Perinatal Cardiovascular Physiology and Recognition of Critical Congenital Heart Defects

Understanding the perinatal cardiovascular physiology is essential for timely diagnosis and management of congenital heart defects (CHDs) in neonatal period. The incidence of CHDs is reported in 7 to 9 out of 1000 live births, with around 25% of them being critical congenital heart disease, defined as a congenital heart condition needing surgery/intervention or leading to death within 1 month after birth. Around 50% to 60% of the critical CHDs are detected on fetal anomaly screening. The signs and symptoms of critical congenital heart defects are often nonspecific during early neonatal period. The routine newborn physical examination often fails to detect many of these critical CHDs during the transitional circulation because of lack of signs soon after birth. While routine pulse oximetry screening typically performed at 24 to 48 hours after birth may help in detecting cyanotic heart conditions, noncyanotic CHDs such as coarctation of aorta may go undetected on pulse oximetry screening in asymptomatic infants. Some infants may deteriorate early while waiting for pulse oximetry screening, and this risk is much higher if the pulse oximetry screening is not performed to detect congenital heart conditions. There should be high degree of suspicion of critical CHDs in infants presenting with shock or hypoxia. Delay in diagnosis of CHDs has been reported to be associated with poor outcomes, and hence, it is extremely important to detect them in asymptomatic well-infants. Timely recognition and therapy with prostaglandin E1 infusion can be lifesaving in neonatal cardiac emergencies, and they should be urgently discussed with a pediatric cardiologist. This article reviews diagnosis and management of CHD in the delivery room and before surgery in the NICU.