Is this drop in INR a normal variation?

[3mm]

I just had open heart surgery 7 weeks ago on Sep 14th, so I am still learning about my INR measurements. Yesterday my INR dropped to 1.8 after being in the 2-2.8 range for 4 weeks. Graph is shown below. Should I be worried? I'm being told by the nurse managing my warfarin dose to keep the same dose and we'll check again in 1 week. Since Oct 5th I have taken 5mg warfarin for 3 days each week (Monday, Wed, and Friday), and 4 mg of warfarin on 4 days each week.

The coagulation clinic (CAT) that manages my measurements and dosing asked me about any changes to medications, diet, etc. My diet has not changed. I did stop taking Lasix (furosemide) 10 days ago per my cardiologist. Over the last month I've gained about 2 lbs to 137 lbs. Prior to surgery i was about 138 lbs.

The nurse's plan to keep my current warfarin dose schedule is consistent with various guidelines for INR management that I found on hospital and health agency websites. But that downward trend for 2 weeks bothers me. Is this variation in INR normal? Should we be retesting sooner than 1 week?

Thanks!

 

[Protimenow]

Your INR will vary while you're healing from your OHS. It's normal.

There was a time when doctors couldn't even PRESCRIBE a home meter for 90 days after surgery because the INR changes during that time.

I'm not comfortable with the clinic telling you to stick with your current dose if your INR was 1.8. Personally, if it was me, I'd slightly increase the dose, just to be safe (say, from 4 mg one day to 4.5). I'm also not real comfortable with the dosing schedule that they've given you -- your INR on the meter will change from day to day because your DOSE isn't consistent.

If you can talk them into it, I suggest that you should have a daily dose of 4.5 mg - this brings the weekly dose to 31.5 (.5 higher than what you're taking now), or you can do 4.0 one day. They'll have to prescribe 1 mg pills so you can do the .5 mg.

You might try to educate them to the variation in readings that result from the variation in dosing. Maybe they'll get their heads out of their protocols and listen to you.

You INR will probably continue to change slightly while you're healing.

Which valve do you have? If it's an ON-X, they marketed that the INR can be as low as 1.5. There's no reason to keep it that low, and there are reported bad outcomes for people who do. Living with an INR of 1.5 and an INR between 2 and 3 makes no changes in your life, and there really isn't any reason to go below 2.

 

[dick0236]

From your bio you have an Onyx valve so the 1.8 INR should be OK (per the Onyx guidelines) but I agree that since you have shown a couple weeks of trending down I would get another INR about midweek. It will take a little while to get your warfarin dose adjusted after recent surgery and as your body becomes normal again.

I see no benefit of being below 2 INR. My valve is an old model valve but I have never had a "bleed" due to a high INR but I have had a "stroke" due to a low INR.

PS: You seem a good candidate for self-testing after three months on warfarin.

 

[Chuck C]

Hi Mark.

Should I be worried?

No. A brief dip out of range is not a reason to worry. If they told you to re-test in a month, that would be different.

You did not mention your target range in this thread, but in another thread you said the following:

"I'm new to this (surgery 09/14/2023), so I am targeting INR in the range of 2 to 3 for these first 3 months"
"I have an On-X aortic valve, and my Coagulation clinic said we'll lower my target range to (I think) 1.5 to 2.5 after 3 months. "

So, in this context, it sounds like the clinic is doing exactly what I would expect they would do. You are almost at the 2 month point past surgery and they plan to move your INR target from 2.0 to 3.0 down to 1.5 to 2.5 by month 3. From their perspective, you are just getting there a little earlier than scheduled, and the On-x is approved for 1.5 to 2.0. So, it makes sense as to why they are not showing any concern and maintaining your dosage.

As to whether it is wise to let one's INR go below 2.0, even with an On-x valve, that is a separate issue and subject to much debate. You will find several threads here discussing that issue. Some members with the On-x target 1.5 to 2.0, and some prefer to be at 2.0 to 3.0, avoiding the typical stroke zone of below 2.0.

I would also add that I prefer not to alter my daily dosage more than I need to. Currently I'm at 6.5mg/day. To achieve this I take a 6mg tablet and half of a 1mg tablet. The pills are made with a score in the middle, designed to make them easy to break in half. Your clinic is giving guidance as most do, having you take whole pills, and alternating the dosage. Personally, I find it does not make sense to vary the dosage by 25% per day, as they're having you do, when this can be avoided with breaking a 1mg pill in half. Their plan has you with a daily average of 4.43mg/day. Why not take exactly 4.5mg/day? Perhaps they don't trust that patients will properly break the pills in half?

Now, my range is different that yours, meaning that there is no plan to bring me to 1.5 to 2.5 soon, but I will share how I handled it 5 months ago when I got an INR reading of 1.8, just below my range of 2.0 to 3.0. To add a little more context, I had been drifting towards the bottom end of my range for the past 3 weeks. I upped my dosage on that day of the 1.8 reading by 1mg. So, instead of taking 6.5mg, that day I took 7.5mg. I then made what I would call a micro-adjustment to my daily dosage and increased by daily dosage by only 0.25mg per day, from 6.5mg to 6.75mg. To achieve this, I started alternating taking 6.5mg one day, then 7mg the next day. I retested only two days after my 1.8 reading and got a reading of 2.0. Some would say that I should have given it a few more days and tested too soon, but I don't like hanging out under INR of 2.0, and want to make sure that there is not something causing downward velocity in my INR. I also know from my experience, testing myself over the past few years, that even just increasing one daily dose by 1mg is enough to see my INR move a little in just 2 days. It is always helpul to "know thyself". So, seeing the reading of 2.0, I'm good and will give it a few more days to see how moving to 6.75mg/day is affecting my INR. I then re-tested again 4 days later and got an INR of 2.5, right where I want it to be. So, I just kept my dosage at the new level of 6.75mg/day. It seems that about every 2 to 4 months I need to make a 0.25mg/day tweak, sometimes up, sometimes down. After staying at 6.75mg for 3 months, I found myself drifting near the top of my range and so went back to 6.5mg/day. I would mostly chalk it up to changes in my level of exercise, but sometimes the reason is unclear. Change in weather? Who knows? Also, I will typically make these tweaks when I am near the top or bottom of my range- so as to steer things back towards the center before falling out of range. This keeps me in range over 90% of the time.

I do self test, and would encourage you to consider self testing.

 

[3mm]

Thank you everyone for your helpful advice! I asked my coagulation clinic to advance my next INR check, and they agreed to schedule it for Monday the 13th. instead of Thursday the 16th. I feel much better about that.

My current target range is 2.0-3.0 INR. I have an On-X aortic valve, but my cardiologist and I agree to stay with a long term target range of 2.0-3.0. We both prefer to treat the 1.5-2.0 range as an extra safety margin. FYI, my cardiologist prefers that I stay on 81 mg aspirin, even though she says current guidelines say that it isn't required. She feels that since I tolerate the aspirin well, it is worth taking.

I currently have some 350 1 mg warfarin pills, so I take either 4 or 5 of them depending on the day. I will request changing my dose to be 4.5 mg daily; I am comfortable cutting the warfarin pills. In fact, I came home from Mayo clinic on a dose of 2.5 mg daily, so I was cutting pills at the beginning. Next refill of my prescription, we will start using a combination of 4 mg and 1 mg pills.

I am already scheduled to get an INR meter, but that won't be until January per Medicare rules.

 

[pellicle]

Good Morning

I just had open heart surgery 7 weeks ago on Sep 14th, so I am still learning about my INR measurements. Yesterday my INR dropped to 1.8 after being in the 2-2.8 range for 4 weeks.

it happens ...

Graph is shown below. Should I be worried?

no, not really, as long as they are doing something about that drop, because looking at your graph its part of a trend down.

I'm being told by the nurse managing my warfarin dose to keep the same dose and we'll check again in 1 week. Since Oct 5th I have taken 5mg warfarin for 3 days each week (Monday, Wed, and Friday), and 4 mg of warfarin on 4 days each week.

View attachment 889667

Weekly measurements are pretty sufficient for most things and you only benefit from more frequent readings when you're trying to see exactly what is happening.

Overall I'd say that the "problem" is that they are shooting a little low and that the target there seems to be INR = 2 not INR = 2.5 ... in my view thinking in "range" rather than thinking in "target" leads many people to think that the threshold of the "range" is dangerous or worthy of becoming anxious. In reality its just a trigger to adjust dose up or down a smidge (and maybe return it again next week based on the test).

Looking at that variation I'd say that if you took 5mg daily then you'd probably see that same variation but shifted up a bit. Roughly speaking like this:

also what the hell is "normal range" doing in there? Seriously what is that adding?

Almost nothing in life is steady state, so accepting variation is just par for the course, one only acts when its out of bounds into an area which over time will increase your chances of an event significantly. Re read that sentence once more.

Refer again to "that graph" I like to cite (source)

and you can see that the risk of being between 1.5 and 1.9 is like 26.6 events per 100 years, meaning that the risk per week even is very minor. A slightly incorrect simplification would be that if you sat there for a year you'd be risking an event, but in a day or even a week its not a real risk.

Driving is riskier

The coagulation clinic (CAT) that manages my measurements and dosing asked me about any changes to medications, diet, etc. My diet has not changed.

that's normal, and part of the script (I'd even ask you), because you just never know.

The nurse's plan to keep my current warfarin dose schedule is consistent with various guidelines for INR management that I found on hospital and health agency websites. But that downward trend for 2 weeks bothers me. Is this variation in INR normal?

post surgical recovery means that you will require higher doses as your body recovers from the surgery. You're at about that time ... this article isn't well phrased for "the general public" but then its a scientific journal article

https://pubmed.ncbi.nlm.nih.gov/10532508/

...Thus, patients starting oral anticoagulation after HVR are significantly more sensitive to warfarin than nonsurgical patients. Patients with serum albumin levels below the normal values require less warfarin than patients with normal values during the initial phase of treatment.​

Should we be retesting sooner than 1 week?

its up to you, personally I find that as long as you're looking (and not tinkering) then reading more often can help you to see what happens ... on the off chance its continuing to fall then you'll have a better chance of advising them of this fall and they can do what I recommended above (move to 5mg daily)

Best Wishes

 

[pellicle]

between starting my post and posting my post I see this.

Thank you everyone for your helpful advice! I asked my coagulation clinic to advance my next INR check, and they agreed to schedule it for Monday the 13th. instead of Thursday the 16th. I feel much better about that.

so all good and my above post is only of basic background interests

My current target range is 2.0-3.0 INR.

quick point ... target and range are actually different and competing methodologies.

I have an On-X aortic valve, but my cardiologist and I agree to stay with a long term target range of 2.0-3.0. We both prefer to treat the 1.5-2.0 range as an extra safety margin. FYI, my cardiologist prefers that I stay on 81 mg aspirin, even though she says current guidelines say that it isn't required. She feels that since I tolerate the aspirin well, it is worth taking.

I currently have some 350 1 mg warfarin pills, so I take either 4 or 5 of them depending on the day. I will request changing my dose to be 4.5 mg daily; I am comfortable cutting the warfarin pills. In fact, I came home from Mayo clinic on a dose of 2.5 mg daily, so I was cutting pills at the beginning. Next refill of my prescription, we will start using a combination of 4 mg and 1 mg pills.

I am already scheduled to get an INR meter, but that won't be until January per Medicare rules.

bolded point is a good point that I'm glad to read.

PS: I see that the above indicates you don't have you own meter, so daily testing would be onerous. However I don't disagree with the mid point test.

 

[pellicle]

As to whether it is wise to let one's INR go below 2.0, even with an On-x valve, that is a separate issue and subject to much debate.

I hope you don't mean us?

Surely such debate can only be performed by those fully qualified as cardiologists ... always listen to your Doctor (even if they aren't a cardiologists) or Nurse ; not some random person on the internet ;-)

I'm not even employed (even as a Real Estate Agent)

 

[dick0236]

You and your Cardio have the right idea. 2-3 is a reasonable, and safer, INR range.

I'd also have my Rx written for 4mg tabs and splitting the 1mg tabs you have. The fewer tablets you have to take lessons the chance of error.

 

[pellicle]

@Mark Miller
I agree with this fully and it reminded me that I missed something

You and your Cardio have the right idea. 2-3 is a reasonable, and safer, INR range.

given your diligence to testing I'm sure that you are putting yourself outside (better than) the statistics of long term warfarin because you are not only testing but because you are testing you are more conscious of your dose and not missing it. Further you are a good candidate for self testing and probably full self management

Keep up the good work

Best Wishes

 

[Protimenow]

A few points:

I strongly suggest that you self--test. Meters on eBay are often not very expensive (I've written about this before), and I've even bought some at $29.95, including shipping. Of course, you could pay more. If you're on Medicare, they're supposed to provide a meter and strips.

On another matter - an INR of, IIRC, 6.75 is actually easy to reach (I did it once to please the ***** who ran an anticoagulation clinic that I was told I HAD to go to to keep coverage). Just get a 7.5 mg tab and break it in half to get 3.75. From there, you can add three 1 mg, or a 2 plus a 1 mg, or -- well, you get the point.

Sometimes an increase or drop of .25 makes a difference in INR that may be helpful - although it can be argued that this small adjustment may not really be worth the trouble.

 

[carolinemc]

Hi Mark.


No. A brief dip out of range is not a reason to worry. If they told you to re-test in a month, that would be different.

You did not mention your target range in this thread, but in another thread you said the following:

"I'm new to this (surgery 09/14/2023), so I am targeting INR in the range of 2 to 3 for these first 3 months"
"I have an On-X aortic valve, and my Coagulation clinic said we'll lower my target range to (I think) 1.5 to 2.5 after 3 months. "

So, in this context, it sounds like the clinic is doing exactly what I would expect they would do. You are almost at the 2 month point past surgery and they plan to move your INR target from 2.0 to 3.0 down to 1.5 to 2.5 by month 3. From their perspective, you are just getting there a little earlier than scheduled, and the On-x is approved for 1.5 to 2.0. So, it makes sense as to why they are not showing any concern and maintaining your dosage.

As to whether it is wise to let one's INR go below 2.0, even with an On-x valve, that is a separate issue and subject to much debate. You will find several threads here discussing that issue. Some members with the On-x target 1.5 to 2.0, and some prefer to be at 2.0 to 3.0, avoiding the typical stroke zone of below 2.0.

I would also add that I prefer not to alter my daily dosage more than I need to. Currently I'm at 6.5mg/day. To achieve this I take a 6mg tablet and half of a 1mg tablet. The pills are made with a score in the middle, designed to make them easy to break in half. Your clinic is giving guidance as most do, having you take whole pills, and alternating the dosage. Personally, I find it does not make sense to vary the dosage by 25% per day, as they're having you do, when this can be avoided with breaking a 1mg pill in half. Their plan has you with a daily average of 4.43mg/day. Why not take exactly 4.5mg/day? Perhaps they don't trust that patients will properly break the pills in half?

Now, my range is different that yours, meaning that there is no plan to bring me to 1.5 to 2.5 soon, but I will share how I handled it 5 months ago when I got an INR reading of 1.8, just below my range of 2.0 to 3.0. To add a little more context, I had been drifting towards the bottom end of my range for the past 3 weeks. I upped my dosage on that day of the 1.8 reading by 1mg. So, instead of taking 6.5mg, that day I took 7.5mg. I then made what I would call a micro-adjustment to my daily dosage and increased by daily dosage by only 0.25mg per day, from 6.5mg to 6.75mg. To achieve this, I started alternating taking 6.5mg one day, then 7mg the next day. I retested only two days after my 1.8 reading and got a reading of 2.0. Some would say that I should have given it a few more days and tested too soon, but I don't like hanging out under INR of 2.0, and want to make sure that there is not something causing downward velocity in my INR. I also know from my experience, testing myself over the past few years, that even just increasing one daily dose by 1mg is enough to see my INR move a little in just 2 days. It is always helpul to "know thyself". So, seeing the reading of 2.0, I'm good and will give it a few more days to see how moving to 6.75mg/day is affecting my INR. I then re-tested again 4 days later and got an INR of 2.5, right where I want it to be. So, I just kept my dosage at the new level of 6.75mg/day. It seems that about every 2 to 4 months I need to make a 0.25mg/day tweak, sometimes up, sometimes down. After staying at 6.75mg for 3 months, I found myself drifting near the top of my range and so went back to 6.5mg/day. I would mostly chalk it up to changes in my level of exercise, but sometimes the reason is unclear. Change in weather? Who knows? Also, I will typically make these tweaks when I am near the top or bottom of my range- so as to steer things back towards the center before falling out of range. This keeps me in range over 90% of the time.

I do self test, and would encourage you to consider self testing.

Mine fluctuates depending on antibiotics and physical activity. Or nothing at all. But always do what you do to dose yourself.

 

[Protimenow]

Again, if you take a different dose on alternating days, your INR results will be different on different days, depending on how many days since your dose you take it. It's much more accurate to be able to use the same daily dose, so your results won't vary much (and you won't have to change your dose based on a semi-accurate rest result).

 

[pellicle]

Again, if you take a different dose on alternating days, your INR results will be different on different days,

it will of course depend on the variation as a percentage of the dose you take because "half life"
this models what the accumulation of warfarin is in the system assuming a baseline of half life.

5mg settles, alternating 4.5 and 5.5 is a bit of a ripple effect and alternating 3 and 7mg is a big one ...

Good luck on predicting what the INR is at any given moment with that last curve

 

[Protimenow]

What I meant to say was that a DOSE of 6.75 is easy to reach, NOT an INR of 6.75 (although this isn't too hard either if you take way too much warfarin).

Thanks, Pellicle, for the graph. Years ago, before I started testing, and when I didn't have the sense to get regular blood draws, I felt okay with taking 2.5 mg on days with a T in them (tuesday, thursday, saturday) and 5 mg on the other days. If I WAS testing, I would have seen a considerable variation from day to day. I didn't have a stroke. I didn't have excessive bleeding. This worked for me (fortunately) but is nothing I would ever do again.

I believed that I could FEEL if my INR was too high or too low. Maybe. But I sure don't EVER want to take that risk.

There was a period where I felt that going without testing was something like a badge of honor -- maybe it was me feeling that this was a growing risk that I pushed through. Maybe I felt I couldn't afford testing (I couldn't, but the alternative if things went wrong, would have been much more expensive). Whatever it was, it was careless and pretty damned stupid.

Today, with affordable meters and consumables, I'm able to test regularly (weekly), not rely on labs, and self-manage my dosing.

Self-testing is less expensive than labs. Self management is less expensive than these 'services' that get your results, fax or call them in to your doctor, and overcharge your insurance for what you can probably figure out more accurately. It's less expensive than the 'coumadin clinics' that take your results, perhaps ask a few things about activity and diet, then give you dosing advice that they get from a printed algorithm (something you can do if you self manage) -- the algorithms may be outdated, the advice may not be optimal (for example, recommending different doses on different days when it's easy to take the same dose daily), or it's based on advice from a doctor who doesn't really understand how warfarin works (I went to a clinic that tried to make me follow this course). Also, for some clinics, if your INR is steady for more than two or three weeks, they increase the amount of time between tests - I managed my INR and went to a clinic because I had to - my INR was always in range, and the clinic scheduled me for a test every two weeks, then for monthly testing, and finally, for testing EVERY TWO MONTHS -- this was definitely dangerous advice (from a major university's satellite hospital.) IIRC, someone on another forum was also given this dangerous advice -- from 'experts.'

Still, for some, using a service to give you dosing advice is necessary. For others, it's a requirement. For still others, it may be necessary because this is more difficult than just running a self test. And for others still, self-testing is a non-option -- and for some of these people, there may be a friend or relative who can help with the self test.

For all of the above, self testing (and management by yourself, a service, a clinic, or a doctor) - weekly (if possible) is the best approach.

You are probably the best advocate for your health -- trusting doctors and clinics is okay, but you should feel free to question them, to accept that they're aren't infallible, ----hey, how far off the original topic have I gone?

 

[3mm]

I was back up to 2.1 INR on Monday, so I'm happy again. The coagulation clinic nurse suggested waiting 2 weeks for a retest; I politely asked for 1 week, which she agreed to. I will continue to politely insist on weekly tests, even though the clinic seems to want less frequent tests when patients are stable...

On Jan 25th I will get my Medicare funded training to take my own INR measurements. After that I will continue testing weekly, even if I must buy test strips myself. I don't know how many strips Medicare will provide.

I may ask the coagulation clinic to change my dose to 4.5 mg daily instead of the altering 4 mg and 5 mg doses. It is easy for me to cut a 1 mg pill.

Again, thanks for everyone's advice.

 

[3mm]

the risk of being between 1.5 and 1.9 is like 26.6 events per 100 years, meaning that the risk per week even is very minor.

Is there some accumulated junk on the mechanical valve each time the INR drops too low? From some of what I've read, I visualized this as a few microscopic clots that attach to the valve when the INR gets too low. Then the next time the INR gets too low, those microscopic clots grow a tiny bit, and this can keep happening over, perhaps, many years until the clots become big enough to be a problem. Is this not an accurate model for 1 of the paths that leads to a problem?

 

[pellicle]

Is there some accumulated junk on the mechanical valve each time the INR drops too low? From some of what I've read, I visualized this as a few microscopic clots that attach to the valve when the INR gets too low. Then the next time the INR gets too low, those microscopic clots grow a tiny bit, and this can keep happening over, perhaps, many years until the clots become big enough to be a problem. Is this not an accurate model for 1 of the paths that leads to a problem?

its hard to answer yes directly but its something which the valve makers like to mention in their promotional material or are developing other coatings that impede it.
For instance this link (promotional) has some good images and discussion on the activated platelets which are attached to the leaflets
https://media.corporate-ir.net/media_files/irol/64/64106/ATS_Forcefield.pdf
As I understood it, the move to bileaflet valves from single "tilting disc" types avoided the thrombosis obstruction of the tilt by the "open pivot"

https://aneskey.com/prosthetic-valves-2/
I understood that St Jude had its open hinge
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4112919/
So the places of interest are:

• hinges
• valve edges
• surfaces

There is also the problem of floating stuff (not attached and then breaking off)

https://www.nyp.org/healthlibrary/multimedia/venous-thrombus-and-embolus
So basically if your INR is higher, then any embolus formation will be destroyed before it grows in size to cause a blockage or ischemic event

https://www.stroke.org/en/about-stroke/types-of-stroke/tia-transient-ischemic-attack
HTH

 

[dick0236]

Is there some accumulated junk on the mechanical valve each time the INR drops too low? From some of what I've read, I visualized this as a few microscopic clots that attach to the valve when the INR gets too low. Then the next time the INR gets too low, those microscopic clots grow a tiny bit, and this can keep happening over, perhaps, many years until the clots become big enough to be a problem. Is this not an accurate model for 1 of the paths that leads to a problem?

That is an interesting question. In the early years (1960s-70s) after my surgery, doctors maintained my PT (pre-INR) at a fairly low clotting time, about 18 seconds PT, today's 1.6 INR and I compounded the problem by going several days without warfarin (on a fishing trip).......and I had my one and only stroke a few days after returning from the trip. Using your theory I could have built up a clot layer over time at 18 seconds PT and then gone without warfarin for several days forming the clot which broke loose from the "ball" of the valve. Since that event, I have been careful to maintain my INR at 2.5-3.5, never below 2, and have had no further issues. This is another reminder as to the importance of regularly testing INR. The damage done by stroke is very seldom 100% repairable.

 

[pellicle]

Using your theory I could have built up a clot layer over time at 18 seconds PT and then gone without warfarin for several days forming the clot which broke loose from the "ball" of the valve.

that's the thing I suspected happened