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You are here: Contents > 2012 > Volume 21 Number 3 May 2012 > AORTIC VALVE DISEASE > Correlation of Calcification on Excised Aortic Valves by Micro-Computed Tomography with Severity of Aortic Stenosis

Correlation of Calcification on Excised Aortic Valves by Micro-Computed Tomography with Severity of Aortic Stenosis

Sam Chitsaz, Namrata Gundiah, Charlie Blackshear, Nebiyu Tegegn, Kimberly S. Yan, Ali N. Azadani, Michael Hope, Elaine E. Tseng

Department of Surgery, University of California at San Francisco and San Francisco Veterans Affairs Medical Center, San Francisco California, USA, Department of Mechanical Engineering, Indian Institute of Science, Bangalore, India Department of Radiology, University of California at San Francisco, San Francisco, California, USA

Background and aim of the study: The quantification of incidentally found aortic valve calcification on
computed tomography (CT) is not performed routinely, as data relating to the accuracy of aortic valve calcium for estimating the severity of aortic stenosis (AS)
is neither consistent nor validated. As aortic valve calcium quantification by CT is confounded by wall and coronary ostial calcification, as well as motion artifact, the ex-vivo micro-computed tomography (micro-CT) of stenotic aortic valves allows a precise measurement of the amounts of calcium present. The study aim, using excised aortic valves from patients with confirmed AS, was to determine if the amount of calcium on micro-CT correlated with the severity of AS.
Methods: Each of 35 aortic valves that had been excised from patients during surgical valve replacement were examined using micro-CT imaging. The amount of calcium present was determined by absolute and proportional values of calcium volume in the specimen. Subsequently, the correlation between calcium volume and preoperative mean aortic valve gradient (MAVG), peak transaortic velocity (Vmax), and aortic valve area (AVA) on echocardiography, was evaluated.

Results: The mean calcium volume across all valves was 603.2 ± 398.5 mm3, and the mean ratio of calcium volume to total valve volume was 0.36 ± 0.16. The mean aortic valve gradient correlated positively with both calcium volume and ratio (r = 0.72, p <0.001). Vmax also correlated positively with the calcium
volume and ratio (r = 0.69 and 0.76 respectively;
p <0.001). A logarithmic curvilinear model proved to be the best fit to the correlation. A calcium volume of 480 mm3 showed sensitivity and specificity of 0.76 and 0.83, respectively, for a diagnosis of severe AS, while a calcium ratio of 0.37 yielded sensitivity and specificity of 0.82 and 0.94, respectively.
Conclusion: A radiological estimation of calcium amount by volume, and its proportion to the total valve volume, were shown to serve as good predictive parameters for severe AS. An estimation of the calcium volume may serve as a complementary measure for determining the severity of AS when aortic valve calcification is identified on CT imaging.

The Journal of Heart Valve Disease 2012;21:320-327

Correlation of Calcification on Excised Aortic Valves by Micro-Computed Tomography with Severity of Aortic Stenosis

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