Friday, December 28, 2012

Postural tachycardia syndrome (POTS)

A heterogenous and multifactorial disorder.

Benarroach EE, Mayo Clin Proc 2012; 87:(12) 1214-1225.

A recent review article by the amazing Eduardo Benarroch. 

Definition POTS:  (IN ADULTS) HR increase of 30 bpm within 10 minutes of standing or head up tilt (HUT) without orthostatic hypotension.  Definition may be inadequate for yong teens or those with low resting HR.  Lesser degrees of abnormality is called "orthostatic intolerance."

Symptoms: of cerebral hypoperfuson and (reflex) sympathetic hyperactivity relieved by incumbency.  They include, light headedness, blurred vision, cognitive difficulty, generalized weakness (for hypoperfusion) and palpitations, chest pain, tremulousness (for sympathetic part).   One third have secondary vasovagal syncope with typical exacerbating factors (heat exposure, heavy meals, exertion, prolonged incumbency, menses and certain drugs).

Demography:  females have more (4.5:1), age usually 15-25, half have preceding viral illness and 25 % have a positive family history of.Deconditioning, psychological factors are important and autonomic defined abnormalities are relatively uncommon. 

1.  "Neuropathic" POTS is a subtype with LE sympathetic denervation with loss of sweating, quantitative sudomotor testing, impaired NE release in LE's in response to orthostatic stress. Its probably due to inpaired vasoconstriction and venous pooling in legs. They are also the high flow subtype in blood flow testing of legs. 14 % have ganglionic acetylecholine receptor antibody, hence may be autoimmune/

2.  Hyperadrenergic POTS-- 30-40 % have high NE levels (>600 pg/mL), HTN during HUT, tachycardia, HTN and hyperhidrosis episodes triggered by orthostasis OR emotional stimuli/physical activity.  This is low volume group with supine vasoconstiction, supine tachycardia, pale and cold skins.  Hyperadrenergic state due to norepinephrine transporter (NET) blockade by drugs (TCA's. methylphenidate and related stimulants and others) or secondary to mast cell disorders.  Consider hyperthyroidism or pheochromocytoma in these patients. 

3.  Hypovolemic POTS (28 %).  May be due to low renin/aldosterone secretion or to inappropriately high ACE-2 activity.  May be related to primary GI disorder of N/V/D. 

4. Comorbidities:  Visceral pain and dysmotility, CFS, FM, sleep disorders, myofascial pain, Ehler Danlos syndrome especially type III with variations in tenascin X.  May be related to early onset of chronic pain, with anxiety and sensory amplification state.  Headache with or without CSF leak.