Understanding the problem

People with atrial fibrillation or mechanical heart valves who need a surgical or invasive medical procedure, are often asked to stop taking warfarin 4-5 days before their procedure to reduce the risk of bleeding during and after the procedure. To reduce their risk of clotting while warfarin has been stopped, they may be advised by their doctor to inject themselves with another type of blood thinner for a few days before the procedure. The injectable blood thinner (for example, Fragmin®) doesn't stay in the blood as long as warfarin does and thus, can be stopped closer to the day of the procedure.

People usually start taking warfarin again, either on the same day as their procedure or 1-2 days later. Warfarin takes several days to reach a protective level after it is restarted. During that time, the risk of developing blood clots may be increased. To reduce this risk, people may be advised to restart injecting Fragmin®, while taking warfarin at the same time. Unlike warfarin, Fragmin® starts to work quickly after injection. This means that if Fragmin® is started too soon, it could cause more bleeding than just taking warfarin alone. Once bleeding occurs, blood thinners are often stopped for a much longer period of time which then puts people at higher risk of developing blood clots.

Researchers wanted to know if starting warfarin alone (without using Fragmin®) after a surgical or invasive medical procedure, would reduce the risk of bleeding without increasing the risk of strokes, TIAs, heart attack, blood clots in arteries, PEs, DVTs, or death due to these causes.