The pathophysiologic mechanisms associated with hypotensive susceptibility.
Patients with vasovagal syncope (VVS) and positive tilt table test (TTT) were not found to benefit from pacing in the ISSUE-3 trial despite the presence of spontaneous asystole during monitoring. "Hypotensive susceptibility" unmasked by TTT was reported as a possible explanation. The purpose of this study was to assess the pathophysiologic mechanisms associated with hypotensive susceptibility.



366 consecutive patients with the diagnosis of VVS who also had TTT were identified. Baroreflex gain (BRG) in addition to blood pressure (BP) and heart rate (HR) responses during the first 20 min of TTT were analyzed and compared between patients with positive TTT (n = 275, 75 %) and negative TTT (n = 91, 25 %).



The mean BRG was similar between the groups (12.5 ± 6.3 versus 12.4 ± 6.3 ms/mmHg, p = 0.72); however, an age-dependent decrease was noted (17.6 ± 4.8, 15.0 ± 6.0, 10.6 ± 4.2, 10.3 ± 6.4 and 9.9 ± 8.5 ms/mmHg for patients <21, 21-40, 41-60, 61-80 and >80 years old, respectively; p < 0.001). In addition, we saw a main effect of age on the type of response with a greater prevalence of a vasodepressor response in older subjects (p < 0.001). During the first 20 min of TTT, BP was similar in patients with tilt-positive VVS when compared with patients with tilt-negative VVS; however, HR was significantly lower.



BRG is similar in tilt-positive VVS patients when compared with tilt-negative VVS patients. An age-dependent decrease in BRG was noted with a higher prevalence of a vasodepressor response seen in older patients. The clinical significance of the blunted HR response in tilt-positive VVS remains to be determined.
Division of Cardiovascular Medicine, School of Medicine and Public Health, University of Wisconsin, H4/534 Clinical Science Center, 600 Highland Avenue, Madison, WI, 53792-3248, USA.
Ashish
A
Chaddha
Geriatric Cardiology and Medicine, University of Florence and Azienda Ospedaliero-Universitaria Careggi, Florence, Italy.
Martina
M
Rafanelli
Ospedali del Tigullio, Lavagna, Italy.
Michele
M
Brignole
National Heart and Lung Institute, Imperial College, London, UK.
Richard
R
Sutton
Division of Cardiovascular Medicine, School of Medicine and Public Health, University of Wisconsin, H4/534 Clinical Science Center, 600 Highland Avenue, Madison, WI, 53792-3248, USA.
Kevin E
KE
Wenzke
Division of Cardiovascular Medicine, School of Medicine and Public Health, University of Wisconsin, H4/534 Clinical Science Center, 600 Highland Avenue, Madison, WI, 53792-3248, USA.
Stephen L
SL
Wasmund
Division of Cardiovascular Medicine, School of Medicine and Public Health, University of Wisconsin, H4/534 Clinical Science Center, 600 Highland Avenue, Madison, WI, 53792-3248, USA.
Richard L
RL
Page
Division of Cardiovascular Medicine, School of Medicine and Public Health, University of Wisconsin, H4/534 Clinical Science Center, 600 Highland Avenue, Madison, WI, 53792-3248, USA. mhamdan@medicine.wisc.edu.
Mohamed H
MH
Hamdan
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D017704:Baroreflex; D001794:Blood Pressure; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate; D006801:Humans; D007022:Hypotension / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D019462:Syncope, Vasovagal / Q000503:physiopathology*; D018667:Tilt-Table Test
Baroreflex gain; Blood pressure; Tilt table test; Vasovagal syncope