title: Hemodynamic mechanisms underlying prolonged post-faint hypotension.
abstract: OBJECTIVE
  During hypotension induced by tilt-table testing, low presyncopal blood pressure (BP) usually recovers within 1 min after tilt back. However, in some patients prolonged post faint hypotension (PPFH) is observed. We assessed the hemodynamics underlying PPFH in a retrospective study.
  
  
  METHODS
  Seven patients (2 females, aged 31-72 years) experiencing PPFH were studied. PPFH was defined as a systolic BP below 85 mmHg for at least 2 min after tilt back. In 6 out of 7 presyncope was provoked by 0.4 mg sublingual NTG, administered in the 60° head-up tilt position following head-up tilt for 20 min. Continuous BP was monitored and stroke volume (SV) was computed from pressure pulsations. Cardiac output (CO) was calculated from SV × heart rate (HR); and total peripheral resistance (TPR) from mean BP/CO. Left ventricular contractility was estimated by dP/dt                            (max) of finger pressure pulse.
  
  
  RESULTS
  Systolic BP (SYS), diastolic BP (DIAS) and HR during PPFH were lower compared to baseline: SYS 75 ± 14 versus 121 ± 18 mmHg, DIAS 49 ± 9 versus 71 ± 9 mmHg and HR 52 ± 14 versus 67 ± 12 beats/min (p < 0.05). Marked hypotension was associated with a 47% fall in CO 3.1 ± 0.6 versus 5.9 ± 1.3 L/min (p < 0.05) and decreases in dP/dt, 277 ± 77 versus 759 ± 160 mmHg/s (p < 0.05). The difference in TPR was not significant 1.1 ± 0.3 versus 1.0 ± 0.3 MU (p = 0.229). In four patients, we attempted to treat PPFH by 30° head-down tilt. This intervention increased SYS only slightly (to 89 ± 12 mmHg).
  
  
  CONCLUSIONS
  PPFH seems to be mediated by severe cardiac depression.
authors.affiliation: Department of Medicine, Academic Medical Centre, University of Amsterdam, The Netherlands. W.Wieling@amc.uva.nl
authors.forename: Wouter
authors.initials: W
authors.lastname: Wieling
authors.forename: Josien
authors.initials: J
authors.lastname: Rozenberg
authors.forename: Ingeborg K
authors.initials: IK
authors.lastname: Go-Schön
authors.forename: John M
authors.initials: JM
authors.lastname: Karemaker
authors.forename: Berend E
authors.initials: BE
authors.lastname: Westerhof
authors.forename: David L
authors.initials: DL
authors.lastname: Jardine
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006439:Hemodynamics; D006801:Humans; D007022:Hypotension / Q000209:etiology* / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013575:Syncope / Q000503:physiopathology*; D013997:Time Factors