Assessment of the aortic annulus with transesophageal echocardiography, CT-scan and magnetic resonance compared to direct surgical sizing: a prospective double-blinded study

Purpose: To derive the most adequate procedures for measurements of the aortic annulus by multi-detector computed tomography (MDCT), magnetic resonance (MR) and transesophageal echocardiography (TEE) from comparisons with intra-operative sizing. Methods: 45 patients, (48.9% males, age 78.9±3.7) underwent AVR for severe aortic stenosis after TEE, MDCT, and MR evaluation. In TEE, the annulus was measured at the base of leaflet insertion in the mid-esophageal long-axis view. In MDCT and MR, the diameter was derived after testing the accuracy of the left ventricle outflow tract measurement (basal ring) and of the basal attachment of the aortic commissures (virtual ring). Two double-blinded operators prospectively performed all assessments for each imaging technique. Intra-operative evaluation was performed after leaflet removal and decalfication by using Hegar (H) dilators. Statistical analysis are summarized in Table 1. The percentage of measurements falling within ± 2 mm from the H value constituted a further estimate of practical reliability. Results: The most accurate results for MDCT and MR were obtained using for the former the average of the “basal ring” and “virtual ring”, and for the latter the “basal ring” measurement. Inter-operator variability was verified with the paired t-test and the non-parametric Wilcoxon test. Table 1 summarizes the main statistical results obtained when comparing the three imaging procedures to the Hegar sizing H. Conclusion: The proposed procedures for MDCT and MR allow an assessment of the aortic annulus superior to TEE. In particular the basal ring is the one able to warrant MR data as the highest accuracy and reliability. The ± 2mm “surgical allowance” highlights the real scenario in the non-invasive measurements and gives a valuable and trustworthy answer to the reliability of indirect measurements.