Doppler flow parameters of left ventricular filling in infants: How long does it take for the maturation of the diastolic function in a normal left ventricle to occur?

Objective: To study the impact of the maturational process of diastolic left ventricular function on transmitral Doppler flow parameters. Methods and Participants: In a survey we examined pulsed-wave Doppler signals and diastolic time intervals from 238 healthy neonates and infants. Using multiple linear regression analysis, we evaluated the impact of physiological determinants on parameter expression. Results: Early-filling and atrial-filling peak velocities, early-filling acceleration and deceleration rates, and the atrial-filling time velocity integral reached a climax within 2 months after birth, while early-filling time velocity integral followed increasing throughout the study period. The isovolumic relaxation time was found to be significantly longer for neonates than for infants older than 2 months. The observed parameter movements could be attributed to changes of stroke volume and mitral valve area for early filling-time velocity integral (R-2 = 0.93), and of heart rate, stroke volume, and mitral valve area for early filling peak velocity (R-2 = 0.84), and atrial-filling time velocity integral (R-2 = 0.65). Isovolumic relaxation time and atrial-filling peak velocity became heart rate dependent not before 3 months after birth. Conclusions: The observed parameter changes are powerful indicators for the maturational process in diastolic function. This process is mainly completed by 3 months of age.