Document Detail

Elevated parasympathetic nerve tone in isoproterenol-induced neurally mediated syncope during head-up tilt testing.
MedLine Citation:
PMID:  11316131     Owner:  NLM     Status:  MEDLINE    
To clarify the autonomic nerve mechanisms whereby isoproterenol induces vasovagal reaction, 32 patients with recurrent syncopal episodes of unknown origin underwent head-up tilt testing. Syncope was induced in 11 patients by a control tilt (control/+ group). The remaining 21 patients (control/- group) underwent the procedure during isoproterenol infusion. Syncope was induced in 13 (isoproterenol/+ group), but not in the remaining 8 patients (isoproterenol/- group). High-frequency component (HF) and low-frequency component (LF)/HF, which are indices of heart rate variability, were assessed for 2-min intervals at baseline (T1) during the initial phase (T2) and at the end (T3) of tilting in each test. The ratios of HF and LF/HF at T2/T1 and T3/T2 were calculated. The HF value at T3 in the control/+ group was greater than that in the control/- group (1.47+/-0.91 vs 0.75+/-0.34; p<0.05). The HF value at T3 in the isoproterenol/+ group was significantly greater than those in the isoproterenol/- group (1.19+/-1.04 vs 0.43+/-0.23; p<0.05). The HF value at T2 in the isoproterenol/+ tended to be greater than in the isoproterenol/- group (1.30+/-0.85 vs 0.66+/-0.53; p=0.07). The ratio of HF for T2/T1 in isoproterenol/+ was greater than in the other groups (2.04+/-1.26 in isoproterenol/+ vs 0.58+/-0.39 in control/-, 0.47+/-0.18 in control/+ and 0.71+/-0.45 in isoproterenol/-; p=0.0001), whereas that of HF for T3/T2 in the control/+ group was greater than in the other groups (1.48+/-0.62 in control/+ vs 0.97+/-0.33 in control/-; p<0.05, 0.79+/-0.35 in isoproterenol/- and 0.88+/-0.37 in isoproterenol/+; p<0.01). No difference was observed in either LF/HF or the ratio of LF/HF among the groups. The early and persistent increase in parasympathetic nerve tone provoked by isoproterenol plays an important role in enhancing the vasovagal reaction during head-up tilt testing.
A Takei; Y Ohnishi; M Yokoyama
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Japanese circulation journal     Volume:  65     ISSN:  0047-1828     ISO Abbreviation:  Jpn. Circ. J.     Publication Date:  2001 Apr 
Date Detail:
Created Date:  2001-04-23     Completed Date:  2001-09-20     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  7806868     Medline TA:  Jpn Circ J     Country:  Australia    
Other Details:
Languages:  eng     Pagination:  320-4     Citation Subset:  IM    
First Department of Internal Medicine, Kobe University School of Medicine, Japan.
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MeSH Terms
Adrenergic beta-Agonists / diagnostic use*
Afferent Pathways / physiopathology
Blood Pressure / drug effects
Electrocardiography, Ambulatory
Heart Rate* / drug effects
Isoproterenol / diagnostic use*
Mechanoreceptors / physiology
Middle Aged
Parasympathetic Nervous System / physiopathology*
Sympathetic Nervous System / drug effects,  physiopathology
Syncope, Vasovagal / chemically induced,  diagnosis,  etiology,  physiopathology*,  ultrasonography
Tilt-Table Test*
Vagus Nerve / physiopathology
Reg. No./Substance:
0/Adrenergic beta-Agonists; 7683-59-2/Isoproterenol

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