Abstract 10992: Left Atrial Volume is Associated With the Intra-left Atrial Vortex Formation: Analysis With Phase-resolved Three-dimensional Cine Phase Contrast MRI (4D-Flow MRI)

Background: The intra-left atrial (LA) blood flow from pulmonary veins (PVs) to the left ventricle (LV) changes under various conditions and may contribute to global cardiac function and thrombogenesis. 4D-Flow MRI can visualize velocity vectors of intra-cardiac blood flow. We aimed to examine the characteristics of intra-LA flow dynamics and factors that affect it using 4D-Flow MRI. Methods: Thirty two patients with and without organic heart diseases (59±14 years) underwent 4D-Flow MRI with routine cardiac MRI, and trans-thoracic echocardiography (TTE). Four planes were set to traverse each exit of PVs, and the intra-LA velocity vectors from each PV were post-processed to delineate streamline images during a cardiac cycle. The flow direction from each PV into LA was also analyzed. Results: (1) The streamline images revealed the intra-LA vortex formation in 20 patients but did not in 12 patients. The representative images are shown in Figure. All the vortices showed characteristic counter-clockwise flow patterns when viewed from the cranial side. The streamlines from the right PVs lengthened predominantly toward the vortex and partly toward LV, whereas those from the left PVs joined the vortex periphery or retained near the LA wall (arrows). (2) The LV end-diastolic volume (LVEDV), end-systolic volume (LVESV) in cine-CMR and LA volume in TTE were less in patients with vortex than in those without vortex (LVEDV: 104±34 ml vs. 155±67 ml, LVESV: 46±28 ml vs. 88±59 ml, and LA volume: 37±13 ml vs. 59±16 ml, respectively, means±SD, p Conclusions: Streamline images derived from 4D-Flow MRI can clearly depict the intra-LA vortex formation. The vortex formation was dependent on the LA volume, but not on the flow direction from PVs.