title: Preload dependency of left ventricular torsion: the impact of normal saline infusion.
abstract: BACKGROUND
  left ventricular (LV) rotation results from contraction of obliquely oriented myocardial fibers. The net difference between systolic apical counterclockwise rotation and basal clockwise rotation is left ventricular torsion (LVT). Although LVT is altered in various cardiac diseases, determinants of LVT are incompletely understood.
  
  
  RESULTS
  LV end-diastolic volume, LV apical and basal rotation, peak systolic LVT, and peak early diastolic untwisting rate were measured by speckle-tracking echocardiography in healthy subjects (n=8) before and after infusion of a weight-based normal saline bolus (2.1±0.3 L). Saline infusion led to a significant increase in end-diastolic LV internal diameter (45.9±3.7 versus 47.6±4.2 mm; P=0.002) and LV end-diastolic volume (90.0±21.6 versus 98.3±19.6 mL; P=0.01). Stroke volume (51.3±10.9 versus 63.0±15.5 mL; P=0.003) and cardiac output (3.4±0.8 versus 4.4±1.5 L/min; P=0.007) increased, whereas there was no change in heart rate and blood pressure. There was a significant increase in the magnitude of peak systolic apical rotation (7.5±2.4° versus 10.5±2.8°; P<0.001) but no change in basal rotation (-4.1±2.3° versus -4.8±3.1°; P=0.44). Accordingly, peak systolic LVT increased by 33% after saline infusion (11.2±1.3° versus 14.9±1.7°; P<0.001). This saline-induced increase in LVT was associated with a marked increase in peak early diastolic untwisting rate (72.3±21.4 versus 136.8±30.0 degrees/s; P<0.001).
  
  
  CONCLUSIONS
  peak systolic LVT and peak early diastolic untwisting rate are preload-dependent. Changes in LV preload should be considered when interpreting results of future LVT studies.
authors.affiliation: Division of Cardiology, Massachusetts General Hospital, Boston, Mass., USA.
authors.forename: Rory B
authors.initials: RB
authors.lastname: Weiner
authors.forename: Arthur E
authors.initials: AE
authors.lastname: Weyman
authors.forename: Abigail May
authors.initials: AM
authors.lastname: Khan
authors.forename: Jason S
authors.initials: JS
authors.lastname: Reingold
authors.forename: Annabel A
authors.initials: AA
authors.lastname: Chen-Tournoux
authors.forename: Marielle
authors.initials: M
authors.lastname: Scherrer-Crosbie
authors.forename: Michael H
authors.initials: MH
authors.lastname: Picard
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Wang
authors.forename: Aaron L
authors.initials: AL
authors.lastname: Baggish
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D002306:Cardiac Volume / Q000187:drug effects; D018618:Echocardiography, Doppler, Color / Q000379:methods; D005260:Female; D006352:Heart Ventricles / Q000000981:diagnostic imaging; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007262:Infusions, Intravenous; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D015588:Observer Variation; D012016:Reference Values; D012965:Sodium Chloride / Q000494:pharmacology*; D014102:Torsion Abnormality / Q000000981:diagnostic imaging* / Q000628:therapy*; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging* / Q000503:physiopathology; D016277:Ventricular Function, Left / Q000187:drug effects*
chemical_list: D012965:Sodium Chloride
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