Abstract 2237: Left Ventricular Systolic Torsion by 2-D Speckle Tracking Imaging is Load Dependent
Background: 2-D ultrasound speckle tracking imaging (STI) is a promising tool to assess LV rotation and torsion non-invasively, and correlates well with MRI tagging. The effect of preload on LV torsion is controversial. To explore this issue, we studied 12 healthy men by lower body negative pressure (LBNP).
Methods: LBNP was applied using a chamber enclosing lower body to reduce central venous pressure and preload. LBNP at −40 mmHg corresponds to reduction in capillary wedge pressure of about 4 mmHg. At baseline and LBNP at −20 and −40 mmHg, LV basal and apical short axes images were acquired to measure LV rotation by STI. LV torsion was defined as difference of LV rotation between apex and base. Stroke volume (SV) was measured by pulsed Doppler in LV outflow tract. LV areas were calculated from endocardial traces of short axis images.
Results: See table⇓. By multiple regression the only independent predictor of changes in peak systolic torsion was changes in SV, r = 0.59, r2 = 0.35, p < 0.05. The figure⇓ shows representative area/torsion loops at baseline (solid line) and LBNP at −40 mmHg (broken line).
Conclusion: Peak systolic torsion was significantly reduced, corresponding to a decrease in SV. Reduction of torsion seems to be caused by a decrease in apical rotation. Reduction in preload results in left and downward shift of the area/torsion loop, which indicates that loading is important for LV torsion.