Increased LV apical untwist during preload reduction in healthy humans. An echocardiographic speckle tracking study during lower body negative pressure (LBNP)

Abstract

Background: We sought to investigate the effect of reduced preload on LV untwist and early diastolic filling in healthy individuals. Methods: Twelve healthy men, 22 (22,23) years of age, were examined at rest and during applied lower body negative pressure (LBNP) of -20 mmHg and -40 mmHg, respectively. Regional untwist and untwist rate during IVRT were calculated at LV basal, papillary, sub-papillary and apical short axis levels by two dimensional speckle tracking echocardiography. LV early diastolic filling was assessed by transmitral E-wave (E) peak velocity by pulsed Doppler and flow propagation velocity (Vp) by color M-mode Doppler and early diastolic pulsed Doppler tissue velocities (E`) from septal and lateral mitral annulus. Results: From rest to LBNP -40 mmHg the LV untwist and untwist rate at sub-papillary level increased from 2.3 (1.4,3.5) to 4.5 (3.1,7.6) degrees and from -36 (-51,-25) to -69 (-127,-42) °/s (p<0.001, p=0.003), respectively, while apical untwist and untwist rate increased from 3.9 (2.3,4.3) to 7.6 (6.4,10.5) degrees and from -51 (-69,-40) to -118 (-170,-84) °/s (p<0.001, p<0.001), respectively. Since untwist and untwist rate at the basal level were unchanged, this created markedly larger base to apical untwist and untwist rate gradients from rest to LBNP -40 mmHg. E, Vp and E` were reduced by 34, 32 and 39 %, respectively. Conclusions: LV untwist and untwist rate during IVRT were increased at apical levels, which might be a physiological mechanism to minimize the impairment in LV early diastolic filling during preload reduction.