NEW YORK (Reuters Health) – A lower INR for low-risk anticoagulated patients with mechanical aortic valve replacement reduces the risk of bleeding without increasing the rate of thromboembolic events, according to study results published in the American Heart Journal for July.
Dr. Michele Torella, of the Second University of Naples, Italy, and colleagues note, “The optimal intensity of anticoagulant therapy, defined as the level at which the incidence of both thromboembolic and bleeding complications is lowest, remains a delicate equilibrium.”
The researchers point out that several trials have looked at this issue, “but prospective randomized trials in which different levels of anticoagulation were compared are few.”
One trial found that bleeding and thromboembolic events were similar at INRs ranging from 2.0 to 4.0, the team notes. Meanwhile, current guidelines recommend an INR of 2.0 to 3.0 “for low-risk patients with isolated aortic valve disease undergoing single bileaflet mechanical aortic valve replacement.”
To see if the anticoagulation intensity level could be lowered in this patient population, Dr. Torella and colleagues tested the safety of an oral anticoagulant regime with an INR range between 1.5 and 2.5 compared to the recommended INR range of 2.0 to 3.0. On a random basis, 210 patients were assigned to the low-level regimen and 210 to the conventional protocol.
After a median follow-up of 5.6 years, 396 patients remained in the study. There was 1 thromboembolic event in the low-INR group and 3 in the conventional-INR group (p=0.62). The number of hemorrhagic events in the two groups were 6 and 16, respectively (p=0.04).
“The proposed low anticoagulation has similar effects on thrombotic events, and it appears safer than the standard INR target because it reduces the bleeding occurrence,” the researchers conclude.
Nonetheless, they add, larger randomized trials are still needed to confirm the effectiveness of the lower anticoagulation strategy over currently recommended protocols.
Lowering the Intensity of oral anticoagulant Therapy in patients with bileaflet mechanical aortic valve replacement: Results from the “LOWERING-IT” Trial
Am Heart J 2010;160:171-178.