Three dimensional flow in the human left atrium

Background-Abnormal flow patterns in the left atrium in atrial fibrillation or mitral stenosis are associated with an increased risk of thrombosis and systemic embolisation; the characteristics of normal atrial flow that avoi d stasis have not been well defined. Objectives-To present a three dimensional particle trace visualisation of n ormal left atrial flow in vivo, constructed from flow velocities in three d imensional space. Methods-Particle trace visualisation of time resolved three dimensional mag netic resonance imaging velocity measurements was used to provide a display of intracardiac flow without the limitations of angle sensitivity or restr iction to imaging planes. Global flow patterns of the left atrium were stud ied in I I healthy volunteers. Results-In all subjects vortical flow was observed in the atrium during sys tole and diastolic diastasis (mean (SD) duration of systolic vortex, 280 (7 7) ins; and of diastolic vortex, 256 (118) ms). The volume incorporated and recirculated within the vortices originated predominantly from the left pu lmonary veins. Inflow from the right veins passed along the vortex peripher y, constrained between the vortex and the atrial wall. Conclusions-Global left atrial flow in the normal human heart comprises con sistent patterns specific to the phase of the cardiac cycle. Separate paths of left and right pulmonary venous inflow and vortex formation may have be neficial effects in avoiding left atrial stasis in the normal subject in si nus rhythm.