The impact of preload reduction with head-up tilt testing on longitudinal and transverse left ventricular mechanics: A study utilizing deformation volume analysis

Abstract

Background: Left ventricular (LV) function is dependent on load, intrinsic contractility and relaxation with a variable impact on specific mechanics. Strain (ε) imaging allows the assessment of cardiac function; however, the direct relationship between volume and strain is currently unknown. The aim of this study was to establish the impact of preload reduction through head-up tilt (HUT) testing on simultaneous left ventricular (LV) longitudinal and transverse function and their respective contribution to volume change. Methods: A focused transthoracic echocardiogram was performed on 10 healthy male participants (23±3 years) in the supine position and following 1min and 5min of HUT testing. Raw temporal longitudinal ε (Ls) and transverse ε (Ts) values were exported and divided into 5% increments across the cardiac cycle and corresponding LV volumes were traced at each 5% increment. This provided simultaneous LV longitudinal and transverse ε and volume loops (deformation volume analysis – DVA). Results: There was a leftward shift of the ε-volume loop from supine to 1min and 5min of HUT (P<0.001). Moreover, longitudinal shortening was reduced (P<0.001) with a concomitant increase in transverse thickening from supine to 1min, which was further augmented at 5min (P=0.018). Conclusions: Preload reduction occurs within 1min of HUT but does not further reduce at 5min. This decline is associated with a decrease in longitudinal ε and concomitant increase in transverse ε. Consequently, augmented transverse relaxation appears to be an important factor in the maintenance of LV filling in the setting of reduced preload. DVA provides information on the relative contribution of mechanics to a change in LV volume and may have a role in the assessment of clinical populations.