Endogenous Fibrinolysis Research Articles

Relationship between lipoprotein(a) and endogenous fibrinolytic status in patients with STEMI

Abstract Background The risk of myocardial infarction is at least doubled in individuals with lipoprotein(a) (Lp[a]) levels >90th percentile.[1] Lp(a) may exert pro-thrombotic effects by impairing fibrinolysis. Lp(a) has a high degree of homology to plasminogen and can competitively inhibit tissue plasminogen activator (tPA)-mediated plasminogen activation and tPA-mediated clot lysis.[2] Furthermore, Lp(a) stimulates the activity of plasminogen activator inhibitor-1, the major inhibitor of the fibrinolytic system. In patients with ST-segment elevation myocardial infarction (STEMI), impaired endogenous fibrinolysis is a strong, independent risk factor for recurrent cardiovascular events,[3] but the drivers of this are not fully understood. Whether impaired endogenous fibrinolysis is related to increased Lp(a) levels in patients with STEMI, is not known. Purpose We aimed to assess the relationship between Lp(a) and endogenous fibrinolysis in patients with STEMI. Methods In a prospective, observational study, venous blood samples were drawn from patients presenting with STEMI immediately before revascularisation, after dual antiplatelet therapy but before heparin administration. Endogenous fibrinolysis was measured immediately in non-anticoagulated whole blood using the point-of-care Global Thrombosis Test, which measures the time for occlusive thrombus formation under high shear (occlusion time) and the time for spontaneous lysis of the thrombus (lysis time).[3] Assessment of Lp(a) levels, measured by particle enhanced immunoturbidimetric assay, was performed with paired plasma samples, standardized against the International Federation of Clinical Chemistry reference material SRM2B for nmol/L. Lp(a) >32 nmol/L is associated with increased risk of ischaemic heart disease. Results A total of 80 patients were included (age 64±14y, 25% females and 86% Caucasian). There was a positive correlation between Lp(a) level and lysis time (r = 0.330, P = 0.003) (Figure 1). Lysis time was significantly longer in patients with Lp(a) >32 nmol/L (2782 [1626-3683] vs. 1725 [1259-2955] s, P = 0.044). Using a cut-point of lysis time ≥2500 s previously associated with a significantly increased cardiovascular risk in patients with STEMI, we showed that Lp(a) was significantly higher in patients with lysis time ≥2500 s (40 (22-111) vs. 18 (7-73) nmol/L, P = 0.045). Table 1 shows the relationship between clinical characteristics and Lp(a) and lysis time. Lp(a) level was higher in non-Caucasian patients. There was no correlation between Lp(a) and occlusion time (r = 0.156, P = 0.168). Conclusion In patients with STEMI, longer endogenous fibrinolysis time is related to higher Lp(a) level. Raised Lp(a) levels may, in part, contribute to impaired endogenous fibrinolysis. Future studies are required to assess whether reduction in Lp(a) with novel therapies currently in phase 3 trials can favourably modulate fibrinolysis and improve clinical outcomes.Figure 1

Targeting Fibrinolytic Inhibition for Venous Thromboembolism Treatment: Overview of an Emerging Therapeutic Approach.

Venous thrombosis and pulmonary embolism (venous thromboembolism) are important causes of morbidity and mortality worldwide. In patients with venous thromboembolism, thrombi obstruct blood vessels and resist physiological dissolution (fibrinolysis), which can be life threatening and cause chronic complications. Plasminogen activator therapy, which was developed >50 years ago, is effective in dissolving thrombi but has unacceptable bleeding risks. Safe dissolution of thrombi in patients with venous thromboembolism has been elusive despite multiple innovations in plasminogen activator design and catheter-based therapy. Evidence now suggests that fibrinolysis is rigidly controlled by endogenous fibrinolysis inhibitors, including α2-antiplasmin, plasminogen activator inhibitor-1, and thrombin-activable fibrinolysis inhibitor. Elevated levels of these fibrinolysis inhibitors are associated with an increased risk of venous thromboembolism in humans. New therapeutic paradigms suggest that accelerated and effective fibrinolysis may be achieved safely by therapeutically targeting these fibrinolytic inhibitors in venous thromboembolism. In this article, we discuss the role of fibrinolytic components in venous thromboembolism and the current status of research and development targeting fibrinolysis inhibitors.

Impaired endogenous fibrinolysis status: a potential prognostic predictor in ischemic stroke.

Stroke confers a severe global healthcare burden, hence exploring risk factors for stroke occurrence and prognosis is important for stroke prevention and post-stroke management strategies. Endogenous fibrinolysis is a spontaneous physiological protective mechanism that dissolves thrombus to maintain vascular patency. Recently, impaired endogenous fibrinolysis has been considered as a potential novel cardiovascular risk factor, but its link with ischaemic stroke in the past has been underappreciated. In this review, we summarize the latest mechanisms of endogenous fibrinolysis, review the current evidence and data on endogenous fibrinolysis in ischemic stroke. It includes the structure of thrombus in ischemic stroke patients, the effect of fibrin structure on the endogenous fibrinolytic efficiency, and the association between intravenous thrombolytic therapy and endogenous fibrinolysis in ischemic stroke. It also includes the single factors (tissue plasminogen activator, urokinase plasminogen activator, plasminogen activator inhibitor-1, thrombin activatable fibrinolysis inhibitor, complement component 3, complement component 5, alpha-2-antiplasmin, plasmin-alpha-2-antiplasmin complex, and lipoprotein[a]), and the global assessments of endogenous fibrinolysis status (thromboelastography, rotational thromboelastometry, and global thrombosis test), and their potential as predictors to identify occurrence or unfavorable functional outcomes of ischemic stroke. All of these assessments present advantages and limitations, and we suggest that the global thrombosis test may be more appropriate for detecting impaired endogenous fibrinolysis status in ischemic stroke patients.

Spontaneous reperfusion in STEMI: Its mechanisms and possible modulation.

Patients with transient ST-segment elevation myocardial infarction or spontaneous reperfusion, which occurs in approximately 20% of patients with ST-segment elevation myocardial infarction (STEMI), have smaller infarcts and more favorable clinical outcomes than patients without spontaneous reperfusion. Understanding the mechanisms underlying spontaneous reperfusion is therefore important since this may identify possible novel therapeutic targets to improve outcomes in patients with STEMI. In this review, we discuss some of the possible determinants of spontaneous reperfusion including pro-thrombotic profile, endogenous fibrinolytic status, lipoprotein(a) (Lp[a]), inflammatory markers, and neutrophil extracellular traps (NETs). Effective (rapid) endogenous fibrinolysis, as assessed in whole blood in vitro, using a point-of-care technique assessment of global thrombotic status, has been strongly linked to spontaneous reperfusion. Lp(a), which has a high degree of homology to plasminogen, may impair fibrinolysis through competitive inhibition of tissue plasminogen activator-mediated plasminogen activation as well as tissue plasminogen activator-mediated clot lysis and contribute to pathogenic clot properties by decreasing fibrin clot permeation. NETs appear to negatively modulate clot lysis by increasing thrombin fiber diameter and inhibiting plasmin-driven lysis of plasma clots. There are limited data that oral anticoagulation may modulate endogenous fibrinolysis but antiplatelet agents currently appear to have no impact. Phase III trials involving subcutaneous P2Y12 or glycoprotein IIb/IIIa inhibitors, oral factor XIa inhibitors, interleukin-6 inhibitors, and apolipoprotein(a) antisense oligonucleotides in patients with cardiovascular disease are ongoing. Future studies will be needed to determine the impact of these novel antithrombotic, anti-inflammatory, and lipid-lowering therapies on endogenous fibrinolysis and spontaneous reperfusion.

A low bleeding risk thrombolytic agent: citPA5.

Alteplase is a cornerstone thrombolytic agent in clinical practice but presents a potential bleeding risk. Stroke patients need pre-screening to exclude haemorrhagic stroke before using alteplase. In this study, we develop a new thrombolytic agent citPA5, characterized by an enhanced safety profile and minimal bleeding tendency. A clot lysis agent, named citPA5, is developed based on rtPA with point mutations to completely suppress its proteolytic activity in the absence of fibrin. In the presence of fibrin, citPA5 exhibited significantly higher fibrinolytic activity (a 15.8-fold increase of kcat/Km). Furthermore, citPA5 showed resistance to endogenous fibrinolysis inhibitor, PAI-1, resulting in enhanced potency. In a series of safety evaluation experiments, including thrombelastography assay, mice tail bleeding assay, and a murine intracerebral haemorrhage (ICH) model, citPA5 did not cause systemic bleeding or worsen ICH compared with alteplase. This highlights the low risk of bleeding associated with citPA5. Finally, we found that citPA5 effectively improved cerebral blood flow and reduced infarct volume in a carotid embolism-induced stroke model. This clot lysis agent, citPA5, not only exhibits a low risk of bleeding but also demonstrates highly effective thrombolysis capabilities. As a result, citPA5 shows great potential for administration prior to the classification of stroke types, making it possible for use in ambulances at the onset of stroke when symptoms are identified. The findings presented in this study also suggest that this strategy could be applied to develop a new generation of fibrinolytic drugs that offer greater safety and specificity in targeting fibrin.

Impact of very low dose rivaroxaban in addition to dual antiplatelet therapy on endogenous fibrinolysis in acute coronary syndrome: The VaLiDate-R study

BackgroundImpaired endogenous fibrinolysis is adverse cardiovascular risk factor in acute coronary syndrome (ACS) patients. Addition of very low dose rivaroxaban (VLDR) to dual antiplatelet therapy (DAPT) reduces cardiovascular events but increases bleeding. ObjectiveWe aimed to assess whether addition of VLDR to DAPT can enhance endogenous fibrinolysis. MethodsIn a prospective, open-label trial, we assessed endogenous fibrinolysis in whole blood, in 549 patients with ACS using the Global Thrombosis Test (GTT) and Thromboelastography (TEG). Patients (n = 180) who demonstrated impaired endogenous fibrinolysis (lysis time [LT] >2000s with the GTT) were randomised 1:1:1 to (i) clopidogrel 75 mg daily; (ii) clopidogrel 75 mg daily plus rivaroxaban 2.5 mg twice daily; or (iii) ticagrelor 90 mg twice daily, for 30 days, in addition to aspirin. Fibrinolytic status was assessed at 0, 2, 4 and 8 weeks. The primary outcome was the change in LT from admission to week 4. We also measured thrombotic occlusion time (OT) at high shear, and rivaroxaban level. ResultsThere was no difference between the groups with respect to LT or clot lysis with TEG, and no change in these parameters compared to baseline during study drug allocation. In the rivaroxaban plus clopidogrel group, OT was prolonged compared to the other groups, although rivaroxaban levels were low, suggesting non-compliance. ConclusionAddition of rivaroxaban 2.5 mg twice daily to DAPT does not affect endogenous fibrinolysis of thrombus formed at either high or low shear. Further studies are needed to determine whether higher doses of rivaroxaban can favourably modulate fibrinolysis. Condensed abstractImpaired endogenous fibrinolysis is a strong risk factor in ACS. We aimed to assess whether adding very low dose rivaroxaban (VLDR) to DAPT can enhance fibrinolysis. Fibrin and clot lysis were assessed in whole blood. ACS patients with impaired fibrinolysis were randomised 1:1:1 to clopidogrel 75 mg daily; clopidogrel 75 mg plus VLDR; or ticagrelor 90 mg twice daily, in addition to aspirin. At 30-days, there was no difference in lysis time between the groups, nor change from baseline. VLDR does not improve fibrinolysis at high or low shear. Further studies are needed to determine whether alternative antithrombotic regimens can enhance endogenous fibrinolysis.

Ethnic Differences in Thrombotic Profiles of Acute Coronary Syndrome Patients and Relationship to Cardiovascular Outcomes: A Comparison of East Asian and White subjects.

East Asians (EAs), compared to white Caucasians (W), have a lower risk of ischemic heart disease and a higher risk of bleeding with antithrombotic medications. The underlying mechanisms are incompletely understood. We sought to compare thrombotic profiles of EA and W patients with myocardial infarction (MI) and relate these to cardiovascular outcomes. In a prospective study in the United Kingdom and Korea, blood samples from patients (n = 515) with ST- or non-ST-elevation MI (STEMI and NSTEMI) were assessed using the Global Thrombosis Test, measuring thrombotic occlusion (OT) and endogenous fibrinolysis (lysis time [LT]). Patients were followed for 1 year for major adverse cardiovascular events (MACE) and bleeding. EA patients showed reduced OT (longer OT) compared to W (646 seconds [470-818] vs. 436 seconds [320-580], p < 0.001), with similar LT. In STEMI, OT (588 seconds [440-759] vs. 361 seconds [274-462], p < 0.001) and LT (1,854 seconds [1,389-2,729] vs. 1,338 seconds [1,104-1,788], p < 0.001) were longer in EA than W. In NSTEMI, OT was longer (OT: 734 seconds [541-866] vs. 580 seconds [474-712], p < 0.001) and LT shorter (1519 seconds [1,058-2,508] vs. 1,898 seconds [1,614-2,806], p = 0.004) in EA than W patients. MACE was more frequent in W than EA (6.3 vs. 1.9%, p = 0.014) and bleeding infrequent. While OT was unrelated, LT was a strong independent predictor of MACE event after adjustment for risk factors (hazard ratio: 3.70, 95% confidence interval: 1.43-9.57, p = 0.007), predominantly in W patients, and more so in STEMI than NSTEMI patients. EA patients exhibit different global thrombotic profiles to W, associated with a lower rate of cardiovascular events.

Point-of-care biomarkers of thrombotic status predict spontaneous reperfusion in ST-segment elevation MI and clinical outcomes

Abstract Background Spontaneous reperfusion, seen in ∼20% of patients with ST-segment elevation myocardial infarction (STEMI), manifests as normal epicardial flow in the infarct-related artery (IRA), with or without ST-segment resolution, before percutaneous coronary intervention (PCI). The drivers mediating this are unknown. Purpose We aimed to assess whether the thrombotic profile of patients with and without spontaneous reperfusion differed significantly, and whether such patients had better outcomes. Methods We performed a prospective, observational study in consecutive patients presenting with STEMI. Blood samples were taken from a 6 Fr arterial sheath immediately before emergency angiography, before PPCI, after dual antiplatelet therapy loading, but before the administration of heparin or other anticoagulant. Blood samples were tested using a point-of-care global test of thrombotic status, measuring occlusion (OT) and endogenous fibrinolysis (LT) times. Spontaneous reperfusion was defined as IRA TIMI III flow pre-PCI. Patients were followed for major cardiovascular events (MACE; death, myocardial infarction, stroke). Results Spontaneous reperfusion was associated with longer OT (435s vs. 366s, p&amp;lt;0.001) and shorter LT (1257s vs. 1616s, p&amp;lt;0.001), lower troponin and better LV function. LT was superior to OT for predicting spontaneous reperfusion (AUC for LT: 0.707, 95% CI 0.661-0.753; AUC for OT: 0.629, 95% CI 0.581-0.677). Amongst patients with spontaneous reperfusion, those with complete, versus partial ST-segment resolution, had longer OT (p=0.002) and shorter LT (p&amp;lt;0.001). Spontaneous reperfusion was unrelated to clinical characteristics or pain-to-angiography times. Over 4-years, patients with spontaneous reperfusion experienced fewer MACE than those without (4.1% vs. 10.6%, p=0.013), especially in those with both spontaneous reperfusion and complete ST-segment resolution (1.5% vs. 10.1%, p=0.029). Conclusions We demonstrate a novel haematological signature in STEMI patients with spontaneous reperfusion, namely reduced platelet reactivity and faster endogenous fibrinolysis, relating to smaller infarcts and improved survival. This indicates a role for modulating thrombotic status early following STEMI-onset, to facilitate spontaneous reperfusion and improve outcomes.Visual abstractThrombotic profile predicts outcome

Pulmonary vasoconstriction plays a major role in the acute phase of pulmonary embolism in pigs

Abstract Background Pulmonary vascular resistance (PVR) increases in acute pulmonary embolism (PE) due to both mechanical obstruction and pulmonary vasoconstriction. Attenuation of adverse pulmonary vasoconstriction has shown promise as a treatment of acute PE in experimental studies. However, clinical trials have failed to replicate these beneficial effects in PE patients. Time may be a factor in this discrepancy between experimental and clinical studies. In experimental PE studies, PVR acutely increases and decreases within hours. Meanwhile in clinical trials, the time from symptom onset to study inclusion is often days, at which time PVR may already be decreased. Whether this decrease in PVR is due to reduced mechanical obstruction by endogenous fibrinolysis or attenuation of adverse pulmonary vasoconstriction is unknown. Purpose To investigate the contribution of the mechanical obstruction and pulmonary vasoconstriction to PVR in two days following PE in pigs. Methods In a controlled animal study, using an estabilished model of autologous PE in pigs (PE, n=12 ∼60 kg), changes in pulmonary hemodynamics and clot burden were evaluated. CT pulmonary angiograms were performed at baseline (BL), after acute PE and the following two days, quantifying clot burden using the Qanadli Obstruction Score. Hemodynamics were evaluated with real-time biventricular catheterization and systemic invasive pressures. To evaluate the vasoactive component, pulmonary vasodilators sildenafil (bolus 0.1 mg/kg) and oxygen (inspired fraction of oxygen 40%) were administered. Results Following PE, both mean PVR (Figure 1A) and pulmonary obstruction scores (Figure 1B) increased. PVR decreased at day one and remained unchanged at day two (Figure 1A). Meanwhile, mean obstruction score decreased slightly at day one but remained elevated throughout the study (Figure 1B). Vasodilatation induced by sildenafil and oxygen (SIL+OXY) decreased PVR at day zero but displayed no effect on the subsequent days (Figure 1A). Conclusion Pulmonary vasoconstriction and mechanical obstruction both contributed to the increase in PVR during the acute phase of PE. PVR decreased towards levels of baseline already day one and remained unchanged at day two. The contribution of pulmonary vasoconstriction decreased at day one and two, while the mechanical obstruction remained significantly increased. Accordingly, the effects of pulmonary vasodilators were only present in the acute phase of PE.Figure 1

Thrombotic profile of East Asian and Western ACS patients and relationship to cardiovascular outcomes

Abstract Background East Asian patients compared to Westerners, have a lower risk of ischemic heart disease and a higher risk of bleeding with antithrombotic medications. The underlying mechanisms are incompletely understood. Genetic differences may underlie lower coagulant and inflammation levels in EA compared to W populations. Objectives We sought to compare thrombotic profiles of East Asian and Western patients with myocardial infarction (MI) and relate these to cardiovascular outcomes. Methods In a 2 centre, prospective, observational study in the U.K. and Korea, blood samples from patients (n=515) with ST- or non-ST-elevation MI (STEMI and NSTEMI) were assessed using the Global Thrombosis Test, measuring thrombotic occlusion (OT) and endogenous fibrinolysis (LT) times. In STEMI patients, blood samples were taken immediately upon arrival, whilst in NSTEMI patients, blood samples were taken after DAPT loading. Patients were followed for 1 year for major adverse cardiovascular events and major bleeding. Results Major adverse cardiovascular events occurred significantly more frequently in Western than in East Asian patients (6.27% vs. 1.92%, p=0.014), driven by a higher rate of cardiovascular death (3.53% vs. 0.38%, p=0.01), with minimal major bleeding events (0.39% vs. 0.38%, p=1.0). East Asian patients showed reduced platelet reactivity (longer OT) compared to Western patients (646s [470-818] vs. 436s [320-580], p&amp;lt;0.001), with similar LT. In STEMI, OT (588s [440-759] vs. 361s [274-462], p&amp;lt;0.001) and LT (1854s [1389-2729] vs. 1338s [1104-1788], p&amp;lt;0.001) were longer in East Asian patients than Westerners. In NSTEMI, OT was longer (OT 734s [541-866] vs. 580s [474-712], p&amp;lt;0.001) and LT shorter (1519s [1058-2508] vs. 1898s [1614-2806], p=0.004) in East Asian than Western patients. While OT was unrelated, LT was a strong independent predictor of MACE after adjustment for risk factors (HR 3.70, 95% CI 1.43-9.57, p=0.007), predominantly in Western patients, and more so in STEMI than NSTEMI. Conclusion East Asian patients exhibit different global thrombotic profiles to Westerners, associated with a lower rate of cardiovascular events. The lower platelet reactivity in East Asian STEMI patients, even before antiplatelet therapy, may explain contribute to the lower risk of subsequent adverse ischaemic events.

Abstract 13625: Laboratory Markers of Effective Endogenous Fibrinolysis in Intermediate-High-Risk Pulmonary Embolism

Introduction: Unselected therapy with fibrinolysis in intermediate risk-pulmonary embolism (iPE) is associated with an unacceptable risk of bleeding. Early identification of iPE patients on anticoagulant therapy with ineffective endogenous fibrinolysis (eFL) could optimize treatment-strategy. Aims: The study aims to determine markers of (in)effective eFL in intermediate-risk PE initially on anticoagulant therapy with UFH. Methods: In course of 24 months, iPE patients were enrolled in the prospective study. At admission, and every 24 hours until day 5, levels of 6 selected markers of eFL (i.e., PAI-1 and tPA active assay and total antigen, TAFI, and PAP) were determined. Upon arrival and following a span of 36 hours,defined i) Clinical (heart rate &gt;100 bpm and spontaneous oxygen saturation &lt;90%), ii) Echo (D-shape, RVd/LVd from PLAX&gt;0.7, RV/RA &gt;30mmHg), and iii) CT (RV/LV&gt;0.9) variables were obtained. An (un)successful therapy was assessed by one point for each clinical, Echo and CT criteria, as at least one parameter from initially altered has adjusted at 36 hours. We performed correlation of laboratory markers with the dynamics of clinical and imaging characteristics. Results: Study population consists of 44 patients, 22 men, mean (SD) age 60 (18.3) yr., first (38), repeat (6) PE. Plasminogen activator inhibitor-1 (PAI-1) active assay showed the most promising results. The cut-off for unsuccessful therapy from AUC for PAI-1 was ≥65 U/ml. Mean (IQR) levels of PAI-1 on day 1 were 119 U/ml (27.1 - 155.8) and were significantly higher on day 1 (p=0.019) and day 2 (p=0.055) in those with/without adjustment of initial pathological findings. PAI-1 elevation was associated with unsuccessful restoration of clinical, Echo and CT parameters at 36 hours (Table1). Overall Tx failure was associated with elevated PAI-1 (p=0.011). Conclusions: PAI-1 active assay could help us in identifying patients who would benefit from early indicated therapeutic fibrinolysis.

#4063 APELIN INCREASES FOREARM BLOOD FLOW IN CHRONIC KIDNEY DISEASE

Abstract Background and Aims Chronic kidney disease (CKD) affects 1 in 10 people and cardiovascular disease is its commonest complication. Despite current standard of care, many patients continue to progress to kidney failure and/or die of cardiovascular disease. Thus, there is an urgent unmet need for new treatments that slow kidney function decline and offer broad cardiovascular protection. The apelin system, comprising the apelin receptor and its two endogenous ligands apelin and elabela, is an attractive therapeutic target for CKD. Apelin is an endothelium-dependent vasodilator and a potent inotrope. Clinical studies show that apelin improves endothelial function in health and heart failure, and pre-clinical studies in models of kidney disease find apelin offers renoprotection. At present, apelin has not been studied in patients with CKD. The aims of this study were to examine the local vascular actions of apelin in CKD. Method Participants with stable, non-diabetic CKD and age- and sex-matched healthy volunteers were recruited to a prospective, randomised, placebo-controlled study. Blood pressure and arterial stiffness (measured using pulse wave velocity) were assessed at baseline. Endothelial function was examined using gold-standard venous occlusion plethysmography. Forearm vasodilatation was measured in response to incremental intra-arterial doses of acetylcholine (7.5, 15 and 30 μg/min, used to assess endothelium-dependent vasodilatation), sodium nitroprusside (1, 2 and 4 μg/min, used to assess endothelium-independent vasodilatation), and pyroglutamated apelin-13 ([Pyr1]apelin-13; 0.3, 1, 3, 10, 30 and 100 nmol/min). Circulating tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) were assessed as measures of endogenous fibrinolysis. Results Fifteen patients with CKD (mean age 55±4 years; 53% male) and 15 healthy volunteers (mean age 51±3 years; 67% male) completed the study. In comparison to healthy volunteers, patients with CKD had a higher blood pressure (mean arterial pressure: 102 mmHg versus 93 mmHg, p&amp;lt;0.05) and increased pulse wave velocity (7.5±2.2 m/s versus 6.0±0.9 m/s, p&amp;lt;0.01). Similar dose-dependent vasodilatation to acetylcholine and sodium nitroprusside was seen in both groups. [Pyr1]apelin-13 increased forearm blood flow by a maximum of ∼30% in both health and CKD (p&amp;lt;0.01 compared to baseline for both) (Figure 1). This response appeared to be dose-dependent. Net tPA antigen release increased 20-70 fold in response to [Pyr1]apelin-13 in both health and CKD, with a trend to a greater release in CKD. There was no change in PAI-1. No relationship was seen between the response to [Pyr1]apelin-13 and kidney function. Conclusion Apelin promotes vasodilatation in optimally managed patients with CKD and may regulate endogenous fibrinolysis. If this effect were maintained in the long-term with systemic apelin treatment, it would be expected to reduce cardiovascular risk. Systemic studies are now justified to investigate the haemodynamic and renal effects of apelin in these patients.

Association between Triglyceride-Glucose Index and Early Neurological Outcomes after Thrombolysis in Patients with Acute Ischemic Stroke.

The triglyceride-glucose (TyG) index is a novel biomarker of insulin resistance which might plausibly influence endogenous fibrinolysis and thus early neurological outcomes in patients with acute ischemic stroke (AIS) treated with intravenous thrombolysis using recombinant tissue-plasminogen activator. We included consecutive AIS patients within 4.5 h of symptom onset undergoing intravenous thrombolysis between January 2015 and June 2022 in this multi-center retrospective observational study. Our primary outcome was early neurological deterioration (END), defined as ≥2 (END2) or ≥ 4 (END4) National Institutes of Health Stroke Scale (NIHSS) score worsening compared to the initial NIHSS score within 24 h of intravenous thrombolysis. Our secondary outcome was early neurological improvement (ENI), defined as a lower NIHSS score at discharge. TyG index was calculated using the log scale of fasting triglyceride (mg/dL) × fasting glucose (mg/dL)/2. We evaluated the association of END and ENI with TyG index using a logistic regression model. A total of 676 patients with AIS were evaluated. The median age was 68 (Interquartile range, IQR (60-76) years old), and 432 (63.9%) were males. A total of 89 (13.2%) patients developed END2, 61 (9.0%) patients developed END4, and 492 (72.7%) experienced ENI. In multivariable logistic regression analysis, after adjustment for confounding factors, TyG index was significantly associated with increased risks of END2 (categorical variable, vs. lowest tertile, medium tertile odds ratio [OR] 1.05, 95% confidence interval, CI 0.54-2.02, highest tertile OR 2.94, 95%CI 1.64-5.27, overall p < 0.001) and END4 (categorical variable, vs. lowest tertile, medium tertile OR 1.21, 95%CI 0.54-2.74, highest tertile OR 3.80, 95%CI 1.85-7.79, overall p < 0.001), and a lower probability of ENI (categorical variable, vs. lowest tertile, medium tertile OR 1.00, 95%CI 0.63-1.58, highest tertile OR 0.59, 95%CI 0.38-0.93, overall p = 0.022). Increasing TyG index was associated with a higher risk of END and a lower probability of ENI in patients with acute ischemic stroke treated with intravenous thrombolysis.

Biomarkers of Thrombotic Status Predict Spontaneous Reperfusion in Patients With ST-Segment Elevation Myocardial Infarction

BackgroundSpontaneous reperfusion, seen in ∼20% of patients with ST-segment elevation myocardial infarction (STEMI), manifests as normal epicardial flow in the infarct-related artery, with or without ST-segment resolution, before percutaneous coronary intervention (PCI). The drivers mediating this are unknown. ObjectivesThe authors sought to relate spontaneous reperfusion to the thrombotic profile. MethodsIn a prospective study, blood from STEMI patients (n = 801) was tested pre-PCI to assess in vitro, point-of-care, occlusion times (OT) and endogenous lysis times (LT). Spontaneous reperfusion was defined as infarct-related artery Thrombolysis In Myocardial Infarction flow grade 3 before PCI. Patients were followed for major cardiovascular events (death, myocardial infarction, or stroke). ResultsSpontaneous reperfusion was associated with a longer OT (435 seconds vs 366 seconds; P < 0.001) and a shorter LT (1,257 seconds vs 1,616 seconds; P < 0.001), lower troponin, and better left ventricular function. LT was superior to OT for predicting spontaneous reperfusion (area under the curve for LT: 0.707; 95% CI: 0.661-0.753; area under the curve for OT: 0.629; 95% CI: 0.581-0.677). Among patients with spontaneous reperfusion, those with complete, vs partial ST-segment resolution, had a longer OT (P = 0.002) and a shorter LT (P < 0.001). Spontaneous reperfusion was unrelated to clinical characteristics or pain-to-angiography times. Over 4 years, patients with spontaneous reperfusion experienced fewer major adverse cardiovascular events than those without (4.1% vs 10.6%; P = 0.013), especially in those with both spontaneous reperfusion and complete ST-segment resolution (1.5% vs 10.1%; P = 0.029). ConclusionsWe demonstrate a novel hematological signature in STEMI patients with spontaneous reperfusion, namely, decreased platelet reactivity and faster endogenous fibrinolysis, relating to smaller infarcts and improved survival. This finding indicates a role for modulating thrombotic status early after STEMI onset, to facilitate spontaneous reperfusion and improve outcomes.

D-Dimer Level Associated with Amount of Sinus involvement Using Digital Subtraction Angiography on Cerebral Venous Thrombosis Patients.

Cerebral venous sinus thrombosis (CVST) is a form of the cerebrovascular disease characterized by varying degrees of obstruction of veins and cerebral sinuses caused by thrombus. Diagnosis is incredibly challenging due to the wide variety of symptoms and the distinct radiological aspects of affected vessels. In patients with venous thrombosis, the presence of D-Dimer is used as an indicator of the presence of endogenous fibrinolysis. D-Dimer is a by-product of fibrin polymer fragmentation. To investigate the relationship between the level of D-Dimer and the number of sinuses in CVST by Digital Subtraction Angiography (DSA). Retrospective data from September 2021 to September 2022 were used in this analytical observational with a cross-sectional study design. Chi-Square is used for data processing relationship analysis. Out of the 54 subjects with elevated levels of D-Dimer, 38 (70.4%) are females, whereas 16 (29.6%) are males. High levels of D-Dimer have been related to a greater risk of sinus thrombosis (p < 0.001). D-Dimer levels were similarly shown to rise in conjunction with the number of sinuses most severely damaged by thrombosis. The most common site for thrombosis to develop in this study were the left sigmoid and left transverse sinuses. Most risk factors were hormonal. There is a statistically significant relationship between an increase in the D-Dimer level and the greater number of sinuses involved as determined by DSA in individuals diagnosed with CVST.

Measuring Thrombus Stability at High Shear, Together With Thrombus Formation and Endogenous Fibrinolysis: First Experience Using the Global Thrombosis Test 3 (GTT-3).

Thrombus formation in a severely stenosed artery is initiated by high shear activation of platelets, with soluble platelet agonists, such as ADP and thromboxane, playing only a secondary role in the growth and stability of the thrombus. Conventional platelet function tests, however, assess only the soluble agonist-dependent pathway of platelet aggregation. As the thrombus evolves, its stability and ability to withstand dislodgement by arterial flow will determine whether complete and persistent vessel occlusion will occur. The Global Thrombosis Test (GTT), an automated point-of-care technique, simulates the formation of thrombus in whole blood under high shear flow (shear rate >12 000 s-1) and measures the time for occlusive thrombus formation and spontaneous, endogenous thrombolysis/fibrinolysis. The latest GTT-3 model subjects the growing thrombus to upstream pressure, resembling that in a medium-sized artery, and provides an additional assessment of thrombus stability and fibrinolysis rate. It can be used in 3 programs, including a new "hypershear" mode, whereby repetitive cycles of pressure are applied to the growing thrombus, increasing shear rate to ∼22 000 s-1, such as that in patients on mechanical circulatory support. In addition to assessing the risk of arterial thrombosis, the GTT-3 could be used to assess the impact of antithrombotic medications on thrombus stability at high shear. Although current antiplatelet medications target the biochemical axis of platelet aggregation (soluble agonists) and also increase bleeding risk, novel shear-selective antiplatelet therapies may prevent thrombosis while preserving hemostasis. Future studies are needed to assess the usefulness of assessing thrombus stability on cardiovascular and pharmacological evaluation.

Plasminogen Activator Inhibitor-1 as a Marker of Thrombosis among Prehypertensive Patients: A Cross-sectional Study

Introduction: Impaired endogenous fibrinolysis has been shown to play a role in the pathogenesis and complications of hypertension. Plasminogen Activator Inhibitor-1 (PAI-1) is said to be a predictor of impaired fibrinolysis and thrombosis. Prehypertension is a common worldwide condition and is known to be an independent risk factor for Cardiovascular Disease (CVD). Aim: Present study aimed to measure plasma PAI-1 levels in prehypertensive patients and normal subjects and to find the correlation between elevated PAI-1 levels with Blood Pressure (BP), triglycerides, total cholesterol, Low-Density Lipoproteins (LDL) cholesterol, High-Density Lipoproteins (HDL) cholesterol, and urine albumin. Materials and Methods: This cross-sectional analytical study included 100 patients, comprising 50 prehypertensive individuals and 50 controls, aged between 35 and 50 years. The study was conducted at Sapthagiri Institute of Medical Sciences and Research Centre in Bangalore, India. Anthropometric measurements, PAI-1 levels, total cholesterol, triglycerides, LDL cholesterol, HDL cholesterol, Systolic Blood Pressure (SBP), Diastolic Blood Pressure (DBP), and urine albumin were measured using standard procedures. The data were statistically analysed using the Statistical Package for Social Sciences (SPSS) version 10.0, applying Student t-test and Chisquare test. Correlation analysis was performed to assess the relationship between PAI-1 and various parameters. Results: A total of 100 patients were included in the study which had 64 men and 36 women with a mean age of 46±7 years. PAI-1 levels were significantly higher in the prehypertensive group compared to the control group (p-value=0.013). Participants with higher plasma PAI-1 levels had significantly elevated BP (p-value=0.001) compared to those with lower PAI-1 levels. Total cholesterol, triglycerides, and LDL cholesterol were significantly increased in prehypertensive individuals (p-value=0.001), whereas HDL cholesterol was significantly lower (p-value=0.001). The study also observed a significant increase in urine albumin in the prehypertensive group with elevated PAI-1 levels compared to the controls (p-value=0.001). The study revealed that elevated plasma PAI-1 levels did not show a significant positive correlation with SBP and DBP (r=0.138 and 0.660, p-value of 0.338 and 0.648, respectively). Plasma PAI-1 levels were weakly correlated with total cholesterol (r=0.145, p-value 0.315), LDL cholesterol (r=-0.068, p-value 0.640), HDL cholesterol (r=0.21, p-value 0.882), and triglycerides (r=0.207, p-value 0.150). There was no significant correlation between increased PAI-1 levels and urine albumin (r=-0.225, p-value of 0.117). Conclusion: Present study demonstrated that plasma PAI-1, total cholesterol, triglycerides, LDL cholesterol, and urine albumin were significantly elevated in prehypertensive individuals, suggesting vascular damage and inflammation. As prehypertension is often asymptomatic, patients with prehypertension should be considered to have an increased risk for CVD.

COVID‐19 patient fibrinogen produces dense clots with altered polymerization kinetics, partially explained by increased sialic acid

BackgroundThrombogenicity is a known complication of COVID‐19, resulting from SARS‐CoV‐2 infection, with significant effects on morbidity and mortality. ObjectiveWe aimed to better understand the effects of COVID‐19 on fibrinogen and the resulting effects on clot structure, formation, and degradation. MethodsFibrinogen isolated from COVID‐19 patients and uninfected subjects was used to form uniformly concentrated clots (2 mg/ml), which were characterized using confocal microscopy, scanning electron microscopy, atomic force microscopy, and endogenous and exogenous fibrinolysis assays. Neuraminidase digestion and subsequent NANA assay were used to quantify sialic acid residue presence; clots made from the desialylated fibrinogen were then assayed similarly to the original fibrinogen clots. ResultsClots made from purified fibrinogen from COVID‐19 patients were shown to be significantly stiffer and denser than clots made using fibrinogen from noninfected subjects. Endogenous and exogenous fibrinolysis assays demonstrated that clot polymerization and degradation dynamics were different for purified fibrinogen from COVID‐19 patients compared with fibrinogen from noninfected subjects. Quantification of sialic acid residues via the NANA assay demonstrated that SARS‐CoV‐2‐positive fibrinogen samples contained significantly more sialic acid. Desialylation via neuraminidase digestion resolved differences in clot density. Desialylation did not normalize differences in polymerization, but did affect rate of exogenous fibrinolysis. DiscussionThese differences noted in purified SARS‐CoV‐2‐positive clots demonstrate that structural differences in fibrinogen, and not just differences in gross fibrinogen concentration, contribute to clinical differences in thrombotic features associated with COVID‐19. These structural differences are at least in part mediated by differential sialylation.

The rationale, design, and methods of a trial to evaluate the efficacy and safety of oxygen therapy in patients with intermediate-risk acute pulmonary embolism

In patients with intermediate-risk pulmonary embolism (PE), reversal of hypoxic vasoconstriction could constitute a target for treatment that protects the right ventricular (RV) function until endogenous fibrinolysis occurs. The Air vs oxygen for Intermediate-Risk pulmonary embolism (AIR) trial aims to assess the effect of oxygen therapy in patients with intermediate-risk acute PE who do not have hypoxemia at baseline. AIR is a prospective, multicenter, randomized, open-label, parallel-group, proof-of-concept trial. A total of 90 patients hospitalized with intermediate-risk PE and an oxygen saturation of 90% or higher at baseline will be randomized in a 1:1 fashion to receive supplemental oxygen or ambient air. The primary outcome is a RV/LV diameter ratio equal or less than 1.0 on echocardiography measured 48 hours after the start of treatment. Secondary efficacy outcomes are the numerical change in the ratio of the RV to the LV diameter measured 48 hours and 7 days after the start of treatment, with respect to the baseline ratio measured at randomization. Clinical adverse events will be also collected. Enrollment started in July 2019 and is expected to proceed until 2022. Median age of the first 50 patients was 74 years (interquartile range, 61-81), and 50% were female. This multicenter trial will provide information about the value of supplemental oxygen in patients with intermediate-risk acute PE who do not have hypoxemia at baseline. The results will contribute to research that may assist patients with intermediate-risk PE in the future.

Determinants of Endogenous Fibrinolysis in Whole Blood Under High Shear in Patients With Myocardial Infarction

Hypofibrinolysis is a recently-recognized risk factor for recurrent cardiovascular events in patients with ST-segment elevation myocardial infarction (STEMI), but the mechanistic determinants of this are not well understood. In patients with STEMI, we show that the effectiveness of endogenous fibrinolysis in whole blood is determined in part by fibrinogen level, high sensitivity C-reactive protein, and shear-induced platelet reactivity, the latter directly related to the speed of thrombin generation. Our findings strengthen the evidence for the role of cellular components and bidirectional crosstalk between coagulatory and inflammatory pathways as determinants of hypofibrinolysis.