The ductus arteriosus: physiology, regulation, and functional and congenital anomalies

Indomethacin administered early in the postnatal period results in reduced glomerular number in the adult rat

Indomethacin and ibuprofen are administered to close a patent ductus arteriosus (PDA) during active glomerulogenesis. Light and electron microscopic glomerular changes with no change in glomerular number were seen following indomethacin and ibuprofen treatment during glomerulogenesis at 14 days after birth in a neonatal rat model. This present study aimed to determine whether longstanding renal structural changes are present at 30 days and 6 mo (equivalent to human adulthood). Rat pups were administered indomethacin or ibuprofen antenatally on days 18-20 (0.5 mg·kg(-1)·dose(-1) indomethacin; 10 mg·kg(-1)·dose(-1) ibuprofen) or postnatally intraperitoneally from day 1 to 3 or day 1 to 5 (0.2 mg·kg(-1)·dose(-1) indomethacin; 10 mg·kg(-1)·dose(-1) ibuprofen). Control groups received no treatment or normal saline intraperitoneally. Pups were killed at 30 days of age and 6 mo of age. Tissue blocks from right kidneys were prepared for light and electron microscopic examination, while total glomerular number was determined in left kidneys using unbiased stereology. Eight pups were included in each group from 14 maternal rats. At 30 days and 6 mo, there were persistent electron microscopy abnormalities of the glomerular basement membrane in those receiving postnatal indomethacin and ibuprofen. There were no significant light microscopy findings at 30 days or 6 mo. At 6 mo, there were significantly fewer glomeruli in those receiving postnatal indomethacin but not ibuprofen (P = 0.003). In conclusion, indomethacin administered during glomerulogenesis appears to reduce the number of glomeruli in adulthood. Alternative options for closing a PDA should be considered including ibuprofen as well as emerging therapies such as paracetamol.

Transcriptional profiling reveals ductus arteriosus-specific genes that regulate vascular tone

Failure of the ductus arteriosus (DA) to close at birth can lead to serious complications. Conversely, certain profound congenital cardiac malformations require the DA to be patent until corrective surgery can be performed. In each instance, clinicians have a very limited repertoire of therapeutic options at their disposal - indomethacin or ibuprofen to close a patent DA (PDA) and prostaglandin E1 to maintain patency of the DA. Neither treatment is specific to the DA and both may have deleterious off-target effects. Therefore, more therapeutic options specifically targeted to the DA should be considered. We hypothesized the DA possesses a unique genetic signature that would set it apart from other vessels. A microarray was used to compare the genetic profiles of the murine DA and ascending aorta (AO). Over 4,000 genes were differentially expressed between these vessels including a subset of ion channel-related genes. Specifically, the alpha and beta subunits of large-conductance calcium-activated potassium (BKCa) channels are enriched in the DA. Gain- and loss-of-function studies showed inhibition of BKCa channels caused the DA to constrict, while activation caused DA relaxation even in the presence of O2. This study identifies subsets of genes that are enriched in the DA that may be used to develop DA-specific drugs. Ion channels that regulate DA tone, including BKCa channels, are promising targets. Specifically, BKCa channel agonists like NS1619 maintain DA patency even in the presence of O2 and may be clinically useful.

A new approach to an old hypothesis; phototherapy does not affect ductal patency via PGE2 and PGI2

OBJECTIVE

Numerous investigations have demonstrated that phototherapy (PT) directly or indirectly causes ductal patency by photorelaxation effect. In this observational study, we aimed to assess the effect of PT on the incidence of patent ductus arteriosus (PDA) together with prostaglandins (PGE2) and (PGI2) levels in preterm infants.

METHODS

Preterm infants whose gestational age<34 weeks and who required PT in the first 3 d of life were enrolled in this prospective study. The clinical signs of PDA, the data of detailed echocardiographic study were recorded and plasma PGE2 and PGI2 levels were measured before and after PT. The outcome measures were the status of ductus arteriosus and alterations of PGE2 and PGI2 levels under the effect of PT.

RESULTS

A total of 44 preterm infants were enrolled in the study, of these 21 (47.7%) were in Group 1 (Non-PDA Group) and 23 (52.3%) were in Group 2 (PDA Group). After PT, ductal reopening occurred in three infants (14.3%) in Group 1, while ductus closed in four infants in Group 2 (17.3%). PT does not seem to effect ductal patency for both groups (p=0.250 and p=0.125, respectively). PGE2 levels were not different before and after PT for both groups (p=0.087, p=0.408, respectively). However, PGI2 levels were significantly decreased after PT in both groups (p=0.006, and p=0.003, respectively).

CONCLUSION

There was no effect of PT on ductal patency. We can conclude that PGs were eliminated simultaneously with ductal closure and photorelaxation effect did not influence PG levels.

Transcatheter closure of patent ductus arteriosus: past, present and future

This review aims to describe the past history, present techniques and future directions in transcatheter treatment of patent ductus arteriosus (PDA). Transcatheter PDA closure is the standard of care in most cases and PDA closure is indicated in any patient with signs of left ventricular volume overload due to a ductus. In cases of left-to-right PDA with severe pulmonary arterial hypertension, closure may be performed under specific conditions. The management of clinically silent or very tiny PDAs remains highly controversial. Techniques have evolved and the transcatheter approach to PDA closure is now feasible and safe with current devices. Coils and the Amplatzer Duct Occluder are used most frequently for PDA closure worldwide, with a high occlusion rate and few complications. Transcatheter PDA closure in preterm or low-bodyweight infants remains a highly challenging procedure and further device and catheter design development is indicated before transcatheter closure is the treatment of choice in this delicate patient population. The evolution of transcatheter PDA closure from just 40 years ago with 18F sheaths to device delivery via a 3F sheath is remarkable and it is anticipated that further improvements will result in better safety and efficacy of transcatheter PDA closure techniques.

Ductal spasm during performance of transcatheter ductal occlusion

OBJECTIVES

Transcatheter patent ductus arteriosus (PDA) occlusion is a staple of pediatric catheterization laboratories. We present the phenomenon of significant PDA spasm to prevent failure to occlude a hemodynamically significant duct.

BACKGROUND

Transcatheter techniques have evolved, allowing safe and effective occlusion of PDAs in younger and smaller patients. Neonatal care is evolving with increasing survival at younger gestational ages. Premature infants often have PDAs, so the proportion of formerly premature children referred for transcatheter ductal occlusion will likely rise.

METHODS

We reviewed all transcatheter PDA occlusions performed at our institution since 2001 (N = 331). Retrospective data included: gestational age, age at catheterization, precatheterization echocardiographic parameters, PDA size (after spasm relief), device specifications, and most recent follow-up data.

RESULTS

Seven cases were identified. Median age was 12 months, median gestational age was 28 weeks. All were born prematurely. All PDAs were restrictive and six had left-heart volume overload. All patients were examined by the interventional cardiologist and had ductal murmurs. When reauscultated (three of seven), murmurs were absent during spasm. Once spasm relieved, PDA diameters ranged from 1.5 to 8 (median 2) mm. All patients accommodated a 6-mm-or larger-Amplatzer device. No significant complications occurred and all patients were well at follow-up.

CONCLUSIONS

Ductal spasm occurs during transcatheter occlusion and may be an unrecognized cause of procedural failure. The phenomenon seems to occur in children born prematurely, and can occur after infancy. Loss of a continuous murmur confirms the diagnosis. Care should be taken to avoid device under-sizing when spasm occurs.

Reference ranges of ductus arteriosus derived by cardio-spatiotemporal image correlation from 14 to 40 weeks of gestation

OBJECTIVE

To construct reference ranges of fetal ductus arteriosus (DA) derived by volume datasets of cardio-spatiotemporal image correlation (cardio-STIC).

METHODS

Cardio-STIC volume datasets were acquired from low-risk singleton pregnancies with a reliable gestational age from 14 to 40 weeks. In offline analysis with 4D View version 9, fetal DA was measured in the transverse ductal arch view with orthogonal control in the multiplanar view. The reference ranges of the DA and Z-score equation were constructed against gestational weeks and biparietal diameter (BPD) as independent variables.

RESULTS

A total of satisfactory 606 volumes were analyzed. The reference ranges for predicting means and SDs of fetal DA were constructed based on the best-fit regression model. Mean DA (mm) was best predicted by linear model as a function of GA (weeks) and BPD (cm) as follows: Predicted DA diameter (cm) = -0.051 + 0.014 × GA (weeks) (r = 0.84) and Predicted DA diameter (cm) = -0.015 + 0.053 × BPD (cm) (r = 0.83). Models for Z-score calculation and centile charts for predicting fetal DA were also provided.

CONCLUSION

Reference ranges of the fetal DA and Z-score model are provided. These may serve as a useful tool in the assessment of fetal DA, especially in fetal cardiac anomalies or in monitoring fetuses exposed to maternal indomethacin.

Should we definitively abandon prophylaxis for patent ductus arteriosus in preterm new-borns?

Although the prophylactic administration of indomethacin in extremely low-birth weight infants reduces the frequency of patent ductus arteriosus and severe intraventricular hemorrhage, it does not appear to provide any long-term benefit in terms of survival without neurosensory and cognitive outcomes. Considering the increased drug-induced reduction in renal, intestinal, and cerebral blood flow, the use of prophylaxis cannot be routinely recommended in preterm neonates. However, a better understanding of the genetic background of each infant may allow for individualized prophylaxis using NSAIDs and metabolomics.