Abstract 717: Spatial And Temporal Nonuniformity Of The Normal Left Ventricle During Isovolumic Contraction And Ejection By 2D Speckle Tracking Imaging

Background: The main purpose of this study was by novel 2D speckle tracking imaging (STI) to determine regional distribution of circumferential shortening, rotation and torsion (twist) and their relation to area ejection fraction (EF) during isovolumic contraction (IVC) and ejection phases in the normal left ventricle (LV). Methods: Twelve healthy subjects (22 ±3 years) were included. M-mode of atrio-ventricular level was used to describe LV longitudinal shortening, while circumferential strain, rotation and area EF were determined at four different LV short axis levels (basal, papillary, sub-papillary, apical) by STI. LV torsion was calculated as apical minus basal rotation. Results: See figure . During IVC, LV torsion demonstrated an “untwist pattern”, and LV shortened more in longitudinal than in circumferential direction. During ejection, the counter clockwise rotation increased from papillary level towards apex, −0.4 ± 3.3° and 9.6 ± 3.4° (p<0.05), respectively, while circumferential shortening was larger in apex than papillary level, −25.4 ± 5.0 and −19.3 ± 2.4% (p<0.05), respectively. EF increased from papillary level to apex, 52 ± 6.1 % and 65 ± 8.4 % (p<0.05), respectively. Conclusion: This study has showed a regional nonuniform pattern of rotation and circumferential shortening, with corresponding changes in regional EF in normal LV through systole. The increased counter clockwise rotation and circumferential shortening towards apex during ejection may be of mechanistic importance for distribution of blood towards LV outflow tract. The greater extent of longitudinal- than circumferential shortening and untwisting suggest a LV spherical form during IVC.