For Researchers

Echo Z-Scores

How do I Calculate Echo Z-Scores?

There are currently two options for calculating the Z-scores for common echo measurements using the PHN models: (1) with an online Z-score calculator; or (2) with a table listing the exponential power to be used with body surface area (BSA), the mean value of the indexed measurement, and the standard deviation (SD) of the indexed measurement.

1. Calculating echo z-scores using an online calculator:

The results from the PHN Echo Z-Score Project are available as a Z-score calculator on the ParameterZ website. In the future, the PHN website will have a Z-score calculator that can be easily accessed.

2. Calculating echo z-scores using the table of exponential power for BSA, mean, and SD:

From the table below, you can take the values listed for the parameter of interest and use them along with the measurement value of the parameter and the BSA in the following formula to calculate the Z-score:

 

 Parameter  α Mean  SD 
  MVAP 0.50  2.31 0.24
  MVLAT 0.50 2.23 0.22
  MVA 1.00 4.06 0.68
  TVAP 0.50 2.36 0.28
  TVLAT 0.50 2.36 0.29
  TVA 1.00 4.39 0.83
  ANN 0.50 1.48 0.14
  ROOT 0.50 2.06 0.18
  STJ 0.50 1.69 0.16
  AAO 0.50 1.79 0.18
  ARCHPROX 0.50 1.53 0.23
  ARCHDIST 0.50 1.36 0.19
  ISTH  0.50 1.25 0.18
  LMCA 0.45 2.95 0.57
  LAD  0.45 1.90 0.34
  RCA 0.45 2.32 0.55
  PVSAX 0.50 1.91 0.24
  PVLAX 0.50 2.01 0.28
  MPA 0.50 1.82 0.24
  RPA 0.50 1.07 0.18
  LPA 0.50 1.10 0.18
  LVEDD 0.45 3.89 0.33
  LVPWT 0.40 0.57 0.09
  LVST 0.40 0.58 0.09
  LVEDL 0.45 6.31 0.46
  LVEDLEPI 0.45 6.87 0.45
  LVEDA 0.90 11.91 1.89
  LVEDAEPI 0.90 20.00 2.59
  LVEDV 1.30 62.02 11.94
  LVEDVEPI 1.30 113.14 17.85
  LVM 1.25 53.02 9.06
  LVMTV 0 0.88 0.16
  LVTTD 0 0.15 0.03
  LVSI 0 1.63 0.17

 

What is the relationship between echo measurements and BSA?

The calculated regression equations from PHN data were:

Echo measurement = intercept + slope * BSAα

Measurement Alpha Intercept Slope
  MV (AP) (cm) 0.5 0.082924814 2.208397289
  MV (LAT) (cm) 0.5 0.142783317 2.058261615
  MVA (cm2) 1.0 0.196597638 3.757279658
  TV (AP) (cm) 0.5 -0.060825454 2.431341306
  TV (LAT) (cm) 0.5 0.249147894 2.064415385
  TVA (cm2) 1.0 0.186568091 4.117988499
  ANN (cm) 0.5 -0.016599775 1.506884773
  ROOT (cm) 0.5 0.025841881 2.034421612
  STJ (cm) 0.5 -0.010501014 1.706720717
  AAO (cm) 0.5 0.037633274 1.742197392
  ARCH (PROX) (cm) 0.5 -0.164254288 1.729068410
  ARCH (DIST) (cm) 0.5 -0.064930281 1.436019255
  ISTH (cm) 0.5 0.060606576 1.182100289
  LMCA (mm) 0.45 0.110674881 2.820117190
  LAD (PROX) (mm)  0.45 0.052951441 1.839996768
  RCA (PROX) (mm) 0.45 0.012047694 2.301336377
  PV (SAX) (cm) 0.5 0.009528205 1.907058780
  PV (LAX) (cm) 0.5 -0.220768333 2.286834232
  MPA (cm) 0.5 0.117718176 1.682071763
  RPA (cm) 0.5 -0.008988176 1.088778500
  LPA (cm) 0.5 0.001348966 1.109745289
  LVEDD (cm) 0.45 0.045047560 3.843553561
  LVPWT (cm) 0.4 -0.006805387 0.572766918
  LVST (cm) 0.4 0.008416262 0.566410942
  LVEDL (cm) 0.45 -0.079863429 6.410199218
  LVEDL (EPI) (cm) 0.45 -0.067593474 6.950057220
  LVEDA (cm2) 0.9 0.230577153 11.707701221
  LVEDA (EPI) (cm2) 0.9 0.456500737 19.404203636
  LVEDV (cm3) 1.3 -0.378916534 64.201157201
  LVEDV (EPI) (cm3) 1.3 -1.416047154 116.66554843
  LVM (gm) 1.25 -2.652765755 57.253578598
  LVESD (cm) 0.5 0.257530334 2.361910336
  LVESV (cm3) 1.3 -0.942421777 27.499070729
Regression equations for raw echo = intercept + slope * BSAα
Alpha = power used for BSA transformation (BSAα)

Parameter Abbreviations: AAO=ascending aortic diameter; ANN=aortic annular diameter; ARCHDIST=distal transverse arch diameter; ARCHPROX=proximal transverse arch diameter; ISTH=aortic isthmus diameter; LAD=proximal left anterior descending coronary artery diameter; LMCA=left main coronary artery diameter; LPA=left pulmonary artery diameter; LVEDA=LV (LV) short-axis end-diastolic endocardial area; LVEDAEPI=LV short-axis end-diastolic epicardial area; LVEDD=LV short-axis end-diastolic endocardial diameter; LVEDL=LV long-axis end-diastolic endocardial length; LVEDLEPI=LV long-axis end-diastolic epicardial length; LVEDV=LV short-axis end-diastolic endocardial volume; LVEDVEPI=LV short-axis end-diastolic epicardial volume; LVM=LV mass; LVMTV=LV mass-to-volume ratio; LVPWT=LV short-axis end-diastolic posterior wall thickness; LVSI=LV sphericity index; LVST=LV short-axis end-diastolic septal thickness; LVTTD=LV thickness-to-dimension ratio; MPA=main pulmonary artery diameter; MVAP=mitral anteroposterior diameter; MVLAT=mitral lateral diameter; MVA=mitral area; PVLAX=pulmonary annular long-axis diameter; PVSAX=pulmonary annular short-axis diameter; RCA=proximal right coronary artery diameter; ROOT=aortic root diameter; RPA=right pulmonary artery diameter; STJ=sinotubular junction; TVAP=tricuspid anteroposterior diameter; TVLAT=tricuspid lateral diameter; TVA= tricuspid area.

Measurement Abbreviations: AAO = ascending aortic diameter; ANN = aortic annular diameter; ARCH (DIST) = distal transverse aortic arch diameter; ARCH (PROX) = proximal transverse aortic arch diameter; ISTH = aortic isthmus diameter; LAD (PROX) = proximal left anterior descending coronary artery diameter; LMCA = left main coronary artery diameter; LPA = left pulmonary artery diameter; LVEDA = left ventricular (LV) short-axis end-diastolic endocardial area; LVEDA (EPI) = LV short-axis end-diastolic epicardial area; LVEDD = LV short-axis end-diastolic endocardial diameter; LVEDL = LV long-axis end-diastolic endocardial length; LVEDL (EPI) = LV long-axis end-diastolic epicardial length; LVEDV = LV short-axis end-diastolic endocardial volume; LVEDV (EPI) = LV short-axis end-diastolic epicardial volume; LVM = LV mass; LVPWT = LV short-axis end-diastolic posterior wall thickness; LVESD = LV short-axis end-systolic diameter; LVESV = LV end-systolic volume; LVSI = LV sphericity index; LVST = LV short-axis end-diastolic septal thickness; MPA = main pulmonary artery diameter; MV (AP) = mitral annular anteroposterior diameter; MV (LAT) = mitral annular lateral diameter; MVA = mitral annular area; PV (LAX) = pulmonary annular long-axis diameter; PV (SAX) = pulmonary annular short-axis diameter; RCA (PROX) = proximal right coronary artery diameter; ROOT = aortic root diameter; RPA = right pulmonary artery diameter; STJ = aortic sinotubular junction; TV (AP) = tricuspid annular anteroposterior diameter; TV (LAT) = tricuspid annular lateral diameter; TVA = tricuspid annular area.