A four-dimensional study of the aortic root dynamics

• Published in: European journal of cardio-thoracic surgery 2002-10, Vol.22 (4), p.497-503
• Main Authors: Lansac, E., Lim, H.S., Shomura, Y., Lim, K.H., Rice, N.T., Goetz, W., Acar, C., Duran, C.M.G.
• Format: Article
• Language: English
• Subjects: Animals; Aorta - diagnostic imaging; Aorta - physiology; Aortic root expansion; Aortic valve; Aortic Valve - anatomy & histology; Aortic Valve - physiology; Biological and medical sciences; Cardiovascular system; Dynamic anatomy; Echocardiography, Doppler, Color; Imaging, Three-Dimensional; Investigative techniques of hemodynamics; Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Myocardial Contraction - physiology; Rheology; Sheep; Systole
• ISSN: 1010-7940; 1873-734X
• DOI: 10.1016/S1010-7940(02)00405-0

Objective: Although aortic root expansion has been well studied, its deformation and physiologic relevance remain controversial. Three-dimensional (3-D) sonomicrometry (200 Hz) has made time-related 4-D study possible. Methods: Fifteen sonomicrometric crystals were implanted into the aortic root of eight sheep at each base (three), commissures (three), sinuses of Valsalva (three), sinotubular junction (three), and ascending aorta (three). In this acute, open-chest model, the aortic root geometric deformations were time related to left ventricular and aortic pressures. Results: During the cardiac cycle, aortic root volume increased by mean±1 standard error of the mean (SEM) 33.7±2.7%, with 36.7±3.3% occurring prior to ejection. Expansion started during isovolumic contraction at the base and commissures followed (after a delay) by the sinotubular junction. At the same time, ascending aorta area decreased (−2.6±0.4%). During the first third of ejection, the aortic root reached maximal expansion followed by a slow, then late rapid decrease in volume until mid-diastole. During end-diastole, the aortic root volume re-expanded by 11.3±2.4%, but with different dynamics at each area level. Although the base and commissural areas re-expanded, the sinotubular junction and ascending aorta areas kept decreasing. At end-diastole, the aortic root had a truncated cone shape (base area>commissures area by 51.6±2.0%). During systole, the root became more cylindrical (base area>commissures area by 39.2±2.5%) because most of the significant changes occurred at commissural level (63.7±3.6%). Conclusion: Aortic root expansion follows a precise chronology during systole and becomes more cylindrical – probably to maximize ejection. These findings might stimulate a more physiologic approach to aortic valve and aortic root surgical procedures.