Multiplanar visualization of blood flow using echocardiographic particle imaging velocimetry.

E C H O C A R D I O G R A P H I C P A R T I C L E I M A G I N G V E L O C I M E T R Y ( E C H O P I V ) is noninvasive technique where acoustic reflections from ultrasound contrast agents are tracked frame by rame for characterizing 2-dimensional cardiac and vascular flow fields. Three-dimensional asymmetries in ow sequence can be interpreted by using multiplanar reconstructions of echo-PIV images obtained by iplane echocardiography (Fig. 1, Online Videos 1, 2, and 3). For example, the sequence of flow in a normal eft ventricle (LV) (Fig. 2, Online Video 4) is consistent with the formation of asymmetric toroidal vortex ring n early diastole (Online Video 5). The asymmetric vortex is cleared in systole as blood is ejected through a arrow jet in the LV outflow with surrounding shear layers (Fig. 3, Online Video 4). Asymmetry of filling ortex and shear layers during ejection explain previously reported Doppler recordings of skewed velocity istributions in the LV cavity (1). The left atrial (LA) flow (Fig. 4, Online Video 6) illustrates the presence of ultiple small circulating vortices. The jet from the right upper pulmonary vein passes peripherally along the all with minimal entrainment. The vortices in the cavity vanish with the onset of mitral valve opening. The resence of multiple transient vortices in the normal subject may have beneficial effects in avoiding LA stasis n sinus rhythm. Flow in the descending thoracic aorta (Fig. 5, Online Video 7) shows skewed axial velocity rofiles. Although high velocity forward motion is underestimated, retrograde streaming in systole is isualized. In addition, strong secondary recirculating flows are seen in diastole. Presence of flow asymmetry nd retrograde flow from descending thoracic aorta has been recently identified as a potential pathway for etrograde cerebral embolism of plaques formed in descending thoracic aorta (2).