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(Circulation. 1999;100:II-54.)
© 1999 American Heart Association, Inc.

Surgery for Valvular Heart Disease

Deformational Dynamics of the Aortic Root

Modes and Physiologic Determinants

Paul Dagum, MD, PhD; G. Randall Green, MD; Francisco J. Nistal, MD; George T. Daughters, MS; Tomasz A. Timek, MD; Linda E. Foppiano, MD; Ann F. Bolger, MD; Neil B. Ingels, Jr, PhD; D. Craig Miller, MD

From the Department of Cardiovascular and Thoracic Surgery (P.D., G.R.G., F.J.N., G.T.D., T.A.T., N.B.I., D.C.M.), the Division of Cardiovascular Medicine (A.F.B.), and the Department of Anesthesia (L.E.F.), Stanford University School of Medicine; the Cardiology Section (A.F.B.), Department of Veterans Affairs Medical Center; and the Department of Cardiovascular Physiology and Biophysics, Research Institute of the Palo Alto Medical Foundation (G.T.D., N.B.I.), Palo Alto, Calif.

Correspondence to D. Craig Miller, MD, Department of Cardiovascular and Thoracic Surgery, Falk Cardiovascular Research Center, Stanford University School of Medicine, Palo Alto, CA 94305-5247. E-mail dcm{at}leland.stanford.edu

Background—Current surgical methods for treating aortic valve and aortic root pathology vary widely, and the basis for selecting one repair or replacement alternative over another continues to evolve. More precise knowledge of the interaction between normal aortic root dynamics and aortic valve mechanics may clarify the implications of various surgical procedures on long-term valve function and durability.

Methods and Results—To investigate the role of aortic root dynamics on valve function, we studied the deformation modes of the left, right, and noncoronary aortic root regions during isovolumic contraction, ejection, isovolumic relaxation, and diastole. Radiopaque markers were implanted at the top of the 3 commissures (sinotubular ridge) and at the annular base of the 3 sinuses in 6 adult sheep. After a 1-week recovery, ECG and left ventricular and aortic pressures were recorded in conscious, sedated animals, and the 3D marker coordinates were computed from biplane videofluorograms (60 Hz). Left ventricular preload, contractility, and afterload were independently manipulated to assess the effects of changing hemodynamics on aortic root 3D dynamic deformation. The ovine aortic root undergoes complex, asymmetric deformations during the various phases of the cardiac cycle, including aortoventricular and sinotubular junction strain and aortic root elongation, compression, shear, and torsional deformation. These deformations were not homogeneous 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 relaxation, and diastole.

Conclusions—These complex 3D aortic root deformations probably minimize aortic cusp stresses by creating optimal cusp loading conditions and minimizing transvalvular turbulence. Aortic valve repair techniques or methods of replacement using unstented autograft, allograft, or xenograft tissue valves that best preserve this normal pattern of aortic root dynamics should translate into a lower risk of long-term cusp deterioration.

Key Words: aorta • valves • surgery • structure • physiology