Understanding Anticoagulation in Atrial Fibrillation

Patients who have been diagnosed with atrial fibrillation (AF) and who are above the age of 65 or have co-morbidities such as high blood pressure, Diabetes, heart failure or vascular disease have a 5-fold higher risk of suffering strokes. A significant proportion of the strokes are believed to be as a consequence of blood clots which have formed within the heart and then been dislodged and travelled to the brain blocking vital blood supply to parts of the brain. Certain anticoagulants such as warfarin and the DOACs have been shown to reduce the risk of strokes in AF by 60%. It is believed that they exert this benefit by delaying the clotting of blood and therefore reducing the risk of clot formation within the heart. It is
therefore recommended that patients who have been diagnosed with AF and who are at a higher risk of strokes take anticoagulants lifelong.

The seatbelt analogy

Taking anticoagulants in AF is like wearing a seatbelt when we get in our cars. We do not wear seatbelts because in some way they improve our quality of life. We wear them because they could potentially save our lives or reduce our chances of coming to harm. Similarly, anticoagulants do not have a measurable impact on how we feel. They simply reduce the likelihood of blood clots forming within the heart. We take them because they could improve our lifespan, not our quality of life.

Many people suffer from paroxysmal AF which means that their AF can come and go episodically. Such patients often ask whether they can take their anticoagulant only when they are in AF. I advise against this for several reasons.

1) A significant proportion of patients can also have episodic ‘silent’ AF which means that they may be in AF at times when they don’t even know about it. Usually the episodes of AF that are felt by patients is when the AF is accompanied with a fast heart rate. However episodes of AF which are not accompanied with a fast heart rate may be asymptomatic to the patient.

2) Several studies of patients with implantable monitors have shown that there is no good correlation between the episodes of AF and timing of strokes. Once you have been diagnosed with AF, the risk stays regardless of whether you remain in AF or whether the AF goes away. The risk of stroke is dependent on your CHADS2VASC score which is based on age and the presence or absence of co-morbidities. As age is an important determinant of risk, the risk can only ever go up as we can only ever get older.
Finally many patients ask me whether they could use a ‘natural’ anticoagulant such as Ginger, Garlic, Motherwort or Nattokinase. Again I recommend against this. To understand this we should go back to the seatbelt analogy. We wear seat-belts because somewhere there has been reliable research that has been undertaken which shows that certain types of seatbelt reliably reduce the risk of harm or death in the eventuality of an accident. We can not assume that every single contraption called a seatbelt will offer the same protection and therefore car manufacturers should only use those makes of seat-belt which have the evidence base supporting their claim. When it comes to anticoagulants, Warfarin and the DOACs have been extensively studied in hundred of thousands of patients and been found to reliably reduce the risk of strokes by 60%. The natural alternatives do not have this weight of evidence to back their routine use.

In summary:

Anticoagulants are recommended because they reduce risk of strokes

The risk is dependant on age and co-morbidities rather than the presence or absence of AF

Anticoagulation should be taken for life

Natural anticoagulants do not have the same weight of evidence in terms of stroke prevention as Warfarin or the DOACs


If you found this blog useful, please consider visiting my youtube channel: YORKCARDIOLOGY where i post twice a week on subjects related to heart health.

About the Author:

I'm Dr Sanjay Gupta, a Consultant Cardiologist with specialist interest in Cardiac Imaging at York Teaching Hospital in York, UK. I believe that high quality reliable jargon-free information about health should be available at no cost to everyone in the world.


  1. Sandy 28th October 2018 at 7:33 am - Reply

    This was so useful. Very clear and reassuring. I have read so many comments that paroxysmal AF will lead to permanent that this was particularly reassuring. Thank you

  2. Sandy 28th October 2018 at 7:37 am - Reply

    Sorry posted comment above on wttong thread. It was relat d to the video on paroxysmal and permanent AF. The article on anti coagulation above was also very clear and good to read.

  3. pauline edmunds 28th October 2018 at 8:15 am - Reply

    Thankyou, most informative.

  4. Kate Smith 28th October 2018 at 8:41 am - Reply

    I was going to stop taking anticoagulants but you have convinced me to stay on them. Especially after reading that article on other benefits in taking them. Thank you so much.

  5. Al Craig 28th October 2018 at 9:06 pm - Reply

    With thinner blood, is there a higher risk of a brain bleed?

  6. Liz Barnes 20th October 2019 at 2:23 pm - Reply

    Thanks for this – very informative. I was put on warfarin when my AF was diagnosed, but taken off it after my 2nd successful catheter ablation. However, about 6 months after this, I suffered a TIA (mini-stroke), which was related to my AF. I have since been put on Dabigatran (a NOAC), and I imagine that I will be on it for life. It’s not so bad – and worth it to avoid another TIA or stroke!

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