AF Association
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INR level for Cardioversion

This is my first post here, my husband has been in AF for two years due to Graves Disease. He is 52, he has finally been scheduled for a Cardioversion this Friday, 3rd June. His INR was checked yday and is 1.9, target is 2 or above . His previous reading was 2.4 on 5th May, and 2.3 on 7th April. We though he was on track. The healthcare asst has not adjusted his dosage of Warfarin and has kept him on the dose calculated on 5th May. Is there anything he can do between now and Friday to get the INR up to 2 again. I wondered if the warmer weather could be causing a bit dehydration & therefore thicker blood? I am also wondering whether the HA should have upped the Warfarin? Many thanks.

20 Replies

It does seem strange that they haven't upped his warfarin by at least 1mg per week. Is the healthcare assistant aware that he is awaiting a cardioversion? Will they still do it as his INR level has dropped? It may be an idea to phone and talk to the department who are carrying out your husbands cardioversion. I know my AF nurse would tell me to up the dose. Not eating any greens will help his INR go up too.


Warfarin doesn't thin the blood it is an anticoaguant. BUT, this warm weather it is important to keep well hydrated even if this is not the reason for his variation. Small variations on diet can affect INR. The blood lady will be operati8ng under instruction from the computer with little regard to any plans your husband has. That is how they work.

I couldn't possibly suggest that you add to the dose even by 1mg per week.


Firstly phone your hospital and check what the range is that they require because certainly mine insists on a 2.5 to 2.5 range and for 4 weeks beforehand (ie 5 consecutive readings over 4 weeks). I know that our CCG Coagulation Service (covers 3 hospitals) by default has patients on 2.5 to 3.5 even if they are going outside the CCG area (which I do).

I would certainly phone the nurse at the clinic or GPs (whichever is responsible for doing the INR tests as it varies) and explain. Certainly a small increase in warfarin over the next few days would increase the level. However they would need to decide since they know the dose and have the history.

They apply different criteria for "maintenance" as opposed to a "procedure" (which a DCCV is).


Many thanks for your advice, I am going to call GP. The letter states the procedure requires INR target of 2.5. We are so keen that this is not cancelled, my husband has a T4 Spinal Cord Injury & has been paralysed for 33 years now, he has other health issues which cannot be addressed until this AF is dealt with. I appreciate your support.


Good luck.


My EP wanted four consequtive weeks in range so I had to arrange weekly tests


I had that requirement (well 5 tests in a row so covered 4 weeks) and INR between 2.5 and 3.5 for a cardioversion immediately after an ablation. At that point my INR was all over the place and would SWING by 2.5 from week to the next even though watching diet like a hawk and NO green veg or salads. On the day of the ablation I was only 2.2 and had not been in range for a few of the previous 5 tests but EP was pragmatic and objective and still went ahead and bridged with heparin. I could have been waiting 6 months or more to have met the requirements!!!!


The letter with my appointment said my INR should be 3.00 to 3.5 for the month before the cardioversion. It suddenly dropped below 3.0 two days before and was 2.8 when checked on the day. The Matron doing the cardioverion said it didn't matter.


I think I am right: fasting will put up the INR. Even half fasting will do it. Discovered that when I had a tummy upset. For three days I was on half rations, mainly carbohydrates.

I am puzzled why they have the requirement for, a) four consecutive readings in range b) that 'in range' is a criteria at all!

1. The biggest clot risk is on the day of the cardioversion, then the next week, month, three months, therefore what matters is the actual day, and afterwards. I think mine was at least 4.2 on the big day.

2. Given the extra clot risk, my doctor, rightly, told me to keep it high for the next three months. He meant any INR higher than 3.5, and up to 5 was fine.


I think in range is actually key on the lower limit rather than the upper.

When I had my lone cardioversion I was on apixaban so INR was not an issue.

The hospital in London where I had my ablation done wanted 2.5 to 3.5. The local Anticoagulation service (covers 4 hospitals and a wide area) queried this because they said most only wanted 2.0 to 3.0 for ablations and the increased range for cardio versions. However I found out that (certainly in my case - possibly as I was in persistent AF) that they assumed that a cardioversion would be necessary. In the event INR was 2.2 and had not been in range and was unlikely to be in range for the period. They did a TOE as planned, then ablation then cardioversion, all on the Monday before the long Easter weekend in 2014. Warfarin not stopped even for a day. My EP decided that he permanently wanted me to be in 2.5 to 3.5 range (still am). However by Saturday my CoaguChek showed INR was down to 1.8 (so glad I bought it) and as I couldn't get any answers from hospital or 111 I just decided to take some extra warfarin that morning and again for the next few days to get it higher. They had not warned me that INR would dip after an ablation.


Right. I understand 'in range' meaning 'at least xx.xx. That is how I understand it. Pity the poor patients who miss out on their cardioversion because of one reading that is too high! Also, I fail to see why it needs to be *four* successive readings in range. The figure on the actual day + frequent testing afterwards should be quite adequate.


Partly because my range fluctuated so much and partly because I like asking the analytical questions and search for information I was able to find out quite a bit from the cardiac nurse and the EP because it wasn't straight forward. Obviously (for the benefit of others) this only relates to my case.

They want 4 successive readings to see how stable someone is. If within range for 4 weeks before then the patient likely to be in range afterwards. They are less worried about someone being over the upper limit than the lower (0.5 high not an issue but 0.5 low would be). If they only took on the morning and it was say 2.2 they might decide to go ahead anyway but it could be that the patients INR had been below 2.0 for most of the previous 4 weeks in which case clots could have started to form and there is very much more chance of a clot in the weeks afterwards because of having the procedures and also INR does drop after an ablation.

The INR testing is variable. Apparently the CCG where I am in is noted for being good. Others at some surgeries are not so good. Also by doing weekly tests prior to cardioversion the test results are individually reassessed and more likely to be adjusted (as we all know the computer program does not address trends properly). They also allow for the fact that someone could miss one or be out. In fact they would have increased warfarin by 0.5mg early on (I was on 3.5mg then to 4.0mg so it would have been 4.0 then 4.5nmg).

The readings (oldest first) leading up to ablation were 2.1; 1.8; 3.2; 2.0; 1.7 and then 5 days later on the morning 2.1. This meant that it was only on 1 occasion that I was in range and in fact 2 out of 5 were no anticoagulation.

Certainly the heart centre where I go (in my case certainly) did an individual assessment and hence why they went ahead but did a TOE first and also gave heparin (that maybe standard there - I don't know). So I didn't miss out on either the ablation or the cardioversion. However I have read on here that some hospitals / EPs do stick rigidly to the ranges.

Apparently people and blood clinics are much more proactive at doing the tests before than afterwards!!!


You make a good defense of the four successive readings. Perhaps better would be four readings in a row which never dip below the minimum.

There is also a strong argument, for the three months after CV, to make sure you use a HIGHER range. So, if you are used to 2.5 to 3.5, that you really should be 3.0 to 4.0+ ie anything up to 5.0.

Of course, self dosers can make these adjustments afterwards regardless of what the medics think.

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My initial range was 2.0 to 3.0 then changed to 2.5 to 3.5 for the ablation and immediate cardioversion. I was told by the heart hospital that they do like it above the minimum and they would have ramped it up sooner but in the month before that it had gone up as high as 4.3. With what I know now I must admit that I would have ramped it up a bit so I was aiming for mid range and accepting that it could go up to 4.0.

When my EP saw me in the morning after the ablation he said that he wanted me to remain on the higher range until at least the following three months and probably longer (which now has remained the case) and wanted it swinging around the 3.0 mid point and not hovering at or below the minimum and wanted weekly testing continued. Initially the local CCG Anticoagulation Service questioned both range and testing frequency as they said that was not the norm. However they did accept it (even though the EP had not put it in writing).

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Really helpful to have some specialists coming to similar conclusions to me own!! Thanks. Seriously, I, like you, had done the reasoning, but until now it had never been subjected to expert comment/comparison. Your evidence confirms my thinking exactly.


Glad of that. Obviously I don't know whether he had that approach with me because of the problems I had with large INR swings from week to week (I naturally have some intollerance to warfarin) even though green veg and salad were off the menu or whether that is his permanent approach. He did say something like being objective / realistic about the INR levels both pre-procedure and after.


Large INR swings. I tried recently to pin this down from the literature, without success. It seems so fundamental and basic. Even if the data exist, they are never considered when artificially setting a range, which is not right. Somewhere someone must by now have established the natural background swings using either data from the decades when people were not fussy, or using data from self dosers who are not fussy. Without it, there is no logic to setting a narrow range of 1. When I looked at my own data I found my baseline background range was 2.34, which means accepting 2.5 to 5.0 without changing the dose.

My biological background range is wider than any published expert I have read would accept. Therefore these experts are wrong.

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FYI, my data over 23 years is:

2.33 to 4.66 range 2.33

1.8 to 3.85 range 2.05

2.4 to 4.8 range 2.4

2.5 to 4.48 range 2.18

2.24 to 4.6 range 2.34

1.8 to 4.11 range 2.31

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I think the answer is no. There are a few possibilities as to why not. When initial studies, etc were done computers didn't exist. Then when the calculation program came in years ago computers were basic and storage, memory, etc were very limited so it was a basic program. From the weekly printout I get I can tell that it was originally set up for a dot matric printer (but they do use a laser one now). Whoever owns the program probably doesn't want to spend the money making it into a sophisticated program as would be the case today if starting from scratch because they would not be able to recover their investment since CCGs and practices would be loathed to buy new programs. Also with warfarin there is a tolerance and as warfarin is cheap there is no incentive to fine tune if it goes over the upper limit. Hence little incentive to do a big study / data analysis.

We were told at the AFA patients day last October that a program modification was going to be released this summer which looked at the trend (up or down) and then did adjustments accordingly rather than waiting to drop out of limit (which it does now). There maybe other enhancements.


This discussion is interesting! You ask some good questions.

Why the need for computers? I still have, and use faithfully, the little orange booklet. All results from other sources are put in there.

There must be patient records available somewhere. It would take a skilled eye only a few minutes per data set to identify the background ranges, as I have done.

It is a fundamental point of human biology. Unless you know the natural range, you have no means of knowing if you are striving for the impossible, or striving for something realistic. I know from my own data that my background range is as high as 2.4. Therefore a range of 1.0 would be absurd.

As for the use of computers to tell me about dose change. I really puzzle as to why that is needed. A small set of simple guidelines is enough.

The new program, inferring from the trend, still faces the same problem. If you set the range too narrow, and you start going out of range, and correct too soon, then you will get big swings and instability. If you let the body manage itself you will have less problems.


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