The Critical Congenital Heart Disease (CCHD) screen is a simple, non-invasive test given to all newborns before they leave the hospital. This quick bedside procedure uses pulse oximetry to estimate the amount of oxygen saturation in a baby’s blood. The screening detects severe heart defects that are life-threatening if not diagnosed and treated shortly after birth, allowing medical teams to intervene promptly and prevent serious complications.
Understanding Critical Congenital Heart Disease
Critical Congenital Heart Disease refers to structural heart defects that form during early fetal development and require surgery or catheter intervention in the first year of life. These conditions affect approximately three out of every 1,000 live births. The term “critical” is used because these defects severely impair the heart’s function, reducing the oxygenated blood delivered to the body’s organs and tissues.
Many newborns with CCHD initially appear healthy, and routine prenatal ultrasounds or physical exams may not detect the condition. This happens because while in the womb, a baby’s circulation uses temporary pathways that bypass the lungs, which can mask the severity of the defect. Once these temporary pathways begin to close after birth, the baby’s health can rapidly decline, often within the first few days or weeks of life.
Examples of CCHDs include Transposition of the Great Arteries, where the two main arteries leaving the heart are switched, and Hypoplastic Left Heart Syndrome, where the left side of the heart is severely underdeveloped. Other defects, such as Tetralogy of Fallot and Total Anomalous Pulmonary Venous Return, are also included in the CCHD screening target group.
How the Screening Test Is Performed
The CCHD screening uses a pulse oximeter, a small machine that measures the percentage of oxygen saturation in the blood. This painless test involves placing soft, bandage-like sensors on the baby’s skin, typically while the infant is calm and breathing room air. The process usually takes only a few minutes to complete, and the results are available immediately.
The procedure requires two simultaneous measurements to compare oxygen levels. One sensor is placed on the baby’s right hand, which provides a pre-ductal measurement, meaning it measures oxygenated blood before it passes through a temporary fetal blood vessel called the ductus arteriosus. The second sensor is placed on one of the baby’s feet, which provides a post-ductal measurement, reflecting blood oxygen after it has mixed with any potentially deoxygenated blood flow.
The difference in oxygen saturation between the right hand and the foot is a key indicator for certain CCHDs, as some defects cause poor mixing of oxygenated and deoxygenated blood. Screening is usually scheduled when the baby is at least 24 hours old, but no later than 48 hours after birth, or just before hospital discharge if that occurs earlier. Waiting until this time reduces false-positive results, as the baby’s circulatory system is still adjusting.
What the Screening Results Indicate
The CCHD screening results fall into three main categories: a Pass, a Fail (or positive screen), or an Indeterminate (or repeat) result.
A screening is considered a “Pass” if oxygen saturation is 95% or greater in both the right hand and the foot, and the difference between the two readings is three percentage points or less. A passing result is highly reassuring, and no further cardiac evaluation is typically needed unless other symptoms arise.
An Indeterminate result occurs when the oxygen saturation in either limb is between 90% and 94%, or when the difference between the hand and foot reading is greater than three percent, even if one reading is above 95%. In this case, the baby is monitored for signs of distress, and the screening is repeated one hour later. If a second screen is also indeterminate, a third screen is performed after another hour.
A result is considered a “Fail,” or a positive screen, if any initial oxygen saturation reading is below 90% in either the hand or the foot. It is also a fail if, after three attempts, the saturation remains below 95% in either limb or the difference between the two readings remains greater than three percent. A failed screen requires immediate medical attention, but it does not automatically confirm a CCHD diagnosis.
A positive screen can be triggered by other health issues, such as respiratory problems or infection, but it mandates rapid follow-up evaluation for a potential heart defect. The next step is typically an urgent consultation with a pediatric cardiologist and a diagnostic echocardiogram (detailed ultrasound of the heart structures). This specialized imaging provides a definitive look at the heart to determine if a CCHD is present before the baby leaves the hospital.