Preductal Hemodynamic Redistribution in Preterm Infants with Patent Ductus Arteriosus

A patent ductus arteriosus is a common entity in preterm infants. Literature is lacking regarding physiological effects on preductal circulation. This report describes 3 patients with abnormal flow Doppler pattern in brachiocephalic artery. Further research is warranted to better understand the impact of PDA on preductal circulation.


Introduction
A patent ductus arteriosus (PDA) is a common entity in preterm infants.Unlike in the term population, 57-70% of preterm infants weighing less than 1000 grams will still have an open PDA at 7-10 days of age [1].Numerous studies described the physiological efects of the PDA, particularly a hemodynamically signifcant one.When hemodynamically signifcant, the immature pulmonary vascular bed in this population is exposed to variable degrees of volume overload.Tis contributes to neonatal morbidities including bronchopulmonary dysplasia, pulmonary haemorrhage, necrotizing enterocolitis, and life-threatening complications [2][3][4][5].
PDA is also associated with extra-pulmonary morbidities [5][6][7].Historically, it was thought that preductal vessels were protected from the efects of left-to-right ductal shunting.Tis theory, however, is being re-examined.Lemmers et al. suggest that a persistent PDA may infuence brain growth because of insufcient cerebral oxygenation thus afecting neurodevelopmental outcomes [8].Breatnach et al. found that the brachiocephalic artery tended to have reversal of fow in infants with a PDA at 5 to 7 days of age, whereas those without a PDA had forward fow in this artery postulating that reversal of fow may be an early indicator of impaired cerebral circulation [9].Sellmer et al. showed that a large PDA early on is associated with a 6-fold increase in the development of an intraventricular haemorrhage (IVH) [10].
Te defnition of hemodynamically signifcant PDA has not been standardized [11,12].However, it appears that detailed echocardiographic assessment looking at multiple indices is the key to assessing the hemodynamic signifcance using TnECHO.

Case Report
We are reporting 3 cases of preterm infants with hemodynamically signifcant PDAs confrmed by targeted neonatal echocardiogram (TnECHO), presenting with abnormal brachiocephalic artery fow Doppler pattern.Table 1 summarizes the patients' clinical characteristics, and Table 2 summarizes their PDA characteristics.From the arch view, the brachiocephalic artery was visualized and Dopplered during the echocardiogram.Each of these patients had abnormal Doppler fow pattern in the brachiocephalic artery shown as reversal of diastolic fow (Figure 1).

Discussion
In this clinical case, we report on three preterm infants with hemodynamically signifcant PDAs beyond the frst week of life.All three infants were noted to have a reversal of diastolic blood fow in the brachiocephalic artery upon assessment by TnECHO, and all were found to have varying degrees of intraventricular hemorrhage.Tose scans were the frst scans for those infants when they were diagnosed with hemodynamically signifcant PDA with diferent ages at the diagnosis for the infants.Also, unfortunately, the subsequent follow-up scans did not interrogate the brachiocephalic fow Doppler pattern.Infants developed mild BPD diagnosed at 36 weeks corrected, but all infants came of respiratory support and were discharged home between 38 and 40 weeks corrected gestation.Tere are no other insignifcant morbidities.

Case Reports in Pediatrics
Establishing the impact of the PDA and its signifcance is a comprehensive process combining clinical, radiological, chemical, and echocardiographic assessment.While a causal relationship cannot be established based on this case report, it appears that a hemodynamically signifcant PDA might be associated with abnormal Doppler fow patterns in the brachiocephalic artery of preterm infants.Whether this is related to fow redistribution or steal phenomenon remains unclear.Tere is a paucity of literature on this subject, and therefore, further studies investigating the relationship between abnormal brachiocephalic artery Doppler fow, hemodynamically signifcant PDAs, and the development of IVH are warranted.As the brachiocephalic artery is easily interrogated and easy to Doppler, if abnormal, this should alert clinicians to the possibility of developing an IVH.

Table 2 :
Echocardiographic assessment of all patients.