Deformational dynamics of the aortic root - Modes and physiologic determinants

Background-Current surgical methods for treating aortic valve and aortic ro ot pathology vary widely, and the basis for selecting one repair or replace ment alternative over another continues to evolve. More precise knowledge o f the interaction between normal aortic root dynamics and aortic valve mech anics may clarify the implications of various surgical procedures on long-t erm valve function and durability. Methods and Results-To investigate the role of aortic root dynamics on valv e function, we studied the deformation modes of the left, right, and noncor onary aortic root regions during isovolumic contraction, ejection, isovolum ic relaxation, and diastole. Radiopaque markers were implanted at the top o f the 3 commissures (sinotubular ridge! and at the annular base of the 3 si nuses in 6 adult sheep. After a 1-week recovery, ECG and left ventricular a nd aortic pressures were recorded in conscious, sedated animals, and the 3D marker coordinates were computed from biplane videofluorograms (60 Hz). Le ft ventricular preload, contractility, and afterload were independently man ipulated to assess the effects of changing hemodynamics on aortic root 3D d ynamic deformation. The ovine aortic root undergoes complex, asymmetric def ormations during the various phases of the cardiac cycle, including aortove ntricular and sinotubular junction strain and aortic root elongation, compr ession shear, and torsional deformation. These deformations were not homoge neous among the left, right, and noncoronary regions. Furthermore, changes in left ventricular volume, pressure, and contractility affected the degree of deformation in a nonuniform manner in the 3 regions studied, and these effects varied during isovolumic contraction, ejection, isovolumic relaxati on, and diastole. Conclusions-These complex 3D aortic root deformations probably minimize aor tic cusp stresses by creating optimal cusp loading conditions and minimizin g transvalvular turbulence. Aortic valve repair techniques or methods of re placement using unstented autograft, allograft, or xenograft tissue valves that best preserve this normal pattern of aortic root dynamics should trans late into a lower risk of long-term cusp deterioration.