Intra- and interobserver reliability in measuring aortic root rotation with cardiac magnetic resonance imaging

Background: The rotational position of the aortic root (AoR) is of substantial clinical interest as it has been associated with severe aortic complications, such as aortic dissections. We described a cardiac magnetic resonance (CMR)-based method for measuring AoR rotation and evaluated the reliability of measurements. Methods: CMR was used for measuring AoR rotation in 50 consecutive healthy subjects. Intraand interobserver reliability were assessed by comparing repeated measurements by the same analyst and by three independent analysts. The angles of the non-coronary sinus (NCS), right coronary sinus (RCS), and left coronary sinus (LCS) were measured relative to the interatrial septum (IAS). The angle between IAS and posterior atrial wall was measured to examine the reliability of the IAS as a key anatomical landmark. Intraand interobserver agreement were determined using intraclass correlation coefficients (ICCs). Results: Images of 47/50 (94%) subjects were analyzed; three were excluded due to insufficient image quality. The mean +/- standard deviation (SD) AoR rotation angles of NCS, RCS, and LCS were 25.9 degrees +/- 12.9 degrees, 37.5 degrees +/- 15.2 degrees, and 97.0 degrees +/- 13.1 degrees, respectively. For measurements of AoR rotation, both intraobserver [NCS: ICC =0.94, 95% confidence interval (CI): 0.88-0.96; RCS: ICC =0.93, 95% CI: 0.87-0.96; LCS: ICC =0.91, 95% CI: 0.84-0.95] and interobserver agreement (NCS: ICC =0.90, 95% CI: 0.84-0.94; RCS: ICC =0.86, 95% CI: 0.77-0.92; LCS: ICC =0.87, 95% CI: 0.80-0.92) were excellent. The IAS angle was 79.2 degrees +/- 8.9 degrees; its intraobserver agreement was somewhat higher (ICC =0.94, 95% CI: 0.88-0.96) than the interobserver agreement (ICC =0.76, 95% CI: 0.63-0.85). Conclusions: The present study in healthy subjects reports a CMR-based approach for measuring AoR rotation. CMR allows to quantify AoR rotation with excellent intra- and interobserver agreement.