title: The type of the functional cardiovascular response to upright posture is associated with arterial stiffness: a cross-sectional study in 470 volunteers.
abstract: In a cross-sectional study we examined whether the haemodynamic response to upright posture could be divided into different functional phenotypes, and whether the observed phenotypes were associated with known determinants of cardiovascular risk.
  
  
  
  Volunteers (n = 470) without medication with cardiovascular effects were examined using radial pulse wave analysis, whole-body impedance cardiography, and heart rate variability analysis. Based on the passive head-up tilt induced changes in systemic vascular resistance and cardiac output, the principal determinants of blood pressure, a cluster analysis was performed.
  
  
  
  The haemodynamic response could be clustered into 3 categories: upright increase in vascular resistance and decrease in cardiac output were greatest in the first (+45 % and -27 %, respectively), smallest in the second (+2 % and -2 %, respectively), and intermediate (+22 % and -13 %, respectively) in the third group. These groups were named as 'constrictor' (n = 109), 'sustainer' (n = 222), and 'intermediate' (n = 139) phenotypes, respectively. The sustainers were characterized by male predominance, higher body mass index, blood pressure, and also by higher pulse wave velocity, an index of large arterial stiffness, than the other groups (p < 0.01 for all). Heart rate variability analysis showed higher supine and upright low frequency/high frequency (LF/HF) ratio in the sustainers than constrictors, indicating increased sympathovagal balance. Upright LF/HF ratio was also higher in the sustainer than intermediate group. In multivariate analysis, independent explanatory factors for higher pulse wave velocity were the sustainer (p < 0.022) and intermediate phenotypes (p < 0.046), age (p < 0.001), body mass index (p < 0.001), and hypertension (p < 0.001).
  
  
  
  The response to upright posture could be clustered to 3 functional phenotypes. The sustainer phenotype, with smallest upright decrease in cardiac output and highest sympathovagal balance, was independently associated with increased large arterial stiffness. These results indicate an association of the functional haemodynamic phenotype with an acknowledged marker of cardiovascular risk.
  
  
  
  ClinicalTrials.gov NCT01742702.
authors.affiliation: School of Medicine, University of Tampere, Tampere, Finland. anna.tahvanainen@fimnet.fi.|School of Medicine / Internal Medicine, FIN-33014 University of Tampere, Tampere, Finland. anna.tahvanainen@fimnet.fi.
authors.forename: Anna M
authors.initials: AM
authors.lastname: Tahvanainen
authors.affiliation: School of Medicine, University of Tampere, Tampere, Finland.
authors.forename: Antti J
authors.initials: AJ
authors.lastname: Tikkakoski
authors.affiliation: School of Medicine, University of Tampere, Tampere, Finland.
authors.forename: Jenni K
authors.initials: JK
authors.lastname: Koskela
authors.affiliation: Department of Mathematics and Statistics, University of Turku, Turku, Finland.
authors.forename: Klaus
authors.initials: K
authors.lastname: Nordhausen
authors.affiliation: School of Medicine, University of Tampere, Tampere, Finland.
authors.forename: Jani M
authors.initials: JM
authors.lastname: Viitala
authors.affiliation: School of Medicine, University of Tampere, Tampere, Finland.
authors.forename: Miia H
authors.initials: MH
authors.lastname: Leskinen
authors.affiliation: School of Medicine, University of Tampere, Tampere, Finland.|Department of Clinical Physiology, Tampere University Hospital, P.O. Box 2000, Tampere, 33521, Finland.
authors.forename: Mika A P
authors.initials: MA
authors.lastname: Kähönen
authors.affiliation: Department of Clinical Physiology, Tampere University Hospital, P.O. Box 2000, Tampere, 33521, Finland.
authors.forename: Tiit
authors.initials: T
authors.lastname: Kööbi
authors.affiliation: School of Medicine, University of Tampere, Tampere, Finland.|Department of Electronics and Communication Engineering, Tampere University of Technology, BioMediTech, Tampere, Finland.
authors.forename: Marko T
authors.initials: MT
authors.lastname: Uitto
authors.affiliation: Department of Electronics and Communication Engineering, Tampere University of Technology, BioMediTech, Tampere, Finland.
authors.forename: Jari
authors.initials: J
authors.lastname: Viik
authors.affiliation: School of Medicine, University of Tampere, Tampere, Finland.|Department of Internal Medicine, Tampere University Hospital, P.O. Box 2000, Tampere, 33521, Finland.
authors.forename: Jukka T
authors.initials: JT
authors.lastname: Mustonen
authors.affiliation: School of Medicine, University of Tampere, Tampere, Finland.|Department of Internal Medicine, Tampere University Hospital, P.O. Box 2000, Tampere, 33521, Finland.
authors.forename: Ilkka H
authors.initials: IH
authors.lastname: Pörsti
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D000367:Age Factors; D000368:Aged; D001341:Autonomic Nervous System / Q000503:physiopathology*; D015992:Body Mass Index; D002302:Cardiac Output; D002307:Cardiography, Impedance; D002318:Cardiovascular Diseases / Q000175:diagnosis / Q000503:physiopathology*; D002319:Cardiovascular System / Q000294:innervation*; D016000:Cluster Analysis; D003430:Cross-Sectional Studies; D005260:Female; D006339:Heart Rate; D006439:Hemodynamics; D006801:Humans; D006973:Hypertension / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D010993:Plethysmography, Whole Body; D011187:Posture; D011237:Predictive Value of Tests; D063177:Pulse Wave Analysis; D018667:Tilt-Table Test; D014655:Vascular Resistance; D059289:Vascular Stiffness; D055815:Young Adult
keywords: Arterial stiffness; Cardiac output; Head-up tilt; Heart rate; Systemic vascular resistance