Deformation Dynamics and Mechanical Properties of the Aortic Annulus by 4-Dimensional Computed Tomography Insights into the Functional Anatomy of the Aortic Valve Complex and Implications for Transcatheter Aortic Valve Therapy

J Am Coll Cardiol. 2012; 59(2):119-127

Hamdan A, Guetta V, Konen E, Goitein O, Segev A, Raanani E, Spiegelstein D, Hay I, Di Segni E, Eldar M, Schwammenthal E

OBJECTIVES: The purpose of this study was to assess deformation dynamics and in vivo mechanical properties of the aortic annulus throughout the cardiac cycle. Understanding dynamic aspects of functional aortic valve anatomy is important for beating-heart transcatheter aortic valve implantation.

METHODS: Thirty-five patients with aortic stenosis and 11 normal subjects underwent 256-slice computed tomography. The aortic annulus plane was reconstructed in 10% increments over the cardiac cycle. For each phase, minimum diameter, ellipticity index, cross-sectional area (CSA), and perimeter (Perim) were measured. In a subset of 10 patients, Young’s elastic module was calculated from the stress-strain relationship of the annulus.

RESULTS: In both subjects with normal and with calcified aortic valves, minimum diameter increased in systole (12.3 ± 7.3% and 9.8 ± 3.4%, respectively; p < 0.001), and ellipticity index decreased (12.7 ± 8.8% and 10.3 ± 2.7%, respectively; p < 0.001). The CSA increased by 11.2 ± 5.4% and 6.2 ± 4.8%, respectively (p < 0.001). Perim increase was negligible in patients with calcified valves (0.56 ± 0.85%; p < 0.001) and small even in normal subjects (2.2 ± 2.2%; p = 0.01). Accordingly, relative percentage differences between maximum and minimum values were significantly smallest for Perim compared with all other parameters. Young’s modulus was calculated as 22.6 ± 9.2 MPa in patients and 13.8 ± 6.4 MPa in normal subjects.

CONCLUSIONS: The aortic annulus, generally elliptic, assumes a more round shape in systole, thus increasing CSA without substantial change in perimeter. Perimeter changes are negligible in patients with calcified valves, because tissue properties allow very little expansion. Aortic annulus perimeter appears therefore ideally suited for accurate sizing in transcatheter aortic valve implantation.

PMID: 22222074

2 Responses

  1. Paul Schoenhagen  on January 25th, 2012

    See also:

    Aortic root dimension changes during systole and diastole: evaluation with ECG-gated multidetector row computed tomography.
    de Heer LM, Budde RP, Mali WP, de Vos AM, van Herwerden LA, Kluin J.
    Int J Cardiovasc Imaging. 2011 Dec;27(8):1195-204.
    PMID: 21359833 http://www.ncbi.nlm.nih.gov/pubmed/21359833

  2. Paul Schoenhagen  on February 13th, 2012

    Aortic annulus dimension assessment by computed tomography for transcatheter aortic valve implantation: differences between systole and diastole.
    Bertaso AG, Wong DT, Liew GY, Cunnington MS, Richardson JD, Thomson VS, Lorraine B, Kourlis G, Leech D, Worthley MI, Worthley SG.
    Int J Cardiovasc Imaging. 2012 Feb 9.
    PMID: 22318541 http://www.ncbi.nlm.nih.gov/pubmed/22318541


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