Three-dimensional flow velocity quantification of Freestyle aortic stentless bioprosthesis by magnetic resonance imaging: surgical consideration.

The characteristics in flow dynamics of stentless bioprosthetic valve implanted in aortic position has been reported using Doppler echocardiography and beneficial results have been demonstrated in patients. Because some disturbed flow characteristics were seen clinically with existence of pressure gradient, the nature of flow-velocity characteristics was evaluated in patients receiving Freestyle stentless aortic bioprosthesis using new three-dimensional MRI method. In 19 patients after AVR with Freestyle bioprosthesis, flow-velocity study was conducted using velocity-encoding phase-contrast magnetic resonance imaging (MRI). Three-dimensional flow profiles were reconstructed. The implantation techniques were subcoronary (SC) in 10, root inclusion (Incl) in 6, and full root (FR) in 3 patients. These results were compared to 4 pts with stented bioprosthesis and 4 healthy volunteers. In 3-D flow velocity profiles, there were variations from almost normal pattern to some disturbed flow pattern. All patients of FR showed the parabolic flow pattern nearly equal to normal subjects. Over half of the patients with SC and Incl showed disturbed flow pattern with increased pressure gradient. Although hemodynamically acceptable, Freestyle aortic bioprosthesis showed some degree of flow disturbance in subcoronary or inclusion method with increased transvalvular velocity that may cause late problems, and these findings evaluated by 3-D method should be implicated in surgical consideration.