatment angiotensin-converting enzyme and plasminogen activator inhibitor-1 plasma levels in patients with acute myocardial infarction may influence the choice and outcomes of the thrombolytic agents. The presence of a high plasma level of either angiotensin-converting enzyme or plasminogen activator inhibitor-1 is significantly associated with adverse short-term outcomes after treatment with reteplase or metalyze.

Predictors of the rise in vWF after ST elevation myocardial infarction: implications for treatment strategies and clinical outcome

AIMS

Prior studies suggest that acute coronary syndromes (ACSs) are associated with endothelial activation and that this is of prognostic significance. We hypothesized that endothelial activation, as measured by a rise in von Willebrand Factor (DeltavWF), was influenced by the thrombolysis in myocardial infarction flow grade (TFG), the corrected TIMI frame count (CTFC) and the choice of anticoagulant therapy after fibrinolysis in ST elevation myocardial infarction (STEMI).

METHODS AND RESULTS

Data were drawn from the enoxaparin and tenecteplase tissue plasminogen activator (TNK-tpa) with or without GPIIb/IIIa inhibitor as the reperfusion strategy in the STEMI trial (ENTIRE-TIMI 23). Three hundred and fourteen patients had serial measurements of vWF (baseline and 48-72 h) and angiographic data available. TFG<3 (P=0.0042) or CTFC>/=40 at 60 min (P=0.0035) were associated with a higher DeltavWF. DeltavWF >/=75th percentile was associated with a higher incidence of death or myocardial infarction (MI) at 30 days, compared with <75th percentile (11.2 vs. 4.1%, P=0.027). Enoxaparin independently reduced the DeltavWF (P=0.019) and also the composite of death or MI (OR 0.33, 95% CI 0.12-0.91, P=0.03) compared with unfractionated heparin.

CONCLUSION

In STEMI treated by fibrinolysis, coronary flow at 60 min and choice of adjunctive anticoagulant appear to be independent determinants of DeltavWF. Enoxaparin is independently associated with a reduction in DeltavWF and a reduction in death or MI. The clinical benefits of enoxaparin as an adjunctive treatment in STEMI may be mediated in part by a reduction in vWF release.

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

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

C-reactive protein and coronary artery disease

Evidence suggests that inflammation plays a key role in the pathogenesis of atherosclerosis. The chronic inflammatory process can develop to an acute clinical event by the induction of plaque rupture and therefore cause acute coronary syndromes. The aim of this study was to determine the serum levels of the circulating acute-phase reactant C-reactive protein (CRP), which is a sensitive indicator of inflammation, in patients with chronic stable coronary artery disease (CAD) and acute coronary syndromes (ACS). We studied 56 subjects: 1) 25 consecutive patients (18 men, 7 women; mean age, 68.5 +/- 14.3 years, range, 40-86) with unstable angina (UA) or acute myocardial infarction (AMI); 2) 31 consecutive patients (25 men, 6 women; mean age 64 +/- 12.7; range, 47-83, years) with signs and symptoms of clinically stable CAD. High-sensitivity-C-reactive protein (hs-CRP) levels were determined with a commercially available enzyme-linked immunoassay method. In patients with unstable angina and AMI before reperfusion therapy, CRP levels were not significantly different to those in patients with stable CAD (5.96 +/- 2.26 versus 4.35 +/- 2.6 mg/L; P = 0.12), but tended to be higher in patients with unstable angina and AMI. Baseline CRP levels in the subgroup of patients with AMI (6.49 +/- 2.28 mg/L) were significantly higher than levels in patients with stable CAD (4.35 +/- 2.6 mg/L; P = 0.02). CRP levels in patients with unstable angina and AMI were measured four times during a 72-hour period (0, 12, 24, and 72 hours). The lowest value was observed at baseline and differed significantly from values measured at any other time of the observation period (P < 0.001; 5.96 +/- 2.26; 9.5 +/- 9.04, 18.25 +/- 11.02; 20.25 +/- 10.61). CRP levels after 12, 24, and 72 hours were also significantly different to the initial values for patients with stable CAD (P < 0.01). There was no correlation between CRP and creatine kinase (CK), CK-MB isoenzyme, or troponin I positivity as markers for the extent of the myocardial injury during the observation period. Baseline levels of serum CRP tended to be higher in patients with unstable angina or AMI but were not significantly different from levels in patients with chronic stable CAD. In the subgroup of patients with AMI, baseline CRP levels were significantly higher than the levels in patients with stable CAD. CRP as a marker of inflammation is significantly increased in patients with AMI and unstable angina shortly after the onset of symptoms (after a period of 12 hours), supporting the hypothesis of an activation of inflammatory mechanisms in patients with an acute coronary syndrome or AMI.

Serum neopterin and activity of coronary artery disease

Inflammation plays a key role in the pathogenesis of atherosclerosis. In coronary artery disease (CAD), the release of different cytokines activates cellular defense. Infiltration of neutrophils and monocytes/macrophages is detected in the vessel wall in patients with CAD. Macrophages activated by interferon gamma synthesize metalloproteinases and neopterin, a pteridin derivative that has been used as an immune marker. To determine neopterin levels in patients with chronic CAD and acute coronary syndromes, the authors studied 116 subjects: 1) 25 consecutive patients (18 men, 7 women; mean age 68.5 +/- 14.3, range 40 to 86 years) with unstable angina or acute myocardial infarction (AMI); 2) 31 consecutive patients (25 men, 6 women; mean age 64 +/- 12.7, range 47 to 83 years) with signs and symptoms of clinically stable CAD; and 3) 60 consecutive healthy blood donors (38 men, 22 women; mean age 54.4 +/- 6.23, range 44 to 66 years). Neopterin levels were determined with a commercially available enzyme-linked immunosorbent assay method. In patients with unstable angina and AMI before thrombolytic therapy, neopterin levels were not significantly different from levels in patients with stable CAD (5.97 +/- 1.4 versus 7.84 +/- 3.56 nmol/L; P = 0.15). Neopterin levels in both patient groups did not significantly differ from levels in control subjects (P > 0.1). Neopterin levels in patients with unstable angina and AMI were measured four times during a 72-hour period. The lowest value was observed at baseline and differed significantly from values after 72 hours (P < 0.001; 5.97 +/- 1.4 versus 9.25 +/- 2.36). Neopterin levels after 72 hours were also significantly different from initial values in patients with stable CAD (P < 0.001). There was no correlation between neopterin and creatine kinase (CK) levels, CK-MB isoenzyme, or troponin I as markers for the extent of the myocardial injury during the observation period. These data do not support previous reports of higher baseline levels of serum neopterin in patients with unstable angina or AMI compared with patients with chronic, stable CAD and healthy controls. Neopterin as a marker of macrophage activation is significantly increased in patients with AMI and unstable angina shortly after the onset of symptoms (after a period of 72 hours), supporting the hypothesis of monocyte and macrophage activation in patients with an acute coronary syndrome or AMI.

Low molecular weight heparins

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

Effects of various anticoagulant treatments on von Willebrand factor release in unstable angina

OBJECTIVES

We tested the hypothesis that different anticoagulant treatments may produce different platelet effects and von Willebrand factor (vWf) release in unstable angina.

BACKGROUND

The early increase of vWf has been reported to be a risk factor for adverse outcome in unstable angina. Anticoagulant drugs play a key role in stabilization of unstable angina, but they may not have the same efficacy and the same effects on acute vWf release.

METHODS

We studied 154 patients enrolled in several clinical trials testing four different anticoagulant treatments in unstable angina or non-Q-wave myocardial infarction. Patients were treated during at least 48 h by either intravenous unfractionated heparin, one of two different low molecular weight heparins (enoxaparin or dalteparin) or the direct thrombin inhibitor PEG-hirudin. All patients received aspirin but no Ib/IIIa inhibitors.

RESULTS

The release of vWf over the first 48 h (delta vWf) did not relate to the baseline clinical characteristics. At 30 days of follow-up, delta vWf was sevenfold higher in patients with an end point (death, myocardial infarction, revascularization) than in patients free of events (+53 +/-7% vs. +7 +/-14%, p = 0.004). The same trend was present for each component of the composite end point with the highest levels for one-month mortality (+87 +/- 32% vs. +26 +/- 8%, p = 0.09). The vWf values did not increase over 48 h in patients receiving either enoxaparin or PEG-hirudin (+10 +/- 9% and -5 +/- 20%, respectively). A serious rise ofvWf was measured in unfractionated heparin-treated patients (+87 +/- 11%), which differed significantly from the enoxaparin group (p = 0.0006) and PEG-hirudin group (p < 0.0001). In dalteparin-treated patients, delta vWf was elevated (+48 +/- 8%) and did not differ from the unfractionated heparin group (NS).

CONCLUSIONS

We confirm that, in unstable angina patients, a rise of vWf over the first 48 h is associated with an impaired outcome at 30 days. Moreover, the four different anticoagulant treatments tested here do not provide the same protection with regards to vWf release, which may have important prognostic implications and explain different results observed in recent clinical trials.

Enhanced inflammatory response in patients with preinfarction unstable angina

OBJECTIVES

We assessed the extent and the time course of the acute phase response following myocardial cell necrosis and its relationship with the presence of preinfarction unstable angina (UA).

BACKGROUND

Elevated levels of acute phase proteins have been reported in patients with UA and in patients with acute myocardial infarction (MI).

METHODS

C-Reactive Protein (CRP), serum amyloid A protein (SAA) and interleukin-6 (IL-6) were measured in 36 patients with MI admitted within 3 h from symptoms onset. All patients had normal levels of creatine kinase and of troponin T on admission, rising above diagnostic levels within 6 to 12 h. Blood samples for CRP, SAA and IL-6 measurements were taken on admission, at 6, 24, 48, 72 h and at discharge.

RESULTS

Twenty of the 36 patients studied presented an unheralded MI (Group 1); the remaining 16 patients had symptoms of unstable angina in the preceding 7 days (Group 2). Group 2 patients have much higher levels of CRP and SAA on admission (median values 8.8 vs. 3 mg/L and 28 vs. 3.4 mg/L, respectively, all p<0.001). Following the necrotic insult, despite similar infarct size and clinical signs of reperfusion, Group 2 patients had strikingly higher peaks of IL-6 (median values 85.2 vs. 19 pg/ml, p<0.05), CRP (50 vs. 31.4 mg/L, p<0.05) and SAA (228 vs. 45 mg/L, p<0.001).

CONCLUSIONS

Our data demonstrated that the acute phase response is greatly enhanced in patients with preinfarction UA compared with those presenting with an unheralded MI. The significant differences in acute phase response observed in these two clinical presentations of MI indicate a major difference in their underlying pathogenetic components.

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

BACKGROUND

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

METHODS AND RESULTS

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

CONCLUSIONS

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

Relation of von Willebrand factor to occurrence of Q waves and thrombolytic treatment in acute myocardial infarction

We measured the changes of plasma von Willebrand factor antigen and fibrinogen levels in patients with acute myocardial infarction treated with recombinant tissue plasminogen activator and patients not given fibrinolytic drugs. The von Willebrand factor levels are greater in patients with Q-wave than in patients with non-Q-wave myocardial infarction and are independent of thrombolytic treatment. Fibrinogen levels are depressed by thrombolytic treatment but are unrelated to the presence or absence of Q waves.

Rebound increase of plasminogen activator inhibitor type 1 after cessation of thrombolytic treatment for acute myocardial infarction is independent of type of plasminogen activator used

Plasma concentrations of tissue-type plasminogen activator (t-PA), plasminogen activator inhibitor type 1 (PAI-1), and D-dimer were investigated in 50 patients treated intravenously for acute myocardial infarction with either streptokinase (n = 23), urokinase (n = 17), or recombinant t-PA (rt-PA, n = 10). The fibrinolytic variables were measured by enzyme immunoassay on admission; 1, 2, 4, 6, 8, 12, and 24 h later; and then daily until day 7 after admission. In each subgroup of patients treated with different thrombolytic agents, PAI-1 increased significantly (P &lt;0.01) ∼3 h after cessation of thrombolytic therapy. PAI-1 peak concentrations did not differ significantly (P = 0.82) among these three subgroups. t-PA and D-dimer did not differ significantly (P &gt;0.14) among subgroups except for higher t-PA in the rt-PA group attributable to detection of the therapeutically administered exogenous rt-PA by the t-PA assay. Our findings demonstrate a marked PAI-1 increase after thrombolytic therapy for acute myocardial infarction, which seems to be a common, drug-independent antifibrinolytic rebound phenomenon in response to thrombolytic treatment.

Increased neopterin in patients with chronic and acute coronary syndromes

OBJECTIVES

The aim of our study was to determine neopterin levels in patients with chronic and acute coronary syndromes.

BACKGROUND

In chronic and acute coronary syndromes the release of different cytokines activates cellular defense. Infiltration of neutrophils and monocytes/macrophages is detected in the vessel wall as well as in the myocardium. Neopterin, which is a by-product of the guanosine triphosphate-biopterin pathway, is a marker for those activated macrophages.

METHODS

We studied 123 subjects: 1) 21 consecutive patients (17 men, 4 women; mean age +/- SD 66 +/- 15 years, range 31 to 87) with acute myocardial infarction (AMI); 2) 62 consecutive patients (50 men, 12 women; mean age 61 +/- 8 years, range 43 to 81) with signs and symptoms of clinically stable coronary artery disease (CAD); and 3) 40 healthy blood donors (28 men, 12 women; mean age 35 +/- 13 years). Neopterin levels were determined with a commercially available enzyme-linked immunosorbent assay method.

RESULTS

In patients with AMI before thrombolytic therapy, neopterin levels were significantly higher than levels in patients with CAD and control subjects (13.7 vs. 8.6 and vs. 6.8 nmol/liter, p < 0.0001). Values also differed significantly between patients with CAD and control subjects (p < 0.0001). Neopterin levels in patients with AMI were measured seven times during a 72-h period. Within-group comparison showed significant differences over this period (p < 0.00001). The lowest value (11.4 nmol/liter) was observed after 4 h and differed significantly from the initial value and values after 24 and 72 h (p < 0.05). After 72 h, neopterin increased to 14.9 nmol/liter, a value significantly different from all values other than the initial one. There was no correlation between neopterin and creatine kinase (CK); CK, MB isoenzyme; or lactate dehydrogenase as markers for the extent of the myocardial infarction during the observation period.

CONCLUSIONS

Our data support the hypothesis of an activation of monocytes and macrophages in patients with an acute or chronic coronary syndrome. Neopterin as a marker for macrophage activation is significantly increased in patients with chronic CAD and more pronounced in patients with AMI shortly after the onset of symptoms.

Serum lipoprotein(a) level is related to thrombin generation and spontaneous intermittent coronary occlusion in patients with acute myocardial infarction

BACKGROUND

Thrombotic occlusion of the infarct-related coronary artery is often intermittent in the early, evolving phase of acute myocardial infarction. To assess their relationship to this pattern of coronary occlusion, serum or plasma concentrations of cholesterol, triglyceride, lipoprotein(a), and coagulation and fibrinolytic factors were measured in venous blood before the initiation of thrombolytic therapy.

METHODS AND RESULTS

Thirty-two patients (23 men, 9 women: age, 30 to 70 years) with acute myocardial infarction received intravenous recombinant tissue plasminogen activator (20 to 60 megaunits) within 6 hours of the onset of symptoms. Continuous ECG ST-segment recording demonstrated intermittent occlusion of the infarct-related coronary artery in 12 patients (group 1) before the start of thrombolytic treatment and persistent occlusion in 20 patients (group 2). Groups 1 and 2 were similar in age, sex, race, duration of symptoms, blood sample collection time, location of the infarct-related coronary artery, and extent of coronary artery disease. The serum level (median [interquartile range]) of lipoprotein(a) was 34 (13 to 47) mg/dL versus 11.5 (5 to 27) mg/dL (P = .02), and the plasma level (median [interquartile range]) of thrombin-antithrombin III complex was 10.85 (6.4 to 21.5) versus 6.8 (4.2 to 8.7) micrograms/L-1 (P < .04) in groups 1 and 2, respectively. The levels of the other factors were similar in both groups.

CONCLUSIONS

The phenomenon of spontaneous intermittent closure and reopening of coronary arteries early during acute myocardial infarction in humans is associated with a higher level of lipoprotein(a) and of a marker of thrombin generation, suggesting that lipoprotein(a) and thrombin are closely related to coronary patency in these patients.

Von Willebrand factor in patients evolving Q-wave versus non-Q-wave acute myocardial infarction

We assessed the changes in plasma von Willebrand factor level concentration in 10 patients with Q-myocardial infarction and in six patients with non-Q-myocardial infarction who did not receive thrombolytic treatment. Concentrations of von Willebrand factor antigen were measured by an enzyme-linked immunoassay method in plasma samples obtained twice daily for 4 consecutive days. In patients with Q-wave myocardial infarction, a significant rise in von Willebrand factor antigen levels (P < 0.05) occurred after admission and persisted for 3 days. No significant changes were found in plasma concentration of fibrinogen. In conclusion, von Willebrand factor antigen levels were greater in patients with Q-wave compared to patients with non-Q-wave myocardial infarction.

t-Plasminogen activator and von Willebrand factor in patients with unstable angina

We investigated whether the clinical evolution of symptoms in patients admitted with unstable angina is associated with changes in t-plasminogen activator antigen (t-PA) and von Willebrand (vW) factor levels. Concentrations of vW factor antigen and t-PA antigen were measured by an enzyme-linked immunoassay method in 10 patients who became clinically stable within 24 h of admission and remained so for 5 days. A significant rise in morning t-PA plasma level occurred 24 h after the admission (15.15 +/- 2.1 ng/ml, P < 0.05), whereas the vW factor remained unchanged. No significant changes were found in the night concentration in t-PA and vW factor during the 5 day period. Thus t-PA level is significantly raised 24 h after admission in patients with unstable angina who stabilize in response to medical treatment.

Early spontaneous intermittent myocardial reperfusion during acute myocardial infarction is associated with augmented thrombogenic activity and less myocardial damage

OBJECTIVES

This study investigated the influence of early spontaneous intermittent reperfusion on the extent of myocardial damage and its relation to endogenous hemostatic activity.

BACKGROUND

In the early phase of acute myocardial infarction coronary occlusion is often intermittent, even before thrombolytic therapy is administered. The relation between this phenomenon, myocardial damage and hemostatic activity is unknown.

METHODS

Holter ST segment recording and pretreatment plasma tissue-type plasminogen activator (t-PA) antigen, plasminogen activator inhibitor-1 (PAI-1) antigen, prothrombin fragment F1 + 2 and soluble fibrin levels were measured in 57 patients with acute evolving myocardial infarction. Spontaneous intermittent myocardial reperfusion, defined as two or more episodes of transient resolution of ST segment elevation to within 0.05 mV of baseline, lasting > or = 1 min, before the start of recombinant t-PA (rt-PA) treatment was present in 28 patients (group 1) and absent in 29 (group 2). Left ventriculography and coronary angiography were performed 90 min after intravenous rt-PA administration. Plasma creatine kinase-MB fraction (CK-MB) levels were measured every 6 h for 24 h, and C-reactive protein levels were measured daily for 3 days.

RESULTS

Group 1 had lower peak plasma CK-MB (141.9 +/- 28.3 vs. 203.8 +/- 23.3 IU/liter [mean +/- SEM], p < 0.014) and C-reactive protein levels (16 +/- 4 vs. 28 +/- 4 mg/liter on day 1; 26.6 +/- 5.5 vs. 61.8 +/- 14.4 mg/liter on day 2; 19.6 +/- 4.2 vs. 40.6 +/- 6.5 mg/liter on day 3, p < 0.012) and a higher left ventricular ejection fraction (62.9 +/- 4% vs. 51.1 +/- 5%, p < 0.04) than group 2. Group 1 had lower plasma t-PA antigen levels (15.6 vs. 27 micrograms/liter, p < 0.006) but higher prothrombin fragment F1 + 2 (1.8 vs. 1.1 nmol/liter, p < 0.003) and soluble fibrin levels (66.8 vs. 31 nmol/liter, p < 0.01). Coronary patency at 90 min was similar.

CONCLUSIONS

Early spontaneous intermittent reperfusion during acute myocardial infarction is associated with augmented thrombogenic activity and less subsequent myocardial damage. This finding is consistent with a protective effect of intermittency on the myocardium and a procoagulant effect of spontaneous lysis on blood. It may also reflect a different rate of evolution of coronary thrombosis and myocardial infarction in patients with and those without spontaneous intermittent myocardial reperfusion.

Fibrinogen after coronary angioplasty as a risk factor for restenosis

BACKGROUND

Fibrinogen is a risk factor for cardiovascular disease and is related to the severity of coronary atherosclerosis. Its role in restenosis after coronary angioplasty remains unknown. Although platelets and thrombosis contribute to the pathogenesis of restenosis, few clinical data are available concerning the relations between restenosis and proteins of the coagulation and fibrinolytic systems.

METHODS AND RESULTS

In 107 consecutive patients undergoing coronary angioplasty, we measured plasma levels of tissue-type plasminogen activator (t-PA), plasminogen activator inhibitor-1 (PAI-1), von Willebrand factor, and fibrinogen before and immediately after angioplasty and at a 6-month follow-up. The individual changes of intraluminal diameter were measured by quantitative coronary angiography, and patients were classified according to four definitions of restenosis: (1) a final stenosis > 50%, (2) a loss of minimal luminal diameter during the follow-up period greater than the measurement variability in our laboratory (> 0.52 mm), (3) a loss of at least 50% of the gain in luminal diameter achieved by angioplasty, and (4) the combination of definitions 1 and 2. The relations between coagulation variables and each definition of restenosis were assessed univariately; then with the clinical variables included, the relations were analyzed multivariately. Angiographic follow-up was obtained in 92% of patients with a primary success of angioplasty. Global restenosis rates were 38%, 43%, 48%, and 30% for definitions 1 through 4, respectively. Plasma levels of t-PA antigen and PAI-1 antigen were not associated with any of the four definitions of restenosis. Multivariate analysis demonstrated that von Willebrand factor measured immediately after angioplasty predicted restenosis according to definitions 2 and 3. Fibrinogen measured within 6 months of follow-up was significantly increased in all restenosis groups of the four definitions. Patients with a fibrinogen concentration > 3.5 g/L at follow-up had higher restenosis rates than patients with a concentration < 3.5 g/L: 55% versus 22% (P = .001), 68% versus 31% (P = .002), 63% versus 37% (P = .01), and 74% versus 26% (P = .002) for definitions 1 through 4, respectively. The loss index was lower (P = .003) and the net gain higher (P = .03) in patients with a fibrinogen level < 3.5 g/L. There was a significant correlation between fibrinogen level and angiographic loss index (r = .41; P < .0001). Multivariate analysis confirmed that the fibrinogen level predicted restenosis with all definitions.

CONCLUSIONS

An independent relation exists between von Willebrand factor measured immediately after angioplasty and restenosis defined by the degree of intraluminal renarrowing. An elevated fibrinogen level during follow-up is a strong biochemical predictor of restenosis. Therefore, fibrinogen should be considered at least as an independent marker of restenosis and perhaps as a common risk factor for both spontaneous coronary atherosclerosis and postangioplasty restenosis, which is an accelerated form of atherosclerosis.

The prognostic value of C-reactive protein and serum amyloid a protein in severe unstable angina

BACKGROUND

The pathogenesis of unstable angina is poorly understood, and predicting the prognosis at the time of hospital admission is problematic. Recent evidence suggests that there may be active inflammation, possibly in the coronary arteries, in this syndrome. We therefore studied the prognostic value of measurements of the circulating acute-phase reactants C-reactive protein and serum amyloid A protein, which are sensitive indicators of inflammation.

METHODS

We measured C-reactive protein, serum amyloid A protein, creatine kinase, and cardiac troponin T in 32 patients with chronic stable angina, 31 patients with severe unstable angina, and 29 patients with acute myocardial infarction.

RESULTS

At the time of hospital admission, creatine kinase and cardiac troponin T levels were normal in all the patients, but the levels of C-reactive protein and serum amyloid A protein were > or = 0.3 mg per deciliter (exceeding the 90th percentile of the normal distribution) in 4 of the patients with stable angina (13 percent), 20 of the patients with unstable angina (65 percent), and 22 of the patients with acute myocardial infarction (76 percent). The 20 patients with unstable angina who had levels of C-reactive protein and serum amyloid A protein > or = 0.3 mg per deciliter had more ischemic episodes in the hospital than those with levels < 0.3 mg per deciliter (mean [+/- SD] number of episodes per patient, 4.8 +/- 2.5 vs. 1.8 +/- 2.4; P = 0.004); 5 patients subsequently had a myocardial infarction, 2 died, and 12 required immediate coronary revascularization. In contrast, no deaths or myocardial infarction occurred among the 11 patients with levels of C-reactive protein and serum amyloid A protein < 0.3 mg per deciliter, and only 2 of them required coronary revascularization. Among the patients admitted with a diagnosis of acute myocardial infarction, unstable angina preceded infarction in 14 of the 22 patients (64 percent) with levels of C-reactive protein and serum amyloid A protein > or = 0.3 mg per deciliter but in none of the 7 patients with levels < 0.3 mg per deciliter.

CONCLUSIONS

Elevation of the sensitive acute-phase proteins C-reactive protein and serum amyloid A protein at the time of hospital admission predicts a poor outcome in patients with unstable angina and may reflect an important inflammatory component in the pathogenesis of this condition.

Release of von Willebrand factor by cardiopulmonary bypass, but not by cardioplegia in open heart surgery

von Willebrand Factor (vWF) is released from endothelial cells. Increased vWF in the coronary circulation during cardiac surgery could be a potential indicator of coronary endothelial injury or stimulation, and thus a possible tool to evaluate regimens of myocardial protection. Release of vWF was investigated in 12 patients undergoing coronary artery bypass surgery with cardiopulmonary bypass (CPB). Concomitant samples of arterial and coronary sinus blood for measurement of vWF (antigen method) were drawn before start of CPB and 1, 4, 10 and 30 min after release of the aortic cross clamp. Additional arterial samples were drawn pre-, per-, and postoperatively. Preoperative arterial vWF was 1.58 +/- 0.59 IU/ml (mean +/- SD), and increased during CPB (highest level 2.37 +/- 0.76 IU/ml, p < 0.0026). No difference between arterial and coronary sinus vWF levels was found. Arterial vWF increased further the first postoperative day (3.96 +/- 0.92 IU/ml, p < 0.0026). In conclusion, systemic vWF is increased during CPB, and may be a possible marker of endothelial injury/activation to evaluate deleterious effects of different equipment for CPB. Reperfusion of the ischaemic, cardioplegic heart did not release vWF in the coronary circulation.

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.

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.

Increased plasma plasminogen activator inhibitor activity after coronary spasm

To examine whether ischemic attack induced by coronary spasm changes fibrinolytic activity, we examined plasma levels of tissue-plasminogen activator antigen and plasminogen activator inhibitor activity before and after hyperventilation test in patients with variant angina and in control subjects. In 12 patients with variant angina, ischemic attack associated with ST-segment elevation on the electrocardiogram was induced by hyperventilation and plasma plasminogen activator inhibitor activity levels increased significantly 15 min after the attacks (pre, 5.1 +/- 0.8; immediately after, 5.8 +/- 1.1; and 15 min after, 7.2 +/- 0.9 IU/ml, P < 0.01). In 12 control subjects, plasminogen activator inhibitor activity levels did not change. Plasma tissue-plasminogen activator antigen levels did not change in both two groups. We conclude that coronary artery spasm increases plasma plasminogen activator inhibitor activity and that it may thereby lead to the coronary thrombus formation.

Association of patency of the infarct-related coronary artery with plasma levels of plasminogen activator inhibitor activity in acute myocardial infarction

To examine the fibrinolytic capacity in patients with acute myocardial infarction (AMI), baseline levels of plasma plasminogen activator inhibitor (PAI) activity and tissue-type plasminogen activator (t-PA) antigen were measured in 47 patients with Q-wave AMI who underwent emergent coronary angiography 3.0 +/- 0.2 hours after the symptom onset. They received intracoronary injection of urokinase if their infarct-related arteries were occluded. They were classified into 3 groups according to the patency of the infarct-related artery before and after thrombolytic therapy: the patent group (13 patients), the recanalized group (23 patients) and the occluded group (11 patients). The mean level of plasma PAI activity (IU/ml) was higher in patients with AMI as a whole than in the control group (12.8 +/- 1.6 vs 5.4 +/- 0.5, p less than 0.01). The level was lower in the patent group (3.0 +/- 1.1) and higher in the recanalized (18.6 +/- 2.2) and occluded (10.8 +/- 2.5) groups than in the control group (each p less than 0.01). The level was lower in the occluded than in the recanalized group (p less than 0.01) and 62% of the patients in the occluded group had levels within range of the control group. The mean level of plasma t-PA antigen (ng/ml) was higher in patients with AMI as a whole than in the control group (10.3 +/- 0.8 vs 5.8 +/- 0.3, p less than 0.01). There was no difference in the level among the 3 groups with AMI.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of propranolol (long-acting) on the circadian fluctuation of tissue-plasminogen activator and plasminogen activator inhibitor-1

The incidence of myocardial infarction and sudden cardiac death is highest in the morning. Inhibition of fibrinolytic activity in blood also peaks in the morning and this inhibition may favor the development of arterial thrombosis. It has been reported that patients treated with beta blockers do not show the typical circadian pattern of onset of myocardial infarction and sudden cardiac death. This study was undertaken to investigate whether beta blockade alters the circadian rhythm of 2 major fibrinolytic factors, tissue-plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1). Repeated blood samples were taken over a 24-hour period in 13 healthy volunteers: 7 taking 160 mg/day of long-acting propranolol orally for 14 days, and the other 6 taking no medications. Blood samples were analyzed for the plasma levels of t-PA activity, t-PA antigen, PAI activity and PAI-1 antigen. A significant circadian variation of all 4 parameters was present in both groups. No significant differences in peak and nadir values, 24-hour mean, amplitude of fluctuation, and time of peak and nadir were found between the treated and untreated subjects. The data therefore suggest that propranolol treatment does not affect the plasma concentrations at rest or the endogenous circadian rhythm of t-PA and PAI-1 in healthy volunteers. The reported alteration in the circadian pattern of onset of myocardial infarction and sudden cardiac death by beta blockers does not appear to be mediated by effects on the fibrinolytic system.

Circadian variation of fibrinolytic activity in blood

Approximately 35 years ago, it was discovered that spontaneous fibrinolytic activity in blood showed a sinusoidal variation with a period of 24 h; it increased severalfold during the day, reaching a peak at 6:00 p.m. and then dropped to trough levels at 3:00-4:00 a.m. The range of the fluctuation and the 24-h mean levels were highly reproducible within an individual; moreover, the timing of the oscillation was remarkably consistent among individuals, with a fixed phase relationship to external clock time. The biorhythm could not be accounted for simply by variations in physical activity, body posture, or sleep/wake schedule. Gender, ethnic origin, meals, or resting levels of blood fibrinolytic activity also did not influence the basic features of the rhythm. Older subjects, compared to younger ones, showed a blunted diurnal increase in fibrinolytic activity in blood. Recent studies have established that, of the known components of the fibrinolytic system, only tissue-type plasminogen activator (tPA) and its fast-acting inhibitor, plasminogen activator inhibitor-1 (PAI-1), show a marked circadian variation in plasma. In contrast, levels of plasminogen, alpha 2-antiplasmin, urinary-type plasminogen activator, and a reversible tPA inhibitor vary little or none during the 24 h. Quenching antibodies to tPA have shown that the circadian rhythm of fibrinolytic activity in blood is due exclusively to changes in tPA activity. However, the 24-h fluctuation of plasma tPA activity is phase shifted in relation to the rhythm of immunoreactive tPA, but shows a precise phase inversion with respect to the 24-h variation of PAI-1 activity and antigen. Therefore, plasma tPA activity, as currently measured in vitro, is tightly and inversely related to the levels of PAI-1 throughout the 24-h cycle. The factors controlling the rhythmicity of plasma PAI-1 are not fully elucidated but probably involve a humoral mechanism; changes in endothelial function, circulating platelet release products, corticosteroids, catecholamines, insulin, activated protein C, or hepatic clearance do not appear to be responsible. Shift workers on weekly shift rotations show a disrupted 24-h rhythm of plasma tPA and PAI-1. In acute and chronic diseases, the circadian rhythmicity of fibrinolytic activity may show a variety of alterations, affecting the 24-h mean, the amplitude, or the timing of the fluctuation. It is advisable, therefore to define the 24-h pattern of plasma tPA and PAI-1 in patient groups, before levels based on a single blood sampling time are compared to those of a control population.(ABSTRACT TRUNCATED AT 400 WORDS)