Making sense of the evidence: designing randomised controlled trials for preterm infants with high-shunt volume patent ductus arteriosus.

Management of the patent ductus arteriosus (PDA) in preterm infants remains controversial. Randomised controlled trials (RCTs) have shown that administering pharmacotherapy, predominantly ibuprofen, a cyclooxygenase (COX) inhibitor, to infants selected based on the standard echocardiography approach to diagnosis (eg, duct diameter and shunt direction), does not improve outcomes and may lead to harm. It remains uncertain, however, whether eliminating or reducing PDA shunt volume using an intervention with higher efficacy and fewer adverse effects, or in a more selective population, would show different results. It is possible that an imprecise approach to patient selection exposes low-risk infants to the adverse effects of pharmacotherapy without benefit and high-risk infants to the synergistic adverse effects of pharmacotherapy and persistent high volume pathological shunt when treatment fails. Whether targeted management of moderate-high volume PDA shunts, informed by comprehensive echocardiography adjudication, in the highest risk infants is beneficial remains untested in an RCT setting. Furthermore, both pharmacological and non-pharmacological interventions warrant further investigation. High quality practice changing research requires a collaborative approach between haemodynamic specialists, epidemiologists and trial methodologists to (1) define the study population based on phenotypic profiles of high-risk infants; (2) enhance the choice and timing of intervention; and (3) identify outcome measures that are relevant and clinically meaningful to families. In this review, we summarise evidence from RCTs and observational studies by discerning discrepancies and exploring potential explanations. Such an approach is essential to establish whether active PDA treatment confers any measurable benefit for high-risk preterm infants.