Aortic Valve Stenosis (AVS) is a specific type of congenital heart defect (CHD) that involves a structural problem with the heart’s outflow valve. Present at birth, AVS restricts the flow of blood leaving the heart and supplying the body. CHDs are the most common type of birth defect, affecting nearly one in every 100 newborns.
Understanding Aortic Valve Stenosis
Aortic Valve Stenosis (AVS) is a condition where the aortic valve is narrowed. This valve is situated between the left ventricle, the heart’s main pumping chamber, and the aorta, the body’s largest artery. Normally, the valve has three pliable flaps, or cusps, that open fully to allow oxygen-rich blood to flow efficiently to the rest of the body.
Stenosis means a narrowing or obstruction. When the aortic valve is stenotic, its cusps are often thickened, malformed, or fused, preventing them from opening completely. This forces the left ventricle to pump with greater force to push blood through the restricted opening. Over time, this extra effort can cause the left ventricle wall to thicken and stiffen, potentially leading to heart failure if the condition is severe. The most common congenital cause is a bicuspid aortic valve, which forms with only two cusps instead of the usual three.
Analyzing Prevalence and Incidence Rates
The congenital form of Aortic Valve Stenosis is relatively uncommon among all live births, though it is one of the more frequently seen valve defects. The incidence of congenital AVS is estimated to be between 3.8 and 4.9 cases for every 10,000 live births.
Congenital Heart Defects (CHDs) occur in approximately 0.8% to 1.2% of live births. Aortic Valve Stenosis is a distinct subset of these defects, accounting for roughly 3% to 6% of all diagnosed congenital heart malformations.
Statistics regarding AVS are complicated by the presence of a bicuspid aortic valve (BAV). BAV is the most common congenital heart malformation overall, affecting between 1% and 3% of the general population. While BAV is a structural defect, many individuals do not experience significant stenosis at birth. However, the BAV defect makes the valve prone to developing stenosis later in life, which is why congenital AVS figures focus on cases where the narrowing is clinically significant in the newborn period.
Detection and Diagnosis Timeline
The timeline for diagnosing congenital AVS ranges from before birth to several weeks after delivery. Prenatal detection is possible through a specialized ultrasound called a fetal echocardiogram, which provides a detailed view of the heart structure and blood flow. This test is often performed around 20 to 24 weeks of gestation, particularly if a routine anatomy scan raises suspicion or if there is a family history of heart defects.
A prenatal diagnosis allows the baby to be delivered at a medical center equipped with specialized pediatric cardiac care, which is important for severe cases. However, mild or moderate cases of AVS may not be apparent on a fetal echocardiogram until later in the pregnancy or may not be detected at all. Aortic stenosis can also progress during the third trimester, meaning a normal mid-pregnancy scan does not rule out the condition developing by the time of birth.
Postnatal detection often begins with a physical examination, where a doctor may hear a heart murmur caused by turbulent blood flow through the narrowed valve. Newborn screening protocols, such as pulse oximetry, are also widely used to check for critical congenital heart defects. This non-invasive test measures oxygen saturation in the baby’s blood and is typically performed after 24 hours of life. While effective for detecting defects that cause low oxygen levels, pulse oximetry can sometimes miss left-sided obstructive lesions like AVS that do not immediately cause hypoxemia.
The definitive diagnostic tool for AVS in a newborn is a full echocardiogram, which uses sound waves to create moving images of the heart. This allows the medical team to visually assess the structure of the aortic valve and measure the pressure gradient across the valve. An abnormal echocardiogram confirms the diagnosis and helps determine the severity of the obstruction, which guides the need for immediate intervention.