HeartCalc / Echo Z

Echo Z-Scores Experimental

Pediatric Heart Network (Lopez 2017) Z scores for 2D measurements, with Detroit (Pettersen 2008) alongside

Patient

BSA, Haycock m²—

PHN Z scores use Haycock BSA, as the paper specifies; you cannot pick another formula. Age under 1 year: enter a decimal (6 months = 0.5). Nothing on this page is saved or sent anywhere.

Unit

Diameters and lengths entered inRequired. Areas are always cm².

Derived values are calculated, not typed: mitral and tricuspid annular areas (π/4 × AP × lateral), LV volumes (5/6 × area × length), LV mass (1.05 × epicardial − endocardial volume) and the LV ratios. They appear in the results when their components are entered. Measure as PHN did: 2D, inner edge to inner edge, at the view listed under each field.

Model, equations and sources

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

PHN (Lopez 2017 Table 2; LVESD Lopez 2021 Table 3) and Detroit [unverified]
ParameterUnitαMeanSDDetroit b0, b1, b2, b3 / MSE

Not included

References

Z scores are computed in this browser from the published equations; nothing you enter is stored or sent.

Decision aid only. A Z score depends on how and where the structure was measured; compare like with like.