title: Reduced Systolic Volume: Main Pathophysiological Mechanism in Patients with Orthostatic Intolerance?
abstract: BACKGROUND
  Orthostatic intolerance patients' pathophysiological mechanism is still obscure, contributing to the difficulty in their clinical management.
  
  
  OBJECTIVE
  To investigate hemodynamic changes during tilt test in individuals with orthostatic intolerance symptoms, including syncope or near syncope.
  
  
  METHODS
  Sixty-one patients who underwent tilt test at - 70° in the phase without vasodilators were divided into two groups. For data analysis, only the first 20 minutes of tilting were considered. Group I was made up of 33 patients who had an increase of total peripheral vascular resistance (TPVR) during orthostatic position; and Group II was made up of 28 patients with a decrease in TPVR (characterizing insufficient peripheral vascular resistance). The control group consisted of 24 healthy asymptomatic individuals. Hemodynamic parameters were obtained by a non-invasive hemodynamic monitor in three different moments (supine position, tilt 10' and tilt 20') adjusted for age.
  
  
  RESULTS
  In the supine position, systolic volume (SV) was significantly reduced in both Group II and I in comparison to the control group, respectively (66.4 ±14.9 ml vs. 81.8±14.8 ml vs. 101.5±24.2 ml; p<0.05). TPVR, however, was higher in Group II in comparison to Group I and controls, respectively (1750.5± 442 dyne.s/cm5 vs.1424±404 dyne.s/cm5 vs. 974.4±230 dyne.s/cm5; p<0.05). In the orthostatic position, at 10', there was repetition of findings, with lower absolute values of SV compared to controls (64.1±14.0 ml vs 65.5±11.3 ml vs 82.8±15.6 ml; p<0.05). TPVR, on the other hand, showed a relative drop in Group II, in comparison to Group I.
  
  
  CONCLUSIONS
  Reduced SV was consistently observed in the groups of patients with orthostatic intolerance in comparison to the control group. Two different responses to tilt test were observed: one group with elevated TPVR and another with a relative drop in TPVR, possibly suggesting a more severe failure of compensation mechanisms.
authors.affiliation: Hospital de Clínicas, Universidade Federal do Paraná, Curitiba, PR, Brazil.
authors.forename: Maria Zildany P
authors.initials: MZ
authors.lastname: Távora-Mehta
authors.affiliation: Hospital de Clínicas, Universidade Federal do Paraná, Curitiba, PR, Brazil.
authors.forename: Niraj
authors.initials: N
authors.lastname: Mehta
authors.affiliation: Hospital de Clínicas, Universidade Federal do Paraná, Curitiba, PR, Brazil.
authors.forename: Adriano
authors.initials: A
authors.lastname: Magajevski
authors.affiliation: Hospital de Clínicas, Universidade Federal do Paraná, Curitiba, PR, Brazil.
authors.forename: Larissa de
authors.initials: L
authors.lastname: Oliveira
authors.affiliation: Hospital de Clínicas, Universidade Federal do Paraná, Curitiba, PR, Brazil.
authors.forename: Débora Lee Smith
authors.initials: DL
authors.lastname: Maluf
authors.affiliation: Hospital de Clínicas, Universidade Federal do Paraná, Curitiba, PR, Brazil.
authors.forename: Letícia
authors.initials: L
authors.lastname: Concato
authors.affiliation: Hospital de Clínicas, Universidade Federal do Paraná, Curitiba, PR, Brazil.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Doubrawa
authors.affiliation: Hospital de Clínicas, Universidade Federal do Paraná, Curitiba, PR, Brazil.
authors.forename: Márcio Rogério
authors.initials: MR
authors.lastname: Ortiz
authors.affiliation: Hospital de Clínicas, Universidade Federal do Paraná, Curitiba, PR, Brazil.
authors.forename: Cláudio L Pereira da
authors.initials: CL
authors.lastname: Cunha
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000886:Anthropometry; D001794:Blood Pressure / Q000502:physiology*; D016022:Case-Control Studies; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D054971:Orthostatic Intolerance / Q000503:physiopathology*; D012016:Reference Values; D012189:Retrospective Studies; D016683:Supine Position / Q000502:physiology; D013575:Syncope / Q000503:physiopathology; D013599:Systole / Q000502:physiology; D018667:Tilt-Table Test / Q000379:methods*; D013997:Time Factors; D055815:Young Adult