Bicuspid aortic valves undergo excessive strain during opening: a simulation study.
OBJECTIVE
The objective of this study was to examine the influence of the morphologic characteristics of the bicuspid aortic valve on its disease progression by comparing the motion, stress/strain distribution, and blood flow of normal and stenotic tricuspid valves using simulation models.


METHODS
Bicuspid, stenotic tricuspid with commissural fusion or thickened leaflet, and normal aortic valves were modeled with internal blood flow. Blood flow and the motion of aortic valve leaflets were studied using fluid-structure interaction finite element analysis, and stress/strain (curvature) distributions were calculated during the cardiac cycle. To mimic disease progression, we modified the local thickness of the leaflet where the bending stress was above a threshold.


RESULTS
Transvalvular pressure gradient was greater in the bicuspid valve compared with the stenotic tricuspid valve with a similar valvular area. The bending strain (curvature) increased in both stenotic tricuspid and bicuspid valves, but a greater increase was observed in the bicuspid valve, and this was concentrated on the midline of the fused leaflets. During disease progression analysis, severity of the stenosis increased only in the bicuspid aortic valve model in terms of valvular area and pressure gradient.


CONCLUSIONS
The characteristic morphology of the bicuspid valve creates excessive bending strain on the leaflets during ventricular ejection. Such mechanical stress may be responsible for the rapid progression of this disease.
Department of Human and Engineered Environmental Studies, School of Frontier Sciences, The University of Tokyo, Tokyo, Japan.
Susumu
S
Katayama
Nobuyuki
N
Umetani
Toshiaki
T
Hisada
Seiryo
S
Sugiura
D001024:Aortic Valve Stenosis / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D001783:Blood Flow Velocity; D018450:Disease Progression; D020342:Finite Element Analysis; D006801:Humans; D008943:Mitral Valve / Q000502:physiology*; D008955:Models, Cardiovascular; D011312:Pressure; D012720:Severity of Illness Index; D013312:Stress, Physiological