In vitro characterization of hemodynamics in bicuspid aortic valves: The impact of valve and ascending aortic morphologies.

PURPOSE: This study investigated the effect of bicuspid aortic valve (BAV) morphology and ascending aortic curvature (AAAc) bending angles on aortic hemodynamics, focusing on transvalvular jets and secondary helical flows that contribute to systolic hemodynamic stress linked to aortic complications.

METHODS

Using an MRI-compatible pulsatile flow and pressure system, 24 configurations involving six aortic valves (three Type 1 asymmetric BAVs, two Type 0 symmetric BAVs, and one tricuspid aortic valve [TAV]) across four ascending aortic morphologies-two diameters (30 mm and 40 mm) and two AAAc angles (130° and 109°)-were analyzed through four-dimensional-flow MRI measurements.

RESULTS

Three Type 1 BAVs displayed highly deviated transvalvular jets directed toward the aortic wall on the side of the nonfused cusp. Particularly, the right-noncoronary and left-noncoronary cusp fusion phenotypes exhibited markedly eccentric secondary helical flows, thereby increasing hemodynamic stress on the ascending aortic wall. A narrower AAAc further amplified these effects by elevating jet velocity and circulation. Conversely, Type 0 BAVs and TAV were suggested to have lower hemodynamic forces, characterized by less-deviated jets and reduced secondary helical flow eccentricity. Aortic dilation, while enhancing secondary flow circulation, appeared to reduce eccentricity, suggesting a compensatory mechanism in response to altered hemodynamics.

CONCLUSION

The combination of the position of the nonfused cusp and AAAc emerges as a critical determinant of secondary helical flow eccentricity and circulation during peak-to-late systole. The risk assessment based on these hemodynamic parameters offers a novel strategy for identifying individuals at elevated risk of future aortic events.