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The safety of two intravenous heparin doses as adjunct to PCI in ACS patients treated with fondaparinux: results from the FUTURA/OASIS 8 trial

Results from the FUTURA/OASIS 8 study presented today at the ESC Congress provide initial evidence that a low dose of unfractionated heparin does not reduce the incidence of bleeding or vascular complications in PCI patients treated with the anticoagulant fondaparinux. Findings showed that the rates of peri-PCI major bleeding were 1.4% in those given low dose heparin and 1.2% the standard dose.

“There has been a widely held view that lowering heparin dose also lowers bleeding rates during PCI," said principal investigator Dr Sanjit Jolly, Assistant Professor of Medicine in the Michael G. DeGroote School of Medicine at McMaster University, "but randomised trial data have been lacking. Now, results from this study challenge that view."

An earlier trial, OASIS 5, also co-ordinated by McMaster University, had shown that anticoagulation with fondaparinux was more effective in reducing mortality and serious bleeding rates in post-MI patients than with enoxaparin. However, rates of catheter thrombosis during angioplasty with fondaparinux were found to be higher than with enoxaparin, which prompted the adjunctive use of unfractionated heparin to prevent clotting in patients treated with fondaparinux. "However," explained Dr Jolly, "there was uncertainty about the optimal dose."

FUTURA/OASIS 8, designed to resolve that uncertainty, was a phase 3, multicentre, randomised trial in 2026 patients undergoing PCI within 72 hours of hospital admission for unstable angina or MI. As soon as possible after arrival, they received fondaparinux 2.5 mg daily, and those requiring PCI were randomised to low fixed dose heparin (50 U/kg) or standard dose heparin (85 U/kg or 60 U/kg with glycoprotein IIb/IIIa inhibitors).

The primary outcome was a composite of peri-PCI major bleeding, minor bleeding or major vascular complications, and results showed there was no difference between the two dose regimes in this endpoint. However, while the low dose regimen did not lower the risk of major bleeding, it did lower minor bleeding rates by 60%. And there was also a trend towards higher risk of death, MI or target vessel revascularisation (secondary endpoint) with the lower dose. The rates of catheter thrombosis were very low in both groups (0.5% and 0.1% in the low and standard dose respectively).

It was also noted that the rates of major bleeding in FUTURA-OASIS 8 (1.4% low dose and 1.2% standard dose) were not significantly different from that observed in the fondaparinux arm of the OASIS 5 trial (1.5%) but lower than in the enoxaparin arm (3.6%).

“What these results imply," said Dr Jolly, "is that the standard dose of unfractionated heparin may be the optimal treatment strategy in PCI patients on fondaparinux - while maintaining the major advantage of fondaparinux which is a low rate of major bleeding."