Adult echocardiography · CITED I reference values

Aortic root Z-scores, allometrically scaled

Expected diameters from multivariate allometric equations in sex, age, height and weight. Each measurement is reported as percent of expected, as a Z-score, and against the published limits of normal.

Yao G, Hu X, Chen X, … Bossone E, Zhang Y. Comparison of body surface area and optimized multivariate allometric model approaches in correcting echocardiographic aortic dimensions for physiological variances (CITED I). MedComm. 2026;7(6):e70788. doi:10.1002/mco2.70788

Reference cohort
Sex
years
SiteMeasured mmExpected% expZZ −3 to +3
Z for this patient Published limits of normal (mm) select a site to see the math →

The report includes only the measurements you have entered. Nothing is saved or sent.

How the Z-score works
Z = (Yc − mean) / SD

Yc is just percent of expected ÷ 100

Yp = a × bfemale × agex × heighty × weightz, with age in years, height in cm and weight in kg. Each cohort has its own equation for each site; terms that dropped out of the stepwise regression are absent.

Yc = measured / Yp. The paper reports the mean, SD and 95% limits of Yc in healthy adults. Z uses the mean and SD; the flag uses the 95% limits, as the authors recommend. Because the limits are asymmetric and are not exactly mean ± 1.96 SD, a Z near ±2 can fall on either side of a limit.

High-normal and low-normal mean inside the limits but beyond the 95th or 5th percentile. That label is this calculator's addition.

The combined cohort has no published reference values. This calculator uses the sex-specific validation-group mean and SD (Table 4) with limits at ± 1.96 SD. Treat it as provisional.

Coefficients

Equation reference

Expected diameter Yp in mm; a dash means the term is not in that equation. Reference values are for Yc. Combined-cohort mean and SD are shown as male / female.

Before you use it
  1. Population: healthy, normotensive, non-obese Han Chinese and Italian adults aged 18 to 79 (BMI under 30). No athletes, no pregnancy. Other populations are an extrapolation.
  2. Age is in every equation, so age-related widening counts as normal. Fixed cutoffs, or cutoffs indexed to height alone, will read older patients more strictly.
  3. Measurement method: all three sites were measured leading edge to leading edge at end-diastole in the parasternal long axis, averaged over three beats. That differs from the ASE convention for the annulus (inner edge, mid-systole).
  4. Cohort choice matters. The same patient can be normal under one cohort and abnormal under another; the comparison table in the calculation panel shows all three.
  5. Reference limits: the paper does not say how its 95% limits were derived. They are asymmetric and not mean ± 1.96 SD.