Left atrial ejection force in healthy newborn infants.

Background: Atrial ejection force (AEF) expresses the force exerted by the left atrium to the mass of blood passing through the mitral valve during atrial systole. It provides a diagnostic and predictive parameter for evaluating left ventricular diastolic abnormalities and a physiologic assessment of atrial systolic function.

Methods: We obtained normal values of AEF in a group of 47 newborn infants with normal heart function and structure, using Doppler echocardiographic parameters of transmitral filling flow. AEF is defined as the product of the density of blood, the mitral valve area, and the square of peak A velocity [AEF = 0.5 x rho x mitral valve area x (peak A velocity)(2)].

Results: Mean and SD of AEF was 1.12 +/- 0.42 kilodynes. Atrial filling fraction (r = 0.74, P value = .000), A acceleration rate (r = 0.67, P value = .000), A deceleration rate (r = 0.64, P value = .000), and heart rate (r = 0.70, P value = .000) showed a positive correlation with AEF. Rapid filling fraction (r = -0.71, P value = .000) and E/A ratio (r = -0.6, P value = .000) had a negative correlation with AEF.

Conclusion: AEF index in neonatal period is augmented and comparable with the values in adult population that could be explained by the specific pattern of slow ventricular relaxation in newborn infants. Complex aspects of diastolic function in newborn infants could be assessed beyond a simple E to A ratio by providing an estimate of normal values for AEF in this age group.