Methods

From October 2012 to December 2014, consecutive patients who underwent TAVI at 4 heart centers in Asia and Europe (Asan Medical Center, Korea; Saiseikai Yokohama City Eastern Hospital, Japan; National Taiwan University Hospital, Taiwan; and Ferrarotto Hospital, Italy) were enrolled. Exclusion criteria were as follows: patients who did not undergo preprocedural MDCT; patients underwent TAVI for bicuspid aortic valve; patients underwent valve-in-valve TAVI for degenerated bioprostheses. Finally, 308 patients were included and compared between Asian group (patients from Asan Medical Center, Saiseikai Yokohama City Eastern Hospital, and National Taiwan University Hospital) and Caucasian group (patients from Ferrarotto Hospital).

In each center, the heart team determined TAVI eligibility on the basis of a systematic assessment with clinical condition as well as angiography, computed tomography, and echocardiography information. For the current analysis, patient data were pooled from 4 institutions, and all computed tomography Digital Imaging and Communications in Medicine data were collected and retrospectively analyzed at core laboratory in Asan Medical Center. Data collection was approved by the institutional review board at each center, and all patients provided written informed consent for analysis of their anonymized data.

All measurements of aortic root dimension were performed by SHY and DHY using 3mensio Structural Heart software (3mensio Structural Heart, version 6.0; 3mensio Medical Imaging BV, Bilthoven, The Netherlands), as previously described. Three-dimensional MDCT annulus measurements included minimal diameter, maximal diameter, area, and perimeter. Annular eccentricity was described using the ellipticity index, defined as maximal diameter divided by minimal diameter. Aortic root measurements were performed as previously described. In brief, the left ventricular outflow tract (LVOT) was defined as the plane 5 mm inferior to the annulus plane; the sinus was defined as the plane showing the largest cusp dimensions; the sinotubular junction defined as the distal end of the sinus portion; and the ascending aorta was defined as 30 mm superior to the annulus plane. All aortic root measurements were performed in midsystole. Retrieved from 20 randomly selected data files, annulus area measurements were performed by another observer to determine interobserver agreement and by the same observers subsequently to determine intraobserver agreement. All observers were blinded to previous measurements. Lower height of left coronary artery ostia was determined as <12 mm, and small sinus of Valsalva was determined as left coronary cusp diameter <30 mm according to reported study.

For the assessment of calcification, calcium volume was measured using 3mensio Structural Heart software with the thresholds of 850 Hounsfield units. Calcium in left, right, and noncoronary cusp was quantified separately using the “Mercedes Benz” tool for localization. For the calcium quantification, the aortic root was separated in the craniocaudal axis along the double oblique long axis of the aortic root into the following parts: leaflet (from annulus plane to superior edge of leaflets); LVOT (from 5 mm inferior to annulus plane to annulus plane); and aortic root (from 5 mm inferior to annulus plane to superior edge of leaflets), as previously described. Asymmetry was assessed using the maximum absolute difference in calcium volume between any 2 leaflets.

For the analysis of device sizing, the appropriate size was selected according to the published data for Edwards SAPIEN XT transcatheter heart valve and Medtronic CoreValve. Briefly, device sizing for SAPIEN XT was based on a sizing algorithm with an optimal goal of modest annulus area oversizing (5% to 10%) with upper and lower limits of 1% to 20%. When >20% area oversizing was anticipated, intentional underexpansion of the device was suggested. Device sizing for Medtronic CoreValve was based on manufacture’s recommendation: annulus area of 254.5 to 314.2 mm2, 314.2 to 415.5 mm2, 415.5 to 572.6 mm2, and 530.9 to 660.5 mm ² for the 23-, 26-, 29-, and 31-mm CoreValve prosthesis.

Continuous variables are presented as mean ± standard deviation, whereas categorical variables are expressed as counts and percentages. Between-group comparisons were performed using the Pearson bivariate test and the chi-square or Fisher’s exact test for categorical variables and the Student t test for continuous variables. Pearson correlation was used to compare the aortic root measurements and anatomic characteristics. The Kolmogorov–Smirnov test was used to compare the distribution of aortic root calcium volume. Linear regression analysis was used to estimate the annulus area. Interobserver and intraobserver agreement was evaluated by calculating intraclass correlation coefficients. All p values reported are 2-sided, and p values <0.05 were considered significant. All data were analyzed using the Statistical Package for the Social Science (SPSS) software version 20 (SPSS Inc., Chicago, Illinois).

Results

A total of 308 patients with mean age of 81.0 ± 6.1 years and 182 women (59.1%) were included in this study. Compared to Caucasian group, Asian group was smaller in height, weight, body mass index, and body surface area ( Table 1 ). Renal insufficiency, peripheral vascular disease, and previous percutaneous coronary intervention were more frequent, and NYHA classes III or IV was less common in Asian group compared with Caucasian group.

Overall and race-specific dimensions of the aortic root are provided in Table 2 . We demonstrated satisfactory interobserver and intraobserver reproducibility for aortic root measurement (interobserver intraclass correlation coefficients = 0.97 and intraobserver intraclass correlation coefficients = 0.98). Compared to Caucasian group, annulus area, perimeter, and maximal and mean diameter were smaller in Asian group. Similarly, LVOT area, perimeter, and maximal and mean diameter were smaller in Asian group than in Caucasian group. In terms of other parts of aortic root, diameter of left coronary cusp, height of all 3 cusps, and sinotubular junction dimension (area, perimeter, and maximal/minimal/mean diameter) were smaller in Asian group than in Caucasian group, but the ascending aorta dimensions were similar between 2 groups. With respect to height of coronary ostium, height of left coronary artery ostia was shorter in Asian group than in Caucasian group (12.0 ± 2.5 vs 13.4 ± 3.4 mm; p <0.001), but there were no differences in right coronary artery ostia between 2 groups (16.8 ± 2.6 mm vs 16.9 ± 3.6 mm; p = 0.82).

Among the baseline anatomic characteristics including weight, height, body mass index, and body surface area, height showed the highest linear association with aortic annulus dimensions (annulus area, Pearson correlation r = 0.64; p <0.001; annulus perimeter, Pearson correlation r = 0.64; p <0.001; annulus mean diameter, Pearson correlation r = 0.65; p <0.001; Table 3 and Figure 1 ). On linear regression analysis, annulus area was estimated as following formulas: (annulus area for Asian) = 4.93 × (height) − 350 ± 66 mm ² ; (annulus area for Caucasian) = 5.24 × (height) − 410 ± 102 mm ² ( Figure 1 ). Regardless of the type of devices, the appropriate device size showed continuous distribution pattern, with association with body height ( Figure 2 ).

Correlation of aortic root dimensions and body height. Correlations between body height and the annulus area for overall (A) , Asian (B) , and Caucasian (C) are shown. Fitted lines present the predicted values from the linear regression, and dotted lines present the predicted values ± standard deviation.

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