Background: It is not clear if long-term antithrombotic treatment has a beneficial effect on the incidence of thromboembolism in chronic heart failure (CHF). The HELAS study (Heart failure Long-term Antithrombotic Study) is a multicentre, randomised, double-blind, placebocontrolled trial to evaluate antithrombotic treatment in patients with CHF. Methods: 197HF patients (EF < 35%) were enrolled. Patients with Ischaemic Heart Disease were randomised to receive either aspirin 325mg or warfarin. Patients with Dilated Cardiomyopathy (DCM) were randomised to receive either warfarin or placebo. Results: Analysis of the data from 312 patient years showed an incidence of 2.2 embolic events per 100 patient years, with no significant difference between groups. The incidence of myocardial infarction, hospitalisation, exacerbation of heart failure, death and haemorrhage were not different between the groups. No peripheral or pulmonary emboli were reported. Echocardiographic follow-up for 2 years showed an overall increase in left ventricular ejection fraction from 28.2 T 6 to 30.3 T 7 p < 0.05, which was most obvious in patients with DCM taking warfarin (EF 26.8 T 5.3 at baseline, 30.7 T 10 at 2 years, p < 0.05). Conclusions: (1) Overall embolic events are rare in heart failure regardless of treatment. (2) Treatment does not seem to affect outcome.

We have tested the effect of thrombin on endothelial cell tube formation in vitro and angiogenesis in vivo. Thrombin induces the differentiation of endothelial cells into capillary structures in a dose-dependent fashion (0.1-0.3 units thrombin/ml) on Matrigel, a laminin-rich reconstituted basement membrane matrix. At higher thrombin concentrations (1.0 unit/ml), a suppression of tube formation is evident, probably due to downregulation (desensitization) of the thrombin receptor. D-Phe-Pro-Arg-CH2Cl-thrombin is without effect when used alone, but it abolishes the tube-promoting effect of thrombin when used in combination with thrombin, indicating the involvement of the catalytic site of thrombin. Activation of protein kinase C (PKC) seems to be the transduction mechanism involved in the stimulation of tube formation by thrombin. Ro-318220 (3 micrograms/ml), a specific inhibitor of PKC, completely abolishes the stimulatory effect of thrombin. In the in vivo Matrigel system of angiogenesis, there is a 10-fold increase in endothelial cell infiltration in response to thrombin. These results provide evidence for the angiogenesis-promoting effect of thrombin in vivo and the induction by thrombin of the angiogenic phenotype of endothelial cells in vitro in the absence of other cell types such as smooth muscle cells, pericytes, and inflammatory cells.

The involvement of nitric oxide (NO) in the regulation of angiogenesis was examined in the in vivo system of the chorioallantoic membrane (CAM) of the chick embryo and in the matrigel tube formation assay. Sodium nitroprusside (SNP) (0.37–28 nmol/disc), which releases NO spontaneously, caused a dose‐dependent inhibition of angiogenesis in the CAM in vivo and reversed completely the angiogenic effects of α‐thrombin (6.7 nmol/disc) and the protein kinase C (PKC) activator 4‐β‐phorbol‐12‐myristate‐13‐acetate (PMA) (0.97 nmol/disc). In addition, SNP (28 × 10−6 m) stimulated the release of guanosine 3′‐5′‐cyclic monophosphate (cyclic GMP) from the CAM in vitro. In the matrigel tube formation assay, an in vitro assay of angiogenesis, both SNP (1–3 × 10−6 m) and the cell permeable cyclic GMP analogue, Br‐cGMP (0.3–1.0 × 10−3 m) reduced tube formation. The inhibitors of NO synthase, NG‐monomethyl‐l‐arginine (l‐NMMA) (3.8–102 nmol/disc) and NG‐nitro‐l‐arginine methylester (l‐NAME) (1.3–34.2 nmol/disc) stimulated angiogenesis in the CAM in vivo, in a dose‐dependent fashion. d‐NMMA and d‐NAME on the other hand had no effect on angiogenesis in this system. l‐Arginine (10.9 nmol/disc), although it had a modest antiangiogenic effect by itself, was capable of abolishing the angiogenic effects of l‐NMMA (34.2 nmol/disc) and of l‐NAME (3.8 nmol/disc). Dexamethasone, an inhibitor of the induction of NO synthase, at 0.2–116.1 nmol/disc, stimulated angiogenesis in the CAM, whereas at 348.4–1161 nmol/disc it inhibited this process. Combination of 38.7 nmol/disc dexamethasone with l‐NAME (9.3 nmol/disc) resulted in a potentiation of the angiogenic effect of the former. It appears therefore that both the constitutive and the inducible NO synthase may contribute to the NO‐mediated inhibition of angiogenesis. Superoxide dismutase (SOD), which prevents the destruction of NO, at 300 i.u./disc had a modest antiangiogenic effect in the CAM, by itself. In addition, SOD, prevented α‐thrombin (6.7 nmol/disc) and PMA (0.97 nmol/disc) from stimulating angiogenesis in the CAM. These results suggest that NO may be an endogenous antiangiogenic molecule of pathophysiological importance.

The anthracycline antibiotics, daunorubicin, doxorubicin, and epirubicin, which are widely used for treatment of malignancies, have been evaluated for their effect on angiogenesis in relation to the inhibition of collagenase type IV reported previously. In the chick chorioallantoic membrane (CAM) system of angiogenesis, anthracyclines inhibited vascular density at doses of 5-20 micrograms/disc as well as collagenous protein biosynthesis, which is a reliable index of angiogenesis. Similarly, all three anthracyclines inhibited tube formation in the in vitro system of angiogenesis using human umbilical vein endothelial cells (HUVECs) plated on Matrigel. The inhibition was dose-dependent and caused 50% inhibition at concentrations of 2.5-15 micrograms/mL. At concentrations of anthracyclines which prevented tube formation and angiogenesis, there were no cytotoxic effects, as evidenced by methylene blue uptake, and the growth of these endothelial cells was not inhibited. The experimental antitumor agent titanocene dichloride inhibited collagenase type IV from Walker 256 carcinosarcoma with IC50 approximately 0.2 mM. Titanocene also prevented angiogenesis in the CAM and tube formation by HUVECs on Matrigel at concentrations that were without effect on growth or cytotoxicity of endothelial cells or Walker 256 cells in culture. The antiangiogenic effect of the aforementioned antitumor agents at therapeutically attainable concentrations may explain, at least in part, their antitumor properties because angiogenesis is an essential process for tumor growth and metastasis. The antiangiogenic effect is, however, unrelated to metalloproteinase inhibition because higher concentrations are required for that effect than for inhibition of angiogenesis.

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