Congenital heart disease (CHD) affects about 1 percent of newborn babies per year in the United States, and approximately one quarter of those will have critical congenital heart disease (CCHD) that requires catheter or surgical intervention during the first year. CHDs are a leading cause of birth defect-associated infant illness and death. Babies born with these conditions are living a longer and healthier life, thanks to advancement in cardiac care. Newborn pulse oximetry screening for critical congenital heart disease helps identify those at risk.
Why Is Early Screening for CCHD Important?
Lakshmi Nagaraju, MD
Many infants with CCHD are symptomatic and diagnosed soon after birth; however, there is a significant number who are discharged from the birth hospitalization and not diagnosed until after they present in critical illness, which leads to an increased risk of mortality and morbidity. Newborns who have CCHD are susceptible to intense, sudden worsening in hemodynamic status during the first few days of life. These acute physiological changes are secondary to drop in pulmonary vascular resistance and closure of the ductus arteriosus. With the advent of prostaglandin therapy to maintain patency of ductus arteriosus, many previously lethal congenital heart conditions that present with severe hypoxemia, shock and acidosis in the newborn period are now survivable. Amongst sequelae of neonatal hemodynamic compromise, the most important long-term effects related to the degree of brain injury are from ischemia and reperfusion.
Because timely recognition of CCHD could improve outcomes, it is important to identify and evaluate strategies that can enhance early detection. A common feature of many forms of CCHD is hypoxemia. Pulse oximetry screening is an accepted test that improves detection of CCHD. According to the AAP, “Some states [including Texas] now mandate that all newborns be screened by pulse oximetry for CCHD as part of newborn screening.”
How Is the Screening Done?
The American Academy of Pediatrics recommends that all newborns be screened for CCHD and has put forward a guideline that is the most commonly used algorithm for CCHD screening.
“Screening [is] performed after 24 hours of life or as late as possible if early discharge is planned. Screening within the first 24 hours of life [can be less] specific as hypoxemia commonly occurs during the transition [phase after birth]. ... Screening should be performed by qualified and trained personnel,” according to a summary from UpToDate.
Screenings should be performed using a motion-tolerant pulse oximeter with either disposable or reusable probes.
“Measurements should not be performed when the infant is crying or moving because this reduces the quality of the signal and accuracy of the test,” the UpToDate summary continues. Oxygen saturation is measured preductal — in the right hand — and postductal — in either foot — which is either done simultaneously or in direct sequence.
How Are the results Interpreted?
The baby passes screening if the oxygen saturation is 95 percent or greater in the right hand and foot and the difference is 3 percentage points or less between the two. A positive screen includes any of the following:
- Oxygen saturation less than 90 percent in either extremity
- Oxygen saturation between 90 and 94 percent in both upper and lower extremities on three measurements, each separated by an hour
- Oxygen saturation difference greater than 3 percent between the upper and lower extremities on three measurements, each separated by an hour
What Happens When the Baby Has a Positive Screen?
Any newborn with a positive screen requires a comprehensive evaluation for causes of hypoxemia. In the absence of other findings to explain hypoxemia (infectious or pulmonary causes), CCHD needs to be excluded on the basis of a diagnostic echocardiogram with interpretation by a pediatric cardiologist or a consultation by a pediatric cardiologist. Newborns with a negative screen may still have critical CHD because hypoxemia may not be the presenting symptom in some CCHD lesions. If there is clinical suspicion for critical CHD, additional evaluation should be pursued even in the setting of a normal pulse oximeter screen. Because of the importance of establishing the diagnosis of CCHD in a timely manner, hospitals and birthing centers following the screening program need to establish a protocol to ensure timely evaluation and follow-up of positive screens.
The screening procedure to detect CCHD in newborns may require modification in certain settings such as high-altitude, out of hospital births and infants admitted to the NICU. The benefits of screening must be weighed against the downside of false positives. Infants with false positive screening undergo further additional testing and/or are transferred to centers with a higher level of care. This has the potential to cause anxiety in the parents and discomfort or harm to the newborn. However, it is important to recognize that in many cases the evaluation results in identification of other causes of hypoxemia.
For more information or to make a referral to the Heart Center at The Children’s Hospital of San Antonio, please call 210-704-4708.
Sources: AAP.org/newborn screening: critical congenital heart disease