Abstract 13873: Quantitative Characteristics of Left Ventricular Vortex Flow in the Short and Long Axis Views by High Frame Rate Echocardiographic Particle Image Velocimetry

Abstract

Background: Vortex flow in the left ventricle (LV) has three-dimensional structure and plays an important role in avoiding excessive dissipation of energy. However, quantitative characteristics of long and short axis (LAX and SAX) vortex flow have not been elucidated. Echocardiographic particle image velocimetry (Echo-PIV) is an emerging technique to evaluate instantaneous vortical flow inside the LV. However, it has a limitation of underestimation of high velocities due to limited frame rate. Moreover, previous investigations have mainly focused on vortex from LAX view. Therefore, we used high frame rate Echo-PIV to quantitate vortex flow in SAX as well as in LAX views to understand characteristics of vortex three-dimensionally. Methods: Echocardiographic contrast images of the LV SAX and LAX were acquired from 8 open-chest healthy dogs. The acquisition frame rate was 135 frames per second and the contrast bubbles density was optimized for blood flow analysis. Echo-PIV analysis was performed off-line by using commercially available software and vorticity data were calculated in the region of interest (ROI) throughout the cardiac cycle. ROI was manually placed on the vortex. Vortex strength was defined as the averaged vorticity within the ROI. Results: In SAX, counterclockwise vortex was seen near the anterior wall, and in LAX clockwise vortex was seen in the anterior mid-ventricle. Both in SAX and LAX views, vortex strength showed significant phasic variations being largest in isovolumic contraction (vortex strength, SAX 9.2±2.3/s, p<0.001; LAX -12.0±2.4/s, p<0.001), and smallest in isovolumic relaxation (SAX -0.8±0.8/s, p<0.001; LAX -1.9±1.9/s, p<0.001). Conclusion: High frame rate Echo-PIV successfully demonstrated a complicated pattern of intracardiac vortex with phasic variation of its strength throughout a cardiac cycle in both SAX and LAX. This method may be a useful tool to assess physiological role of vortex in the flow dynamics.