Long-term treatment with ximelagatran, an oral direct thrombin inhibitor, persistently reduces the coagulation activity after a myocardial infarction

Considerations for use of direct oral anticoagulants in arterial disease

Cardiovascular diseases including coronary heart disease, stroke, and peripheral arterial disease were responsible for an estimated 18 million deaths in 2017. Despite advances in management over the past several decades, these patients continue to have substantial risk of subsequent cardiovascular events. We provide a narrative review of randomized clinical trials evaluating direct oral anticoagulants (DOACs) for the treatment of acute coronary syndromes, noncardioembolic ischemic stroke, embolic stroke of undetermined source, and peripheral arterial disease. In these conditions, considerations for use of single antiplatelet therapy, dual antiplatelet therapy, or low-dose DOACs used together with antiplatelet therapy are presented.

Non-Vitamin K Antagonist Oral Anticoagulants in Medical Conditions at High Risk of Thromboembolism beyond Atrial Fibrillation

Non-Vitamin K antagonist oral anticoagulants (NOACs) have been extensively investigated in medical conditions at high risk of venous or arterial thrombosis other than atrial fibrillation (AF), including hip or knee arthroplasty, acute venous thromboembolism (VTE), cancer-associated VTE, acute coronary syndrome (ACS), stable atherosclerotic vascular disease, chronic heart failure, and embolic stroke of undetermined source (ESUS). Two large ESUS trials failed to show the benefit of rivaroxaban or dabigatran, and large randomized controlled trial (RCT) data of NOACs are lacking for another potential candidates of patent foramen ovale-related stroke, acute ischemic stroke, and cerebral venous thrombosis. On the other hand, high quality evidences of NOACs have been compiled for VTE prophylaxis after hip or knee arthroplasty, acute VTE, cancer-associated VTE, and concomitant ACS and AF, which have been reflected in clinical practice guidelines. In addition, RCTs showed the benefit of very low dose rivaroxaban in combination with antiplatelet therapy in patients with ACS and in those with stable cardiovascular disease. This article summarizes the accumulated evidences of NOACs in cardiovascular diseases beyond AF, and aims to inform healthcare providers of optimal regimens tailored to individual medical conditions and help investigators design future clinical trials.

The role of oral anticoagulant therapy in patients with acute coronary syndrome

Dual antiplatelet therapy (DAPT) with aspirin and a P2Y₁₂ receptor antagonist represents the current standard of care to prevent atherothrombotic recurrences in patients with acute coronary syndrome (ACS). However, despite the use of DAPT, the recurrence rate of cardiovascular ischemic events still remains high. This persistent risk may be in part attributed to the sustained activation of the coagulation cascade leading to generation of thrombin, which may continue to play a key role in thrombus formation. The use of vitamin K antagonists (VKAs) as a strategy to reduce atherothrombotic recurrences after an ACS has been previously tested, leading to overall unfavorable outcomes due to the high risk of bleeding complications. The recent introduction of non-VKA oral anticoagulants (NOACs), characterized by a better safety profile and ease of use compared with VKA, has led to a reappraisal of the use of oral anticoagulant therapy for secondary prevention in ACS patients. The present article provides an overview of the rationale and prognostic role of oral anticoagulant therapy in ACS patients as well as recent updated clinical data, in particular with NOACs, in the field and future perspectives on this topic.

Novel oral anticoagulants in the management of coronary artery disease

Despite advances in interventional and pharmacologic therapy, survivors of myocardial infarction remain at an increased risk of subsequent cardiovascular events. Initial pharmacological management includes both platelet inhibition and parenteral anticoagulation, whereas long-term pharmacological therapy relies on antiplatelet therapy for prevention of thrombotic complications. Biomarkers showing ongoing thrombin generation after acute coronary syndromes suggest that anticoagulants may provide additional benefit in reducing cardiovascular events. We review the pharmacokinetics of novel anticoagulants, clinical trial results, the role of monitoring, and future directions for the use of novel oral anticoagulants in the treatment of coronary artery disease. Clinical trials have shown that long-term use of oral anticoagulants decreases the risk of cardiovascular events, but they do so at a cost of an increased risk of bleeding. Future studies will need to identify optimal treatment combinations for selected patients and conditions that address both the appropriate combination of therapy and the appropriate dosage of each agent when used in combination.

Rivaroxaban as an Antithrombotic Agent in a Patient With ST-Segment Elevation Myocardial Infarction and Left Ventricular Thrombus: A Case Report

The incidence of left ventricular (LV) thrombi in the setting of an anterior myocardial infarction has declined significantly since the advent of primary percutaneous coronary intervention coupled with contemporary antithrombotic strategies in ST-segment elevation myocardial infarctions (STE-ACS). Despite oral anticoagulation with the currently accepted, standard-of-care vitamin K antagonist, warfarin, major bleeding complications still arise. Rivaroxaban is a novel, direct oral factor X anticoagulant that has several advantageous properties, which can attenuate bleeding risk. We present a case in which a patient successfully underwent a 3-month course of rivaroxaban in addition to his dual antiplatelet regimen of aspirin and ticagrelor for his STE-ACS and LV thrombus with resultant complete dissolution.

Role of Oral Anticoagulants in Patients After an Acute Coronary Syndrome

After an acute coronary syndrome, patients continue to be at risk of adverse cardiovascular events despite treatment with the current standard of antithrombotic therapy. The risk may be in part secondary to thrombin, which remains elevated after an acute coronary syndrome event. Several studies have investigated the utility of adding oral anticoagulation to post-acute coronary syndrome medical regimens, with the most promising results coming from the addition of low-dose oral direct anticoagulants. Focusing on optimal dosing strategies and applying therapies to the appropriate populations provide the ability to maximize benefit and minimize risk.

Low-dose of oral factor Xa inhibitors in patients with a recent acute coronary syndrome: a systematic review and meta-analysis of randomized trials

BACKGROUND

Recently, randomized controlled trials (RCTs) have shown that therapy with new oral activated factor X (Xa) inhibitors in acute coronary syndrome (ACS) yielded a reduction of ischemic events. However, this therapy was associated with a dose-related increase in major bleeding complications. We aimed to perform a systematic review and meta-analysis to appraise the clinical efficacy and safety of the lowest doses of oral factor Xa inhibitors compared with placebo in patients after a recent ACS.

METHODS

The primary endpoint was cardiovascular mortality. The rate of new myocardial infarction (MI) was the secondary efficacy endpoint, whereas major bleeding complications were recorded as a safety endpoint. Five RCTs were included in the meta-analysis enrolling a total of 25,643 patients.

RESULTS

There was no significant difference in mortality between patients treated with new antithrombotics compared with those receiving the standard therapy: odds ratio (OR), [95% confidence interval (CI)] = 0.97 [0.72-1.31], p = 0.86. Recurrent MI rates were decreased in the anti-Xa group: OR [95%CI] = 0.86 [0.76-0.98], p = 0.02, number needed to treat (NNT) = 189. The administration of new oral anticoagulants was associated with a strongly increased risk of major bleedings compared with the standard treatment: OR [95%CI] = 3.24 [2.29-4.59], p < 0.001, number needed to harm (NNH) = 104; similarly, intracranial bleeding rates were significantly higher in the anti-Xa arm.

CONCLUSIONS

The addition of the new oral anticoagulants on top of standard therapy in the setting of ACS results in an excessive risk of major bleedings without any clear evidence of outweighing clinical benefits.

Antithrombotic strategies to reduce adverse clinical outcomes in patients with acute coronary syndrome

Acute coronary syndromes (ACSs), which include ST-segment elevation myocardial infarction, non-ST-segment elevation myocardial infarction, and unstable angina, present a considerable burden to the health care system. Furthermore, many patients with a first ACS event will develop another event within 1 year. To prevent this, higher-risk patients with ACS are revascularized when possible after presentation and then prescribed ongoing treatments to prevent recurrent vascular events. These include agents that prevent platelet aggregation and subsequent coronary thrombosis. However, some patients will develop a recurrent event despite treatment with these drugs, prompting a search for additional strategies to augment the effectiveness of current therapies. One such approach is add-on therapy with oral anticoagulant drugs. These agents may act synergistically with antiplatelet agents in preventing thrombosis. In conclusion, new oral anticoagulants might represent an attractive therapeutic strategy if they do not result in unacceptable bleeding.

Treatment with an oral direct thrombin inhibitor decreases platelet activity but increases markers of inflammation in patients with myocardial infarction

BACKGROUND

Thrombin has a role not only in the coagulation process but also in inflammatory responses. Oral direct thrombin inhibitors (DTIs) are currently being evaluated in patients with thromboembolic diseases.

OBJECTIVE

To investigate whether an oral DTI affects markers for platelet and inflammatory activity after myocardial infarction (MI).

METHODS

A total of 518 patients with MI were randomly assigned to ximelagatran treatment (four different dose groups) in combination with aspirin, or aspirin alone for 6 months. The levels of soluble (s) P-selectin, soluble tissue factor, C-reactive protein (CRP), interleukin (IL)-10 and IL-18 were analysed in serial blood samples.

RESULTS

sP-selectin concentration increased after 1 week and persisted at an elevated level for 6 months in all study groups (P < 0.001). In the two highest ximelagatran dose groups, there was a reduced increase in sP-selectin compared to treatment with lower doses of ximelagatran and aspirin alone (P = 0.01 and P = 0.002, respectively). IL-18 levels did not change in the aspirin alone treatment group. By contrast, there was an elevation in IL-18 level in the lower and higher ximelagatran dose groups after 6 months (P = 0.006 and P < 0.001, respectively). Ximelagatran increased IL-10 levels (P = 0.002) and reduced the decrease in CRP levels after 6 months compared to treatment with aspirin alone (P = 0.002).

CONCLUSION

A persistent elevation of platelet activity is found in patients with a recent MI after the cessation of acute antithrombotic treatment, and the addition of an oral DTI at higher doses decreases the activity. By contrast, long-term treatment with a DTI increases the levels of several markers of inflammation. Further studies with prolonged exposure of oral DTIs are needed for evaluation of the effect on inflammatory processes and to determine whether these agents influence clinical outcomes.

The influence of direct thrombin inhibitors on the formation of platelet-leukocyte aggregates and tissue factor expression

INTRODUCTION

High concentrations of platelet-monocyte aggregates (PMAs) have been found in patients with myocardial infarction (MI). Oral direct thrombin inhibitors (DTIs) are under evaluation as long-term antithrombotic treatment. The aim was to evaluate whether DTIs affect the formation of platelet-leukocyte aggregates, TF expression and procoagulant microparticles (MPs).

MATERIAL AND METHODS

DTIs were added to an experimental whole blood model before platelet activation with thrombin or ADP. The concentrations of PMAs, platelet-granulocyte aggregates (PGAs), the amount of platelets bound per leukocyte and MPs were investigated by flow cytometry. TF mRNA and activity were recorded in all settings. TF activity was evaluated in a MI population treated with or without an oral DTI.

RESULTS

In vitro, thrombin and ADP increased the formation of PMAs and PGAs as well as TF mRNA expression. DTIs reduced the amount platelets bound to monocytes (p=0.02) and to granulocytes (p=0.001) upon thrombin stimulation together with a reduction of TF mRNA. In contrast, the ADP-induced formation of PMAs, PGAs and TF mRNA was not affected by the DTIs. Both thrombin and ADP stimulation increased the amount of TF-expressing MPs, which was effectively inhibited by the DTIs (p=0.02-0.002). In the MI population, the DTI reduced the TF activity (p<0.001).

CONCLUSION

DTIs modulate the formation of PMAs, PGAs and the TF production therein. Together with a reduction of procoagulant MPs, these results may contribute to the clinical benefit found of oral DTIs. Targeting different mechanisms in platelet and coagulation activation may be of importance due to the lack of effect of DTIs on ADP-induced platelet-leukocyte aggregates and TF production.

Therapeutical potential of direct thrombin inhibitors for atherosclerotic vascular disease

Adverse cardiovascular events are the consequence of a molecular chain reaction at the site of vulnerable plaques. Key players are platelets and coagulation factors that are activated following plaque rupture and often cause arterial obstruction. Thrombin, a plasma serine protease, plays a role in hemostasis of coagulation as well as in thrombosis and cell growth, leading to restenosis and atherosclerosis. Interesting and promising new molecules, the direct thrombin inhibitors, have been shown to be as effective as the combination of glycoprotein IIb-IIIa inhibitors and heparin for the prevention of arterial thrombosis. Until recently, direct thrombin inhibitors could be applied only parenterally; therefore, therapy was limited to hospitalized patients. As a result of recent drug development, orally active direct thrombin inhibitors are now available and have been evaluated for the long-term treatment of venous thrombosis and arterial fibrillation. Due to their specific pharmacodynamic characteristics by binding directly to thrombin--and thus inhibiting platelet aggregation and fibrin generation--these novel drugs may also have therapeutic potential for the treatment of atherothrombotic disease and its complications such as myocardial infarction, stroke or limb ischemia.

Anticoagulant action of melagatran: a comparison between neonates and adults using calibrated automated thrombography (CAT)

In the present study, we comparatively evaluated the anticoagulant efficacy of the new direct thrombin inhibitor melagatran in cord vs. adult plasma. In contrast to heparin, melagatran does not require antithrombin as a cofactor. Thus, anticoagulant treatment with melagatran is of special interest in neonatal patients, whose plasma is relatively deficient in antithrombin. We evaluated the anticoagulant action of increasing amounts of melagatran (0.1-2.0 micromol/l) in both cord and adult plasma by means of calibrated automated thrombography (CAT) with respect to the lag time until the onset of thrombin formation, time to thrombin peak maximum (TTP), endogenous thrombin potential (ETP), and thrombin peak height. Melagatran exhibited approximately the same ability to prolong lag times or TTPs in both cord and adult plasma. Similar concentrations (IC(50)) of melagatran were required to double the lag times (0.44+/-0.04 micromol/l vs. 0.52+/-0.05 micromol/l) or to double the TTPs (0.91+/-0.08 micromol/l vs. 1.06+/-0.09 micromol/l) in cord vs. adult plasma. Melagatran exhibited a higher ability to suppress ETPs or thrombin peak heights in cord vs. adult plasma. Markedly lower concentrations (IC(50)) of melagatran were required to suppress ETPs (0.27+/-0.03 micromol/l vs. 0.70+/-0.06 micromol/l) or thrombin peak heights by 50% (0.29+/-0.03 micromol/l vs. 0.53+/-0.04 micromol/l) in cord vs. adult plasma. We conclude that our results suggest a higher ability of melagatran to suppress thrombin formation in cord vs. adult plasma. Thus, lower amounts of melagatran might be required in neonates undergoing antithrombotic therapy.

Effects of melagatran on activated partial thromboplastin time and on ecarin clotting time in cord versus adult plasma

Melagatran is the active form of the oral direct thrombin inhibitor ximelagatran. Melagatran does not require antithrombin as a cofactor. Its administration is therefore of special interest in neonatal patients, whose plasma is relatively deficient in antithrombin. We investigated the effects of increasing amounts of melagatran (0.05-1 micromol/l) on the activated partial thromboplastin time (APTT) and ecarin clotting time (ECT) in cord versus adult plasma. Both the APTT and ECT were dose-dependently prolonged in the presence of increasing amounts of melagatran. Furthermore, the ECT revealed a higher susceptibility of cord plasma to addition of melagatran than adult plasma. Whereas similar amounts of melagatran were required in cord and adult plasma samples to double the APTT (IC(50), 0.47 vs 0.46 micromol/l), significantly less melagatran was required in cord versus adult plasma to double the ECT (IC(50), 0.26 vs 0.56 micromol/l). Based on APTT measurements, similar plasma levels of melagatran might be required in neonates and in adults to treat thromboembolic complications. The APTT, however, is relatively insensitive to plasma melagatran concentrations. When the sensitive indicator ECT is used, results suggest that lower amounts of melagatran might be required in neonates than in adults. This has to be scrutinized in future clinical studies.