title: Beat-to-beat analysis of pressure wave morphology for pre-symptomatic detection of orthostatic intolerance during head-up tilt.
abstract: OBJECTIVE
  The aim of this study was to noninvasively define the hemodynamic profile characterizing the early response to tilting.
  
  
  BACKGROUND
  The mechanisms causing orthostatic intolerance have not been fully elucidated. Usually, patients undergoing tilt test are studied in a time-consuming way. Moreover, the test can cause discomfort to the patient and even be potentially hazardous.
  
  
  METHODS
  Nineteen orthostatic intolerant patients (OIP), compared with 22 healthy subjects (HS), performed head-up tilt test while their arterial pressure waveform was noninvasively recorded. We elaborated data using the Pressure Recording Analytical Method to obtain hemodynamic parameters, then analyzing the variables by discriminant analysis.
  
  
  RESULTS
  Compared with HS, OIP showed lower stroke volume index (SVI) values even in baseline conditions associated with higher values of systemic vascular resistance (SVR) and heart rate (HR). From the third minute of the tilted position and until symptoms appeared, patients exhibited lower values of blood pressure (BP) and SVI and higher HR values but no difference in SVR. At termination, patients showed a further significant reduction in BP and SVI and a persistent increase in HR.
  
  
  CONCLUSIONS
  This investigation underlines: 1) the possibility of beat-to-beat monitoring of hemodynamic changes during tilting; 2) the cardiovascular profile of OIP at rest, characterized by lower SVI and higher SVR and HR; 3) the maladaptive response to postural challenge of OIP mainly identifiable in impaired vascular regulation; and 4) the possibility of detecting parameters that enable prompt identification of the positive response to tiltingin these patients, thus guiding the duration of the test.
authors.affiliation: Department of Internal Medicine and Cardiology, University of Florence, School of Medicine, Florence, Italy. m.romano@dac.unifi.it
authors.forename: Salvatore M
authors.initials: SM
authors.lastname: Romano
authors.forename: Chiara
authors.initials: C
authors.lastname: Lazzeri
authors.forename: Marco
authors.initials: M
authors.lastname: Chiostri
authors.forename: Gian Franco
authors.initials: GF
authors.lastname: Gensini
authors.forename: Franco
authors.initials: F
authors.lastname: Franchi
mesh_terms: D000328:Adult; D000368:Aged; D001274:Atmospheric Pressure; D001794:Blood Pressure / Q000502:physiology; D004244:Dizziness / Q000503:physiopathology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007024:Hypotension, Orthostatic / Q000503:physiopathology; D007558:Italy; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction / Q000502:physiology; D011187:Posture; D013223:Statistics as Topic; D013318:Stroke Volume / Q000502:physiology; D018667:Tilt-Table Test; D013997:Time Factors; D014655:Vascular Resistance / Q000502:physiology