ALTERATIONS IN PULMONARY-ARTERY FLOW PATTERNS AND SHEAR STRESS DETERMINED WITH 3-DIMENSIONAL PHASE-CONTRAST MAGNETIC-RESONANCE-IMAGING IN FONTAN PATIENTS

Objectives: This study compares in vivo pulmonary blood how patterns a nd shear stresses in patients with either the direct atrium-pulmonary artery connection or the bicaval tunnel connection of the Fontan proce dure to those in normal volunteers, Comparisons were made with the use of three-dimensional phase contrast magnetic resonance imaging, Metho ds: Three-dimensional velocities, flows, and pulmonary artery cross-se ctional areas were measured in both pulmonary arteries of each subject , Axial, circumferential, and radial shear stresses were calculated wi th the use of velocities and estimates of viscosity. Results: The axia l velocities mere not significantly different between subject groups, However, the flows and cross-sectional areas were higher in the normal group than in the two patient groups in both pulmonary arteries, The group with the bicaval connection had circular swirling in the cross s ection of both pulmonary arteries, causing higher shear stresses than in the controls, The disorder caused by the connection of the atrium t o the pulmonary artery caused an increase in some shear stresses over the controls, but not higher than those found in the group having a bi caval tunnel, Conclusions: We found that pulmonary how was equally red uced compared with normal flow in both patient groups, This reduction in how can be attributed in part to the reduced size of the pulmonary arteries in both patient groups without change in axial velocity. We a lso found higher shear stress acting on the wall of the vessels in the patients having a bicaval tunnel, which may alter endothelial functio n and affect the longevity of the repair.