Questions on morbid event rates

[Randy & Robyn]

I have been looking over morbid event rate statistics for the different valve choices available and have a couple of questions that I was hoping someone could help me with.

First question: When they state thromoembolic event rates, I assume they cannot separate valve-related events from non-valve-related events. So a certain number of those patients would have had the TE regardless of the valve. Am I correct? I have been looking for a baseline TE rate for the general population but I haven't been able to find any statistics like that.

Second question: It appears to me that TE rates for mechanical valves with the benefit of anticoagulation therapy are nearly equal to the TE rates for biological valves without anticoagulation. Therefore, the only increased risk with a mechanical valve is the heightened risk of a bleeding event. Does that make sense?

I hope I am not becoming too obsessed with the statistics. I just want to make the most informed decision I can.

Randy

 

[RCB]

Questions of this nature are better posed in the coumadin section where
we are blessed to have a resident expert. This question was discussed somewhat here:
http://www.valvereplacement.com/forums/showthread.php?t=9667

 

[tobagotwo]

I agree with your assessment of the first question. I mostly agree with your assessment in the second case as well.

There are caveats to the statistics. They bring value, but should be looked at within some kind of a context. They are often facts, but not information.

Many of the statistics available are becoming well-aged, especially as this has been a very fast-moving field. Be cautious of the study dates and what they may mean to the results. There have been many advances made in all of the valve products, and even more importantly in the surgeries themselves. You should consider when and how to take them into account.

Also, keep in mind that the research you mention is concerned entirely with morbid (fatal) events. It does not include events that may range from annoying to damaging, or even life-altering, such as paralysis.

If you can stand to, try to look through the whole study document, as many people simply look at the summaries, and they miss many cogent observations and cautions brought up by researchers in the larger documents. A synopsis is to a study what a Reader's Digest Condensed version is to a great novel. You can discuss the main points of the plot after reading it, but you've likely missed the true value of the work.

Consider patient age factors. Most often, studies are not "windowed" by age group. That can be unintentionally misleading. For example, the average age of tissue valve recipients is notably higher than that of mechanical recipients, due to a common practice of giving tissue valves to senior patients. Then you must consider how much of a given study relates events caused by valves, and how much is relating events that may be due to age. As you pointed out, there is a substantial independent risk factor that grows with age alone.

On occasion, I have also scouted for the baseline TE rate for the general public, cross-sectioned by age (or at least age group), but it is an elusive number to find. I believe that is because it is so much more devastating and convincing to say that something triples your risk of having a stroke, than to say your risk just rose from .0002% to .0006%. (Of course, those numbers are made up, but you get the idea.) One of these days, I'll devote some serious time to finding that table. Based on the number of studies that seem to use a standard, but unacknowlegded baseline figure source for stroke risk, the table must exist.

It is a daunting task to try to make the best choice for yourself. Get facts, listen to anecdotes, understand the differences in the choices certainly. Try them on your future like new shoes. But in the end, through the cacaphony of opinions, try to listen most to the quiet voice inside you.

Best wishes,

 

[Randy & Robyn]

Thanks, guys. I think maybe I am getting too analytical. Sometimes the best choices come from your gut instinct.

 

[Ross]

Thanks, guys. I think maybe I am getting too analytical. Sometimes the best choices come from your gut instinct.

Exactly. I've said it before and I'll say it again, stats don't mean squat when it comes right down to it. You can go in, get what you want and be happy or you can go in get what you want and have major problems too. It's up the creator and you how it goes.

 

[Karlynn]

Exactly. I've said it before and I'll say it again, stats don't mean squat when it comes right down to it. You can go in, get what you want and be happy or you can go in get what you want and have major problems too. It's up the creator and you how it goes.

I agree with Ross. According to stats, driving my car puts me more at risk than having had my valve replaced. You make your choice and then live life to your fullest.

Good luck.

 

[Bryan B]

Sometimes the best choices come from your gut instinct.

I agree as well. I think it's smart to do your research, but you can also drive yourself crazy overanalyzing things. I relied heavily on my "gut" after researching the options and trying to decide where to have my surgery. I had a gut instinct that the Ross Procedure was right for me but was having 2nd thoughts. Then when I decided to have my surgery at Duke and researched surgeons, the best surgeon for me also happened to be an expert at the Ross Procedure. So my research, my gut instinct, and fate all came together to seal the deal in my decision making process.

Good luck with your decision!

 

[Moo]

...

...

Therefore, the only increased risk with a mechanical valve is the heightened risk of a bleeding event. Does that make sense?

Randy

I wish. Not quite as easy as that...

Coumadin, comes with a not a just a piece of paper with warnings, but a whole book containing what seems to be an endless amount of warnings, side effects, interactions, etc.

While this drug has been in use for decades, it is very dangerous in and of itself. Just the fact that you can have sudden death makes me check my e-mail everyday to see if my application for the asprin-only trial has arrived yet.

Rich

 

[Karlynn]

I wish. Not quite as easy as that...

Coumadin, comes with a not a just a piece of paper with warnings, but a whole book containing what seems to be an endless amount of warnings, side effects, interactions, etc.

While this drug has been in use for decades, it is very dangerous in and of itself. Just the fact that you can have sudden death makes me check my e-mail everyday to see if my application for the asprin-only trial has arrived yet.

Rich

While I agree that the coumadin vs. tissue isn't quite as simple as a heightened risk for bleeding, I would disagree with the context of the "dangerous in and of itself" statement. Any drug, when reading the precautions and side effects could have this statement applied to it. If aspirin were invented today, chances are it would never be approved for over-the-counter use. When over used, it can be dangerous. A friend's mother committed suicide with aspirin. Tylenol is quite leathal when taken in excess. In fact, continued consistant use of Tylenol is having some very serious questions raised. My brother-in-law teaches pharmacology to psychiatric physicians at a well known institute in Chicago and he tells us we should NEVER use Tylenol. Yes, warfarin is dangerous when used without precautions and monitoring. But this is the reason we have "prescription only" drugs. They are all substances that can be dangerous, or even leathal, without precautions and monitoring.

 

[Ross]

I wish. Not quite as easy as that...

Coumadin, comes with a not a just a piece of paper with warnings, but a whole book containing what seems to be an endless amount of warnings, side effects, interactions, etc.

While this drug has been in use for decades, it is very dangerous in and of itself. Just the fact that you can have sudden death makes me check my e-mail everyday to see if my application for the asprin-only trial has arrived yet.

Rich

If your getting your INR checked on time and as much as you should and keep it in range, the incidence of problems is so greatly reduced that it's hardly worth mentioning.

 

[ALCapshaw2]

WHOA Bob,

Morbid => gruesome

Mortal => fatal

MORTALITY Rate refers to Death Rate
MORBIDITY Rate refers to 'undesirable outcome' rate

'AL'

 

[PapaHappyStar]

I have been looking over morbid event rate statistics for the different valve choices available and have a couple of questions that I was hoping someone could help me with.

First question: When they state thromoembolic event rates, I assume they cannot separate valve-related events from non-valve-related events. So a certain number of those patients would have had the TE regardless of the valve. Am I correct? I have been looking for a baseline TE rate for the general population but I haven't been able to find any statistics like that.

Second question: It appears to me that TE rates for mechanical valves with the benefit of anticoagulation therapy are nearly equal to the TE rates for biological valves without anticoagulation. Therefore, the only increased risk with a mechanical valve is the heightened risk of a bleeding event. Does that make sense?

I hope I am not becoming too obsessed with the statistics. I just want to make the most informed decision I can.

Randy

Al Lodwick gave a reference to a long term study at the U. of Ottawa of
embolic stroke risk after Aortic and Mitral Valve replacement. There was a
commentary to the paper in the same journal that pointed out some of the
flaws in the study. My take on the study was even with the flaws there
was probably a higher incidence of embolic events with mechanical aortic and
especially with mechanical mitral valves of the bileaflet and tilting disk
type ( St. Judes, Carbomedics, ON-X etc. were in the study with varying
recommended INR's ).

The objections that the commentary raised were that the patients lost to
followup ( 23% ) were more likely to have a higher incidence of events since
many may have been lost due to an inability to come to outpatient clinic
visits. Another was a mismodeling of age-related backgrounds due to the
difference in age among mechanical and tissue valve recipients. A third was
the use of "Modern" recommended INR in the study -- which might be too low
in the commentators opinion.

The effect of corecting the first two would raise the event count for stroke
with possibly different distributions across the mechanical and bio-prosthetic
groups. The third ( increasing recommended INR to "old" values ) would
decrease the stroke rate for mechanical valves.

I think statistical study provides the best perhaps the only logical way of
deciding between our options. Studies have limitations -- and its possible
in almost any case to twist results -- but its a good idea to pay attention
to large sample, peer-reviewed, academically motivated studies. I do have
misgivings about the actuarial analysis ( tons of assumptions ) that these
studies perform.

Taking as a reference a healthy individual with just average risk factors
for stroke and no artificial valves almost all valve replacement procedures
create a higher risk of TE events ( there are always sutures or stents ).
With mechanical valve and anti-coagulation they want to approach the
reference -- but all mechanical valves create thrombosis, and the biological
valves at best approach the natural situation asymptotically.

Apologies for ranting...especially since I am not in this field of research...

Here is a link to the previous thread ( I did do quite a bit of ranting
there as well )

http://www.valvereplacement.com/forums/showthread.php?t=8450

( as far as gut is concerned -- mine never agreed to the surgery at all )