title: Changes in circulatory biogenic amines during head-up tilt testing in neurocardiogenic syncope.
abstract: The pathogenesis of neurocardiogenic syncope is not completely understood. To examine the possible role of biogenic amines in patients with neurocardiogenic syncope, 18 consecutive patients (age 30 +/- 13 years, 15 males, 3 females) of unexplained syncope were subjected to Head-Up Tilt Testing (HUTT). Blood was sampled by an indwelling cannula at baseline, end of tilt test (or at syncope) and 1 min after returning to the supine position. Biogenic amines, epinephrine (E), norepinephrine (NE), serotonin (5-HT) and their metabolites, homovanillic acid (HVA) and 5-hydroxy indole acetic acid (5-HIAA), were measured in the serum after serial organic phase extraction by high-performance liquid chromatography (HPLC) using ultraviolet detection at a wavelength of 280 nm. Twelve patients were found to be HUTT negative while 6 patients were HUTT positive. Baseline E, NE and 5-HT levels were significantly greater in the HUTT positive patients [E 510 +/- 154 versus 302 +/- 96 pg/ml (p < 0.01), NE 253 +/- 99 versus 159 +/- 62 pg/ml (p < 0.05), 5-HT 174 +/- 32 versus 118 +/- 22 pg/ml (p < 0.01)]. E and HVA levels at the end of the test were significantly higher in HUTT positive patients [E 788 +/- 268 versus 465 +/- 119 pg/ml (p < 0.01), HVA 308 +/- 91 versus 112 +/- 12 pg/ml (p < 0.001)]. A significantly greater rise of E from the baseline was observed in HUTT positive patients (510 +/- 154 versus 112 +/- 12 pg/ml (p < 0.01)]. The increase in the levels of E and HVA both at baseline and after the tilt test, without a corresponding rise in NE levels indicates enhanced activity of the adrenomedullary axis which is not paralleled by NE release from sympathetic nerve endings in patients of neurocardiogenic syncope.
authors.affiliation: Cardiothoracic Sciences Centre, All India Institute of Medical Sciences, New Delhi.
authors.forename: B
authors.initials: B
authors.lastname: Bhargava
authors.forename: S
authors.initials: S
authors.lastname: Chandra
authors.forename: V
authors.initials: V
authors.lastname: Kacker
authors.forename: Y K
authors.initials: YK
authors.lastname: Gupta
authors.forename: U
authors.initials: U
authors.lastname: Kaul
authors.forename: S D
authors.initials: SD
authors.lastname: Seth
authors.forename: H S
authors.initials: HS
authors.lastname: Wasir
mesh_terms: D000293:Adolescent; D000328:Adult; D001679:Biogenic Amines / Q000097:blood*; D003937:Diagnosis, Differential; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008297:Male; D012016:Reference Values; D019462:Syncope, Vasovagal / Q000097:blood* / Q000503:physiopathology; D018667:Tilt-Table Test
chemical_list: D001679:Biogenic Amines