[New anticoagulants]

A large number of newly developed platelet aggregation inhibitors and anticoagulants are currently being investigated in clinical studies. Most of these new agents are targeted to haemostatic pathways that have recently been shown to be of importance in vivo and usually have a higher efficacy than the currently available anticoagulants. The new platelet aggregation inhibitors can be divided into thienopyridine derivatives (ticlopidine, clopidogrel) and glycoprotein IIb/IIIa receptor antagonists (abciximab, eptifibatide, tirofiban). The new inhibitors of fibrin synthesis can be divided into direct thrombin inhibitors (hirudine, melagatran, ximelagatran), specific factor Xa inhibitors (pentasaccharides: fondaparinux, idraparinux) and inhibitors of the tissue thromboplastin factor VIIa complex (recombinant nematode anticoagulant protein c2, inactivated factor VIIa, recombinant tissue factor pathway inhibitor). In some cases this also results in a (relatively modest) increase in the risk of bleeding. The clinical use of the new compounds is often much more convenient than that of the presently available anticoagulants.

Thrombospondin-2 polymorphism is associated with a reduced risk of premature myocardial infarction

OBJECTIVE

Recently, polymorphisms in thrombospondin (THBS) genes coding for THBS-1 (N700S), THBS-2 (T>G substitution in 3'-untranslated region), and THBS-4 (A387P) genes were proposed to modulate the risk of premature coronary artery disease (CAD) or myocardial infarction (MI). It was our objective to verify this hypothesis in an independent cohort.

METHODS AND RESULTS

We performed a case-control study among patients (n=503) referred to our institution for symptomatic CAD that occurred before the age of 50 years and a group of age- and sex-matched population-based controls free of CAD (n=1071). The THBS-1 variant allele was not associated with an altered risk of premature CAD or MI. Homozygosity for the THBS-2 variant allele and the THBS-4 variant (387P) allele was significantly associated with a reduced risk of premature MI compared with wild-type individuals (OR=0.44, 0.24 to 0.84 and OR=0.43, 0.22 to 0.85, respectively). The latter observation is in contrast with a previous report, although confidence intervals overlap.

CONCLUSIONS

We conclude that a relationship between the THBS-1 N700S polymorphism and premature CAD is unlikely. For the THBS-4 A387P polymorphism, additional studies are required to elucidate its role in premature CAD. Finally, we conclude that the THBS-2 polymorphism is associated with a reduced risk of premature MI.

Ability of recombinant factor VIIa to reverse the anticoagulant effect of the pentasaccharide fondaparinux in healthy volunteers

BACKGROUND

The novel anticoagulant fondaparinux proved to be effective and safe in the postoperative prevention of venous thrombosis. Current phase III trials with this synthetic selective factor Xa inhibitor focus on its use in the treatment of patients with venous and arterial thrombosis. As with any anticoagulant therapy, there is a risk of bleeding complications; hence, a strategy to reverse the effects of fondaparinux is desirable. The aim of this study was to investigate whether recombinant factor VIIa (rFVIIa) could neutralize the anticoagulant effects of subcutaneously administered fondaparinux.

METHODS AND RESULTS

In a randomized, placebo-controlled design, 16 healthy male subjects received either a single subcutaneous dose of fondaparinux (10 mg) and a single intravenous bolus of rFVIIa (90 microg/kg; n=8), fondaparinux and placebo (n=4), or placebo and rFVIIa (n=4). Fondaparinux (or placebo) was administered 2 hours before rFVIIa (or placebo). Injection of rFVIIa after fondaparinux normalized the prolonged activated partial thromboplastin and prothrombin times and reversed the decrease in prothrombin activation fragments 1+2 (F(1+2)), as observed with fondaparinux alone. Thrombin-generation time and endogenous thrombin potential, which were inhibited by fondaparinux, normalized up to 6 hours after rFVIIa injection.

CONCLUSIONS

rFVIIa is capable of normalizing coagulation times and thrombin generation during fondaparinux treatment. The duration of this effect ranged from 2 to 6 hours after rFVIIa injection. These results suggest that rFVIIa may be useful to reverse the anticoagulant effect of fondaparinux in case of serious bleeding complications or need for acute surgery during treatment with fondaparinux.

Recombinant nematode anticoagulant protein c2, a novel inhibitor of tissue factor-factor VIIa activity, abrogates endotoxin-induced coagulation in chimpanzees

Systemic activation of coagulation leading to disseminated intra-vascular coagulation (DIC) is an important feature in patients with severe sepsis. Tissue factor has been shown to play a primary role in this pathological response, as revealed by the use of specific inhibitors and antagonists of the tissue factor/factor VIIa pathway. This class of agents has been demonstrated to attenuate the coagulation response in human volunteers with induced low-grade endotoxemia and to reduce mortality in primate models of Gram-negative sepsis. The efficacy of these agents in attenuating the activation of coagulation and formation of microvascular thrombosis in sepsis may depend on the mechanism of inhibition. Here we demonstrate the efficacy of recombinant nematode anticoagulant protein c2 (rNAPc2) that specifically inhibits the tissue factor/factor VIIa complex by a novel mechanism, in a model of endotoxin-induced coagulation activation in chimpanzees. Administration of a low dose of Gram-negative endotoxin induced marked increases of thrombin generation as measured by plasma levels of prothrombin activation fragment F(1+2) and thrombin-antithrombin complexes, which were completely blocked by rNAPc2. In chimpanzees receiving rNAPc2 alone, there was a significant reduction in the activation of factor X but not factor IX, compared to animals receiving placebo. In contrast to the effect of rNAPc2 on thrombin generation, there was no effect of this inhibitor on the well known enhanced systemic fibrinolytic response induced by endotoxin. In conclusion, the recombinant peptide rNAPc2 is an effective inhibitor of tissue factor-driven thrombin generation during low grade endotoxemia. These results suggest that rNAPc2 may be a promising therapeutic option to inhibit coagulation activation in patients with sepsis.

Rebound thrombin generation after heparin therapy in unstable angina. A randomized comparison between unfractionated and low-molecular-weight heparin

OBJECTIVES

This study compared rebound coagulation in patients with acute coronary syndrome patients after discontinuation of unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH).

BACKGROUND

Up to a quarter of patients hospitalized for unstable angina experience recurrent ischemia after discontinuation of UFH or LMWH therapy, which may be the result of rebound coagulation activation and subsequent thrombosis. It is unknown whether UFH and LMWH differ in this respect.

METHODS

We randomized 71 patients admitted with unstable angina to intravenous UFH or subcutaneous LMWH (dalteparin) and measured plasma markers of coagulation before, during, and after treatment.

RESULTS

A complete series of measurements was obtained in 59 patients. Plasma prothrombin fragment 1+2 (F(1+2)) levels decreased in both groups during treatment. After loss of therapeutic plasma drug levels, F(1+2) increased (within 3 h) to a maximum level at 12 to 24 h that was higher than before or during treatment in both groups (p < 0.0001). In both groups, F(1+2) levels remained higher than pretreatment up to 24 h after discontinuation. Similarly, thrombin-antithrombin (TAT) levels exceeded treatment and pretreatment levels, at a slower rate after dalteparin than after UFH. However, after dalteparin a higher peak value of TAT was observed.

CONCLUSIONS

Rebound coagulation activation occurs within hours after discontinuation of both UFH and dalteparin. With both drugs, thrombin generation is significantly greater after treatment than before or during treatment. A longer duration or weaning of treatment, or continuation with another anticoagulant treatment, may reduce rebound coagulation activation and ischemic events.

Tissue factor and coronary artery disease

Plaque disruption with superimposed thrombosis is the main cause of acute coronary events such as acute myocardial infarction and unstable angina. Among other factors, tissue factor seems to play an important role determining plaque thrombogenicity. Tissue factor is a potent initiator of the coagulation cascade situated within the vessel wall and is highly exposed to the blood after plaque rupture. Several mediators involved in the process of atherosclerotic plaque formation are capable of inducing tissue factor expression in cells such as monocytes, macrophages and endothelial cells, which under normal conditions do not express tissue factor or to a limited extent only. The increased expression of tissue factor is not limited to the plaque but is also found in circulating monocytes in patients with acute coronary syndromes. In addition, studies have shown an important contribution of tissue factor in the pathogenesis of thrombosis and restenosis after balloon angioplasty. Recent basic studies focus on the therapeutic inhibition of tissue factor. Specific and non-specific inhibitors of tissue factor or the tissue factor/factor VIIa complex have been developed or identified, and have been tested in experimental studies. Clinical studies are currently being initiated. In this review, we present the current knowledge on the role of tissue factor in atherosclerosis, arterial intervention and potential pharmacological approaches, with focus on acute coronary syndromes.

Cardiovascular screening at a public event: results from 'For your heart's sake'

BACKGROUND

At the public event 'For your heart's sake' ('Het leven is hart...Zorg er goed voor'), the opportunity to measure the well-known major cardiovascular risk factors was offered to visitors.

METHODS

The screening took place at seven risk assessment stations. Blood pressure was taken with an Omron manometer in a sitting position, and the total plasma cholesterol was measured. Risk for future cardiovascular events was calculated with the Framingham risk formula.

RESULTS

A cardiovascular risk profile was obtained in 784 persons. Their mean age was 48 years. Smoking prevalence was 21%. The mean cholesterol concentration was 5.2 mmol/L. Only 3% of the subjects had cholesterol levels above 8 mmol/L. The prevalence of hypertension (systolic blood pressure of at least 140 mmHg) was 16%. Risk for a cardiac event in the next ten years >10% was found to be present in 4%, while 1% (7 men) had a calculated risk >20%.

CONCLUSIONS

Although the cardiovascular screening programme attracted a relatively healthy sample of the Dutch population, prevalence of high blood pressure and elevated cholesterol levels was high, and the risk for future atherosclerotic disease elevated in many older men and women. These results are another plea for continued efforts to reduce the burden of atherosclerotic cardiovascular disease through primary prevention.

A guideline for uniform and optimal atherosclerotic risk factor assessment across clinical specialities in a large hospital

Solid evidence is available concerning the beneficial effect of atherosclerotic risk factor management both in primary and secondary prevention. However, recent registries have indicated considerable potential for improvement of clinical practice concerning secondary prevention of atherosclerosis. The guideline 'Secondary Prevention of Atherosclerosis' is aimed at the improvement and standardisation of atherosclerotic risk factor assessment in cardiovascular patients hospitalised at the Academic Medical Centre in Amsterdam. The guideline was developed by a task force, consisting of physicians from the Departments of Cardiology, Cardiothoracic Surgery, Internal Medicine, Interventional Radiology, Neurology, Pharmacology and Vascular Surgery. The guideline offers a standardised method for the identification of atherosclerotic risk factors and provides thresholds for treatment, treatment goals and the treatment of choice. A form listing all relevant data is completed before discharge and is mailed with the discharge letter to the referring physician and to the general practitioner.

Intermittent jamming of a mitral valve prosthesis

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