Serial echocardiographic and Doppler evaluation of left ventricular systolic performance and diastolic filling in premature infants

To examine the effects of somatic growth on left ventricular systolic and diastolic functions in premature infants, we performed serial two-dimensional, M-mode and Doppler echocardiograms of 18 premature infants in the early neonatal period (mean of 14 days) and on the day when they were discharged from the hospital (mean of 94 days). The relation between rate-corrected mean velocity of fiber shortening and end-systolic wall stress relation was used as a load-independent estimate of contractility. Diastolic function was assessed by transmitral Doppler filling velocity patterns. The end-systolic wall stress was significantly lower in the first examination than in the second examination (38+/-8 vs. 46+/-10 g/cm2, P < 0.005). However, there was no significant difference in the rate-corrected velocity of fiber shortening between the two examinations. An inverse linear relation between the end-systolic wall stress and the rate-corrected mean velocity of fiber shortening was found in each examination. The slopes of these two regression lines showed no significant difference, suggesting that the left ventricular contractility is on the same level during this study period. The transmitral Doppler flow velocity patterns markedly altered between the two observations. The peak E wave, peak A wave, peak E/A ratio, flow velocity time integral of E/A wave, the first third filling fraction, and the normalized peak filling rate to stroke volume increased significantly during the study period (78+/-14 vs. 31+/-9 cm/s, 61+/-12 vs. 33+/-7 cm/s, 1.29+/-0.18 vs. 0.93+/-0.19, 1.75+/-0.58 vs. 1.17+/-0.24, 0.42+/-0.07 vs. 0.37+/-0.05, and 9.48+/-1.71 vs. 7.30+/-0.96/s, respectively, P < 0.001), suggesting a relative shift of Doppler filling into the early diastole. We demonstrated that the age- and growth-related alterations in the transmitral Doppler filling patterns occurred dramatically without changes in contractility during the first 3 months after birth. This diastolic filling change may be related to the age-related maturation in the left ventricular diastolic properties.