Question on probability of later problems due to coumadin

[Ross]

I for one appreciate Andys dedication to seeing both sides. He doesn't even have one yet but I know he's made up his mind. People have to know that their is life with and without Coumadin. Why do they make a tissue valve? I don't know the answer to that but there has to be a legitimate reason they spent the millions of dollars in research. I'm glad I chose the Tissue valve and I hope I still am 15 years from now. I'm also glad that everyone else is doing so well on Coumadin.

But what I want to know is, why are women such beautiful creatures?

(Sorry People, I've had an upsetting day and I'm looking for an outlet, so pardon my thread interuptions. I'll behave now. (For a little while anyway).

 

[JohnnyV_46]

Just to drive men Crazy Ross.....and Ellen and Rosie too I guess...gotta be PC nowdays...Sheesh.

 

[PJmomrunner]

(.98 to the 20 + .98 to the 19 + .98 to the 18...+ .98) = 16.99653115%

Whoops! Didn't divide by the 20 years. What I'm saying is that you can't say the chance of not having a bleeding accident is 66.7% over the course of 20 years because after the first year has past there are only 19 years left in the original period and the odds of not having a bleeding accident remain the same for each subsequent year. So I figured the odds for each of those 20 years and then averaged those odds to come up with:

(.98 to the 20 + .98 to the 19 + .98 to the 18...+ .98) = 16.99653115%/20=.8498265575 or 85% chance of not having a bleeding event over the course of 20 years. Andy, I'm not really sure of my math, but it makes sense to me!

 

[geebee]

I don't have to worry about coumadin anymore. My head just exploded and there are 3 quarts of blood on the floor.
Al - I think that is more than we can mop up with a towel.

 

[MikeHeim]

Mmmm, don't think that quite works out that way. Technically that's the way you could put it, but it's kind of like saying those who play the lottery every time have a better chance of winning than those who are playing for the first time.

If you're saying that there is a 1% chance, it multiplies out the same way if you take one person for 100 years, or one year and 100 people. It certainly doesn't mean that if a person is on Coumadin for 99 years, there is a 100% chance that there will be a "bleeding event" the next year. I'm not sure if that's what you mean saying that statistics aren't "cumulative".

More redundancy coming. If I flip a coin one time, there is a 50% chance that I will get "heads". If I flip it again, there is still a 50% chance that it will come up "heads". However, there is only a 25% chance that I will flip "heads" both times. Each time you flip the coin, there is a 50% chance that you will get "heads". However, by time I flip the coin 10 times, there is only a 0.09% chance that you will not have gotten one "heads". The chances of a "bleeding event" work the same way. If you are on Coumadin for one year, the chances of a bleeding event are 1%. If you are on it for 20 years, the chances are 1%X20 = 20%.

I would actually like to see somebody challenge the 1% per year probability of a bleeding event. There are a whole lot of people on this list that are on Coumadin, and I can only recall 1-2 posts from people talking about a serious bleeding event. In that respect, 1% sounds really high. I feel the same way about surgical mortality. Even if the mortality rate for a 1st time heart surgery is 1% (I've often seen in quoted much higher, usually around 3%), people on this list seem to have a much lower rate than that.

 

[Karlynn]

Maybe I'm getting too confused here! Gina - my blood may be mingling with yours shortly.

I've been on Coumadin for 14 years - so my chances are 14% that I'll have a serious bleed. Sorry Mike, but I think that's a flawed look at it. (or if you're looking at 2% - then 28% for 14 years.) I'm going back to my original premise - that if being on Coumadin and risks thereof, was that cumulative, the replacement with a the mechanical valve would not be as widely used. The issue here is obtaining longevity in as healthy a form as possible. So placing a mechanical valve in a 30 year old, expecting them to have a 25 or 50% chance of having a bleeding incident at the age of 55 just doesn't make sound medical sense.

And what is considered a bleeding event? I sliced my knuckle off a bit about 4 years ago while chopping onions. I bled for a while, but it stopped with pressure (probably should have gone in for a stitch or two, but didn't) So if that is considered a bleeding event, then yes - I've probably had 1 or 2 a year. But so has my husband, who has made it his life's goal to try and cut off every finger at least once, while doing yard work.

If a bleeding event is one that happens because of being on Coumadin that otherwise wouldn't happen if not on Coumadin. Then I've had no bleeding events in 14 years. Are we talking spontaneous bleeding for no apparent reason other than a high anticoagulation factor, or are we talking bleeding that was exacerbated by Coumadin, causing a medical crisis? Anyone know the definition of a "bleeding event"?

Ross, what I want to know is- why hasn't George Clooney moved heaven and earth to find me and profess his undying love? Maybe because he knows I'd just have to break his heart.

 

[geebee]

Karlynn,
Honey, I am hiding George Clooney here in Cincinnati. He came once to visit his father and I kidnapped him. The stories about him living in Italy are just bogus. You have heard of his home on Lake Como? Hah - Lake Como is the name of a little pond in an old amusement park called Coney Island east of Cincinnati. I inserted that into the news stories as a red herring.
If you are very, very good, I might let you come visit.

 

[Naomi]

I've been on Coumadin for 14 years - so my chances are 14% that I'll have a serious bleed. Sorry Mike, but I think that's a flawed look at it. (or if you're looking at 2% - then 28% for 14 years.)

Maybe he means that you'd have a 14% chance of having one bleeding event sometime in your 14 years on coumadin????

 

[ks1490]

Thanks, everyone, for your replies. Thank you, Andy, for checking my math. By bleeding event I mean something caused by coumadin - some kind of hemmorhage or stroke, etc. I can see pros and cons on both sides. I agree that neither tissue or mechanical would be recommended if one presented significantly greater benefits than the other.

 

[Karlynn]

Thanks, everyone, for your replies. Thank you, Andy, for checking my math. By bleeding event I mean something caused by coumadin - some kind of hemmorhage or stroke, etc. I can see pros and cons on both sides. I agree that neither tissue or mechanical would be recommended if one presented significantly greater benefits than the other.

There is a somewhat official definition of a "bleeding event", I just don't remember what it is. Gina jogged my memory with Al Lodwick's saying that it is when you need more than a towel to mop it up.

One thing you may find helpful is that bleeding because of Coumadin that may seem spontaneous, often results in the doctors finding a situation that would not have been discovered until later without the Coumadin. Certain types of cancer can be discovered earlier, as well as other issues. This isn't to say that this is the reason to take Coumadin, it has just been know to bring to light a serious medical problem much sooner than it normally would have.

 

[Mary]

Thanks, everyone, for your replies. Thank you, Andy, for checking my math. By bleeding event I mean something caused by coumadin - some kind of hemmorhage or stroke, etc. I can see pros and cons on both sides. I agree that neither tissue or mechanical would be recommended if one presented significantly greater benefits than the other.

Dear KS,
Does your last reply mean that you're satisfied with the responses you've received and want to move on?
I sure hope so!
There's been enough statistical debate in this thread to tucker my brains out!
And all bets are off as to who was right and who was wrong with their numbers!

 

[Lynlw]

I don't have to worry about coumadin anymore. My head just exploded and there are 3 quarts of blood on the floor.
Al - I think that is more than we can mop up with a towel.

somehow I don't think your heart/valve/comadin has anything to do with how much blood landed on the floor, after following this thread the same thing happened to me and I never had heart surgery lol,

 

[twinmaker]

I think a bleeding event is exactly what I had happen when my ovarian cyst ruptured. I've had ovarian cysts rupture before and just had some pain and felt kind of yucky. Because my PT was so far off the charts, the ruptured cyst just kept bleeding into my abdomen. I can't remember how much blood they had to replace, but it was a lot. I was, I guess, on my way to bleeding to death internally. They really didn't even know where the bleeding was coming from exactly until they opened me up. They thought I was having a tubal pregnancy, but I kept telling them that I wasn't pregnant. I don't know the exact meaning of a bleeding event, but in my mind, I had one. LINDA

 

[Andyrdj]

To PJMomrunner

To PJMomrunner

Whoops! Didn't divide by the 20 years. What I'm saying is that you can't say the chance of not having a bleeding accident is 66.7% over the course of 20 years because after the first year has past there are only 19 years left in the original period and the odds of not having a bleeding accident remain the same for each subsequent year. So I figured the odds for each of those 20 years and then averaged those odds to come up with

I sort of see why you might think that, but it's not quite the way things work. (please don't consider me impolite here!)

Let me re-iterate that these odds are for what you don't know yet - for no bleeding events the coming, unknown 20 year period.

From the point of view of the time at the start, how can that happen?
If, and only if, every subsequent year is bleed free.

So I think most people are happy with the (0.98)^20 figure.

If you were to do the maths you've done, and average out (0.98)^20 + (0.98)^19 +(0.98)^18... etc, what question does that answer? Well, it sort of averages out the worry you'd have to face per year.
Let's imagine your sole goal was to survive 20 years - e.g if you knew they'd have an immortality serum and a cure for everything. To simplify matters, we assume it's either survive or die (which is not the real situation!!!!)
So all you'd focus on was this 20 year period. At the start of each year you'd calculate the prob of surviving the rest - at the start, this would be (0.98)^20. The next year, having survived, you'd calculate (0.98)^19 and so on - each year, if and only if you'd survived, the odds of surviving the rest get better.

Averaging these gives us a measure of "the average worry faced by someone who survives all 20 years". Clearly, if the person only survived 4 years, it would be (0.98)^20 + (0.98)^19 +(0.98)^18+
(0.98)^16. It's not actually a very meaningful figure.

Always be careful of adding numbers in probability, and averaging probabilty needs to be done with care too! Remember that probability is already an average.

 

[Dustin]

So I think most people are happy with the (0.98)^20 figure.

Looking at the severity of my aortic stenosis, doing nothing will most certainly lead to my early departure from this beautiful world in about one perhaps two years tops. So getting a 66% chance to live another 20 years without problems is a generous offer indeed. I'll take it with both hands.

 

[Andyrdj]

To MikeHeim

To MikeHeim

The chances of a "bleeding event" work the same way. If you are on Coumadin for one year, the chances of a bleeding event are 1%. If you are on it for 20 years, the chances are 1%X20 = 20%

Just to be pedantic again, Mike - It doesn't quite work that way.

The "number of years x probability" gives you the average number of bleeding events in that time - not the same as "probability of at least one event"

Because, if it's 2%, then during 50 years you will have on average 0.02x50 =1 bleeding event, but there is still a possibility (0.98^50) that you have been lucky enough to have no events at all.

If Mike's argument were true, then you would be certain to have an event after 50 years.

I'm sorry to keep blowing people's heads up with this stuff (ah, yer love it really) but I think it's really valuable for people to learn this stuff, because it should avoid panic and give people the tools they need to understand their choices.

 

[sue943]

I am going back about twenty years and I don't know any details other than that my former domestic help died when she was mid-forties with complications from taking warfarin. Short of telephoning her family I cannot get details. I was just told by a friend who they had seen her in hospital and when they spoke, the woman told my friend that she was 'seeping everywhere', she died shortly afterwards. In fairness to warfarin, it is quite possible that she wasn't getting her INR checked as often as she should, I don't know, just guessing, back then it would have been costly to have it checked (not free as it is today) so she might have skipped hving regular tests. But she still died on it.

Then we have my father, and this is much longer ago, forty years in fact. He was taking warfarin after having had a coronary, I don't know the dosage but it was half a tablet (no idea as to the size), he had a blood test on the Thursday morning in preparation for seeing his cardiologist on Friday. At that time we did not have a telephone and used a neighbour for emergency messages. The neighbour came to say that the hospital had phoned to tell my father not to take any more warfarin. Next the police turned up on the doorstep with a message to tell him not to take any more warfarin. Then finally our doctor turned up on the doorstep to tell him not to take any more. He would have only taken half a tablet before seeing the cardiologist so that surely couldn't make so much difference to set up such a fuss. He died about three weeks later of another coronary.

Yes, both incidents were a long time ago and testing has improved. That doesn't stop me worrying about taking warfarin and wishing that I had gone for tissue valves. I don't fear death at all, but what I really fear is having a severe stroke and being unable to care for myself - I live alone. If only I could turn back the clock twelve months, my anniverary is at the end of this month. If only I had found this site prior to my surgery and realised how the testing works, the problems if the dosage isn't right. It might be fine for you people who can home test but I cannot home test, I cannot afford the costs involved. I just wish that I wasn't on warfarin. Even looking for a job, I am having to tell prospective employers that I need time off every few weeks to get a blood test, not condusive to gaining employment.

 

[Andyrdj]

Regarding jobs

Regarding jobs

Sue, I've just been accepted for a new job. I haven't had to declare anything prior to accepting the job, but for my induction I will be required to declare any serious health problems as per usual.

OK, I get a 6 month probationary period before I become a full time employee. I intend to be fully honest and say that yes, at some time in the future I will need time off for my operation - but bear in mind that will most likely be around a month to 6 weeks maybe.

Which is far less time than a woman who takes maternity leave - so I can't be that bad a prospect for them.

I know certain laws exist to prevent discrimination against people for illness, it would be interesting to find out more. I don't think you're forced to declare it beforehand.

 

[Karlynn]

Sue, I'm sorry to read that you are regretting the valve that was installed. Did you have a choice or did they just pick one? I wish I could ease your mind about the stroke issue. Yes, it is a possibility, but that is why you are on Coumadin. If your INR is kept regulated, your risks are very small. Remember that if stroke was a regular occurance, then mechanical valves would probably not be approved for use.

All of us mech valvers who were on Coumadin when PT (Prothrombin Time) was used to regulate anticoagulation will tell you that it was it was a little trickier to keep theraputic, and I think Al would tell us that there was more incident of events occuring when out of range. Since inception of the INR, the science, while not exact, does a really good job of keeping people theraputically anticoagulated. Much like valve replacement surgery has continued to improve and mortality rates have dropped significantly, so has the management of anticoagulation. We often speak here of our frustration when doctors still operate off the knowledge of warfarin they learned 20 years ago and end up giving people really bad advice.

 

[lance]

Tissue valves requiring ACT?

Tissue valves requiring ACT?

Hii Andy,

I see you have been applying the same thoroughness with stats--again. LOL.

Have you tried comparing the probability of a tissue valve recipient not requiring ACT versus tissue valve recipient that will require ACT?

I just thought this would be interesting.

Cheers

Ok - to work things out from a probability of 2% per year, we turn it on its head and work out the probabilty of something not happening, and subtract that from 1. This gives us the probability of any non zero number of events - i.e. probability of (1 event or 2 events or 3 events....)

Let's do this for 20 years - and bear in mind that this is a "before I start" estimate.

So: prob of no events for 20 years =0.98 x 0.98...... (20 times), or 0.98 to the power of 20 = 0.6676,

i.e a 66.76% chance that you will be event free for 20 years

Therefore there is a 33.24% chance of at least one event (could be 2, could be 3, 4 or 20) within 20 years.

However, bear in mind also that each year is a fresh start. It's the same as rolling a dice 100 times and never getting a six - the probability of a six on the next throw (if indeed you don't have a duff dice!) is still 1/6.

So if you've been "lucky" as in Gina's case, (for 25 years the maths gives us 60.34% chance of freedom from any events) there's no mystic force which is about to make your luck end soon.

You are still playing the chance game on even odds with everyone really - although I would suggest a degree of personal stability and good INR management is likely to contribute to it in Gina's case.

I did the Maths again on other examples, and you have to go for 35 years before your odds drop to less than even for being free from events. Remember, that's a calculation you make for the coming 35 year period.

I hope no-one takes these results the wrong way - all I've done is plug in a little maths.

Try the same for 1% and you get a better result - 81.79% free after 20 years, 70.34% free after 35 years, and you take around 70 years for the odds to go below 50%.

Give me accurate figures, and I'll be interested to calculate this some more.