The question nobody can seem to answer?

If you have just one episode of AF your stroke risk is greatly increased. If the purported mechanism is correct i.e a small blood clot can form in a small pocket in the atrium and then get pumped out to the brain at a later date how come the risk isn't greater for people coming in and out of AF frequently (and apparently there is no evidence for that) And how come if you had one episode as time passes surely that clot would be broken down - nothing remains unchanged in your body for years surely? Also I suspect almost all of the population has at least one episode in their lifetime which would be the whole population has 5x the risk which would mean we all have the same risk!!

Furthermore, if it is thought to be caused by a clot in this pocket it is hard to believe with modern technology that there is no way through use of say, radiochemistry, dye technology or microcameras or some other means of identifying if there is a clot there? Or is it too expensive?

Some of this may sound daft but I've yet to get an explaination from any consultant on this!

47 Replies

  • Hi,

    I don't know if this is the answer, but, my understanding - as it has been explained to me - is that at that brief, precise moment in time, when AF first interfered with the heart, that part of the atria you refer to was irreversibly damaged. That damage can never be undone ! Therefore the risk remains. In other words that part of the heart will always predispose itself to 'chucking a wobbly' - so to speak - and generate the clot - because of the damage.

    So, for those who keep 'coming in and out of AF' the risk doesn't increase. The damage has been done, and from that very first moment of damage pooling of the blood can occur at anytime and the risk always remains. Its a constant ........ irrespective of the number of times the heart actually 'chucks a wobbly'.

    But as I say, only my understanding.


  • The question is, why then having a scoring system? Everyone who has ever had AF should be anti-coagulants?

  • The scoring system is what you should consider, not whether you have AF. AF is only a marker, not a risk factor. Check your CHAD2-VAS2 score (or other risk measures). That will tell you your risk of stroke. Anyone who tells you that AF automatically leads to a "five times risk of stroke" simply hasn't read the research.

  • I think the exact mechanism whereby those with AF have an increased stroke risk is open to some debate. We've probably all been given the explanation that "pooling" of blood in the heart leads to clot formation - but there is some evidence that may not be correct: that the AF itself doesn't cause strokes. The theory, as I understand it, is that it is the co-morbidities that accompany AF that lead to the increased stroke risk. I have to say, this seems strange to me but I'm not medically trained.

    For more info on this see

    Sanjay Gupta is medically trained and his videos are a great explanation of many factors around AF. Of course, others may disagree and I certainly not qualified to decide which is right.

  • If you are referring to the left atrial appendage when you talk about a pocket there is no guarantee that this is where any clots may form although it is a prime suspect. Changes to the surface of the atrium caused by damage from either AF or scar tissue from ablation can also create eddy currents and pooling leading to the possibility of clots forming..

    You are also forgetting the vetting process know as CHADS2VASC. With no co-morbidities the risk is five times nothing or at least five eights of nothing but as other problems such as age, high blood pressure, diabetes etc intrude then risk goes up. This is why anti-coagulation is not always appropriate for everybody .

    Regarding your last question there already exists a mechanism to check for clots called a TOE Trans oesphageal echocardiogram where an ultrasound device is lowered down the throat to look into the heart . This is often used prior to DCCV (cardioversion) or even ablation when anticoagulation has not been continuous.

  • The CHADS2VASC survey does not ask about having AF.

    My wife scores 3 for being female and over 75. I score 4 for hypertension, T2 and being over 75. So do I assume that with an aortic aneurysm and having had an aortic valve replacement and now in permanent AF those factors don't count ?. My GP records scores me as 5.

  • I don't want to sound glib but I think you are right in that numerical scores are probably even more meaningless for you than they are for many of us. If it were me I would judge how I felt by my own body, take any recommended medicine and enjoy my life without thinking about the technicalities. Sounds odd after my original post, I know, but that's what I think :-)

  • You only ever do CHADS2VASC when you have AF. There is currently no stroke risk assessor for people without AF .

  • Well it has been quoted to me. There are whole population statistics.

  • Our GP still mentions a stroke list to my AF free and low BP other half.

    I think that I am beginning to side with Dr Gupta !

  • The CHAD2-VAS2 scores give you the "absolute" risk of stroke - and that risk is the same whether or not you have AF. You don't need to multiply anything by five - such a calculation doesn't reflect existing research.

    The most recent thinking is that the CHAD2-VAS2 scores (and the other stroke risk scores such as ATRIA) predict stroke risk regardless of whether a person has AF.

    This makes sense: if a person has high blood pressure, a previous stroke, coronary artery disease, and diabetes - it would be absurd to ignore these risks just because the person doesn't have AF. They still have a high risk of stroke and should be on anticoagulation.

    The "old school" thinking is that the CHAD2-VAS2 measure only applies to people with AF - but cardiologists now recognize that stroke risks accumulate similarly regardless of the presence of AF, and so these risk calculations apply to everyone, not just those with AF.

    I realize some cardiologists claim that AF confers an *additional* stroke risk - beyond those indicated by the CHAD2-VAS2 score. However, this hunch is based on intuition, not research. It could be true, but it's not well supported by research.

  • I think that you are correct in your assumptions. Though the web sites where you can calculate your CHAD2-VAS2 all seem to have AF in their headings.

  • Agreed. The websites simply reflect that the CHAD2-VAS2 scoring system was originally developed for people with AF. But research suggests stroke risk in AF arises not from AF per se, but from common co-morbidities such as hypertension, heart disease and diabetes.

    Keep in mind most patients with AF (80-90%) do have co-morbidities such as cardiovascular disease and high blood pressure. So most individuals with AF really are at a higher risk of stroke in the absence of anticoagulation.

    Hence the common conception that "AF elevates stroke risk". Most patients and doctors are not researchers, and textbooks don't split hairs. Given most people with AF do have co-morbidities, cardiologists and MD's are simply taught that "AF increases stroke risk" - even though the reality is more complicated :)

  • I partly agree but not entirely :-) Many doctors are researchers and the research would be sufficiently sophisticated to try and differentiate the effects of AF from the other factors. Control groups would be easy to find and research failing to differentiate is unlikely to get peer group scrutiny approval. Having said that, it is complex and the profession by its own admission says that mechanisms aren't fully understood. Nevertheless the good ones will offer what they feel is in the individual patient's best interest so at the moment I guess that's what we have to go along with till someone proves otherwise!


    P.S As is the nature of forums I do think some people on here worry more than they need to and assume a stroke is an almost certainty some time soon. :-(

  • Agreed, original "research" uses control conditions and can disentangle AF from co-morbidities. That's the very research that I read carefully, and that shows it is the co-morbidities, not AF per se, that confers risk for stroke.

    I only meant that Uni textbooks (not the original "research") often gloss over details - so I think we're in agreement.

    Agree these forums can generate unnecessary anxiety. All of us can reduce our stroke risk also by keeping fit, eating well, sleeping well, keeping stress low, etc etc -

  • I'm sure that lack of sleep and digestive problems are two of my main factors .

  • Mine too!

  • I tried Melatonin but that did not help. Hot milk with rum in it used to help but now lies to heavy on my chest..... perhaps just the rum??

  • Dave: They probably have a cardiologist like mine who shouts at reluctant patients 'Do you want to have a stroke? You only need to be in AF for one second for a clot to form'

  • Oh my goodness. What a great bedside manner lol

  • Quite a few of them try to shout people down.

    I once wrote to a senior consultant with a complaint about his department.

    He phoned me and started shouting. He backed down when he found that I could shout more loudly than him.

  • That is shocking

  • I agree Dave re. The worry and certainly for me in the early days reading some of the scaremongering personal opinions and comments about stroke risk on this forum absolutely scared the wits out of me. Great question and thread by the way:)

  • Thanks Vony - I've glad it's got some debate going. I've no more idea than anyone else but I was very scared initially but am pretty relaxed about it all now, although I think I'm lucky in some ways. I do get it frequently, every 10 days or so but it has little effect on me for the 24 hrs it lasts.

  • I never like to temp providence with my rather casual approach to warfarin over the years.

    I took it after going into AF following my aortic valve replacement (with joint pains as a side effect) and stopped it when back in NSR three months after my cardioversion.

    15 months later when back in AF after having a colonoscopy I took it again until three months after the next cardioversion (again with joint pains.

    I was in NSR until January 2015 when my vagus nerve was stimulated by a DRE putting me back into permanent AF. As I was not offered another cardioversion I did not start warfarin again at that point. I chose to go back on it in February of last year when I was considering the Watchman device and had also applied to get on an Amplatzer trial.

  • Well that was pretty much my view and how they seem to do it in the UK. So because I had an inherently low CHAD2-VAS2 score the benefits of anti-coagulents were initially deemed to be marginal. i.e 5x0 = 0. My understanding though is that there is statistical research that shows there is a much higher incidence of fatal and serious strokes with people with AF. I have to presume they didn't have the other high factors such as high BP, heavy smoker/drinker etc as well because they wouldn't be so stupid as to draw those conclusions. SO yes, I don't think the medical evidence is clear cut but the staistical evidence is, moreso and my latest consultant was pretty insistent that Apixaban would be a good idea, even if on a better safe than sorry basis I guess!

  • Thanks for those excellent posts. And Bob - yes I agree about the CHADS2VASC. I avoided anti-coags initially on the basis that I had a very low score, never smoked, normal to low BP, didn't drink much, slim etc. Only factor was I was 65. Now nearly 67 and as offered Apixaban and some slightly differing advice from another consultant decided to go on it. Most consultants do seem to admit to be unsure exactly what goes on so you would hope with so many millions affected worldwide there is a lot of research going on.

  • I agree with this approach Dave i.e. cautious but a bit behind the latest advice which is so often contradicted later e.g. aspirin, statins, animal fats and the list goes on.

    I am 63 at present, stable on Flecainide for 3 yrs, no Coags and flat out on diet, lifestyle and supplements so I can avoid all pills in the next 2 years.

  • On balance I think you made the right choice Dave - there may be other benefits of the new generation anticoagulants: there is now evidence that they can reduce the risk of developing dementia -

  • If that is the case my wife might disagree that it's working;-)

  • There seem to be complex answers to your question but the CHADS2VASC score was the only aspect my cardiologist considered when he prescribed Apixaban - I'm female and over 65.

    John's explanation is very interesting, makes so much sense and is easy to understand. Dr Gupta's video confused me in this regard, especially when applied to younger AF patients - why didn't the atrial damage increase their stroke risk as the AF damage is bound to be present? Back to CHADS2VASC and the company kept by AF to find the culprit?

    I'm still confused about the risks of stroke in younger people and how the lack of co-morbidities negates the damaging effect of their AF.

    Interesting topic and obviously one which is being researched widely. In the meantime, we are fortunate to have the risks understood at all and be able to lessen the chance of something so devastating as an AF stroke.

  • Hi Dave,

    Agree with all BobD has said- one extra point, I heard a GP say that the risk of dislodging the clot in the appendages is higher when one goes in and ut of Af as the heart suddenly contracted with more force as the AF stops- so you may be right about that Also, I think clots do become absorbed by the body over tome but don't know how this applies to the Atrial appending

  • My EP told me tha within 15 seconds of the start of an episode of Afib there is risk of a stroke and that I could be slipping in and out when I'm asleep and not know. I wanted to stop my Xarellto as I've been Afib free for 18 months. Since then I wonder what the risk of a stroke is when the Xarellto is stopped for a medical procedure. I will now be really worried when I finally get my appointment for having 2 teeth removed. I also worry about having a bleed caused by Xarellto, but now feel forced to take it for the rest of my life!

  • Didn't know you had to stop NOACS for teeth extractions you don't stop warfarin as long as INR below 4 at our dental ( well informed) practice

  • Maybe the difference lies in the fact that the effects of warfarin can be reversed, but at the moment the effects of Xarellto can't. My GP told me I would just not take my tablet the evening before and then take one after the risk of a bleed had passed.

  • I am on Warfarin (yes, I know its a different drug to yours) and whilst I have not had tooth extraction, I have had significant surgery ( a partial knee replacement ) . In this case I was given two separate doses of a 'bridging' anticoagulant, Fragmin, immediately post op. Then back to my doses of Warfarin. No problems.

    So, I stopped Warfarin and from the day I stopped when I was in range to the day I returned to being in range was 29 days. At no time did I feel uncomfortable or feel threatened by the prospect of a stroke.

  • Isobel, I take Apixaban which I did not stop to have a large tooth taken out. My dentist observed me for 15 minutes after the tooth came out, packed the socket with dissolving haemostatic gauze and put in two stitches. There was no problem whatever - except my anxiety about bleeding!

    I suggest you discuss this with your dentist - mine was familiar with warfarin but I was his first Apixaban patient and he was quite happy for me not to stop.

  • That was my tooth extraction experience with warfarin

  • Oh sigh... I so empathise!

  • I think it's important to understand risk Isobel. I feel the experts in trying to help are making people frightened. 5x the risk sounds an awful high number. But there are several million people in the UK alone with AF and there are not as many strokes for sure! Even if you had a 1 in 50 risk it would still only be 1 in 10 without medication. It sounds high but would you expect to win a 10 to 1 bet? If the risk was really high by stopping meds for simple procedures like teeth extractions they wouldn't be prescribing them.

  • Well, I was told by my EP, before he discharged me that I could reduce BP medication and Beta Blocker and possibly stop both eventually, but must take the xarellto for the rest if my life!

  • I don't understand why you don't get it, the AF/SVT/Flutter in groups and other factors of a persons health is considered, and combined with an " intermittent condition "

    The use any anticoagulant which is the" stable constant," would balance out the 'risk' of clots travelling around at any given time. Maybe I am not seeing something here!

    As far as interrupting the "constant" for any procedure I would suggest it could be used to protect the surgeon from reprisals at a later stage!

  • Well thanks for all of the interesting replies. It shows that nothing with this is clear cut and it has promoted a healthy debate.

  • Where does the five times greater risk come from? You can be perfectly healthy apart from PAF, with a CHADVASC of 1 at the other side of 65 and still have a stroke. Twenty five percent of strokes do not have an initially identifiable cause.

  • From experience you can have a stroke with a normal heart rate, 120/80 blood pressure, 3.8 total cholesterol with good HDL, good diet, low stress and low exertion. It's described as a "random event". I'm not complaining. I've had three non-AF related conditions when I've been told: first - "you're lucky to be here"; second - "if I had diagnosed that at the time, you would have had emergency surgery"; third - "you were close to death". No one said anything along those lines after the stroke, so that was a positive. We all have different experiences but I'm grateful to be alive courtesy of great clinicians and whatever deities there are. As for the percentage risks, do what you can to lessen the risk but sometimes you make up that percentage. Just don't spend too much time worrying about it, enjoy life.


  • Dr Gupta has posted a video in reply to your post

  • Thanks baba. How kind of him to go to all that trouble to answer a question.

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