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09/13/2011 - POTS

posted Sep 28, 2011, 5:55 PM by Chief Resident   [ updated Oct 10, 2011, 11:01 AM by Purnema Madahar ]
Today in intake, Cruff Renard presented a very nice vignette that taught us about POTS:

A young, healthy lady with a year long history of episodic lightheadedness. The episodes occur every few months after standing for about an hour, start suddenly, are accompanied by a sensation of fullness in her ear but no tinnitus, a sensation of sweating in the legs and the absence of vertigo, nausea, shortness of breath, chest pain, palpitations. She's never fainted. The symptoms resolve spontaneously when she sits down. During the most recent episode, she took her pulse, which was more than 135 bpm.

On exam, she's asymptomatic, appears healthy and has a supine BP of 104/76 with a heart rate of 85 but when sitting up, her BP is 110/78 with a heart rate of 126 at 3 minutes. Otherwise, her exam is unremarkable, including her neuro exam.

Cruff diagnosed her with Postural Tachycardia Syndrome (POTS) and found the attached review article. When browsing the literature, I came upon a great guideline on the diagnosis of management of syncope, which succinctly puts POTS in the context of other etiologies of syncope and provides a very useful framework. Make sure to check out the tables and graphics.

The guideline devides syncope in reflex (neurally mediated) syncope, cardiac syncope and orthostatic hypotension or orthostatic intolerance syndromes:

- reflex syncope refers to a temporary, inappropriate response of the autonomous nervous system, often times to a trigger (reflex), that causes bradycardia and/or vasodilatation; examples are vasovagal syncope and carotid sinus syncope
- cardiac syncope refers to arrythmia and structural heart disease
- orthostatic intolerance refers to a chronic impairment of the autonomous nervous system that leads to postural hypotension; it can be devided into initial/classic/delayed orthostatic hypotension (see Northwest Daily from August 16) and POTS, which the guideline describes as follows:

'Some patients, mostly young women, present with severe complaints of orthostatic intolerance, but not syncope, with very marked heart rate (HR) increases [>30 beats per minute (b.p.m.) or to >120 b.p.m.] and instability of BP.'

It seems that POTS shares the same symptomatology as orthostatic hypotension without the acutal syncope and no or much less postural orthostatic changes. The pathophysiology is incompletely understood. Table 5 in the guidelines gives a good overview.

The lady in the vignette meets the findings associated with POTS: her age, abscence of other vagal symptoms and no orthostatic hypotension. On top of that, she had the full 'million dollar' workup of echo, CT head, tilt table, event monitor in the past - all negative. Seems like dr. Renard could have saved us a few dollars if he'd met her earlier.