Understanding the problem

People with atrial fibrillation who are taking warfarin may need an invasive procedure or surgery. Atrial fibrillation increases the risk of blood clots forming within the heart which can then break loose and travel to the blood vessels in the brain to cause a stroke or TIA. These clots can also travel to other arteries in the body, e.g. within the leg. Warfarin reduces this risk by preventing the formation of blood clots.

Surgeries and invasive procedures create a risk for bleeding. This risk is higher when a person is taking an anticoagulant. Doctors will therefore ask patients to stop anticoagulants before these procedures to reduce the risk of bleeding during and after the procedure.

Sometimes doctors recommend replacing warfarin with injectable anticoagulants (for example, Fragmin®) because they don’t stay in the blood as long as warfarin stays in the blood. These injections are used to “bridge” the gap when the protective effect of warfarin is low before or after a procedure (as measured by a blood test called the INR). This strategy has previously been used to reduce the risk of strokes, TIAs, or blood clots in arteries around the time of procedures. However, if the level of the bridging anticoagulants in the blood is too high, bridging will also increase the risk of bleeding during and after invasive procedures.

Researchers wanted to know if people with atrial fibrillation who do not replace warfarin with bridging injections of another anticoagulant will have similar risks of forming blood clots and a lower risk of bleeding around the time of invasive procedures.