Q&A Report: Initial Orthostatic Hypotension: Don’t Blink or You Will Miss It

Is exercise a known strategy to improve orthostatic tolerance?

S. Raj – There are exercise training program for patients with Postural Orthostatic Tachycardia Syndrome (POTS. While exercise (within limits) is recommended for nOH and VVS patients, there are not data that they are therapeutically effective.

What are the main differences between POTS and IOH? How can you tell them apart?

S. Raj – Quite different presentations. IOH is associated with presyncope (and rarely syncope) almost immediately after standing, and then resolves. The POTS patients will complain of lightheadedness that is worse with sustained standing.

How many were in your study and what was the age range and mean age?

N. Sheikh – 26 participants were enrolled and 24 were included in the final analysis. The mean age was 32 years (age ranged from 21 years to 50 years).

Is it the case that SCI patients more frequently have a delayed OH?

S. Raj – The presentations in SCI patients can vary, but they more typically have classical neurogenic OH. It does not recover quickly with ongoing upright posture.

If you all have taken automated and manual blood pressure, have you noticed differences between measurements? We see this at times (population dependent), and this drastically impacts beat to beat BP

S. Raj – If you are asking whether the continuous BP is different from the cuff BP, the answer is sometimes YES. This is improved by using the height correction tools. Also, sometimes there is “whip” in the signal with an artifactual overshoot. The continuous BP is better for trends/changes in BP than a one-off BP, but it becomes more accurate when it is done carefully.

Several population-based cohort studies have reported a remarkably high prevalence of IOH using the BP cutoff of 40mmHg systolic. A recent clinical autonomic research editorial raised the question as to whether a redefinition of the systolic cutoff values for IOH is needed. What are your thoughts?

N. Sheikh – The 40 mmHg systolic cut-off should only be used in addition to history taking. In that case, if a patient is experiencing presyncope symptoms AND their SBP is dropping >40mmHg IOH seems like an appropriate conclusion. Redefining the SBP cut-off to a higher cut-off may end up excluding patients who do experience IOH.

Which muscle group did you stimulate, and would it make a difference?

N. Sheikh – We stimulated the rectus femoris of the quadricep muscle group. Yes, the muscles stimulated would likely make a difference. We know that the increase in skeletal muscle blood flow from a brief muscle contraction is proportional to the strength of the contraction, therefore, the stronger the muscle, the greater the increase in blood flow prior to standing.

You did not said anything about fluid status. Surely this is relevant?

S. Raj – Fluid status was not formally assessed. It might well be important. Anecdotally, from our clinic experience, this does not respond as well to aggressive hydration as some of the other orthostatic intolerance disorders.

Can you please share the exclusion criteria?

N. Sheikh – Participants were excluded if they: 1) only fainted or experienced presyncope symptoms while already standing for some time; or 2) if they were diagnosed with another form of orthostatic hypotension, including classic neurogenic orthostatic hypotension or delayed orthostatic hypotension; or 3) if they were above the age of 50 or below the age of 18; or 4) if they were pregnant.

Have you found post-prandial exacerbation is common in IOH patients? Maybe due to splanchnic vasodilation and increased burden on the circulation?

N. Sheikh – I have not come across this in IOH. Patients were asked if there were any triggers or times where their symptoms were more frequent/worse and eating was never mentioned as one. Our study was also completed while participants were in a fasting state (excluding water).

S. Raj – This does happen with nOH and to a less extent with POTS.

Does IOH only appear in active standing? Can't I see it in the Tilt table test?

S. Raj – No, IOH is often not apparent on a tilt test with a “passive stand”, but often presents only with active standing.

Could you briefly explain more about the "VOSS" rating system?

S. Raj – VOSS is the “Vanderbilt Orthostatic Symptoms Score”, which is a 9-item scale where patients can rate each symptom on a 0-10 scale acutely as a measure of acute orthostatic intolerance.

Do you have any experience/outcomes with COVID-19 patients with IOH?

S. Raj – Not yet, but they are coming. We have started seeing Long COVID patients, and seeing more of a POTS like presentation. We have a study about to start where the protocol will assess for IOH also.

Do any of the pharmacological medications used for Classical OH prove useful in initial OH?

S. Raj – We have not been using medications. There are a few patients with midodrine, but they can still get IOH symptoms.

How big of a factor is dehydration?

S. Raj – I advise against dehydration, but I have not found aggressive hydration to be an effective strategy for IOH (while it is for VVS and POTS).

You mentioned that IOH is more common in young people and so there are age differences, but are there sex differences in the prevalence of OH, and is this consistent across the subtypes?

S. Raj – I am not sure overall. IOH seems to affect females SLIGHTLY more than males; not sure that this is true for nOH.

Mike Joyner has data on older females and changes in resistance relative to their younger counterparts. What age were the subjects and would you expect these techniques to also help in an aged population?

N. Sheikh – Participant age ranged from 21 years to 50 years. I do think that these methods work in the older patients (anecdotally) but some of the maneuvers may be difficult to perform for elderly patients.

For orthostatic hypotension do individuals need lay down on the floor and stand up from the floor or it can be done from a bed?

S. Raj – It can be done from a bed.

Are there stimuli that trigger IOH that are not neurogenic?

S. Raj – I think that the stimuli is muscle activation and may be mechanical fluid shifting (and responses).

I've read that this is common in individuals who lose weight, why is the case? And what about obesity?

S. Raj – I have not heard this. patients post bariatric surgery (and perhaps after major medical weight loss) can have nOH or delayed OH due to mild autonomic failure; I have not heard of them having more IOH.

N. Sheikh – We have not looked into obesity and IOH, however, the majority of our participants were of average weight (BMI 24±6 kg/m2).

How useful is ITD against OH?

S. Raj – David Benditt has an article on this a few years ago. It acutely improved BP. Patients seemed to have non-neurogenic OH.

Since IOH occurs more in younger people, do they show it less as they age?

S. Raj – We do not have long-term data, but it does seem less common (but still present) in middle aged and older patients.

Can IOH and POTS coexist? And do the interventions that you described also help systems of POTS?

S. Raj – Yes, both IOH and POTS (and VVS) can all co-exist in a single individual. And no – The described interventions are for the IOH symptoms only. POTS management is different.

Watch this on demand webinar to learn more about different methods for POTS management.

Is there a moderate or strong correlation between IOH and vasovagal responses?

S. Raj – Not that we have seen. They seems to be quite different reactions, although they do sometimes co-exist in the same patients.

What is severity of IOH in Type 2 Diabetes patients?

S. Raj – I do not think that IOH is particularly common in T2DM patient. This might be because T2DM occurs more in middle aged and older patients, when IOH is less common. Neurogenic OH is more common in T2DM.

Which sensor based technique is used in these clinical investigations? Did you use any IR based sensor?

S. Raj – We did not use NIRS. We monitored EKG, continuous BP (finger photoplethysmography), and transcranial doppler ultrasound.

Can you speak about OH when the patients have a drop of blood pressure when they change from supine to sit position?

N. Sheikh – This has been known to occur in nOHpatients however, it does not appear to be an issue with IOH. Often IOH patients will sit up first before standing to help with symptoms.

Is there a link with IOH and Ehlers danlos?

S. Raj – Not that we have seen. There is a link between EDS and POTS.

N. Sheikh – We did have one IOH participant who also had EDS.

Have you ever seen orthostatic hypotension as part of a syndrome similar to POTS?

S. Raj – Some POTS patients can intermittently have OH, especially when more dehydrated.

Is there a relationship between sleep and IOH?

S. Raj – We are not aware of a relationship between sleep and IOH.

Which is the most common type of OH out of the three?

S. Raj – My guess is that IOH is the most common, but that nOH is the most recognized.

N. Sheikh – Of the different OH, IOH is the most common when looking at a cohort of unexplained syncope patients. Reflex syncope is the most common form of syncope.