neurally mediated syncope

Last edited 08/2021 and last reviewed 05/2023

Neurally mediated syncope is due to:

• excessive parasympathetic tone
• sympathetic suppression

The cardiovascular results of this disorder are:

• bradycardia
• hypotension
• peripheral pooling of blood

The diagnosis of the neurally mediated syncope has been facilitated by the use of the tilt-table test.

Management options include (1):

• midodrine
  • an alpha-agonist vasoconstrictor, affects smooth muscle cells both in arteries and veins without effecting heart rhythm or negative inotropy
  • is no effect on the central nervous system
  • is metabolized to the active drug desglymidodrine
  • is an oral drug that has been shown in the laboratory to moderate some of the physiologic events that precede syncope
  • can reduce the recurrence of syncope in healthy, younger patients with a high syncope burden (2)
• SSRIs (serotonin reuptake inhibitors)
  • SSRIs may reduce the central sympathetic nervous system activity
  • some open-label studies and one randomized, placebo-controlled trial demonstrated that SRI may reduce recurrent vasovagal syncope
  • however Takata et al reported that paroxetine does not prevent the vasovagal reaction associated with carotid sinus massage and/or lower body negative pressure in healthy volunteers (3)

Reference:

1. Aydin MA, Salukhe TV, Wilke I, Willems S. Management and therapy of vasovagal syncope: A review. World J Cardiol. 2010;2(10):308-315. doi:10.4330/wjc.v2.i10.308
2. Sheldon R et al. Midodrine for the prevention of vasovagal syncope. Annals of Internal Medicine; August 3rd 2021.
3. Takata TS, Wasmund SL, Smith ML, Li JM, Joglar JA, Banks K, Kowal RC, Page RL, Hamdan MH. Serotonin reuptake inhibitor (Paxil) does not prevent the vasovagal reaction associated with carotid sinus massage and/or lower body negative pressure in healthy volunteers. Circulation. 2002;106:1500-1504.