Does crossover treatment of control subjects invalidate results of randomized trials of patent ductus arteriosus treatment?

Optimal management of patent ductus arteriosus (PDA) in extremely preterm infants remains controversial. There is paucity of evidence on the benefits of PDA treatment in reducing mortality and morbidities in extremely preterm infants. Failure of randomized clinical trials to demonstrate beneficial effects of PDA treatment on outcomes has often been attributed to open treatment of control subjects. This perspective examines the PDA treatment trials to date, with specific focus on rates of and ages of subjects at open rescue treatment. Although these trials demonstrate that ductal closure is significantly increased with treatment, that does not translate to a significant decrease in major morbidities or mortality in premature infants, even when trials with high rates of rescue treatment of controls are excluded. Trials in which enrollment occurred after 7 days of age include insufficient numbers of subjects to evaluate this relationship.