These are the default z-score equations currently used on KinetDx/syngoDynamics workstations...
Z scores of 15 cardiac structures including the mitral valve, aortic valve, pulmonary arteries, etc. Regression equations were derived relating cardiac dimensions to the size of the body using a population of 125 normal infants and children. From the Wessex Cardiothoracic Unit, Southampton General Hospital, UK.
Relationship of the dimension of cardiac structures to body size: an echocardiographic study in normal infants and children.
Daubeney PE, Blackstone EH, Weintraub RG, Slavik Z, Scanlon J, Webber SA.
Cardiol Young. 1999 Jul;9(4):402-10.