Ascending Aortic Area Calculator

Why Area/Height?

Ascending aortic dimensions need to be normalized for body size to avoid misclassification, particularly at the extremes of height. However, not all normalization methods work equally well. Commonly used indices like diameter/height and diameter/BSA appear straightforward, but when tested empirically, they leave significant residual associations with body size - meaning they don't fully account for body size.

This study used allometric scaling analysis to determine which normalization method properly removes these residual body size effects. The researchers tested the relationship between aortic dimensions and body size metrics (height and BSA) in healthy reference populations, calculating allometric exponents to characterize these relationships.

Key finding: The area/height relationship exhibited an allometric exponent of approximately 1.0 (95% CI: 0.93-1.15 in UK Biobank; 0.65-1.58 in Penn Medicine BioBank). An exponent of 1.0 means that aortic area scales linearly with height, making a simple ratio appropriate. In contrast, diameter/height and diameter/BSA had exponents significantly different from 1.0, indicating nonlinear relationships that cannot be properly normalized with simple ratios.

Most importantly, after indexing by area/height, there was no residual association with body size (R² = 0.04, P = 0.41 in UK Biobank), confirming it as an appropriate index for normalizing ascending aortic dimensions across different body sizes.

Want to see how different scaling approaches compare? This Reference Comparison Tool lets you visualize how CMR (JACC) area/height indexing compares to echo-based methods (NORRE height-indexed and ASE BSA-indexed) across different body sizes.

Methodology

• Imaging: Cardiac MRI (CMR) using axial scout steady-state free precession (SSFP) image reconstructions
• 3D Reconstruction: Axial CMR images were processed and combined to generate three-dimensional aortic segmentation. The aortic centerline was defined using linear interpolation with 100 points, and cross-sectional measurements were calculated at each point along the centerline.
• Measurement location: The maximum diameter and cross-sectional area within the ascending aorta (AscAo) were used. The AscAo was defined as the segment extending from the aortic root to the apex of the aortic arch. Note: This approach identifies the largest dimension regardless of anatomic location, which may differ from protocols that measure at fixed anatomic landmarks (e.g., sinotubular junction, mid-ascending aorta).
• Upper limit: 97.5th percentile in the reference population

Study Population

The normative values presented in this calculator are based on the UK Biobank reference/healthy subgroup (n = 11,310; age 52 ± 8 years; 37% male), no cardiovascular disease, BMI < 30 kg/m², normal lipids, and never smokers.

Citation

Tavolinejad, H., Beeche, C., Dib, M.-J., Pourmussa, B., Damrauer, S. M., DePaolo, J., Azzo, J. D., Salman, O., Duda, J., Gee, J., Kun, S., Witschey, W. R., & Chirinos, J. A. (2025). Ascending Aortic Dimensions and Body Size: Allometric Scaling, Normative Values, and Prognostic Performance. JACC: Cardiovascular Imaging. https://doi.org/10.1016/j.jcmg.2025.06.019