Strengths and Limitations of Current Adult Nomograms for the Aorta Obtained by Noninvasive Cardiovascular Imaging

Abstract

Normalized measurements for the evaluation of aortic disease severity are preferred to the adoption of generic cutoff values. The purpose of this review is to evaluate the strengths and limitations of currently available aortic nomograms by echocardiography, computed tomography (CT), and magnetic resonance imaging (MRI). A literature search was conducted accessing the National Library of Medicine using the keywords normal values, aorta, echocardiography, CT, and MRI. Addition of these keywords further refined the results: reference values, nomograms, aortic arch, and adults. Thirty studies were included in the final analysis. Despite the strengths noted in the recent investigations, multiple methodological and numerical limitations emerged. The numerical limitations included sample size limitation in most of the studies (only few investigations consisted of >800 subjects and many had 70-300), lack of aortic arch measurements, and paucity of data for non-Caucasian subjects. Methodological limitations consisted of lack of standardization in measurements (systole vs. diastole, internal vs. external border, axial vs. orthogonal planes), heterogeneity and data normalization issues (various age intervals used, body size often not evaluated, data expressed as observed values rather than estimated values by z-score), and study design issues. The designs were mostly retrospective with poorly defined inclusion and exclusion criteria. The nomograms presented range of normality with significant differences, but also with some reproducible pattern. Despite recent advances, multiple methodological or numerical limitations exist in adult nomograms for the aorta. Comprehensive nomograms of aortic dimensions at multiple levels including the aortic arch for different imaging techniques, involving a wide sample size, and using standardized methodology for measurements and data normalization are warranted. The availability of robust nomograms may encourage the use of personalized rather than generic cutoff values.

Sex-specific distributions and determinants of thoracic aortic diameters in the elderly

“…Although the difference in mean aortic diameter between the age group of 55–65 years and ≥75 years was only 1 mm for both the ascending and descending aorta, the aortic diameter above 55 years still increased. Our results show the 95th percentile for persons above the age of 75 years old to be 43 mm for ascending and 35 mm for descending aorta for men and 41 mm and 33 for women, an age group for whom distribution data are currently scarce 11. Our data further establish the range of thoracic aortic diameters, which is similar to data found in a study performed in Germany 16.…”

“…Hence, this threshold of 40 mm6 may not be directly applicable to older individuals, especially given increasing evidence suggesting that aortic diameters change with age 7–9. Together with the finding that aortic complications mostly occur at older age,10 this emphasizes the need for data on the distribution of aortic diameters among older persons 11…”

Normal Reference Intervals for Cardiac Dimensions and Function for Use in Echocardiographic Practice: A Guideline from the British Society of Echocardiography

“…These adult nomograms have some limitations: small sample size, poorly defined 'normal' subjects, bias to BSA (which is adversely affected by obesity), and finally a sharp jump in results when the subject turns 40 owing to a change in the equation used. These problems have been well described elsewhere (65).…”

Adult echocardiographic nomograms: overview, critical review and creation of a software for automatic, fast and easy calculation of normal values

“…RA diameters (15), RV long-axis diameter (15,22), and RV mass (15) increase with age, while data on the RV area were contrasting, with a study reporting a slight increase (21) and other a decrease of the RV area (18). Some studies (15,18,22,27) showed significant relations of cardiac measurements with gender. All chambers diameters, volumes and the LV mass were higher in men (15,18,21,22), even after correction for BSA (18), as well as great arteries (15,22,27).…”

“…Some studies (15,18,22,27) showed significant relations of cardiac measurements with gender. All chambers diameters, volumes and the LV mass were higher in men (15,18,21,22), even after correction for BSA (18), as well as great arteries (15,22,27). BSA correction however mitigated RA diameters and RA volume differences among gender and eliminated differences in LA volume (18).…”