A z-score Based Approach for the Replacement of the Ascending Aorta: Insights from 943 Patients

Objective: The diameters of the ascending aorta (AA) are dynamic and are greatly influenced from the patient's age, gender and somatic characteristics. Despite this dynamic nature, static criteria are recommended in the guidelines for the replacement of the AA in the form of absolute diameters. Aim of the present study was to investigate the decision making process for the replacement of the ascending aorta while taking into consideration the dynamic nature of the ascending aorta diameters.

Methods: Between 1999 and 2013, 974 (742 male, 53.8 ± 14 years) patients underwent isolated or concomitant AA replacement in our institution. Diameters of the ascending aorta were documented in all patients. For each patient a z-score was calculated, based on the patient́s age, gender and BSA according to published equations. Machine learning techniques were employed to investigate the decision boundaries for the replacement of the AA.

Results: The (90%) threshold for replacing the AA increased from 47mm to 49mm to 50mm in the age groups 20–40, 40–60 and 60–80, respectively. The same AA replacement thresholds translated into z-scores of 7.84, 5.05 and 3.91 for the same groups respectively.

Conclusions: Absolute criteria for the replacement of the AA ignore the dynamic nature of the AA diameters. In young patients this lead to a significant stallment in replacing the AA until highly pathological AA diameters in comparison to the normal appear.