Reduced preload elicits increased LV twist in healthy humans: an echocardiographic speckle-tracking study during lower body negative pressure

Clin Physiol Funct Imaging. 2011 Sep;31(5):382-9. doi: 10.1111/j.1475-097X.2011.01029.x. Epub 2011 May 25.

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.

Methods and 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.

MeSH terms

  • Adult
  • Analysis of Variance
  • Biomechanical Phenomena
  • Blood Pressure
  • Heart Ventricles / diagnostic imaging*
  • Humans
  • Lower Body Negative Pressure*
  • Male
  • Myocardial Contraction
  • Rotation
  • Stroke Volume
  • Ultrasonography
  • Ventricular Function, Left*
  • Young Adult