Severity of the ductal shunt: a comparison of different markers

BACKGROUND: When the ductus arteriosus (DA) is patent, the ductal shunt is proportional to the ratio of left ventricular output (LVO) to systemic blood flow. Systemic blood flow can be estimated by measuring flow in the superior vena cava (SVC). OBJECTIVE: To re-evaluate the accuracy of standard echocardiographic markers of patent ductus arteriosus (PDA) using LVO/SVC flow ratio. METHODS: Prospective study. Preterm infants of 24-30 weeks gestational age and postnatal age less than 48 hours. The following echocardiographic criteria were measured: left atrial to aortic root ratio (LA/Ao); DA diameter by B mode and colour Doppler; mean and end diastolic flow velocity of the left pulmonary artery (LPA); LVO; SVC flow. RESULTS: Twenty three preterm infants were enrolled (median gestational age 28 weeks (range 24-30), median birth weight 840 g (500-1440)). The DA was closed in eight (mean (SD) LVO/SVC 2.4 (0.3)) and open in 15 (mean (SD) LVO/SVC 4.5 (0.6)). An LA/Ao ratio > or =1.4, a DA diameter > or =1.4 mm/kg, and a mean and end diastolic flow velocity of LPA respectively > or =0.42 and > or =0.20 m/s identified an LVO/SVC > or =4 with a sensitivity and a specificity above 90%. CONCLUSION: This study indicates that LA/Ao ratio, DA diameter, and mean and end diastolic flow velocity of the LPA are accurate markers of PDA. These standard echocardiographic variables are easy to measure and need less skill and resources than direct measurements of ductal shunt.     

Left ventricular systolic time intervals in preterm infants with patent ductus arteriosus

Left ventricular systolic time intervals were recorded by a non-invasive technique, from the axillary artery, in 13 preterm infants with patent ductus arteriosus. At the onset of clinical symptoms, consistent with a large left-to right ductal shunt, the preejection intervals were shorter than in a control group of nine preterm infants without a patent ductus. The most pronounced difference was found in the shortening of the isovolumic contraction time, 10.7 msec in the ductus group compared with 22.4 msec in the control group. Ductal closure normalized the isovolumic contraction time to 22.1 msec. The very short preejection intervals, associated with a large ductal shunt, are suggested to reflect a combination of reduced aortic diastolic pressure and increased left ventricular filling pressure. In spite of increased volume load to the left ventricle there were no detectable changes in the systolic time intervals indicating impaired left ventricular function. The left ventricle seems to be competent to handle increased volume load in the presence of reduced afterload in preterm infants with symptomatic left-to right ductal shunts.     

Color Doppler flow mapping of the patent ductus arteriosus in very low birthweight neonates: Echocardiographic and clinical findings

Summary Forty-eight preterm infants (mean birthweight 1.0±0.3 kg; mean gestational age 28±3 weeks) underwent serial echocardiograms and physical examinations in order to determine the correlation between color Doppler flow mapping (CDFM) results and physical findings of a patent ductus arteriosus (PDA), the predictive value of early CDFM as an indicator of subsequent requirement for treatment of a PDA, and to determine the direction and duration of ductal shunting and the rate of ductal closure and opening. CDFM analysis and cardiac physical examination of left-to-right ductal shunting were usually concordant in infants with a large PDA shunt, the most reliable physical finding being increased precordial activity. CDFM studies on day 2 or 3 of postnatal life had prognostic value with regard to subsequent need for closing the PDA. Additional findings included the absence of right-to-left PDA shunting in infants <1 kg and <28 weeks gestation and the absence of ductal reopening in infants in whom it had closed spontaneously. After complete PDA closure using indomethacin, subsequent ductal reopening is uncommon, except in infants <25 weeks gestation and <700 g bodyweight.     

LEFT VENTRICULAR SYSTOLIC TIME INTERVALS IN PRETERM INFANTS WITH PATENT DUCTUS ARTERIOSUS

ABSTRACT. Left ventricular systolic time intervals were recorded by a non-invasive technique, from the axillary artery, in 13 preterm infants with patent ductus arteriosus. At the onset of clinical symptoms, consistent with a large left-to right ductal shunt, the preejection intervals were shorter than in a control group of nine preterm infants without a patent ductus. The most pronounced difference was found in the shortening of the isovolumic contraction time, 10.7 msec in the ductus group compared with 22.4 msec in the control group. Ductal closure normalized the isovolumic contraction time to 22.1 msec. The very short preejection intervals, associated with a large ductal shunt, are suggested to reflect a combination of reduced aortic diastolic pressure and increased left ventricular filling pressure. In spite of increased volume load to the left ventricle there were no detectable changes in the systolic time intervals indicating impaired left ventricular function. The left ventricle seems to be competent to handle increased volume load in the presence of reduced afterload in preterm infants with symptomatic left-to right ductal shunts.     

The effect of phototherapy on cerebral blood flow velocity in preterm infants

Cerebral blood flow velocity was studied with two-dimensional/pulsed Doppler ultrasound before, during and after discontinuation of phototherapy in 22 preterm infants (gestational age ≤32 weeks), who were treated for a minimum of 12h with blue-light phototherapy for non-haemolytic hyperbilirubinaemia. Before the cerebral blood flow velocity measurements, patency of the ductus arteriosus was diagnosed by Doppler echocardiography. All infants had normal brain ultrasound scans. Mean cerebral blood flow velocity increased significantly after initiation of phototherapy in all infants. Only in “healthy” (non-ventilated) infants did cerebral blood flow velocity return to pre-phototherapy values (baseline) after discontinuation of phototherapy, whereas in “unhealthy” (ventilated) infants cerebral blood flow velocity did not return to baseline. In 10 infants the ductus arteriosus reopened during phototherapy. In those infants, mean cerebral blood flow velocity returned to pre-phototherapy values after 2h of phototherapy prior to its discontinuation.     

Cardiocirculatory effects of patent ductus arteriosus in extremely low-birth-weight infants with respiratory distress syndrome

BACKGROUND: Cardiocirculatory effects of hemodynamically significant patent ductus arteriosus (hsPDA) have not been systematically studied in extremely low-birth-weight (ELBW) infants with respiratory distress syndrome (RDS). The objective of the present study was to evaluate the effects of hsPDA on the left ventricular output (LVO) and organ blood flows in ELBW infants with RDS. METHODS: Extremely low-birth-weight infants (birth-weight <1000 g) treated with surfactant for RDS were studied by serial Doppler flow examinations. Doppler flow variables in 19 infants in whom hsPDA developed (hsPDA group) were compared with those in 19 infants without hsPDA matched for gestational age, birth-weight, and postnatal age (non-hsPDA group). All infants in the hsPDA group had pharmacologic closure of ductus arteriosus when hsPDA developed. RESULTS: Before pharmacological closure of PDA, the hsPDA group had significantly higher LVO, lower blood flow volume of the abdominal aorta, and lower mean blood flow velocities in the celiac artery, superior mesenteric artery, and renal artery than the non-hsPDA group. These alterations in the hsPDA group reverted to the levels in the non-hsPDA group after the closure of PDA and had no deleterious effects on the cardiorespiratory status. No significant differences between the groups were found in mean blood flow velocities of the anterior cerebral artery throughout the study period. CONCLUSION: These results indicate that although LVO is increased, the splanchnic and renal blood flows are decreased when hsPDA develops in ELBW infants with RDS. The effects of these alterations of LVO and organ blood flows on the cardiorespiratory course seem to be minor when early pharmacologic closure of PDA is done.     

Effect of indomethacin on superior mesenteric artery blood flow velocity in preterm infants

In 15 preterm infants with symptomatic patent ductus arteriosus, blood flow velocity changes in the superior mesenteric artery were investigated with Doppler ultrasound just before and during the first 12 hours after a single dose of indomethacin. Indomethacin administration led to an instantaneous decrease in all infants of temporal mean flow velocity in the superior mesenteric artery, which was maximal 10 minutes after administration of indomethacin, followed by a more sustained recovery, slightly greater than baseline values, 12 hours after indomethacin treatment. Simultaneously determined temporal mean flow velocity of the anterior cerebral artery, used as an indicator of changes in cerebral blood flow, had a similar pattern as in the mean flow velocity in the superior mesenteric artery (r = 0.49; p less than 0.001). Our data suggest that indomethacin lowered blood supply to the bowel, similar to its action on cerebral blood flow.     

Effects of prophylactic indomethacin on renal and intestinal blood flows in premature infants

Background: Prophylactic indomethacin reduces severe intraventricular hemorrhage and symptomatic patent ductus arteriosus in premature infants. The purpose of this study was to investigate the effects of prophylactic low‐dose indomethacin on renal and intestinal blood flow. Methods: Subjects were 19 extremely low‐birthweight infants admitted to our hospital and enrolled in a multicenter randomized control trial to study the efficacy and complications of prophylactic low‐dose indomethacin in the reduction of severe intraventricular hemorrhage and patent ductus arteriosus (indomethacin and placebo groups, ten and nine infants, respectively). We measured blood flow velocity in the right renal artery (right RA) and superior mesenteric artery (SMA) with pulsed Doppler ultrasound before and after the administration of the first dose of 0.1 mg/kg indomethacin or placebo. Results: End‐diastolic blood flow velocity (EDV) in the right RA and SMA increased significantly after the administration of indomethacin (P = 0.0414 and 0.0284, respectively), although the time‐averaged mean blood flow velocity (TAV) did not change significantly in either artery. In the placebo group, the pre‐ and postadministration values for TAV and EDV in the right RA and SMA did not differ. Neither group showed a significant change in the relative vascular resistance (mean blood pressure/TAV) in the right RA or SMA. EDV in the left pulmonary artery was significantly reduced only after the administration of indomethacin (P = 0.0284). Conclusions: Prophylactic low‐dose indomethacin increases the diastolic blood flow in the RA and SMA via a reduction in the ductal shunt volume, with no change in the regional vascular resistance.     

Echocardiographic prediction of patent ductus arteriosus in need of therapeutic intervention

Aim: To evaluate the efficacy of various echocardiographic markers in predicting a patent ductus arteriosus (PDA) in need of treatment. Methods: Forty‐five preterm infants with a mean (SD) gestational age of 27.7 (1.9) weeks underwent echocardiography at a postnatal age of 24 ± 6 and 72 ± 6 h. Four echocardiographic markers were studied: ductus diameter, ductal flow Doppler curves, the left atrial to aortic root (LA/Ao) ratio and Doppler pixels representing ductal shunting. Results: Twenty‐eight infants had a PDA with a detectable left‐to‐right shunt. Of these, 12 (43%) were treated for a shunt through the PDA. Ductal diameter was the most accurate echocardiographic marker when it came to predicting a significant shunt, with a sensitivity of 89%, a specificity of 70%, a positive likelihood ratio of 2.97 and a negative likelihood ratio of 0.16 at the age of 72 h. The efficacy of the method at 72 h of age was 84%. The corresponding efficacy of the pulsatile Doppler curve was 72%, percentage of green colour pixels 63% and the LA/Ao ratio 53%. Conclusion: Ductus diameter appears to be the most important variable in determining the need for therapeutic intervention for PDA in preterm infants.     

Pulsed Doppler measurement of left ventricular output as early predictor of symptomatic patent ductus arteriosus in very preterm infants

High left ventricular output (LVO) values are associated with symptomatic left-to-right ductal shunting in preterm infants. However, LVO data prior to the occurrence of symptomatic patent ductus arteriosus (SPDA) are lacking. To determine whether serial measurements could predict a SPDA, we measured LVO from day 1 until day 10 with pulsed Doppler echocardiography in 25 preterm infants with birth weights of less than 1,250 g and hematocrits of more than 0.40. Eleven infants never developed patent ductus arteriosus symptoms and had LVO values within the normal range (190-310 ml/min/kg) with only minimal daily variations. The remaining 14 infants developed SPDA which required treatment with indomethacin, ductal ligation, or fluid restriction on days 2-5. From day 1 until day 5 their mean LVO values were significantly higher compared to the group without left-to-right ductal shunt and this increase was secondary to higher stroke volume values. An increase in LVO of more than 60 ml/min/kg consistently preceded SPDA by at least 24 h. Serial measurements of LVO using a single-pulsed Doppler approach can be used for early prediction of SPDA.     

Indomethacin and cerebral blood flow in premature infants treated for patent ductus arteriosus

Central blood flow (CBF) was estimated by an intravenous 133-xenon technique in six preterm infants before and after administration of indomethacin for closure of patent ductus arteriosus. CBF fell in all infants (range 12%–40%), the mean fall was 24% (P<0.005). Though none of the infants showed signs of impaired cerebral function during or following the injections, the results do not indicate whether or not the use of indomethacin is a potential hazard.Abbreviations PDA patent ductus arteriosus - CBF cerebral blood flow - PaCO₂ arterial carbon dioxide tension - MAP mean arterial blood pressure     

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 domelike 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.     

Prediction of Symptomatic Patent Ductus Arteriosus in Preterm Infants Using Doppler and M-mode Echocardiography

ABSTRACT. To investigate whether the development of symptomatic patent ductus arteriosus could be predicted, 26 preterm infants dependent on mechanical ventilation were examined daily with Doppler and M-mode echocardiography until 3 days after birth. The presence or absence of a hemodynamically significant ductus shunt, as judged from echocardiographic criteria, was tested for predictive power in terms of sensitivity, specificity and total error rate. Out of the 26 infants 13 developed symptomatic patent ductus arteriosus at a median age of 5 days (range 2–8). These 13 infants developed echocardiographic evidence of a large shunt at a median age of 2 days (range 1–3). The sensitivity of prediction was 18, 46 and 100% at 1, 2 and 3 days after birth. The specificity was 80, 92 and 85% and the total error rate was 52, 32 and 8%. Thus, accurate prediction was possible 3 days after birth.     

Abnormal blood flow patterns in renal arteries of small preterm infants with patent ductus arteriosus detected by Doppler ultrasonography

Blood flow velocities and pulsatory indices in both renal arteries (RAs) and in the internal carotid artery (CAI) were measured by pulsed Doppler ultrasonography in ten preterm infants with patent ductus arteriosus (PDA), before and after surgical ligation. The results obtained in the RAs were compared to those found in a reference group of 22 stable preterm infants. In the RAs the diastolic steal volume of the PDA led to a marked decrease in diastolic blood flow velocity (range 3 to-23 cm/s). Seven infants showed retrograde diastolic flow, whereas only three infants had these flow patterns in the CAI. In the RAs, the peak systolic blood flow velocities (range 56 to 135 cm/s) exceeded the values found in the reference group by 85% on average. The pulsatility indices reached values of above 1,00. In spite of the increase in systolic flow velocities before surgery, the time mean of maximum velocities was significantly lower than those measured after surgery and in the reference group. After PDA ligation, blood flow velocities normalized. The present study shows that a large PDA may induce abnormal flow patterns even in the RAs. These flow patterns may predispose to renal hypoperfusion and subsequent impairment of renal function.Abbreviations CAI internal carotid artery - NFC necrotizing enterocolitis - PDA patent ductus arteriosus - PI pulsatility index - RA renal artery - Vd end-diastolic velocity - V_max time mean of maximum velocity - Vs peak systolic velocity     

Ductal shunting, high pulmonary blood flow, and pulmonary hemorrhage

OBJECTIVE: To describe the relationship among ductal shunting, estimated pulmonary blood flow, and pulmonary hemorrhage in very preterm infants. STUDY DESIGN: A total of 126 babies born before 30 weeks' gestation (median gestation 27 weeks, range 23 to 29 weeks) underwent echocardiography at 5, 12, 24, and 48 hours of age; measurements included right and left ventricular output, superior vena cava flow, and color Doppler diameter of any ductal shunt. Pulmonary blood flow was derived from the sum of right ventricular output and estimated ductal shunt flow. RESULTS: Twelve (9.5%) babies had a pulmonary hemorrhage at a mean age of 38 hours. Compared with the rest of the cohort, these 12 babies were less likely to have had antenatal steroids (59% vs 90%) and were less mature (26 weeks vs 27 weeks). At the echocardiogram closest to the pulmonary hemorrhage, 11 (92%) of the 12 babies had a significant patent ductus arteriosus >1.6 mm in diameter (median 2 mm, range 0.7 to 2.4 mm), and the median pulmonary blood flow was 326 mL/kg/min (range 210 to 598 mL/kg/min). These measurements were significantly higher than those found in the rest of the cohort in the same period (median duct diameter 0.5 mm [range 0 to 2.9 mm], median pulmonary blood flow 237 mL/kg/min [range 107 to 569 mL/kg/min]). At 5-hour echocardiography the babies with pulmonary hemorrhage had significantly larger diameter ducts but similar pulmonary blood flow. CONCLUSIONS: Pulmonary hemorrhage in preterm babies is associated with significant ductal shunting and high estimated pulmonary blood flow.     

Closure of the ductus arteriosus: determinant factor in the appearance of transient peripheral pulmonary stenosis of the neonate

We speculated that a relationship may exist between transient peripheral pulmonary stenosis and the closure of the ductus arteriosus. Fifty preterm infants had pulmonary artery and ductal color Doppler flow velocity assessments performed before and after closure of the ductus arteriosus. No flow turbulence or increase in velocity was observed immediately after birth, although a significant discrepancy in size was observed between the main pulmonary artery and its two branches. After closure of the ductus, 15 infants had signs of transient peripheral pulmonary stenosis of the left pulmonary artery in association with a significant decrease of diameter at the origin of the same artery. In all 50 infants, no significant gradient was observed in the right pulmonary artery. We conclude that, at least in the preterm infant, transient peripheral pulmonary stenosis is not present at birth but is an acquired phenomenon closely related to closure of the ductus arteriosus.     

Ductus arteriosus blood flow during first 48 hours of life.

A volumetric Doppler technique was used to measure net ductus arteriosus shunt during the first 48 hours of life in 30 infants of less than 33 weeks'' gestation, and in 10 full term infants. In the full term infants a left to right shunt of 62 ml/kg/minute (95% confidence limits 43-82) shortly after birth decreased rapidly over the first 12 hours and was not measurable by 48 hours. The preterm infants had smaller left to right shunts shortly after birth--49 ml/kg/minute (95% confidence limits 38-59). There was no obvious subsequent change in the mean shunt, although by 48 hours there was greater variation in the size of the shunt. The respiratory distress syndrome did not affect the size of the ductal shunt, but the shorter the gestation period the larger the shunt by 48 hours. A ductal flow of greater than 70 ml/kg/minute at 48 hours of age predicted the subsequent development of a ductal murmur with 75% sensitivity and 100% specificity.     

EARLY CLOSURE OF PATENT DUCTUS ARTERIOSUS WITH INDOMETHACIN IN PRETERM INFANTS WITH IDIOPATHIC RESPIRATORY DISTRESS SYNDROME

ABSTRACT. Thirty-seven preterm infants with idiopathic respiratory distress syndrome were prospectively studied for the effect of the early closure of patent ductus arteriosus with indomethacin on the course of idiopathic respiratory distress syndrome. Serial retrograde aortograms were performed in all infants in order to visualize the ductus arteriosus, apart from three patients, who died early and were evaluated aortographically only once. The ductus was initially open in 27 infants and closed in 10 infants. The infants with open ductus arteriosus were randomly divided into two groups. The first group consisted of 13 infants, in whom the ductus was closed with indomethacin at a median age of 18 hours. The other 14 infants served as controls. Total time on assisted ventilation and duration of exposure to additional oxygen were significantly shorter in medicated infants than in controls. Oxygenation of infants with an initially closed ductus was better from birth and duration of their ventilatory assistance and oxygen exposure were shorter than in infants with initial ductal shunting. The data suggest that the early closure of the patent ductus arteriosus with indomethacin in distressed preterm infants has a favourable effect on the course of idiopathic respiratory distress syndrome.     

Critical Ebstein Anomaly in a Fetus Successfully Managed by Elective Preterm Delivery and Surgical Intervention Without Delay After Birth

This report describes a case of Ebstein anomaly in a fetus with cardiomegaly, severe tricuspid regurgitation, pulmonary regurgitation, and retrograde ductal flow that showed a marked increase in the size of the right atrium with advancing gestational age. Elective preterm delivery was performed at 35 weeks gestation. The prostaglandin E1 infusion resulted in more pronounced systemic hypotension and acidosis secondary to circular shunt across the patent ductus arteriosus as well as pulmonary regurgitation and tricuspid regurgitation. Emergency surgical intervention consisting of main pulmonary artery ligation, ductus arteriosus ligation, central shunt creation, and plication of the right atrium without cardiopulmonary bypass was performed 4 h after birth. At the age of 16 days, the Starnes procedure was performed. The infant’s postoperative course was uneventful. A fetus that has Ebstein anomaly associated with pulmonary regurgitation is at risk for circular shunt across the patent ductus arteriosus after delivery. Planned delivery and surgical intervention without delay after birth are useful for the treatment of such cases.     

Duration of ductal shunting in healthy preterm infants: an echocardiographic color flow Doppler study

The purpose of this investigation was to assess the duration of ductal shunting after birth in healthy preterm infants (30 to 37 weeks gestational age) without evidence of respiratory distress. Thirty-six infants were evaluated in the first 12 hours of life by means of two-dimensional echocardiography and color flow Doppler techniques, and then once daily until no ductal flow was detected (defined as functional closure). Preterm infants were subdivided into two groups by gestational age: group 1 = 30 to 33 weeks (n = 12); group 2 = 34 to 37 weeks (n = 24). Sixteen full-term infants (38 to 41 weeks) were similarly evaluated as control subjects (Group 3). One infant from each group had a closed ductus at the time of the first study (performed at a mean of 7.7 +/- 3.2 hours). Subsequent studies for the entire group were performed at a mean of 31.3 +/- 5.4 hours (day 2), 55.0 +/- 4.5 hours (day 3), and 80.3 +/- 6.1 hours (day 4). For the three groups, the rates of ductal closure ranged from 50.0% to 58.3% on day 2 and 81.3% to 87.5% on day 3. For the entire group, all but one infant had demonstrated closure of the ductus arteriosus by day 4. Within the range of gestational ages studied, we conclude that prematurity, in the absence of respiratory distress syndrome, does not prolong the initial duration of physiologic ductal shunting.