Aortic root dynamics are asymmetric.
OBJECTIVE
The presence of conformational changes in the aortic root during the cardiac cycle is well known, but precise information on time-related changes at each level of the root is lacking.


METHODS
High-resolution, 3D sonomicrometry (200 Hz) was applied in an acute sheep model. Twelve crystals were implanted in eight sheep at each base (n = 3), commissure (n = 3), sinotubular junction (n = 3) and ascending aorta (n = 3). Under stable hemodynamic conditions, geometric changes of the perimeter of each sinus of Valsalva, sinus height, and twist and root tilt angles were time-related to left ventricluar (LV) and aortic pressures.


RESULTS
Expansion of the perimeter of the three sinuses of Valsalva was homogeneous, but in significantly different proportions (p < 0.001): the right sinus expanded (+32.4 +/- 2.4%) more than the left (+29.3 +/- 3.2%), and more than the non-coronary (NC) sinus (+25.8 +/- 1.7%). A similar pattern was found for aortic root height: right greater than left, and left greater than NC sinus (p < 0.001). This asymmetry resulted in changes of the root's twist and tilt angles. Although the twist deformation was consistent for each sheep, no general pattern was found. The aortic root tilt angle (between the basal plane and the commissural plane) was 16.3 +/- 1.5 degrees at end-diastole (angle oriented posteriorly and to the left). During systole, it was reduced by 6.6 +/- 0.5 degrees, aligning the LV outflow tract with the ascending aorta. This tilt angle returned to its original value after valve closure.


CONCLUSIONS
Aortic root expansion is asymmetric, generating precise changes in its tilt angle. During systole, tilt angle reduction resulted in a straight cylinder that probably facilitates ejection; during diastole, the tilt angle increased, probably reducing leaflet stress. These findings should impact upon surgical procedures and the design of new prostheses.
The International Heart Institute of Montana Foundation at St. Patrick Hospital and Health Sciences Center, The University of Montana, Missoula, Montana 59802, USA.
Emmanuel
E
Lansac
Hou-Sen
HS
Lim
Yu
Y
Shomura
Khee Hiang
KH
Lim
Nolan T
NT
Rice
Wolfgang A
WA
Goetz
Carlos M G
CM
Duran
D000818:Animals; D001011:Aorta / Q000033:anatomy & histology / Q000502:physiology; D001021:Aortic Valve / Q000033:anatomy & histology / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology; D002302:Cardiac Output / Q000502:physiology; D003971:Diastole / Q000502:physiology; D019160:Endosonography / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D023421:Models, Animal; D012756:Sheep; D012850:Sinus of Valsalva / Q000033:anatomy & histology / Q000502:physiology; D013599:Systole / Q000502:physiology; D013997:Time Factors; D016277:Ventricular Function, Left / Q000502:physiology; D017725:Ventricular Pressure / Q000502:physiology