TITLE:

Sympathetic and baroreceptor reflex function in neurally mediated syncope evoked by tilt.

AUTHOR:

Mosqueda-Garcia R; Furlan R; Fernandez-Violante R; Desai T; Snell M; Jarai Z; Ananthram V; Robertson RM; Robertson D

AUTHOR AFFILIATION:

Syncope Service in the Autonomic Dysfunction Unit, Vanderbilt University Medical Center, Nashville, Tennessee 37232-2195, USA. Rogelio.Mosqueda@mcmail.Vanderbilt.edu

SOURCE:

J Clin Invest 1997 Jun 1;99(11):2736-44

NLM CIT. ID:

97313510

ABSTRACT:

The pathophysiology of neurally mediated syncope is poorly understood. It has been widely assumed that excessive sympathetic activation in a setting of left ventricular hypovolemia stimulates ventricular afferents that trigger hypotension and bradycardia. We tested this hypothesis by determining if excessive sympathetic activation precedes development of neurally mediated syncope, and if this correlates with alterations in baroreflex function. We studied the changes in intraarterial blood pressure (BP), heart rate (HR), central venous pressure (CVP), muscle sympathetic nerve activity (MSNA), and plasma catecholamines evoked by upright tilt in recurrent neurally mediated syncope patients (SYN, 5+/-1 episodes/mo, n = 14), age- and sex-matched controls (CON, n = 23), and in healthy subjects who consistently experienced syncope during tilt (FS+, n = 20). Baroreflex responses were evaluated from changes in HR, BP, and MSNA that were obtained after infusions of phenylephrine and sodium nitroprusside. Compared to CON, patients with SYN had blunted increases in MSNA at low tilt levels, followed by a progressive decrease and ultimately complete disappearance of MSNA with syncope. SYN patients also had attenuation of norepinephrine increases and lower baroreflex slope sensitivity, both during tilt and after pharmacologic testing. FS+ subjects had the largest decrease in CVP with tilt and had significant increases in MSNA and heart rate baroreflex slopes. These data challenge the view that excessive generalized sympathetic activation is the precursor of the hemodynamic abnormality underlying recurrent neurally mediated syncope.

MAIN MESH SUBJECTS:

*Baroreflex
Sympathetic Nervous System/*PHYSIOPATHOLOGY
Syncope, Vasovagal/*PHYSIOPATHOLOGY

ADDITIONAL MESH SUBJECTS:

Adult
Female
Hemodynamics
Human
Male
Posture
Support, Non-U.S. Gov't
Support, U.S. Gov't, P.H.S.

PUBLICATION TYPES:

JOURNAL ARTICLE

LANGUAGE:

Eng

On Sabbatical!

When my office lease expired at the end of 2004, I decided to turn it into a "sabbatical" from my private practice. Many years ago, in my grandfather's 89th year of life, he told me, "John, it is important to smell the roses while you can still smell them." His life gave living a very good reputation. It is also true that the pursuit of that philosophy required my grandfather to to re-open his assay office/ore market in Wickenburg, Arizona as a 75-year-old because he had run a little short of retirement money. Thus, if blessed with his luck and health, I'll be back.. --jjh

On Sabbatical

On Sabbatical!

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