Normal versus abnormal: What normative data tells us about the utility of heart rate in postural tachycardia, 2019, Baker and Kimpinski

That's an interesting thought. There are other factors that might influence base line heart rate - for example, the effort of getting to the clinic for those people disabled by their symptoms might result in a much higher baseline heart rate than normal, making it harder to demonstrate an increase upon standing.

I found that periods of worse symptoms did correlate with increased morning resting heart rate, so that would tend to make it harder to demonstrate the necessary heart rate increase. Maybe, as suggested above, more weight should be given to the absolute heart rate when standing after lying down.

It's a point worth repeating, it definitely doesn't make sense to have the same HR increase in both a tilt table test and a standing test when diagnosing POT.

(and of course, as this thread demonstrates, tilt table testing and HR increases may not be very useful when diagnosing POTS).

 

It may not be, but I think there are a few things to think about before the idea is chucked away. Here are my example measures again. I don't think some of those heart rates on standing are normal, and the days when standing heart rates were high coincided to some extent with worse ME/CFS symptoms.

So, maybe there's a problem with

• acknowledging that the increased heart rate phenomenon fluctuates - it's not necessarily a problem every day

• change measures versus absolute measures - because a raised baseline for whatever reason makes it harder to qualify for a required increase in heart rate.

• tilt table testing - maybe it has nothing much to do with the impact of standing; maybe it causes problems for healthy people too

• some people's cardiovascular system may go haywire in different ways, or in different way on different days - e.g. maybe the blood pressure drops, so the heart rate increase is still a problem, but it's not the only one

• Maybe things are more complicated than just a heart rate change on standing, and other factors need to be taken into account too when working out if a heart rate increase means a system that isn't functioning well. e.g. is the increase sustained? is the increase relative to artery stiffness?

 

From the above study:

Yes, I don't think we have to see the orthostatic tachycardia itself as pathologic. It may well be a very normal and helpful reaction to some sort of stressor - to blood or oxygen not getting to where it needs to get to, for example.

 

Standing shock index: An alternative to orthostatic vital signs

Donating 450 ml of blood didn't change supine shock index values in healthy people. It did change standing shock index values by a bit less than 0.1, which is quite significant. And the authors suggest that standing shock index is useful in identifying hypovolemia.

I can't access that paper - I'm interested to know how the shock index changed from supine to standing, before and after the blood donation in these healthy people.

 

There's another paper:
Orthostatic Change in Shock Index: Comparison with Traditional Tilt Test Definitions
The OCSI (change in the shock index after standing) was 0.11 in healthy people and 0.18 in those same people after donating 450ml of blood.

My OCSI was often 0.3 and even up to 0.6.

 

Thanks very much @Nightsong.

So, similar results to that older study I quoted in my last post.

Standing shock index increased from 0.67 to 0.76 after blood donation

The OCSI (orthostatic change in shock index, the difference between supine and standing shock index) increased from 0.11 to around 0.20 after blood donation.