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NORMAL VALUES OF MEAN AORTIC FLOW VELOCITY IN INFANTS AND CHILDREN MEASURED BY PULSED DOPPLER ECHOCARDIOGRAPHY

Traditionally, the estimation of cardiac output by pulsed Doppler echocardiography (PDE) involves the computation of mean aortic flow velocity(MAFV) and aortic cross-sectional area(CSA); as CSA varies with surface area(BSA), we postulated that MAFV should be relatively constant. However, data on normal values of MAFV in infants and children is lacking. Accordingly, 51 normal children aged one month to 15.1 years(m=5.6 years)were prospectively studied by PDE via the suprasternal view using a 3MHz transducer with fast Fourier transform spectral analysis of the doppler shift frequency in the ascending aorta. MAFV was calculated by averaging the planimetered area under the spectral display of three consecutive beats using the outer edge of the display as the defining border. Results showed that MAFV=27.8 + 5.2 cm/sec. This was relatively constant decreasing slightly with age and BSA;MAFV at one year=30.3 cm/sec, and 23.4 cm/sec, at 15 years. MAFV=30.381-0.039 age(R2=0.123, p= 0.05)and MAFV=32.051-5.368 BSA(R2=0.097, p=0.05). Aortic root diameter (Ao.D.) progressively increased with age and BSA with Ao.D.= 1.327+0.06 age(R2=0.806, p<0.001, Ao.D.=0.968+0.956 BSA(R2=0.844, p<0.001)respectively. We conclude that MAFV in infants and children remains relatively constant decreasing slightly with age and BSA. However Ao.D. increases more markedly with age and BSA, and, therefore accounts for the increase in cardiac output when measured by PDE. whether MAFV alone may be used for monitoring cardiac output remains to be validated. *Supported by the B.C. Heart Foundation.