Vasovagal syncope and skeletal muscle vasodilatation: The continuing conundrum

N. M. Dietz, Michael Joseph Joyner, J. T. Shepherd

Research output: Contribution to journalArticle

35 Citations (Scopus)

Abstract

During vasovagal syncope, profound bradycardia and hypotension occur. Atropine administration can prevent the bradycardia but not the hypotension, suggesting that marked peripheral vasodilation is a major ca use of the fall in arterial pressure. This concept has been confirmed since vasovagal syncope can be seen in patients who have undergone heart transplantation and also in patients subject to cardiac pacing. In both cases, there is no bradycardia but hypotension during the syncopal attacks. The major site of the vasodilation is in skeletal muscle and muscle sympathetic nerve activity is suppressed just prior to and during vasovagal attacks, indicating that sympathetic withdrawal contributes to the dilation. However, the skeletal muscle vasodilation seen during syncope is greater than that caused by sympathetic withdrawal alone, and it is absent in limbs that have undergone surgical sympathectomy, or local anesthetic nerve block. These observations suggest a role for neurally mediated 'active' vasodilation during syncope. The afferent neural pathways that evoke the profound vasodilation during vasovagal attacks remain the subject of debate. The neural pathways responsible for the active component of the dilation are also unknown. Recent evidence has demonstrated that cholinergic, β-adrenergic, and nitroxidergic (nitric oxide) vasodilator mechanisms are not essential to observe the dilation, demonstrating that the mechanisms responsible for it remain a continuing conundrum.

Original languageEnglish (US)
Pages (from-to)775-780
Number of pages6
JournalPACE - Pacing and Clinical Electrophysiology
Volume20
Issue number3 II SUPPL.
DOIs
StatePublished - 1997

Fingerprint

Vasovagal Syncope
Vasodilation
Skeletal Muscle
Bradycardia
Hypotension
Dilatation
Neural Pathways
Syncope
Afferent Pathways
Sympathectomy
Nerve Block
Heart Transplantation
Local Anesthetics
Vasodilator Agents
Atropine
Adrenergic Agents
Cholinergic Agents
Arterial Pressure
Nitric Oxide
Extremities

Keywords

  • skeletal muscle dilatation
  • vasovagal syncope

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine

Cite this

Vasovagal syncope and skeletal muscle vasodilatation : The continuing conundrum. / Dietz, N. M.; Joyner, Michael Joseph; Shepherd, J. T.

In: PACE - Pacing and Clinical Electrophysiology, Vol. 20, No. 3 II SUPPL., 1997, p. 775-780.

Research output: Contribution to journalArticle

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