Normal Aortic Root Dimensions
The normal aortic root diameter at the sinuses of Valsalva ranges from 2.1 to 4.3 cm in healthy adults, with men averaging 3.4 ± 0.3 cm and women averaging 3.0 ± 0.3 cm. 1
Sex-Specific Normal Values
- Men: Mean diameter of 3.4 ± 0.3 cm (range 2.5-4.0 cm), with upper normal limit approximately 40 mm 1, 2
- Women: Mean diameter of 3.0 ± 0.3 cm (range 2.1-3.6 cm), with upper normal limit approximately 34-36 mm 3, 1
- Men consistently have larger aortic diameters than women by 2-3 mm across all measurement locations, even when adjusted for body surface area 1, 2
Body Surface Area Indexing
- Indexed values are critical for accurate assessment: men average 1.7 ± 0.2 cm/m² and women average 1.8 ± 0.2 cm/m² 1
- An upper normal limit of 2.1 cm/m² provides 98% specificity for detecting aortic dilatation in both sexes 4
- BSA indexing is particularly important in children and individuals with extreme body sizes, where z-scores should be used 3, 1
Age-Related Changes
- Aortic diameter increases with age at approximately 0.9 mm per decade in males and 0.7 mm per decade in females 3
- The predictive formula incorporating age, BSA, and sex is: 2.423 + (age in years × 0.009) + (BSA in m² × 0.461) - (sex [1=male, 2=female] × 0.267) 1, 2
Clinical Thresholds for Abnormality
- >40 mm in adult males represents "unequivocal aortic root enlargement" and warrants evaluation for underlying aortopathy 3, 1
- >34 mm in adult females (99th percentile) should trigger further assessment 3
- Z-score >2.0 definitively indicates aortic root dilatation, corresponding to the 98th percentile 1
Critical Measurement Technique
- Measurements must be performed using echocardiography in the parasternal long-axis view at end-diastole using the leading-edge to leading-edge technique 3, 1
- For CT/MRI, use the inner-to-inner edge method with the cusp-to-cusp diameter convention, which best correlates with echocardiography 3
- All measurements must be perpendicular to the longitudinal axis of the aorta to avoid overestimation 3, 1
Common Pitfalls to Avoid
- Do not apply M-mode nomograms to 2D echocardiographic measurements—this falsely diagnoses aortic dilatation in 40% of normal children and 19% of normal adults 4
- Do not use a single absolute diameter cutoff for all patients without considering body size, age, and sex 1
- Echocardiographic measurements (sinus-to-sinus) typically yield larger values than CT/MRI measurements (sinus-to-commissure), so serial imaging should use the same modality 3, 1
- A diameter difference >5 mm among root diameters within the same imaging modality indicates root asymmetry, which is important to identify as it generates underestimations 3