Two-dimensional Doppler echocardiographic assessment of closure of the ductus arteriosus in normal newborn infants

Diagnostic value of reversed differential cyanosis in (supra)cardiac total anomalous pulmonary venous return

BACKGROUND

To investigate the occurrence of reversed differential cyanosis (RDC) in case of (supra)cardiac total anomalous pulmonary venous return (TAPVR), we explored the hemodynamic changes and oxygen saturation levels during the fetal-to-neonatal transition in (supra)cardiac TAPVR, thereby revealing determinant factors of RDC.

METHODS

A computational model was used to simulate the cardiovascular fetal-to-neonatal transition up to 24 h after birth. Abnormalities associated with TAPVR, like patent ductus arteriosus (PDA) and persistent pulmonary hypertension of the neonate (PPHN), were imposed on the model. Hemodynamic impact on flow distribution and right-sided pressures as well as oxygen saturations were assessed.

RESULTS

Model findings demonstrated that RDC in (supra)cardiac TAPVR was dependent on two key factors: (1) the type of pulmonary venous connection being supracardiac or cardiac, and (2) the presence of a patent ductus arteriosus exhibiting right-to-left shunting. Persistence of RDC was mainly determined by the latter; an increase in pulmonary-to-systemic pressure difference by PPHN or PDA-induced pulmonary over-circulation contributed to persistence of RDC.

CONCLUSION

This study highlights the significance of RDC in (supra)cardiac TAPVR and suggests to incorporate early screening ( < 24 h after birth) and to consider RDC as an immediate fail in screening protocols to ensure prompt detection of (supra)cardiac TAPVR.

IMPACT

Utilizing a validated computational model for the cardiovascular fetal-to-neonatal transition, this study sheds light on the complex hemodynamics in neonates with (supra)cardiac Total Anomalous Pulmonary Venous Return (TAPVR). Model findings suggest that the often-present pulmonary over-circulation in neonates with TAPVR might significantly contribute to the anomaly's frequent omission during pulse-oximetry screening beyond the first 24 h after birth. This study highlights the diagnostic value of reversed differential cyanosis in early screenings within the first 24 h after birth. By including RDC as an immediate fail in early pulse-oximetry screenings, the likelihood of missing (supra)cardiac TAPVR cases could be reduced.

Cardiovascular fetal-to-neonatal transition: an in silico model

BACKGROUND

Previous models describing the fetal-to-neonatal transition often lack oxygen saturation levels, homeostatic control mechanisms, phasic hemodynamic signals, or describe the heart with a time-varying elastance model.

METHODS

We incorporated these elements in the adapted CircAdapt model with the one-fiber model for myocardial contraction, to simulate the hemodynamics of the healthy term human fetal circulation and its transition during the first 24 h after birth. The fetal-to-neonatal model was controlled by a time- and event-based script of changes occurring at birth, such as lung aeration and umbilical cord clamping. Model parameters were based on and validated with human and animal data.

RESULTS

The fetal circulation showed low pulmonary blood flow, right ventricular dominance, and inverted mitral and tricuspid flow velocity patterns, as well as high mean ductus venosus flow velocity. The neonatal circulation showed oxygen saturation levels to gradually increase to 98% in the first 15 min after birth as well as temporary left ventricular volume overload.

CONCLUSIONS

Hemodynamics of the term fetus and 24-h-old neonate, as well as the events occurring directly after birth and the transition during the first 24 h after birth, were realistically represented, allowing the model to be used for educational purposes and future research.

IMPACT

With the addition of oxygen saturation levels, homeostatic pressure-flow control mechanisms, and the one-fiber model for myocardial contraction, a new closed-loop cardiovascular model was constructed to give more insight into the healthy term human fetal circulation and its cardiovascular transition during the first 24 h after birth. Extensive validation confirmed that the hemodynamics of the term fetus and the fetal-to-neonatal transition were realistically represented with the model. This well-validated and versatile model can serve as an education as well as a research platform for in silico investigation of fetal-to-neonatal hemodynamic changes under a wide range of physiological and pathophysiological conditions.

Cardiopulmonary Adaptation During First Day of Life in Human Neonates

OBJECTIVE

To characterize the natural history of cardiopulmonary physiology in the first 24 hours after birth.

STUDY DESIGN

A prospective observational study of healthy newborns was conducted at a large tertiary perinatal center. Echocardiography was performed at <0.5, 2-3, 7-10, and 22-24 hours of age. Specifically, assessment of pulmonary vascular resistance (PVR) (pulmonary artery acceleration time [PAAT], right ventricular ejection time, right ventricular ejection time:PAAT [PVR index], and PAAT indexed to heart rate [PAATi]), ventricular outputs (right and left), and ventricular function (tricuspid annular planar excursion, right ventricular [RV] fractional area change [FAC], RV/left ventricular [LV] global peak longitudinal strain, and LV ejection fraction) were performed. One-way repeated-measures ANOVA analysis was performed for time-dependent variables.

RESULTS

In total, 15 neonates (9 males), born at 40 ± 0.8 weeks and 3.5 ± 0.5 kg, respectively, were studied. We observed increased PAATi (P < .05) by 2-3 hours, followed by a subsequent decline in all indices of PVR (PVR index, PAATi, midsystolic notching, and right-to-left ductal flow [P < .0001]). Although right and left ventricular stroke volume increased over the study interval (P < .001), LV output remained stable. All indices of RV function (tricuspid annular planar excursion, RV fractional area change 4-chamber, and RV global peak longitudinal strain-3 chamber [P < .001]) increased during the study interval.

CONCLUSION

The immediate transition after birth is characterized by lower PVR, reversal of the transductal shunt, and increased biventricular stroke volume. The differential adaptive response of the RV and LV is novel and may relate to loading conditions and patent ductus arteriosus closure.

Prophylactic and early targeted treatment of patent ductus arteriosus

Treatment of a haemodynamically significant patent ductus arteriosus (PDA) in the very preterm infant has been an accepted approach for several decades. However, the rationale for closure of PDA has recently been challenged due to reports of success with conservative approaches and the lack of evidence for longer-term benefits from treatment. In this article, we address an approach to assess treatment of those babies most likely to benefit.

Measurement of systemic oxygen delivery and inotropy in healthy term neonates with the Ultrasonic Cardiac Output Monitor (USCOM)

INTRODUCTION

The aim of this study was to assess the normal values for Smith-Madigan inotropy (SMI), Smith-Madigan inotropy index (SMII), oxygen delivery (DO2) and oxygen delivery index DO2I in healthy term neonates on the first day of life and during circulatory adaptation over the first three days of life.

METHODS

Hemodynamics of the left heart were measured non-invasively in 71 normal full-term neonates over the first three days using the Ultrasonic Cardiac Output Monitor (USCOM). This was combined with hemoglobin concentration from umbilical cord blood and pulse oximetry to calculate DO2 and DO2I. Blood pressure was measured using automated oscillometry and combined with the hemodynamic measures and hemoglobin concentration using the Smith-Madigan method to calculate inotropy (SMI) and inotropy index (SMII).

RESULTS

SMI and SMII showed no significant change during the study period, ranging from 154 to 168 mW and 694 to 731 mW/m(2). Mean (SD) DO2 and DO2I showed a significant fall over three days from 131 (63) ml/min and 596 (278) ml/m(2)/min to 118 (46) ml/min and 517 (173) ml/m(2)/min (p<0.01 and <0.001 respectively) with a corresponding decrease in cardiac output from 758 (143) ml/min to 658 (131) ml/min, (p=0.002). There was no significant change in stroke volume, heart rate, SMI or SMII within the first day. DO2 and DO2I showed small but significant decreases within the first day from 153 (46) ml/min and 699 (174) ml/min/m(2) to 129 (36) ml/min and 609 (141) ml/min/m(2) (p=0.017 and 0.048 respectively).

CONCLUSIONS

Normal inotropy of the left heart and systemic DO2 values in healthy full-term neonates over the first three days of life were assessed using the USCOM. Subjects showed stable myocardial contractility over the first three days with decreasing DO2 and DO2I in line with the decrease in cardiac output (CO). DO2 and DO2I showed small but significant reductions during the first 24 h. USCOM proved to be a feasible and convenient non-invasive bedside tool to assess inotropy and oxygen delivery in neonates.

A model for educational simulation of hemodynamic transitions at birth

Birth is characterized by swift and complex transitions in hemodynamic and respiratory variables. Unrecognized pathologies or incidents may quickly become fatal or cause permanent damage. This article introduces an essential component of an acute perinatal care simulator, namely a model for educational simulation of normal hemodynamic transitions seen during and shortly after birth. We explicitly formulate educational objectives and adapt a preexisting model for the simulation of neonatal cardiovascular physiology to include essential aspects of fetal hemodynamics. From the scientific literature, we obtain model parameters that characterize these aspects quantitatively. The fetal model is controlled by a time- and event-based script of changes occurring at birth, such as onset of breathing and cord clamping, and the transitory phase up to 24 h after birth. Comparison of simulation results with published target data confirms that realistic simulated hemodynamic vital signs are achieved.

Treatment of patent ductus arteriosus

Patent ductus arteriosus (PDA) continues to be one of the most common problems found in premature infants. The incidence is inversely related to gestation, but may be reduced by use of antenatal steroids, lower volume fluid regimen and judicious use of phototherapy. However, there continues to be controversy as to the appropriate indications for treatment, varying from prophylaxis on the basis of gestation to treatment only when a PDA is demonstrably significant. The situation is further complicated by differing diagnostic criteria for ductal patency or significance. Prophylactic treatment is likely to result in up to 64% of babies being treated unnecessarily. Early treatment of significant or symptomatic PDA depends upon accurate diagnosis. PDA closure can then be achieved using medical means, with surgery reserved for patients in whom this fails or in whom there are contra-indications. However, the optimum timing for intervention remains unknown.

Echocardiographic evaluation of the ductal morphology in patients with refractoriness to lipo-prostaglandin E1 therapy

BACKGROUND

Lipo-prostaglandin (PG)E1 is effective at lower doses and has fewer side effects than PGE1-cyclodextrin (CD). Previous studies, however, have suggested that some patients show refractoriness to lipo-PGE1 in the course of treatment. The present paper examines: (i) whether such cases can be predicted by examining the ductal morphology before and 24 h after the start of lipo-PGE1 infusion; and (ii) whether PGE1-CD dilates the ductus arteriosus in patients with refractoriness to lipo-PGE1.

METHODS

The ductal morphology was evaluated with two echo indices, such as minimal and minimal plus maximal intraluminal diameters of the ductus. Two-dimensional echocardiography was performed in 24 patients with ductus-dependent congenital heart disease. The two echo indices were measured before and 24 h after lipo-PGE1 infusion and also at least twice per week until surgery.

RESULTS

In 19 of 24 patients, ductal patency was maintained until surgical treatment (group A). The remaining five patients (21%) showed ductal closure during the course of the lipo-PGE1 therapy (group B). There were no significant differences between the two groups, in either the maximal or minimal diameters, which were examined before and 24 h after treatment. In the five patients of group B, lipo-PGE1 was replaced with a relatively high dosage of PGE1-CD (50-100 ng/kg per min), resulting in good ductal patency until surgery.

CONCLUSIONS

Patients with refractoriness to lipo-PGE1 therapy could not be predicted from initial intraluminal diameters of the ductus using echocardiography. Therefore, serial echocardiographic examinations are important to detect early findings of ductal closure. In addition, PGE1-CD is still useful as back-up therapy in such patients.

Reference ranges for two-dimensional echocardiographic examination of the fetal ductus arteriosus

OBJECTIVES

To establish reference ranges for 2D-echocardiographic examination of the fetal ductus arteriosus and its relationship to the main pulmonary artery and the aorta.

METHODS

A prospective cross-sectional echocardiographic study was performed in 222 normal fetuses from 13 to 41 weeks of gestation using high resolution/color Doppler ultrasound equipment.

RESULTS

Gestational age-specific reference ranges are given for the diameter of the pulmonary valve anulus, diameter of the ductus arteriosus at its beginning, middle, and end, ductal length, ductal diameter-to-pulmonary valve anulus diameter ratio, and the spatial relationship of the ductus arteriosus to the main pulmonary artery and to the aorta.

CONCLUSIONS

The presented data derived from a study group of 222 normal fetuses provide in-vivo insights into the morphology of the ductus arteriosus and its relationship to the adjacent vessels. The reference ranges may be helpful in prenatal diagnosis of cardiac malformations and abnormalities of the ductus arteriosus, such as obstruction or aneurysm from 13 to 41 weeks of gestation.

Postnatal closure of ductus venosus in preterm infants < or = 32 weeks. An ultrasonographic study

AIM

To assess ultrasonographically the flow pattern and the time of postnatal closure of ductus venosus in preterm infants < or = 32 weeks.

METHODS

Thirty-three preterm infants < or = 32 weeks were studied within the first 1 to 5 days of life and followed every second day with ultrasound until no flow was detected either through the ductus venosus or the ductus arteriosus.

RESULTS

The ductus venosus was closed in only 9% by day 3, in 40% by day 8 and 88% by day 18. All were closed by day 37. This is significantly later than in healthy term neonates. Closure of the ductus venosus was not significantly correlated with closure of ductus arteriosus.

CONCLUSION

The ductus venosus shows a delayed closure in preterm infants, with no significant correlation to the closure of the ductus arteriosus or the condition of the infant. We speculate that immaturity of the ductus venosus and possibly increased levels of dilating prostaglandins leads to a delayed obliteration of the vessel. An open ductus venosus represents a portocaval shunt and may have metabolical and pharmacological consequences.

Prospective echocardiographic analysis of progressive obstruction of the proximal pulmonary artery in congenital heart disease and obstructed pulmonary flow

BACKGROUND

It is uncertain whether proximal pulmonary artery (PA) obstruction exists soon after birth and whether its progress relates directly to postnatal ductal constriction in congenital heart disease and obstructed pulmonary flow.

METHODS

Serial morphometric analyses of the PA branches by echocardiogram were performed in 28 patients (mean age at initial study 2.5 days) until severe constriction of the ductus occurred (mean age 47 days). These patients were divided into 2 groups by subsequent angiographic or postmortem confirmation; 10 with proximal PA obstruction (group 1) and 18 without obstruction (group 2).

RESULTS

At the time of initial examination, the mean indexed diameter of the proximal PA on the side of the ductus arteriosus in group 1 was significantly smaller than that on the contralateral side (5.2+/-0.7 versus 9.0+/-0.7 mm/BSA0.5, P < .001) or that in group 2 (8.0+/-0.4 mm/BSA0.5, P < .001). In group 1, 8 patients had a proximal PA index on the ductal side < or = 5.5 mm/BSA0.5, which was less than those of any group 2 patients. After severe constriction of the ductus, the proximal PA index on the ductal side further decreased only in group 1 (P < .01).

CONCLUSIONS

These data indicate that unilateral obstructive lesion of branch PA is present shortly after birth and its progression relates directly to ductal constriction. Neonates with branch PA obstruction can be identified on their initial echocardiogram as having a proximal PA index on the ductal side < or = 5.5 mm/BSA0.5.

Ultrasonographic study of ductus venosus in healthy neonates

AIM

To assess ultrasonographically the flow pattern and the time of postnatal closure of ductus venosus related to the other fetal shunts.

METHODS

Fifty healthy, term neonates were studied from day 1 up to day 18 using a VingMed CFM 800A ultrasound scanner.

RESULTS

Ductus arteriosus was closed in 94% of the infants before day 3. Ductus venosus, however, was closed in only 12% at the same time, in 76% before day 7, and in all infants before day 18. A closed ductus venosus or ductus arteriosus did not show signs of reopening. Pulsed and colour Doppler flow could be detected across the foramen ovale in all infants during the sequential investigation. At day 1, when the pulmonary vascular resistance was still high, a reversed Doppler flow velocity signal was seen in ductus venosus in 10 infants (20%) and a bidirectional flow in ductus arteriosus in 26 (52%). Closure of the ductus venosus was not significantly correlated with closure of the ductus arteriosus nor related to sex nor weight loss.

CONCLUSIONS

The time of closure of the ductus venosus evaluated by ultrasonography is much later than that of the ductus arteriosus. The flow pattern in ductus venosus reflects the portocaval pressure gradient and the pressure on the right side of the heart and in the pulmonary arteries. Both the flow pattern in the ductus venosus as well as that in the ductus arteriosus may be an indication of compromised neonatal haemodynamics.

Pulmonary artery pressure in term and preterm neonates

Systolic pulmonary artery pressure (PAP) during the first 4 days after birth was determined in 41 healthy term and 46 preterm infants by measuring ductal Doppler flow velocity and systemic arterial pressure (SAP). Among preterm infants, 21 had respiratory distress syndrome (RDS) and 25 did not. Sequential indices within 96 h of age were presented respectively. At the ages of 2 and 12 h the ratio between pulmonary and systemic arterial pressure was significantly higher in term than in preterm infants without RDS (p < 0.05). At the age of 24 h, PAP to SAP ratio was similar in all study groups. Between 48 and 72 h, PAP to SAP ratio was significantly higher in preterm infants with RDS than in infants without RDS (p < 0.05). Our findings indicated that: (1) in healthy fullterm infants pulmonary artery pressure fell to subsystemic level during the first 12 h, indicating the critical time in circulatory transition; (2) prematurity did not affect ductal closure times significantly; and (3) RDS was associated with prolonged ductal patency and delayed postnatal circulatory adaptation characterized by pulmonary hypertension.

Changes in pulmonary venous flow pattern during early neonatal life

OBJECTIVE

To investigate serial changes in the pattern of flow in the pulmonary vein during the early neonatal period.

METHODS

Pulsed Doppler echocardiography was used to measure flow in the right upper pulmonary vein in 26 normal newborn infants. Peak flow velocity during systole (S) and diastole (D) and flow velocity at indents between the systolic and diastolic fraction (O) and between the diastolic and systolic fraction (X) were measured 1, 4-8, 24, and 96 hours after birth. The heart rate and diameter of the ductus arteriosus were measured simultaneously.

RESULTS

Continuous and phasic high flow velocity waveforms were seen 1 and 4-8 hours after birth. The mean (SD) peak flow velocities of X, S, O, and D an hour after birth were 35.2 (13.6) cm/s, 73.1 (23.1) cm/s, 58.5 (20.5) cm/s, and 81.5 (19.2) cm/s respectively. There were significant decreases in X, S, O, and D by 24 hours of age (p < 0.01 v 1 hour after birth) to 8.1 (10.3) cm/s, 52.8 (18.0) cm/s, 38.6 (14.5) cm/s, and 54.4 (11.2) cm/s respectively. These results indicate intermittent flow in the pulmonary vein, with flow stopping between diastole and systole. These flow velocities, X, S, O, and D, correlated well with the diameter of the ductus arteriosus (r = 0.80 v X, r = 0.62 v S, r = 0.63 v O, r = 0.75 v D).

CONCLUSION

This serial study showed changes in normal pulmonary vein flow patterns during the early neonatal period. The continuous and high flow velocity waveform that was seen immediately after birth resembled the pattern of pulmonary vein flow seen in congenital pulmonary stenosis and in cases of acute volume overload. This waveform may reflect a sudden increase in pulmonary circulatory volume with additional left to right shunting through the ductus arteriosus in relatively hypoplastic pulmonary veins.

Changes in left ventricular output from fetal to early neonatal life

Using pulsed Doppler and two-dimensionally directed M-mode echocardiographic techniques, we measured left ventricular (LV) output, stroke volume, heart rate, LV end-diastolic dimension (LVEDD), LV end-systolic dimension, and LV percent fractional shortening (%FS) in 34 normal term infants 12 to 24 hours before parturition and thereafter serially 1, 24, and 96 hours after birth. Stroke volume was calculated as the product of the aortic flow velocity integral and aortic valve area. There was a twofold increase in LV output 1 hour after birth (fetal 170 +/- 46 ml/min/kg vs 1 hour 327 +/- 66 ml/min/kg; p less than 0.01) which was associated with significant increases in stroke volume, %FS, and LVEDD (stroke volume 1.21 +/- 0.33 ml/kg vs 2.25 +/- 0.37 ml/kg; %FS 34.3% +/- 5.8% vs 37.7% +/- 5.4%; LVEDD 15.4 +/- 1.1 mm vs 17.7 +/- 1.4 mm). Heart rate did not change 1 hour after birth. During the subsequent hours after birth, LV output decreased significantly to a value of 245 +/- 56 ml/min/kg (p less than 0.01) at 24 hours, which did not change 96 hours after birth. There were significant declines in stroke volume, LVEDD, and heart rate 24 hours after birth (stroke volume 2.02 +/- 0.42 ml/kg; LVEDD 17.0 +/- 1.1 mm; heart rate 121 +/- 11 beats/min). The %FS remained unchanged within the first 96 hours of age. These results indicate that the major regulator of LV output immediately after birth is stroke volume and not heart rate. The increase in stroke volume is related to an increase in LV size and LV myocardial contractility. Our data provide a useful basis for the interpretation of abnormal LV function in the early neonatal period.

Early hemodynamic indicators of gram-negative sepsis and shock in an infant pig model

To assess the hemodynamics of early shock and to determine to what extent hemodynamic indicators of sepsis and shock can be predictive, we evaluated data from several series of experiments (including 136 piglets) in which animals were subjected to fecal-Escherichia coli peritonitis-induced septic shock. Serial measurements of 39 parameters were obtained and their values taken at baseline, at hyperdynamic sepsis, and at shock were compared by analysis of variance. Piglet weights ranged from 1.2 to 7 kg (mean, 3.5) and ages ranged from 5 to 29 days (mean, 15). Of the 39 parameters assessed, 9 (CO*, CI*, SVI*, LVSWI*, SVR*, a-vDO2, VO2, O2 delivery*, and CaO2*) proved valuable as indicators of sepsis and shock. Of these parameters, seven (*) can be measured or calculated by noninvasive techniques and easily can be determined in human neonates. Serial determinations of these hemodynamics in high-risk neonates may be able to accurately predict gram-negative sepsis and shock before these entities are otherwise clinically apparent.

Interatrial shunt flow profiles in newborn infants: a colour flow and pulsed Doppler echocardiographic study

Interatrial shunt flow profiles in 36 normal term infants were examined serially by colour flow and pulsed Doppler echocardiographic techniques from within an hour of birth to four or five days after birth. Shunt flow across the foramen ovale was detected in 33 normal infants (92%) within an hour of birth (mean 40 minutes). The occurrence of interatrial shunting decreased with age, but a shunt signal was still detected in 17 infants (47%) on the fourth or fifth day of life, by then the ductus arteriosus had already closed in all the normal infants. The direction of interatrial shunt flow was predominantly left-to-right, but in 64% there was a coexistent small right-to-left shunt in diastole within an hour of birth; by four to five days it was found in 19%. In the six patients with persistent fetal circulation the direction of the interatrial shunt flow was predominantly right-to-left with biphasic peaks in diastole and systole at the early stage of the disease, and the period of right-to-left shunt flow during each cardiac cycle was significantly longer than that in normal infants examined within 1 hour of birth. In all patients the ductus closed before the foramen ovale. At the time of ductal closure in all patients with persistent fetal circulation right-to-left shunt flow was seen during diastole and its period was still prolonged. These findings suggest that interatrial shunting, predominantly left-to-right, is common in normal newborn infants. Evaluation of the characteristics of the interatrial shunt by Doppler echocardiography may be useful for predicting the progress of or improvement in neonates with persistent fetal circulation.

Patency of foramen ovale--does it influence haemodynamics in newborn infants?

Colour-coded Doppler ultrasound examination was carried out in 37 healthy newborns at 24 h of age to determine the patency of the foramen ovale. In addition, Doppler-derived cardiac output was measured 5 times during the first 2 days of life in the same infants. Our aim was to examine the influence of foramen ovale on Doppler-derived cardiac output and its association with left-to-right shunting through the ductus arteriosus. In 22 infants the foramen ovale was patent at 24 h of age and in 15 it was closed. Haemodynamic variables measured using non-imaging Doppler-ultrasonic methods did not differ between these two groups. The closure of left-to-right shunt at the ductus was similar in both groups. In a follow-up examination at the age of 1 year, one child had an open foramen ovale without haemodynamic consequences. This study provides evidence that patency of foramen ovale does not influence hemodynamics in early infancy.

Ductal left-to-right flow and pulmonary circulation in normal neonates: pulsed Doppler echocardiographic evaluation

To determine whether ductal left-to-right flow affects pulmonary circulation in the neonatal period, ductal patency and flow patterns of the right ventricular outflow tract were studied using Doppler echocardiography in 40 normal neonates. The ductus arteriosus was defined as being patent when diastolic or continuous flow could be detected at the pulmonary end of the ductus. Evaluation of pulmonary circulation was carried out by examining the flow velocity pattern of the right ventricular outflow tract; pulmonary hypertension was considered to be present when the Doppler echocardiogram pattern was triangular with peak velocity in early systole. Neonates were initially examined within nine hours (mean 5.3 hrs) after birth, and two to three times daily thereafter, until no ductal flow could be detected. In all the neonates, the ductus arteriosus was patent at the initial examination. The predicted time of closure of the ductus arteriosus was within seven hours after birth in 5% of the neonates, within 21 hours in 50%, and within 65 hours in 95%. The flow velocity pattern of the right ventricular outflow tract changed from a triangular shape with peak velocity in early systole soon after birth to a dome-like contour with peak velocity in mid-systole: thus the mean ratio of acceleration time to right ventricular ejection time increased with age. In neonates with patent ductus arteriosus at age 13.6-20.7 hours, the mean ratio of acceleration time to right ventricular ejection time was less than in age-matched neonates with closed ductus arteriosus. These results indicate that the ductal left-to-right flow affects the pulmonary circulation.

Left ventricular output during postnatal circulatory adaptation in healthy infants born at full term

Left ventricular output was measured non-invasively at predefined time intervals from less than 15 minutes to 72 hours after birth in 16 infants who had been born at full term. The blood flow velocity in the ascending aorta was measured by a range gated Doppler technique and multiplied by the cross sectional diameter measured by cross sectional and M mode echocardiography. Left ventricular output remained high in the first two hours, 235-243 ml/min/kg, despite a 10% decrease in heart rate. The fall in heart rate was compensated for by a 15% increase in stroke volume. Between 2 and 24 hours there was a significant fall in mean (SD) left ventricular output to 187 (35) ml/min/kg caused mainly by a reduction in stroke volume. The fall in left ventricle output after two hours may reflect an adaptation to the decreased demand on the left ventricle as the ductus constricts.

Responsiveness of the ductus arteriosus to prostaglandin E1 assessed by combined cross sectional and pulsed Doppler echocardiography

Cross sectional echocardiography combined with Doppler echocardiography was used to record either ductal morphology or the flow profile within the ductus arteriosus before and after infusion of prostaglandin E1 in 25 newborn infants with cyanotic and acyanotic congenital heart disease with ductus dependent blood flow. The ultrasound results were compared with changes in arterial oxygen tension and the overall clinical response to prostaglandin E1 seen during the same period in 24 of the 25 patients in whom the degree of ductal narrowing could be determined with the ultrasound method. At the time of the study, the ductus was widely patent or slightly narrowed in 12 patients and was closed in two patients. These patients did not respond to prostaglandin E1. There was prominent localised narrowing of the ductus in seven patients and generalised narrowing in three. After the infusion of prostaglandin E1 there was no ductal narrowing in these patients, except for one patient who had slight residual localised narrowing. There was also a considerable change in the ductal flow profiles in each patient. In these 10 patients infusion of prostaglandin E1 resulted in an increase in arterial oxygen tension, clinical improvement, or both. The present study indicates that prostaglandin E1 is effective in patients with prominent narrowing of the ductus but is not in patients in whom the ductus is widely patent or closed. Cross sectional echocardiography combined with Doppler echocardiography was useful for predicting the responsiveness of the ductus arteriosus to the infusion.