Determination of flow profiles of different mechanical aortic valve prostheses using phase-contrast MRI.

AIM: After heart valve replacement in aortic position turbulences may occur in the aortic outflow tract. Valve-induced turbulences and retrograde flow represent a loss of efficiency of cardiac output in respect to antegrade kinetic energy of blood flow. Aim of this study is the evaluation of the flow profiles of monoleaflet and bileaflet valves after aortic valve replacement.

METHODS

The flow profiles of three different mechanical aortic heart valve prostheses were compared using phase contrast magnetic resonance imaging (MRI) in vivo. One monoleaflet (group A, 30 patients) was compared with two bileaflet valves (group B, 20 patients, group C, 10 patients). Phase-contrast MRI measurements were taken 3 cm above the valve in the aortic outflow tract. Flow and velocity were evaluated in the aortic cross-section and in nine subregions.

RESULTS

The peak-velocity of Group A was significantly higher (234.79±7.38) than of groups B and C. The right laterodorsal subregion showed significantly higher peak-velocity values in the monoleaflet valve group (group A 196.34±66.94; group B 119.22±75.92; group C 129.26±57.37). In the left lateral subregion group A revealed a significant negative peak velocity, indicating retrograde flow towards the valve. There were no significant differences in the retrograde flow volumes between the three patient groups.

CONCLUSION

Bileaflet valves (groups B and C) have a more homogenous flow profile, lower flow velocities, less retrograde flow and fewer turbulences in the outflow tract of the aortic valve in comparison to the monoleaflet valve (group A).