how long can you go without it?

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pellicle

Professional Dingbat
Joined
Nov 4, 2012
Messages
9,071
Location
Queensland, OzTrayLeeYa
A discussion I had yesterday (@tezza ) led me to discuss a common concern that new warfarin takers ask:

"How long can I go without warfarin"

This is of course a question without specific answers (such as how long is a furlong {ans: 201.168Meters}), and a lot depends on various things. Which valve you have is important in this question because older ball and cage valves have different "risk profiles" associated with them than do modern bileaflet valves. So its not just about your risk factors as a person (some are inherently more likely to have a stroke than others as they age) but also about the valve you have.

I do not intentend to write a piece that suggests you go off warfarin for a long period, the aim of this piece is to allay fears that "dipping so much as a pinky" into the pond of "I missed a dose" will result in something reaching up and pulling you into the swamp of harm.

To return to the question "how long can you go". Well I'd start with this extreme example:


Event free:
  • case 1 = 13 years
  • case 2 = 35 years
both cases had maintained antiplatelet therapy (such as aspirin is). Further it contains this table of others:
Table 1
A summary of cases with long event-free survival in patients with mechanical valve replacement.
CASES​
AGE​
POSITION​
TYPE​
YEARS​
Kucukaksu et al.19​
56​
Aortic​
B-S​
30​
Uzun et al.23​
45​
Aortic​
S-E​
2​
Yildiz et al.20​
42​
Aortic​
B-S​
22​
Ozkokeli et al.21​
58​
Aortic​
S-E​
37​
Ikizler et al.22​
58​
Aortic​
S-E​
34​
Sharma et al.23​
68​
Aortic​
St Jude​
23​
Björk et al.16
–​
Mitral​
–​
–​
Perez-Zaldivar et al.14
26​
Mitral​
St Jude​
10​
Cicekcioglu et al.24​
21​
Tricuspid​
B-S​
15​
Iscan hz et al.25​
25​
Pulmonary​
St Jude​
15​
Enes et al.5
46​
Mitral​
St Jude​
27​
Present case 1​
92​
Aortic​
–​
23​
Present case 2​
66​
Aortic​
B-S​
35​


I recommend you read the rest of the article. But this alone should suggest to you that even 2 consecutive missed doses will perhaps be of low risk.

Next lets look at modern prescription views. I have twice now dipped my pinkie into the pond of cessation of warfarin for the valid reason of perioperative safety. Especially when a risk of an extensive bleed is high (such as with a colonoscopy). Accordingly I wrote up my experiences here:

and wrote that based on an analysis of this article: The perioperative management of anticoagulation

I wrote there that the risks are difficult to quantify due to the lack of randomised trials examining this issue. They vary according to the indication for the warfarin therapy, and cited:


which shows that modern bileaflet aortic valvers are among the lowest risk factors

Its interesting that while on the one hand people will be clear that "adjustment of dose takes time to appear in the INR" (which is the measure of thrombogenesis") yet are concerned about their INR when they are in a different metal context (what if I miss a dose)

So I took the opportunity to actually measure for myself (not the first time I'd done this btw), and I got this


as you see it took some time to drop (and also some time to rise again). {Note: the Pinr in that graph is my "Predicted INR" based on my data model.

You can see that I took a half dose on Saturday (I don't really know why I chose that), then nothing for Sunday, Monday, Tuesday and Wednesday. That's a lot of missed doses and I having a colonoscopy took no aspirin for a week before that too.

No events.

The finding of the article I cited is that : " The need for perioperative anticoagulation in patients with mechanical heart valves has been questioned in a recent review. The authors argue that for every 10 000 patients with mechanical heart valves who are given perioperative intravenous heparin, three thromboembolic events are prevented at the cost of 300 major postoperative bleeding episodes "

so the picture is emerging that the prior emphasis on coagulation is perhaps an over reaction, perhaps resulting from inadequate evaluation of actual needs of patients. Indeed over time study after study is supporting that lower INR's are possible (so case #2's bruising can probably go off the list of problems) and technology is allowing us (valvers) to more accurately and more consistently measure our INR (especially important for anyone hovering on a lower INR)

What I think this means is that some of the veil of ignorance based fear can be lifted and we can breath a little easier.

I encourage you to read that post in detail and consider again if a fear of missing a dose is justified by the data.

Best Wishes
 
Last edited:

Chuck C

Well-known member
Joined
Dec 5, 2020
Messages
1,157
A discussion I had yesterday (@tezza ) led me to discuss a common concern that new warfarin takers ask:

"How long can I go without warfarin"

This is of course a question without specific answers (such as how long is a furlong {ans: 201.168Meters}), and a lot depends on various things. Which valve you have is important in this question because older ball and cage valves have different "risk profiles" associated with them than do modern bileaflet valves. So its not just about your risk factors as a person (some are inherently more likely to have a stroke than others as they age) but also about the valve you have.

I do not intentend to write a piece that suggests you go off warfarin for a long period, the aim of this piece is to allay fears that "dipping so much as a pinky" into the pond of "I missed a dose" will result in something reaching up and pulling you into the swamp of harm.

To return to the question "how long can you go". Well I'd start with this extreme example:


Event free:
  • case 1 = 13 years
  • case 2 = 35 years
both cases had maintained antiplatelet therapy (such as aspirin is). Further it contains this table of others:
Table 1
A summary of cases with long event-free survival in patients with mechanical valve replacement.
CASES​
AGE​
POSITION​
TYPE​
YEARS​
Kucukaksu et al.19​
56​
Aortic​
B-S​
30​
Uzun et al.23​
45​
Aortic​
S-E​
2​
Yildiz et al.20​
42​
Aortic​
B-S​
22​
Ozkokeli et al.21​
58​
Aortic​
S-E​
37​
Ikizler et al.22​
58​
Aortic​
S-E​
34​
Sharma et al.23​
68​
Aortic​
St Jude​
23​
Björk et al.16
–​
Mitral​
–​
–​
Perez-Zaldivar et al.14
26​
Mitral​
St Jude​
10​
Cicekcioglu et al.24​
21​
Tricuspid​
B-S​
15​
Iscan hz et al.25​
25​
Pulmonary​
St Jude​
15​
Enes et al.5
46​
Mitral​
St Jude​
27​
Present case 1​
92​
Aortic​
–​
23​
Present case 2​
66​
Aortic​
B-S​
35​


I recommend you read the rest of the article. But this alone should suggest to you that even 2 consecutive missed doses will perhaps be of low risk.

Next lets look at modern prescription views. I have twice now dipped my pinkie into the pond of cessation of warfarin for the valid reason of perioperative safety. Especially when a risk of an extensive bleed is high (such as with a colonoscopy). Accordingly I wrote up my experiences here:

and wrote that based on an analysis of this article: The perioperative management of anticoagulation

I wrote there that the risks are difficult to quantify due to the lack of randomised trials examining this issue. They vary according to the indication for the warfarin therapy, and cited:


which shows that modern bileaflet aortic valvers are among the lowest risk factors

Its interesting that while on the one hand people will be clear that "adjustment of dose takes time to appear in the INR" (which is the measure of thrombogenesis") yet are concerned about their INR when they are in a different metal context (what if I miss a dose)

So I took the opportunity to actually measure for myself (not the first time I'd done this btw), and I got this


as you see it took some time to drop (and also some time to rise again). {Note: the Pinr in that graph is my "Predicted INR" based on my data model.

You can see that I took a half dose on Saturday (I don't really know why I chose that), then nothing for Sunday, Monday, Tuesday and Wednesday. That's a lot of missed doses and I having a colonoscopy took no aspirin for a week before that too.

No events.

The finding of the article I cited is that : " The need for perioperative anticoagulation in patients with mechanical heart valves has been questioned in a recent review. The authors argue that for every 10 000 patients with mechanical heart valves who are given perioperative intravenous heparin, three thromboembolic events are prevented at the cost of 300 major postoperative bleeding episodes "

so the picture is emerging that the prior emphasis on coagulation is perhaps an over reaction, perhaps resulting from inadequate evaluation of actual needs of patients. Indeed over time study after study is supporting that lower INR's are possible (so case #2's bruising can probably go off the list of problems) and technology is allowing us (valvers) to more accurately and more consistently measure our INR (especially important for anyone hovering on a lower INR)

What I think this means is that some of the veil of ignorance based fear can be lifted and we can breath a little easier.

I encourage you to read that post in detail and consider again if a fear of missing a dose is justified by the data.

Best Wishes
It is this data that helped me not to be anxious about dipping to INR 1.6 with vitamin K therapy. Thanks for sharing
 

Chuck C

Well-known member
Joined
Dec 5, 2020
Messages
1,157
@pellicle.
The next time I need a medical procedure, I will be certain to refer to your graph and other INR/warfarin data- very helpful, thanks.
What are your thoughts on getting Cologuard as an alternative to colonscopy, in order to avoid bringing INR down?

Apparently, Cologuard is highly effective at detecting cancer, 92%, but only detects 40% of polyps. So, there is a downside, but I suppose that needs to be weighed against the small risk of having a low INR for a few days.
 

pellicle

Professional Dingbat
Joined
Nov 4, 2012
Messages
9,071
Location
Queensland, OzTrayLeeYa
What are your thoughts on getting Cologuard as an alternative to colonscopy
to be honest I have zero idea ... but I just recently have had a reminder about my next "follow up" and have been wondering about it.

I did some reading and found this in the Australian Journal of General Practice:

Some Key points

People are not at an equal risk of colorectal cancer. Lifetime risk of colorectal cancer is not normally distributed; a large proportion of the population is below the average 5% risk and a smaller proportion is at higher levels of risk. National Health and Medical Research Council (NHMRC)-endorsed guidelines, which were published in 2017, recommend biennial iFOBT screening for people at or slightly above the average risk of colorectal cancer, from age 50 to 70 years, and limiting colonoscopy only to those who are at increased risk of colorectal cancer





Table 1. NHMRC-endorsed criteria for quantifying risk of colorectal cancer based on family history8*
Near average risk (98% of Australian population)
  • No first-degree or second-degree relative with colorectal cancer
  • One first-degree relative with colorectal cancer diagnosed at age 55 years or older
  • One first-degree and one second-degree relative with colorectal cancer diagnosed at age 55 years or older
Moderately increased risk (relative risk 3–6) (1–2% of the Australian population)
  • One first-degree relative with colorectal cancer diagnosed under 55 years
  • Two first-degree relatives with colorectal cancer diagnosed at 55 years or older
  • One first-degree and at least two second-degree relatives with colorectal cancer diagnosed at 55 years or older
Potentially high risk (relative risk 7–10) (<1% of the Australian population)
  • At least three first-degree or second-degree relatives with colorectal cancer with at least one diagnosed under 55 years
  • At least three first-degree relatives with colorectal cancer diagnosed at 55 years or older
*Examples of family history and risk criteria. Full criteria is available at Colorectal cancer risk according to family history - Cancer Guidelines Wiki
NHMRC, National Health and Medical Research Council
 

Chuck C

Well-known member
Joined
Dec 5, 2020
Messages
1,157
National Health and Medical Research Council (NHMRC)-endorsed guidelines, which were published in 2017, recommend biennial iFOBT screening for people at or slightly above the average risk of colorectal cancer, from age 50 to 70 years, and limiting colonoscopy only to those who are at increased risk of colorectal cancer
This would be good news, as I am in the normal risk group- no family members having had colorectal cancer. it sounds like they would recommend that biennial screening for me and not colonoscopy. My wife had a cologuard done a year ago and got a positive. It was a scary time, until I researched it and discovered that the overwhelming majority of positives are either the detection of polyps and not cancer or false positives. Still it was a concern until she had the colonoscopy and we learned that it was indeed a false positive- no cancer and no polyps. It would have been nice if her physician had shared with us immediately that the chances of the positive turning out to be cancer was really low, but perhaps she does not understand statistics.
 

Protimenow

Well-known member
Joined
Aug 10, 2010
Messages
3,893
Location
California
I'm sure that there are some whose risks, without taking Warfarin, are near zero - as illustrated by the reports that Pellicle sited.

In my case, I had a meter that was telling me that my INR was 2.6. I trusted that damned meter. About two weeks into my voyage at 2.6, I had a TIA. The thing took about two weeks. The hospital's testing told me that my INR was 1.7.

For some of us, going more than a week or two with an INR below 2 (I have a St. Jude Aortic Valve) is risky and, if your experience was like mine, very dangerous.

---

Some specialists (my cardiologist, for example) don't understand anticoagulation very well. I had an attempted ablation, and the cardiologist insisted on bridging. From past experience, I knew that this wasn't necessary if my INR wasn't going to stay down for the few days before surgery. I knew that, within 3 or 4 days after the procedure, on my regular dose, my INR would be back in range.

For some reason, I got the Enoxaparin, and paid $100 for it. I didn't need it. I have ten syringes full of it. I'm sorry I didn't think more carefully about this before I ordered this unnecessary stuff.
 

tom in MO

Well-known member
Joined
Jan 17, 2012
Messages
1,755
Location
MO USA
Per my colorectal surgeon, you can have a colonoscopy on warfarin with an elevated INR. He just cannot take biopsies or remove polyps. If he sees a need, you have to submit to a second colonoscopy and lower your INR.
 

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