HeartCalc / Kawasaki

Kawasaki Coronary Z-Scores Experimental

Coronary z scores from four published models side by side, the AHA 2017 z-score classification with a model-disagreement flag, and the Son 2019 aneurysm risk score

Z scores by model

Each cell shows the z score and its AHA 2017 class for that artery. A ≠ in a column header means the models put that artery in different classes. Rows marked [unverified] use coefficients that could not be checked against the primary paper; they are shown for comparison only and never drive the headline above.

Model	LMCA	LAD	RCA	LCx	Most severe class	BSA
Enter the patient and at least one diameter.

AHA 2017 z-score classification

Class	Criterion
1No involvement	Always z <2
2Dilation only	z 2 to <2.5; or, if initially <2, a decrease in z during follow-up ≥1 (serial criterion not assessed here)
3Small aneurysm	z ≥2.5 to <5
4Medium aneurysm	z ≥5 to <10, and absolute dimension <8 mm
5Large or giant aneurysm	z ≥10, or absolute dimension ≥8 mm

Classes are assigned per artery on the unrounded z and that artery's internal diameter, then the most severe artery is reported. The 8 mm rule is applied as written, whatever the z score. AHA 2017 risk levels for long-term management use the maximum z ever recorded and the current z; this page classifies one study only. Wording as quoted from the AHA 2017 statement by Kim 2022 (Table 1) and Robinson 2021.

Model, equations and sources

Verification status

Model	Coefficients taken from	Status
PHN (Lopez 2017)	Primary paper, Table 2 coronary rows and the Z equation in Results (PMC author manuscript)	Verified
Kobayashi 2016 LMS	The authors' official Z Score Project calculator, version 4 (named in the paper's abstract). The paper's own tables were not retrieved.	Verified against the official calculator
Boston (McCrindle 2007)	As reported: ZSP calculator v4 (mm form) and the NCT00841789 trial protocol (cm form, quoting the McCrindle methods) agree to every digit. McCrindle 2007 full text could not be retrieved.	[unverified] against the primary paper
Dallaire & Dahdah 2011	ZSP calculator v4 only (one secondary implementation). Dallaire 2011 full text could not be retrieved.	[unverified]
AHA 2017 classes	Wording quoted in Kim 2022 Table 1 and Robinson 2021; the statement's own text could not be retrieved here.	Thresholds agree in both reproductions
Son 2019 score	Primary paper (PMC6585355): Results and Table 4	Verified

All 24 LAD z scores in Kim 2022 Table 5 (two boys, four models, three diameters each, from the ZSP calculator) are reproduced exactly to two decimals by this page, and the PHN worked example in Lopez 2017 (mitral diameter 11 mm at BSA 0.3 m² gives Z −1.0) is reproduced by the same allometric function.

BSA (all models)

BSA [m2] = 0.024265 x weight[kg]^0.5378 x height[cm]^0.3964      (Haycock 1978)

Lopez 2017 states PHN used Haycock. Kim 2022 Table 2 lists Haycock for McCrindle, Dallaire and Kobayashi; the ZSP calculator applies Haycock to every model. A different BSA formula shifts every z score.

PHN, Lopez 2017 (Table 2; diameters in mm)

Z = (D[mm] / BSA^alpha - mean) / SD

         alpha   mean   SD
LMCA     0.45    2.95   0.57
LAD      0.45    1.90   0.34
RCA      0.45    2.32   0.55     (no LCx row)

Healthy non-obese children ≤18 years from 19 North American centres; coronary arteries were an optional measurement set (available in 78–91% of studies). Robinson 2021 found PHN LAD z scores systematically higher than Boston (median 1.6 vs 0.3), so switching from Boston to PHN reclassified at least one artery in 59.7% of children and changed the recommended antithrombotic strategy in 13.4%.

Kobayashi 2016, LMS (sex-specific; diameters in mm; b = BSA)

Z = ((D / M)^L - 1) / (L x S)        (L -> 0: Z = ln(D / M) / S)

M(b) = c6 b^6 + c5 b^5 + c4 b^4 + c3 b^3 + c2 b^2 + c1 b + c0

Male       M: c6..c0                                              L                 S
 RCA   0.0183 -0.1867 0.7132 -1.1982 0.6038 1.6558 0.7517          0.292             0.174
 LMCA  0.076  -0.6549 2.1792 -3.3446 1.916  1.5869 0.933           0.336             0.151
 LAD   0.0755 -0.5537 1.4885 -1.6204 0.155  2.0239 0.633           0.6481 b - 0.3205 S1(b)
 LCx   0.078  -0.5761 1.5481 -1.6499 0.0767 1.9436 0.5294          0.4536 b - 0.2542 S2(b)
Female
 RCA   0.0363 -0.3503 1.2615 -2.0255 1.1301 1.4256 0.7727          0.607             0.17
 LMCA  0.1738 -1.4226 4.5095 -6.7646 4.3972 0.662  1.0021          0.363             S3(b)
 LAD   0.1611 -1.2491 3.683  -4.9471 2.5568 1.1944 0.7109          0.204             0.168
 LCx   0.0495 -0.4345 1.4492 -2.188  1.1905 1.1956 0.6348          0.6683 b - 0.2618 0.2

S1(b) =  0.0298 b^6 - 0.2189 b^5 + 0.5974 b^4 - 0.7135 b^3 + 0.2947 b^2 + 0.0411 b + 0.1459
S2(b) =  0.0011 b^6 - 0.0081 b^5 + 0.0239 b^4 - 0.0351 b^3 + 0.0267 b^2 - 0.0037 b + 0.2009
S3(b) = -0.0002 b^6 + 0.0014 b^5 - 0.0032 b^4 + 0.0032 b^3 + 0.0021 b^2 - 0.0367 b + 0.1819

3,851 healthy Japanese children 0 to 18 years. M is the median diameter (Z = 0). L crosses zero for male LAD (BSA 0.49 m²), male LCx (0.56) and female LCx (0.39); the page uses the logarithmic limit there. Derived in a Japanese population; z scores in other populations may differ.

Boston, McCrindle 2007, as reported [unverified] (diameters in cm)

Z = (D[cm] - mean) / SD
LMCA  mean = 0.31747 x BSA^0.36008 - 0.02887   SD = 0.03040 + 0.01514 x BSA
LAD   mean = 0.26108 x BSA^0.37893 - 0.02852   SD = 0.01465 + 0.01996 x BSA
RCA   mean = 0.26117 x BSA^0.39992 - 0.02756   SD = 0.02407 + 0.01597 x BSA     (no LCx)

221 healthy children aged 0 to 18 years, Boston Children's Hospital, 1987 to 2000 (as described in the NCT00841789 protocol). The ZSP calculator gives the same equations in mm (every coefficient ×10).

Dallaire & Dahdah 2011 [unverified] (diameters in mm)

Z = (D[mm] - (k1 x sqrt(BSA) - k0)) / (s0 + s1 x sqrt(BSA))
        k0      k1      s0      s1
LMCA   0.1817  2.9238  0.1801  0.2530
LAD    0.1502  2.2672  0.1709  0.2293
RCA    0.3039  2.7521  0.1626  0.2881     (proximal RCA)
LCx    0.2716  2.3458  0.1142  0.3423

1,033 healthy children (Quebec); square-root-of-BSA regression with weighted least squares (abstract). Coefficients as implemented in the ZSP calculator only.

Son 2019 coronary aneurysm risk score

2 points  baseline max z of proximal LAD or RCA ≥2.00   (Boston z, McCrindle 2007)
1 point   age at fever onset <6 months
1 point   Asian race reported (sole or mixed)
1 point   baseline CRP ≥13 mg/dL
Low 0-1 · Moderate 2 · High 3-5

Outcome: Coronary aneurysm, LAD or RCA z ≥2.5 at 2 to 8 weeks after fever onset.
Baseline: Echo before IVIG or less than 2 days after IVIG; patients treated with IVIG on days 3 to 10 of illness.
Cohorts: Development: 903 patients (Boston Children's, Rady Children's San Diego); c statistic 0.82 for the logistic model, 0.79 for the 3-tier score. Validation: 185 patients from the PHN methylprednisolone trial (8 North American centres); c 0.93 and 0.85.
Observed aneurysms by tier (Table 4): Low: 24 of 585 (4.1%) development, 3 of 124 (2.4%) validation. Moderate: 32 of 170 (18.8%), 10 of 38 (26.3%). High: 61 of 148 (41.2%), 12 of 23 (52.2%).
Cautions: About 2 to 4% of children with a score of 0 still had an aneurysm; the authors state it should not supplant clinical judgement and should undergo prospective testing. Developed for assessment at presentation only. The z item depends on the z-score model: with PHN z the same child can score 2 points higher (see the note in the result).

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
Kobayashi T, Fuse S, Sakamoto N, 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. doi:10.1016/j.echo.2016.03.017. Official calculator: raise.umin.jp/zsp/calculator (version 4, read October 2026).
McCrindle BW, Li JS, Minich LL, et al. Coronary artery involvement in children with Kawasaki disease: risk factors from analysis of serial normalized measurements. Circulation 2007;116(2):174-179. doi:10.1161/CIRCULATIONAHA.107.690875
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, Rowley AH, Newburger JW, et al. Diagnosis, treatment, and long-term management of Kawasaki disease: a scientific statement for health professionals from the American Heart Association. Circulation 2017;135(17):e927-e999. doi:10.1161/CIR.0000000000000484
Jone PN, et al. Update on diagnosis and management of Kawasaki disease: a scientific statement from the American Heart Association. Circulation 2024;150. doi:10.1161/CIR.0000000000001295 (content not reviewed for this page).
Son MBF, Gauvreau K, Tremoulet AH, et al. Risk model development and validation for prediction of coronary artery aneurysms in Kawasaki disease in a North American population. J Am Heart Assoc 2019;8(11):e011319. doi:10.1161/JAHA.118.011319 (CC BY-NC-ND 4.0).
Kim SH, et al. Diagnosis of coronary artery abnormalities in Kawasaki disease: recent guidelines and z score systems. Clin Exp Pediatr 2022;65(9):430-438. doi:10.3345/cep.2021.01459
Robinson DL, Ware AL, Sauer MC, et al. Implications of changing z-score models for coronary artery dimensions in Kawasaki disease. Pediatr Cardiol 2021;42(2):432-441. doi:10.1007/s00246-020-02501-0
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
Boston coronary equations in cm as quoted in the etanercept-in-KD trial protocol (NCT00841789, Seattle Children's Research Institute), section 6.7: protocol PDF.

z scores are computed in this browser from the published equations; nothing you enter is stored or sent. The headline class uses only the verified models (PHN and Kobayashi) and reports the more severe of the two; use the model your echo lab reports, and always state the model next to a z score.

Decision aid only. Anticoagulation, follow-up and IVIG intensification decisions need the full clinical picture and serial imaging.

Kawasaki Coronary Z-Scores Experimental

Patient

Coronary internal diameters

Son 2019 risk score (optional, at presentation)