Z-score Coronary Origin (Pediatric Database) Calculator
- Z-score Coronary Origin (pediatric database): Explanation and Clinical Context
This calculator normalizes measured coronary internal diameters to body size using a log-linear z-score model widely used in pediatric echocardiography. The typical modelling approach (used by Dallaire & Dahdah and others) fits a regression of the natural logarithm of coronary diameter (mm) against the natural logarithm of body surface area (BSA):
ln(diameter_mm) = a + b × ln(BSA)
The z-score is then computed as the number of residual standard deviations that the observed ln(diameter) lies from the predicted ln(diameter):
Z = ( ln(measured_mm) − (a + b × ln(BSA)) ) / sd
This calculator supports selecting a published model (if you populate the `a`, `b`, and `sd` coefficients in the configuration block) or entering custom coefficients directly in the form. Differences between published z-score systems (Dallaire 2011, McCrindle 2007, Kobayashi 2016, Olivieri 2009, etc.) can change the z-score classification for borderline cases; pick the reference most appropriate for your population and echo measurement protocol.
Clinical interpretation (typical thresholds used in Kawasaki disease and pediatric cardiology):
• Z < 2.0 — no enlargement (within expected range).
• Z ≥ 2.0 and < 2.5 — dilation only (some guidelines consider ≥2.5 as small aneurysm).
• Z ≥ 2.5 and < 5.0 — small coronary artery aneurysm.
• Z ≥ 5.0 and < 10.0 — medium aneurysm.
• Z ≥ 10.0 — large/giant aneurysm.
Refer to the original publications for exact coefficients, measurement technique (inner lumen definition, short-axis vs. long-axis views), and demographic applicability. Use this tool only as an aid—always interpret in the clinical context and with knowledge of the exact model you use.
References:
Dallaire F, Dahdah N. New equations and a critical appraisal of coronary artery Z scores in healthy children. J Am Soc Echocardiogr. 2011;24(1):60–74. DOI:10.1016/j.echo.2010.10.004.
McCrindle BW, Li JS, Minich LL, Colan SD, Atz AM, Takahashi M, et al. Coronary artery involvement in children with Kawasaki disease: risk factors from analysis of serial normalized measurements. Circulation. 2007;116(2):174–179.
Kobayashi T, Fuse S, Sakamoto N, Mikami M, Ogawa S, Hamaoka K, et al. A new Z score curve of the coronary arterial internal diameter using the lambda-mu-sigma method in a pediatric population. J Am Soc Echocardiogr. 2016;29(8):794–801.e29.
For online implementation examples and comparative calculators see ParameterZ and other published nomograms.
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