Congenital heart defects (CHDs) are the most common type of birth anomaly. Among these structural malformations is congenital aortic stenosis (AS). Aortic stenosis is defined by a narrowing of the aortic valve, which controls blood flow out of the heart.
Understanding Congenital Aortic Stenosis
The aortic valve sits between the left ventricle and the aorta, the body’s largest artery. Normally, it opens fully to allow oxygenated blood to flow out to the body and then closes tightly to prevent backflow. When congenital aortic stenosis is present, the valve leaflets are often malformed or fused, obstructing the blood’s path.
This obstruction forces the left ventricle to generate higher pressure to push blood through the narrowed opening, known as pressure overload. Over time, this increased effort causes the left ventricular muscle wall to thicken, or hypertrophy. The severity of the condition exists on a spectrum, ranging from mild cases that may never cause symptoms to critical stenosis that results in severely inadequate blood flow. Critical AS is life-threatening and requires immediate intervention shortly after birth to maintain systemic circulation.
Statistical Prevalence in Newborns
Congenital aortic stenosis is a rare congenital heart defect, though it is one of the more common valve anomalies. The condition is estimated to occur in approximately 3.8 to 4.9 out of every 10,000 live births. This incidence is placed within the broader context of all CHDs, which collectively affect an estimated 0.8% to 1.2% of live births.
AS accounts for approximately 3% to 6% of all congenital heart defect diagnoses. Variability in reported prevalence often reflects differences in study methodology, such as whether milder forms diagnosed later are included. The condition occurs more frequently in males than in females, with a reported ratio ranging from 3:1 to 5:1.
Developmental Causes and Associated Risks
The etiology of congenital aortic stenosis is complex, and the exact cause often remains undetermined. Most instances are considered multifactorial, arising from genetic predispositions and environmental factors influencing fetal heart development. The most common underlying structural abnormality is a bicuspid aortic valve, which develops with two leaflets instead of the typical three.
While no single gene is exclusively responsible for most cases, familial inheritance patterns suggest a strong genetic component, especially with the bicuspid valve form. Congenital AS is also associated with specific chromosomal abnormalities and genetic syndromes, including Turner syndrome. Abnormal fetal blood flow dynamics during gestation are theorized to contribute to the malformation of the aortic valve and other left-sided heart obstructive lesions.
Detection and Immediate Management
Diagnosis may begin with the detection of a heart murmur or a distinct clicking sound during a newborn’s physical examination. For severe cases, detection can occur before birth via a fetal echocardiogram. Postnatally, the echocardiogram is the definitive diagnostic tool, used to visualize the malformed valve and quantify the degree of obstruction.
In neonates with critical aortic stenosis, life-saving intervention is required immediately upon diagnosis. Initial medical management often involves administering medications to maintain the patency of the ductus arteriosus, a temporary blood vessel that allows blood to bypass the heart and supply the body. Definitive treatment for significant obstruction typically involves balloon valvuloplasty, a catheter-based procedure that uses a balloon to stretch the narrowed valve opening. Surgical options, such as surgical valvotomy or valve replacement, are also utilized depending on the severity and specific anatomical features of the stenosis.