Idiopathic postural orthostatic tachycardia syndrome: an attenuated form of acute pandysautonomia?, 1993, Schondorf & Low

Abstract
To characterize the idiopathic postural orthostatic tachycardia syndrome (POTS), we reviewed the records of all patients aged 20 to 51 who presented to the Mayo Autonomic Reflex Laboratory and who exhibited tachycardia at rest or during head-up tilt. These patients were usually women who experienced an acute onset of persistent lightheadedness and fatigue or gastrointestinal dysmotility. In seven patients, a viral illness may have preceded the onset of symptoms. In two instances, signs and symptoms of a small-fiber sensory neuropathy were present. Laboratory evaluation of autonomic function revealed increased diastolic blood pressure to tilt (5/16), increased Valsalva ratio, marked decrease in phase II of the Valsalva maneuver with normal phase IV overshoot, and normal forced respiratory sinus arrhythmia. Abnormal quantitative sudomotor axon reflex test and thermoregulatory sweat test and an excessive orthostatic increase of catecholamines were found in some patients. We conclude that in many instances POTS may be a manifestation of a mild form of acute autonomic neuropathy.

Source: https://www.neurology.org/doi/10.1212/wnl.43.1_part_1.132

 

This is a historic paper from 1993 where POTS was first defined.

I am very interested in reading what it says but do not have access to it. Anyone who can share a copy with me in PM?

 

Thanks to @SNT Gatchaman for helping me out.

In the study they had a control group of 20 men and 21 women aged 20 to 50 years. For the control group they report that "between the second and third minute of tilt, HR increased by 20.1 ± 8.9 bpm in men versus 14.8 ± 8.1 bpm in women." So it seems that they only did the tilt testing for 3 instead of 10 minutes.

POTS was defined as follows: (1) a sustained orthostatic HR increase >2 SD of mean HR of a control sex-matched population response, or (2) a baseline HR >110 bpm, with further increase during tilt of >20 bpm, or to >140 bpm.

Perhaps the idea that an increase of > 30 bpm is abnormal comes from the 21 women in this control group as 14.8 + 2*8.1 = 31. The fact this was taken from only 21 women and that their tilt test only took 3 minutes looks problematic (I suspect that for some might have had a higher HR increase if the test was increased to 10 minutes).

 

I remember hearing Satish Raj talk about how the 30bpm cut-off was decided ... unfortunately I cannot remember what he said about it. He did say that autonomic specialists are not particularly happy about it being used in the diagnostic criteria.

 

I have read that this study from 1986 is now considered to be an early POTS study too, except they didn't call it POTS.

Idiopathic hypovolemia
F M Fouad, L Tadena-Thome, E L Bravo, R C Tarazi

Abstract
Eleven patients with orthostatic intolerance had, for no detectable reason, a marked reduction in blood volume (73 +/- 2.29% [SE] of normal). Head-up tilt caused a pronounced increase in heart rate (+ 39 +/- 6 beats/min); one patient had a vasovagal episode after the initial tachycardia.

Extensive diagnostic study excluded pheochromocytoma, hypoaldosteronism, or any obvious cause for hypovolemia (total plasma catecholamines, 372 +/- 53 ng/L; plasma aldosterone level, 14.5 +/- 2.56 ng/100 mL; plasma cortisol level, 18.5 +/- 2.4 ng/100 mL).

The supine hemodynamic pattern (decreased cardiac output and increased total peripheral resistance with normal ejection fraction and mean transit time) was markedly different from that of hyperbeta adrenergic states.

Acute plasma volume expansion (+ 11 +/- 2%) in ten patients using human serum albumin improved both their symptoms and heart rate response to tilt. After long-term blood volume expansion with florinef (E.R. Squibb, Princeton, New Jersey), 0.1 mg twice a day, and a high-salt diet, the head-up tilt test was repeated in five patients. The response was normal in four patients.

These observations outline a syndrome of marked idiopathic hypovolemia with symptomatic labile hypertension and intolerance to head-up tilt, alleviated by volume expansion.


https://pubmed.ncbi.nlm.nih.gov/3511818/

***
Interesting that they chose to give IV albumin rather than IV saline for acute volume expansion.