title: Reduced preload elicits increased LV twist in healthy humans: an echocardiographic speckle-tracking study during lower body negative pressure.
abstract: BACKGROUND
  In normal left ventricles (LV), counterclockwise rotation (CCR) and net twist angle (NTA) have shown important roles during ejection. We investigated the effect of reduced preload by lower body negative pressure (LBNP) on CCR and NTA.
  
  
  RESULTS
  Twelve healthy men were examined at rest, LBNP -20 and -40 mmHg. By two-dimensional speckle-tracking imaging, we measured rotation at four short-axis levels: basal, papillary, sub-papillary and apical. LV NTA was calculated as apex-to-base difference in rotation. Additionally, regional end-diastolic (EDA) and end-systolic area (ESA) were measured and regional area fraction (RAF) calculated [(EDA-ESA)/EDA] × 100). From rest to LBNP -40 mmHg, rotation at basal and papillary levels was unchanged. At sub-papillary level, rotation increased from 3·2 ± 3·6 to 5·8 ± 4·7° (P<0·05), while apical rotation increased from 9·3 ± 3·4 to 12·8 ± 4·7° (P<0·05). Correspondingly, LV NTA increased for each load reduction by 1·6 ± 1·8° (P<0·05) and 4·2 ± 2·3° (P<0·05). RAF increased at sub-papillary and apical levels from 57·6 ± 3·7 to 64·7 ± 8·8% and from 63·4 ± 8·8 to 74·8 ± 10·1%, respectively (P<0·05). From rest to LBNP -40 mmHg, changes in rotation and RAF correlated significantly at sub-papillary and apical levels (r = 0·94, P<0·01, and r = 0·63, P<0·05, respectively).
  
  
  CONCLUSIONS
  Preload reduction in normal LV elicits increased systolic CCR and regional area fraction at sub-papillary and apical levels as well as net twist angle. These findings might be of physiological importance to minimize reduction in stroke volume and maintain arterial blood pressure.
authors.affiliation: Department of Cardiology, Oslo University Hospital Aker and Faculty of Medicine, University of Oslo, Oslo, Norway. anders.hodt@medisin.uio.no
authors.forename: Anders
authors.initials: A
authors.lastname: Hodt
authors.forename: Jonny
authors.initials: J
authors.lastname: Hisdal
authors.forename: Marie
authors.initials: M
authors.lastname: Stugaard
authors.forename: Einar
authors.initials: E
authors.lastname: Stranden
authors.forename: Dan
authors.initials: D
authors.lastname: Atar
authors.forename: Kjetil
authors.initials: K
authors.lastname: Steine
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D001794:Blood Pressure; D006352:Heart Ventricles / Q000000981:diagnostic imaging*; D006801:Humans; D008150:Lower Body Negative Pressure; D008297:Male; D009200:Myocardial Contraction; D012399:Rotation; D013318:Stroke Volume; D014463:Ultrasonography; D016277:Ventricular Function, Left; D055815:Young Adult