Echo Z-Scores

PHN Z score (primary model)

Z = (measurement / BSA^α − mean) / SD
expected mean      = mean × BSA^α
−2 to +2 Z range   = (mean − 2 SD) × BSA^α  to  (mean + 2 SD) × BSA^α
BSA (Haycock 1978) = 0.024265 × weight[kg]^0.5378 × height[cm]^0.3964

α, mean and SD for each parameter are copied verbatim from Lopez 2017, Table 2 (PMC author manuscript PMC5812349): see the table below. Coronary arteries are in mm; all other diameters and lengths in cm; areas cm²; volumes ml; mass g. The three ratios (mass-to-volume, thickness-to-dimension, sphericity) have α = 0 and are not indexed to BSA. The paper found no clinically important effect of age, sex, race or ethnicity, so one equation serves all children. The LV end-systolic diameter row (α 0.5, mean 2.675, SD 0.352) comes from Lopez 2021, Table 3 (PMC7870534), derived with the same PHN method.

Worked example in the paper (reproduced by this page's tests): a mitral diameter of 11 mm at BSA 0.3 m² with α 0.50, mean 2.23, SD 0.22 gives Z −1.0.

Population. 3215 healthy children aged 18 years or younger with measurable images, 19 North American centres; prematurity, obesity, structural heart disease and some family histories were excluded; core-lab measurements by 2 sonographers. No result is shown above 18 years. The paper does not state a BSA range; very small infants get a caution.

Detroit comparison column [unverified]

ln(measurement[cm]) predicted = b0 + b1 BSA + b2 BSA² + b3 BSA³
Z = (ln(measurement[cm]) − predicted) / √MSE
BSA = DuBois: 0.007184 × weight[kg]^0.425 × height[cm]^0.725
Not shown when BSA (DuBois) > 2.0 m² or age > 18 years

The functional form is as described by Lopez 2021, Table 1. [unverified] The Pettersen 2008 paper itself could not be retrieved, so its coefficient table was not read. The coefficients below were reconstructed by exact least-squares fitting to ParameterZ's live Pettersen calculator at 13 body sizes. The fit residual was below 10⁻¹⁴, every coefficient landed on three decimals, and the result reproduces ParameterZ's Z scores to 4 × 10⁻¹⁴. ParameterZ labels its BSA “Dubois”; that the paper used DuBois is also unverified. Detroit never drives the headline number. Lopez 2021 found the Detroit curves diverge from PHN at high BSA (mean correlation with PHN Z 0.92, the lowest of the models compared). The Detroit LV dimensions may be M-mode rather than 2D.

Coefficients

Not included

• Boston (Colan) Z scores: the coefficients are not openly published in one place; use the Boston Children’s calculator.
• Detroit-only sites (RV diameter, systolic septum and wall, LA diameter, descending and abdominal aorta) are left out, so that unverified coefficients are never the only result.
• Kawasaki disease coronary classification (AHA risk levels across several Z models) belongs to a separate tool. The PHN coronary Z scores here are the raw PHN model only.
• PHN LV end-systolic volume (Lopez 2021) is left out because its measurement formula is not stated.

Verification

Checked against the official Pediatric Heart Network Z-score calculator, running its own code, in October 2026: all 34 coefficient sets are identical. The official page rounds BSA to 0.001 m² before computing Z and this page does not, which moves Z by at most 0.012 in a newborn and by 0.002 or less at BSA 0.45 m² and above; given the same unrounded BSA, the official code reproduces this page in 132 of 132 checks. LV end-systolic diameter (not in the official calculator) matches Lopez 2021 Table 3. The Detroit column was not checked against its primary paper and stays labelled [unverified].

References

• Lopez L, Colan S, Stylianou M, et al. Relationship of echocardiographic Z scores adjusted for body surface area to age, sex, race, and ethnicity: the Pediatric Heart Network Normal Echocardiogram Database. Circ Cardiovasc Imaging 2017;10(11):e006979. doi:10.1161/CIRCIMAGING.117.006979
• Lopez L, Frommelt PC, Colan SD, et al. Pediatric Heart Network echocardiographic Z scores: comparison to other published models. J Am Soc Echocardiogr 2021;34(2):185-192. doi:10.1016/j.echo.2020.09.019
• Pettersen MD, Du W, Skeens ME, Humes RA. Regression equations for calculation of z scores of cardiac structures in a large cohort of healthy infants, children, and adolescents: an echocardiographic study. J Am Soc Echocardiogr 2008;21(8):922-934. doi:10.1016/j.echo.2008.02.006
• Haycock GB, Schwartz GJ, Wisotsky DH. Geometric method for measuring body surface area: a height-weight formula validated in infants, children, and adults. J Pediatr 1978;93(1):62-66. doi:10.1016/S0022-3476(78)80601-5
• Du Bois D, Du Bois EF. A formula to estimate the approximate surface area if height and weight be known. Arch Intern Med 1916;17:863-871.
• ParameterZ (Dan Dyar): parameterz.com, moving to rchsd.org/zscore. Used to cross-check this page (outputs matched to 10⁻⁶ or better, October 2026).