Five clinical trials evaluated the effects of warfarin in patients with non-valvular atrial fibrillation. Meta-analysis findings of these studies revealed that the effects of warfarin in reducing thromboembolic events including stroke were similar at either moderately high INR (2.0-4.5) or low INR (1.4-3.0). There was a significant reduction in minor bleeds at the low INR. There are no adequate and well-controlled studies in populations with atrial fibrillation and valvular heart disease. Similar data from clinical studies in valvular atrial fibrillation patients are not available. The trials in non-valvular atrial fibrillation support the 7th ACCP recommendation that an INR of 2.0 to 3.0 be used for warfarin therapy in appropriate AF patients.
First of all, I hope you are aware that this a a peer support forum. As such, no one can "verify" (or dispute, for that matter) an INR range that has been prescribed by your doctor. This site does have an Expert forum that is answered by physicians, so you might try that, as well.
That said, the only two times I personally have heard of a prescribed INR range that went as 1.5 was in something I read about anticoagulation therapy as it is done in Japan and also in something I read about the surgeons at Stanford believing that aortic patients with a CVG (aortic composite valve graft) can go that low in the absence of other thrombus-inducing conditions.
The deal with the Japanese patients may be that they eat so much fish there; I'm not sure. As you probably know, fish oil has anti-platelet properties, and the patients in that study were also on aspirin as well as coumadin. I think that a combo regimen of both aspirin and coumadin is routine in Japan for mechanical valve patients. Those in a higher-INR group (maybe 2.5 to 3.5) had more hemorrhagic complications and no more thrombitic complications than those in a lower-INR group (I believe, 1.5 to 2.5). I'm not absolutely sure about the exact INR ranges in the two study groups, because it has been several years since I read this. But I do remember that in the lower group, the INR range went all the way down to 1.5. But these were ethnically Japanese people, living in Japan, so the results may not be at all generalizable to Westerners, for many reasons.
With regard to the Stanford recommendation, it was only for those with the CVG graft, and the basis for it is that the integrated design of the implant is supposedly less prone to encourage the formation of clots. I have to think that if you had any other condition that made you prone to form clots, though (such as a-fib or DVT), you would have to go with the indicated INR range for that other condition. The caveat here is that these are surgeons making the recommendation for the low range, and they do not actually manage anyone's coumadin. Also, there are no empirical studies to support the extemely low INR range that they are talking about, as far as I know. And 1.5 to 2.0 is so narrow a range that it would be extremely difficult, in a practical sense, to stay within that.
As someone who is not Japanese but who does have an aortic CVG, I personally feel safe with any INR result between 2 and 4. The prescribed range that my own doctor has given me is 2.5 to 3.5, and I try to stay within that. Some doctors give a 2.0 to 3.0 range for mechanical AV patients, and there is pretty wide acceptance for that also. So we are talking anywhere from 2.0 to 3.5 as the usual, standard, commonly accepted INR range for someone with a mechanical AV. Actually, as much as I can, I try to stay in the upper two's (2.5 to 3.0). Again, this is just my opinion, but I feel that 2.5 to 3.0 gives me adequate protection from clots without greatly elevating my risk of a brain bleed if I were to accidentally strike my head. If I get down into the lower two's (2.0 to 2.5), I don't get excited about it.
I would not feel comfortable with a range that went as low as 1.5, if for no other reason than because there is some margin of error in the test, and if I were to get a result of 1.5, I would not absolutely know that my INR was 1.5. It could be lower. I have been told by a pharmacist who is an anticoagualtion expert that someone with a mechanical aortic valve and no other complications probably does have protection down to about 1.6, but I prefer to leave a "cushion" by staying above 2.0. Why go right to the edge?
This is just what I believe and how I do it, based on information I have come across over the years. Take it for what it is worth.
The given statistics provide you a perspective for an insight for discussion with your doctor. How medications effect peers should not be taken seriously as everyone has a unique physiology who may or may not react properly to medication. You doctor would/should be aware of the parameters of the effectiveness and is well aware of any marginal differentials and probabilities in a risk/benefit analysis. The anti-coagulant drugs must be carefully monitored to maintain a balance between preventing clots and causing excessive bleeding
The lower parameter of 1.5 may be appropriate in weighing risk of clots vs. excessive bleeding. It may be appropriate for some individuals with special needs regarding risks of excessive bleeding even after considering a marginal difference. Frankly, I believe when the
low metric was considered within the acceptable range there was a margin of error of about
10% acknowldeged...would be misleading otherwise..IMHO.
Hi Im inthe range of 1.6 and i dont know what to do !!!!!!