Doppler evaluation of normalized peak filling rate in early neonatal period

Diastolic left ventricular function in preterm infants with a patent ductus arteriosus: a serial Doppler echocardiography study

In very low birth weight neonates, a left-to-right shunt via persistent ductus arteriosus (PDA) may interact with diastolic left ventricular function, but specific changes of Doppler parameters have yet to be reported. In a serial transmitral Doppler study, we investigated the impact of a PDA on diastolic function parameters. Twenty-two patients with and without PDA were examined on day 3.8+/-1 and day 14+/-2 after birth. By the first examination, 13 out of 22 patients had a PDA; by the second examination, the number was still 8 out of 22. Peak early and atrial flow velocities (44.8+/-15 and 50.1+/-13 cm/s, respectively) were higher (p<0.05) for neonates with PDA compared to those with closed duct (30.9+/-6 and 34.2 cm/s, respectively). Isovolumic relaxation time (IVRT) was shorter in neonates with PDA (45+/-7 ms, N=21) compared to those with a closed duct (55.3+/-5 ms, N=23) (p<0.01). IVRT correlated inversely with cardiac index (R=-0.79, p<0.01). All observed changes reversed to the normal range after closure of the PDA. When premature infants with a PDA experience a preload challenge, early and atrial peak velocities increase and IVRT shortens significantly. This coincidence of elevated transvalvular pressure differences and decreased IVRT in neonates with immature diastolic function can best be explained as a result of left atrial pressure elevation. Consequently, pulmonary venous pressure must be elevated, with its inherent effect on pulmonary capillary physiology. Thus, the monitoring of left ventricular diastolic function adds significant information to the care of preterm infants with a PDA.

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.

Abnormal left ventricular diastolic filling patterns in small-for-gestational-age infants

Doppler transmitral flow velocity patterns in assessing left ventricular diastolic function in small-for-gestational-age infants have been poorly understood. The purpose of this study is to examine Doppler filling patterns in small-for-gestational-age infants (n = 13) and to compare them with those in age-matched appropriate-for-gestational-age infants (n = 29). We measured peak flow velocities of early diastole (peak E wave) and atrial contraction (peak A wave), ratio of peak E wave to peak A wave (peak E/A wave), velocity time integrals of E wave (VTIE wave) and A wave (VTIA wave), ratio of VTIE wave to VTIA wave (VTIE/A wave), first third filling fraction, peak filling rate normalized to stroke volume, and deceleration time. Mean gestational age and heart rate did not show a significant difference between the appropriate- and the small-for-gestational-age infants. The mean birth weight in the small-for-gestational-age infants was significantly lower than that in the appropriate-for-gestational-age infants (802+/-220 vs. 1184+/-260 g, P<0.01). In the small-for-gestational-age infants, the peak E wave, peak A wave, peak E/A wave,VTIE wave, first third filling fraction, and peak filling rate normalized to stroke volume were significantly lower than those in the age-matched appropriate-for-gestational-age infants (21.9+/-6.7 vs. 32.2+/-6.9 cm/s, 26.5+/-6.2 vs. 34.5+/-6.2 cm/s, 0.82+/-0.15 vs. 0.93+/-0.14, 1.88+/-0.45 vs. 2.39+/-0.51 cm, 0.36+/-0.04 vs. 0.41+/-0.04, 5.86+/-0.75 vs. 7.11+/-0.63/s, P<0.05, respectively). In the small and appropriate for gestational age infants, peak E wave, VTIE wave, and peak E/A increased significantly with increasing body weight. In the small-for-gestational-age infants, the slopes of regression lines between body weights and peak E wave and VTIE wave were significantly lower than those in the appropriate for gestational age infants, suggesting a significant reduction in E wave even when considering a difference in their body weight. This study suggests that the significant decreases in the early diastolic filling in the small-for-gestational-age infants may be related to the reduced left ventricular diastolic function.

Role of left ventricular mass/volume ratio on transmitral flow velocity patterns from infancy to childhood

Age-related changes in left ventricular diastolic filling have been reported to occur in normal children in studies using Doppler echocardiographic methods. However, little information currently exists on the relationships between transmitral flow velocity patterns and the left ventricular mass. We measured left ventricular end-diastolic volume, left ventricular mass, mass/volume ratio, and transmitral flow velocity patterns by M-mode and Doppler echocardiography in 165 normal children aged 5 days to 195 months. Subjects were divided into 6 age groups: <1; 1 to <3; 3 to <5; 5 to <7; 7 to <9; and > or = 9 years old. The left ventricular end-diastolic volume and mass increased progressively with increasing age. However, the mass/volume ratio in infants <1 year was significantly higher than that in infants 1 to <3 years (1.32+/-0.25 vs. 1.14+/-0.16, p<0.01) without any changes of the ratio thereafter. The peak E wave in infants <1 year was significantly lower than that in 1 to <3 years (71+/-18 vs. 92+/-13 cm/s, p<0.01) without changes thereafter. As the flow velocity time integral of E wave increased and that of A wave remained constant, the flow velocity time integral of E/A wave increased with increasing age. The early diastolic tilling fraction in infants <1 year was lower than that in infants 1 to 3 years. (0.61+/-0.07 vs. 0.70+/-0.06, p<0.01). The atrial filling fraction in infants <1 year was higher than that in infants 1 to <3 years (0.40+/-0.08 vs. 0.30+/-0.06, p<0.01) with a little decrease thereafter. The peak E wave, early diastolic tilling fraction, and the atrial filling fraction correlated with the logarithm of age (p<0.01). Age-related changes in these Doppler echocardiographic findings suggest reduced left ventricular early diastolic filling patterns. The mass/volume ratio correlated linearly with peak E wave, early diastolic filling fraction, and atrial filling fraction (r=-0.38, -0.33, and 0.26, p<0.01). No significant relationships between mass/volume ratio and the other Doppler indices were found. Thus, the age-related reduction in the mass/volume ratio may be one of the mechanisms underlying age-related changes in the early diastolic ventricular filling as assessed by Doppler echocardiography.

Changes in left ventricular diastolic filling patterns before and after the closure of the ductus arteriosus in very-low-birth weight infants

To evaluate serial changes in left ventricular diastolic filling patterns in preterm infants, we performed echocardiographic examinations in 18 very-low-birth weight infants and 20 fullterm infants before and after the closure of the ductus arteriosus. In the fullterm infants, the ductal closure induced significant decreases in the peak velocity and flow velocity integral of early diastole, first third filling fraction, and mitral stroke volume. In the preterm infants, by contrast, there were significant increases in the flow velocity integral of early diastole, first third filling fraction, and mitral stroke volume after the ductal closure. No differences following the ductal closure were found in the atrial phase of filling and peak filling rate normalized to stroke volume in either group. When the ductus arteriosus was open, essentially the same left-to-right shunting of the ductus arteriosus was detected in both preterm and fullterm infants, but the Doppler flow patterns of the patent foramen ovale were different: the fullterm infants had a single flow peak mainly during ventricular late systole and early diastole, but the preterm infants had two or three flow peaks with nearly equal amplitudes lasting from ventricular systole to diastole, which resembled the Doppler flow pattern of atrial septal defect. Only a faint Doppler flow signal of the foramen ovale was observed after the ductus arteriosus closed. Our results obtained from the preterms suggest that the left-to-right shunt through the foramen ovale may be one important factor to alter the Doppler transmitral filling patterns during the fetal to neonatal cardiovascular changes.

Effects of cardiac output on Doppler transmitral and transtricuspid flow velocity patterns in very low birth weight infants

We studied effects of cardiac output on Doppler transmitral and transtricuspid flow velocities in 24 appropriate for gestational age premature infants. We measured peak flow velocity of early diastole (peak E) and atrial contraction (peak A), ratio of peak flow velocity of early diastole to atrial contraction (peak E/A), total flow velocity-time integral, the first third filling fraction, peak filling rate normalized to stroke volume, and deceleration time (DT). Cardiac output was calculated as the product of the aortic flow velocity-time integral, aortic valve area, and heart rate. The cardiac output increased significantly with advancing gestational age and body weight (r = 0.78 and 0.86, P < 0.01, respectively). With increasing cardiac output, the transmitral as well as transtricuspid peak E, peak E/A, and total flow velocity-time integral increased significantly without any change in the peak filling rate normalized to stroke volume, peak A, and deceleration time. The transmitral as well as transtricuspid peak E did not correlate with the heart rate. Although these results do not establish whether changes in ventricular relaxation process or in cardiac output is responsible for the progressive increase in the peak E and peak E/A. Unchanged peak filling rate normalized to stroke volume of the left and right ventricles suggest that changes in cardiac output with maturity is, in fact, one of the important contributory factors. This evidence should be borne in mind in interpreting ventricular diastolic filling as an index of ventricular diastolic function in premature infants.