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.