Atrial fibrillation is a common condition. It affects approximately 1% of the population and up to 10% of people over 70 years have AF. At some time, you may need surgery. If you take warfarin there is some additional risk. Most people are concerned that they have an increased risk of bleeding if they keep taking their treatment and an increased risk of a stroke if they stop. How do we decide what is the safest way to manage surgery?
This is the same as I wrote in my last post, but it applies equally to people with AF. If you are going for surgery, you must talk to your surgeon and the anaesthetist at least a week before your operation. It is no good the surgeon finding out the day before surgery that you are still taking warfarin, or there will not be time to sort out your treatment. If you are going for a major operation, you will usually have a chance to talk about your anticoagulants at the preoperative anaesthetic clinic.
Atrial fibrillation is a condition where the top part of the heart (the atrium) beats irregularly. Blood clots can form in the atrium and break off. They travel up the carotid arteries to the brain and can block the blood flow causing a stroke.
When you go for surgery, your doctor has to decide if it is safe for you to stop warfarin for a short period around the time of the operation.
Basically, people with AF can be divided into two groups:-
- Those who have previously had a stroke or transient ischaemic attack (TIA)
- Those who have never had a stroke.
If you have previously had a stroke, you will be treated as a high-risk case for surgery especially if your stroke was within the last few months. You will need to have “bridging anticoagulation”.
Virtually everybody else is regarded as low risk and your warfarin can be safely stopped for surgery.
Transient Ischaemic attack (TIA)
This is often referred to as a “mini-stroke”.
A TIA is caused by a blood clot blocking the blood supply to part of the brain for a brief period. The area of the brain without blood stops working properly. If it is the part of the brain that controls speech you might not be able to talk normally, or if it affects the control of movement you may lose the use of your arm or leg.
The symptoms only last for a few minutes as the blood clot is cleared from the circulation and normal blood flow to the brain is restored.
What about other risk factors?
It is known that the risk of you having a stroke with AF is higher if you have other problems.
- Congestive heart failure
- Hypertension – high blood pressure
- Age over 75 yrs
- Previous stroke
You may have heard of the CHADS score which is used to assess your risk. You get 1 point for each of the following – heart failure, high blood pressure, over 75yrs, and diabetes, – and 2 points for a previous stroke. In the past, this score was used to help determine your risk of a stroke at the time of surgery, but recent studies have shown that the score isn’t very helpful. The only thing that really matters is if you have previously had a stroke.
Not everyone is the same
What I have described above is only a guide. The decision about stopping your warfarin must be a joint decision between you and your surgeon. In some circumstances, it may be possible to have surgery without stopping your warfarin, and in others, your doctor may believe you have a very high risk of thrombosis and recommends bridging anticoagulation. In all cases, these decisions are a balance of risks, between the risk of bleeding and the risk of clotting. Careful planning is important to make the procedure as safe as possible.
This means you need to change to a short-acting anticoagulant for a few days around surgery. This is usually to a low molecular weight heparin; enoxaparin (Clexane) is used in New Zealand. I will discuss more details in a later post.