Chad2 daily risk?

[europeman]

Hi. I'm a surgeon. Quick question. If a patient chad2 score puts them at risk for annual stroke of say 9%...... What is their daily risk?

I'm interested of course with my post op patients when I hold anti coagulation.

Thanks!

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[gutonc]

I know you said you were a surgeon, but I'm sure even a surgeon can use a calculator to divide 9 by 365.

 

[europeman]

Lol. I guess this is more of a stats question. If annual risk is 9%, is it an accurate mathematical statement to then day the daily risk is 9%/365? I'm not sure.

Given cards deals with these questions all the time in the setting of post stent, post op, and post blah blah blah input and risk stratification for patients, I thought you would be best to answer the question!

I'm still not sure that's 9%/365 is the daily risk. U sure?

 

[nstemi]

0-100%

 

[MedUK]

If the probability of having a stroke is x per day, each day it doesn't happen with a probability of 1-x.
A stroke doesn't happen during a whole year with a probability of (1-x)^365

If we know the probability of having a stroke in a year is 0.09, then

0.09=1-(1-x)^365

His daily risk of stroke is 0.0258%

Which (?coincidentally) is close to 0.09/365

 

[oldanddone]

im interested too (neither cards nor sx) postop would seem higher risk than run of the mill chads daily/ yearly risk that calculator was designed for...what is the sense of postop risk>?

 

[europeman]

Why would post op be higher risk for non-new onset a fib? I would think the risks are about the same. New onset is a totally different animal of course

 

[MedUK]

Don't know what the evidence out there is specifically re AFib, but conceptually it might make sense given that post-op is a relatively hypercoagulable state - whatever static blood is in the left atrium might be more likely to form a clot

 

[europeman]

Seems like with a daily risk of 0.03% per day.... Or 3/10000 is so low that for most post operative patients.... The risk of bleeding is much higher than risk of stroke.

The original question came because we have had a run of patients that were restarting on anticoagulation for atrial fibrillation before 7 days post operatively which subsequently developed complications (post op thyroidectomy who developed neck hematoma and needed re-op, a post operative whipple who bled a week out once lovenox full dose starting, etc).

What seems to be happening is the cardiologist/medicine consultants say "restart anti-coagulation as soon as possible" and the surgeons, who have no idea how low the daily risk of them holding off.... Feel obligated to restart soonish.

Now it seems this is the fault of both sets of doctors. On the one hand the generic comment "restart as soon as possible" is, superficially, an okay statement. But it negates the recognition that this treatment is VERY different than attenuating the risk for much more concerning pathologies like mechanical valves, recently placed cardiac drug eluding stents, etc.

I just wish if people reconciled the massive difference in stroke risk when anti-coagulation is held for atrial fibrillation compared to a recent drug eliding stent, practices may be different.



What are your thoughts?

 

[gutonc]

You need different consultants. If all the cardiologist is saying is "restart anticoagulation when safe", and not actually commenting on risks and benefits, ask someone else.

And you also need to be an educated adult and maybe question their recommendation in the setting that you're supposed to be an expert in. Cardiologists and hematologists are much more familiar with the risks of bad things happening if you don't anticoagulate than if you do. I'm a lot less familiar with the relative risks of post op bleeding with particular procedures. So if you tell me the baseline risk of post op bleeding is 0.01, I'll tell you to start the full dose lovenox. If you tell me that risk is 1%, I'll tell you to hold off for awhile and forget the bridging.

Also, the CHADS2 score was developed to determine the role of anticoagulation in new onset a fib, not to help decide on which POD to restart it.

Big picture, this is one of those situations where a 30 second phone conversation will make a huge difference compared to just reading the consultant's note.

 

[nlax30]

In the RE-LY trial (dabigatran vs warfarin), the perioperative risk for stroke seemed to be 0.5%. And looks like this periop period was 7 days pre-op to 30 post.