Influence of the Measurement Plane on Aortic Annulus Indices: Structural and Clinical Implications

Research paper by Maximilian Kütting, Alexander Sedaghat, Araceli White Tapia, Jan Roggenkamp, Nikos Werner, Thomas Schmitz-Rode, Ulrich Steinseifer

Indexed on: 24 May '13Published on: 24 May '13Published in: Cardiovascular engineering and technology


Sizing of transcatheter heart valves relies on the proper determination of the annulus size. Current methods of annulus measurement do not take the angular variability of the annulus structure into consideration. This variability can lead to measurement errors, if the measurement plane is tilted during anatomical analyses. Virtually tilting the measurement plane simulates the influence of operator error during measurement and explores angular variability of the aortic root. Using pre-procedural CT-data of patients referred for transcatheter heart valve implantation, three-dimensional models of the aortic root were created using the programs MIMICS and 3Matic (Materialise, Leuven, Belgium). 9 models were selected based on image resolution and quality. The measurement plane to determine the annulus was tilted in 5° steps and the effect on the determined annulus area, circumference and major axis were assessed. The changes in annulus area, major axis and circumference resulting from measurement plane tilting are statistically significant. The effect is most prominent when determining the major axis, with 5° of tilt leading to changes of up to 9.34% and 10° of tilting leading to changes of up to 18.71%. The effects of measurement plane tilting lead to a different choice in valve prosthesis size in 33% of cases for 5° of tilt and 66% of cases for 10°. The influence of measurement plane tilting is a factor that should be considered in the planning of TAVI procedures in order to consider both post-implantation prosthesis angulation and possible measurement errors.

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