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Normally a narrow PP is seen with hypovolemia (low total blood volume) which has been demonstrated in many cases of POTS. The theory behind this is a glitch in the Renin-Aldosterone system (The Renin-Aldosterone Paradox--Dr. Satish Raj.)

I have come across an alternate, yet corresponding theory/reason and am wanting input from anyone who understands this better. There is a condition called isolated diastolic hypertension that creates a narrow pulse pressure through normovolemic vasoconstriction:

Association of ACE genotype and predominantly diastolic hypertension: a preliminary study

Pablo Martin Jim?nez,*Cecilia Conde,*Ana Casanegra,? Cesar Romero,*Aldo Hugo Tabares, Marcelo Or?as #

http://jra.sagepub.com/cgi/content/abstract/8/1/42

It involves Angiotensin II and NO. Increased Angiotensin II causes systemic inflammation and thus diastolic hypertension which narrows PP. The thing is, it is testable and far less invasive than a blood volume test.

It sort-of crosses that barrier between Dr. Stewart's work and Vanderbilt's.

Any theories? C'mon Ramakentesh--you've got to have a theory.

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This is interesting, unfortunately I am rather ignorant of the renin-aldosterone system so I can't really give you a good theory. However my pulse pressure is usually below 40 and has been documented as low as 8. In fact when I was a research patient at Vanderbilt it was usually below 20. My blood volume taken at both Vanderbilt and Cleaveland Clinic was normal and my vascular resistance was high. I have read that a pulse pressure under 20 means the body is not being adequately profused, however when I asked a doctor what it means after they record a low pulse pressure they say they aren't sure. In my case since I have severe pooling ( 44% drop in circulating blood volume when standing) perhaps the mechanism for response in me is the same as those with low blood volume.

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Definitely interested in this topic as my pulse pressure is usually about 20 or less when I'm feeling really bad. However I also get a depressed ST segment at the same time, so not sure how that correlates into the picture at this time. Hopefully this alternate theory can explain more about why we experience the narrow pulse pressure.

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I spoke with my PCP about this today (I have strep :) ) and he says it is a possibility, but that diastolic hypertension can occur with hypovolemia. The only way to know for sure is to come off all volume expanding drugs and get an angiotensin II level, then build volume back up to where they "think" it ought to be and do it again. There are so many things that effect each other, histamine, nitric oxide, angiotensin II, prostaglandins, estrogen... My brain is fried, so I can't think of proper links right now.

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Yes! This might be me! My veins are VERY small, and maybe they contrict when I stand up or something, or when I don't feel good, and that's why I have SUCH narrow pulse pressure. I hope I'm understanding it correctly. I'm going to bring this up to my doctor, and I'll let you know if it gets me anywhere. My PP is always below 10 when I don't feel good, and it narrows pretty quickly and easily when I'm active.

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Yes! This might be me! My veins are VERY small, and maybe they contrict when I stand up or something, or when I don't feel good, and that's why I have SUCH narrow pulse pressure. I hope I'm understanding it correctly. I'm going to bring this up to my doctor, and I'll let you know if it gets me anywhere. My PP is always below 10 when I don't feel good, and it narrows pretty quickly and easily when I'm active.

Me too, and I have the NO issues with migraines.

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Werner & Ingbar's the thyroid, By Sidney C. Werner, Sidney H. Ingbar, Lewis E. Braverman, Robert D. Utiger

page 776

states that 20%-40% of hypothyroid patients have a narrow pulse pressure due to isolated diastolic hypertension. Melissa, have you had your thyroid checked? There is a great big overlap of symptoms in hypothyroidism symptoms and POTS symptoms. Many of us here (me included) have had, or do have thyroid issues. I wonder if there isn't some sort of TSH level masking or antibodies that make the testing appear normal, but we can't use the thyroid hormone we produce. :)

too many systems, too many symptoms, too much to look at...is it one puzzle or several......

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Yeah that is essentially the same cause as the newly described version of POTS called Low Flow POTs - it just expresses in a different way - rather than hypertension these patients have reduced regional blood flow because the decrease in NO is sufficient enough that it actually restricts blood flow around the body. Elevated angiotensin has a potent effect on the sympathetic nervous system that may result in reduced blood volume.

Elevated Angiotensin II = increased oxidisive stress = reduced NO = reduced regional blood flow and POTS.

Reduced peripheral blood flow seems to be found both in this form of POTS and the form designated Normal Flow POTS. In norm flow pots its believed that inflammatory markers are causing either peripheral vasoconstriuction or stomach pooling.

OR

Elevated pulse pressure could also be a compensatory mechanism to increase blood flow to the upper body in blood pooling.

Elevated pulse pressure could also occur when norepinephrine is not being taken up at the synapse causing cardiovascular excitability and POTS through postural hyperventilation and postural hypocapnia.

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