A female infant is born approximately 10 weeks prematurely (at 30 weeks) and weighs 1710 gm. She has respiratory distress syndrome and is treated with endogenous surfactant. She is intubated endotracheally with mechanical ventilation immediately after bih. Over the first 4 days after bih the ventilator pressure and the fraction of inspired oxygen are reduced. Beginning on the fifth day after bih, she has brief desaturations that become more persistent.She needs increased ventilator and oxygen suppo on the seventh day after bih. She becomes cyanotic. Fuher examination, echocardiogram, and x-rays reveal left atrial enlargement, an enlarged pulmonary aery, increased pulmonary vasculature, and a continuous machine-like murmur. Which of the following is the most likely diagnosis?
Patent ductus aeriosus.The presence of a murmur could be indicative of any of the conditions. The presence of a continuous machine-likemurmur is indicative of a patent ductus aeriosus (PDA). Usually, as in this case, the premature baby with PDA does not acutely become cyanotic and ill, although brief desaturations can occur that become more persistent. An atrial septal defect (ASD), such as a persistent foramen ovale, could be eliminated from the diagnosis because the murmur would be heard as an abnormal splitting of the second sound during expiration (answer a). A patent foramen ovale is a common echo finding in premature babies and is usually not followed up unless it appears remarkable to the pediatric cardiologist or there is a persistent murmur. A patent foramen ovale might result in only minimal or intermittent cyanosis during crying or straining to pass stool. A murmur caused by a ventricular septal defect (VSD, answer c), occurs between the first and second hea sounds (S1and S2) and is described as holosystolic (pansystolic) because the amplitude is high throughout systole. Pulmonary stenosis would be heard as a harsh systolic ejection murmur (answer d). PDA refers to the maintenance of the ductus aeriosus, a normal fetal structure. In the fetus, the ductus aeriosus allows blood to bypass the pulmonary circulation, since the lungs are not involved in CO2/O2exchange until after bih. The placenta subserves the function of gas exchange during fetal development. The ductus aeriosus shunts flow from the left pulmonary aery to the aoa. High oxygen levels after bih and the absence of prostaglandins from the placenta cause the ductus aeriosus to close in most cases within 24 hours. A PDA most often corrects itself within several months of bih, but may require infusion of indomethacin (a prostaglandin inhibitor) as a treatment, inseion of surgical plugs during catheterization, or actual surgical ligation.
Persistent foramen ovale
Patent ductus aeriosus
Ventricular septal defect
Pulmonary stenosis