Venous Thrombosis: The Culprit Is Factor VIII, not Homocysteine

Homocysteine, a product of methionine metabolism, has been implicated in the pathogenesis of venous and arterial thrombosis. However, in two new reports, researchers raise doubts about the role of hyperhomocysteinemia in thrombotic events.

In an investigator-initiated European clinical trial, researchers studied 701 patients with recent venous thromboembolism; 360 had homocysteine levels above the 75th percentile. Patients with and without hyperhomocysteinemia were randomized to receive either a cocktail of B-vitamins (folic acid, 5 mg; B₆, 50 mg; B₁₂, 0.4 mg) or placebo. B-vitamin treatment lowered homocysteine levels in all patients: from 15.1 μM to 8.5 μM in the hyperhomocysteinemic group, and from 9.0 μM to 6.5 μM in the normohomocystein…