Michelle Greiver, M.D., C.C.F.P.
Family Physician
5460 Yonge street, Suite 212
Willowdale, Ontario M2N 6K7
Phone (416) 222-3011
Fax (416) 221-3097
Email  mgreiver@rogers.com

Warfarin for preventing Stroke

 You have recently been diagnosed as having “Atrial Fibrillation”.  This means that your heart beats irregularly.


What are the risks of having atrial fibrillation?

 An irregular heartbeat increases the risk of small blood clots forming in the heart.  These small clots can travel through blood vessels, to the brain.  They then block blood flow to a part of the brain, and cause damage:  this is called a stroke.  A stroke can cause permanent damage, such as loss of the ability to speak, loss of the  ability to use  an arm or a leg, or blindness.  Sometimes a stroke can kill.


What are the benefits of taking warfarin (Coumadin)?

Warfarin is an anticoagulant.  That means that it stops blood clots from forming, by “thinning” the blood.  This reduces the risk of stroke by about 68%.

I use blood tests to make sure that your blood is thin enough to prevent strokes, but not too thin.  The blood test is called an “INR”; your INR needs to be between 2 and 3.  At first, you will need to have blood tests done fairly often; once your INR is stable, you will need to have this test done once a month.  If your test is too high or too low, I will call you to change your warfarin dosage.


What are the risks of taking warfarin?

Warfarin increases the risk of bleeding.  The risk of very serious, life-threatening bleeding (such as bleeding inside the brain causing damage similar to a stroke) is 5% over 5 years.  If you are 80 years old or more, this risk is 17% over 5 years.  Warfarin can also cause less serious, but still worrisome, bleeding (such as blood in the urine or stool), and you may need extra tests if this happens.  The risk of this is 20 to 35% over 5 years.

Some people choose not to take warfarin.  Aspirin (ASA) is another option.  Aspirin reduces the risk of stroke as well, but only by 20%.

Warfarin interferes with many prescription drugs, over-the-counter drugs, and herbals.  Please speak with your pharmacist or me before taking additional medications.  Do not take drugs that increase the risk of bleeding, such as Aspirin, or Ibuprophen (Advil, Motrin) while on warfarin.

Some foods that contain vitamin K, such as liver, broccoli or cauliflower, can interfere with warfarin.  You can continue to eat those foods, but do not change the amount you normally eat. 

Your pharmacist will have additional information for you.  Information is also available at the National Institutes of Health, http://www.nlm.nih.gov/medlineplus

Over the next five years,

Your risk of stroke is:

Warfarin decreases your risk of stroke by:
(To calculate how much warfarin will reduce your risk, multiply your risk by 0.68)

Your risk of serious bleeding with warfarin is: