Aortic valve stenosis (AVS) is a congenital heart defect (CHD) that occurs when the aortic valve, which regulates blood flow from the heart to the rest of the body, does not form correctly before birth. This malformation creates an obstruction, restricting the amount of blood that can leave the heart’s main pumping chamber. This blockage means the heart must work much harder to push oxygen-rich blood into the aorta and onward to the body.
Understanding Aortic Valve Stenosis (AVS)
The aortic valve is positioned between the left ventricle, the powerful lower-left chamber of the heart, and the aorta, the body’s largest artery. Normally, this valve has three thin flaps, called leaflets or cusps, which open and close with each heartbeat to ensure one-way blood flow. Aortic stenosis occurs when these leaflets are fused, thickened, or the valve is malformed, often having only two leaflets (a bicuspid valve) or even one (a unicuspid valve).
This narrowing, or stenosis, forces the muscular left ventricle to generate abnormally high pressure to eject blood past the obstruction. Over time, this increased workload causes the left ventricle’s muscle wall to thicken, a condition known as hypertrophy. While the thickening is initially a compensatory mechanism, the prolonged strain can ultimately lead to heart muscle damage and potentially heart failure if the condition is severe or left untreated.
Incidence and Identified Risk Factors
Congenital Aortic Valve Stenosis is relatively uncommon among live births. Specifically, congenital AVS affects approximately 3.8 to 4.9 per 10,000 live births. The condition represents a small fraction of all heart defects, accounting for about 3% to 6% of all congenital heart disease diagnoses.
The most common underlying cause is a bicuspid aortic valve, which involves the valve having two cusps instead of the usual three. This bicuspid anatomy is the most frequent congenital heart defect overall, occurring in about 1% to 2% of the general population, although not all cases cause significant stenosis in infancy. The condition is observed more often in males than in females, with a reported ratio ranging from 3:1 to 5:1.
While the exact cause of AVS is often unknown, a genetic component is strongly suspected, as the condition can run in families and is sometimes associated with other genetic syndromes, such as Turner syndrome. Environmental factors or maternal illness during pregnancy are less clearly defined but are also investigated as part of the overall risk profile.
Detection and Diagnosis in Infants
Prenatal diagnosis is possible through a fetal echocardiogram, a specialized ultrasound that examines the structure and function of the baby’s heart while still in the womb. This imaging allows doctors to visualize the valve structure and assess the degree of blood flow restriction.
After birth, the first sign that prompts screening is often a distinct heart murmur, an extra sound heard with a stethoscope due to turbulent blood flow across the narrowed valve. Newborns with severe, or critical, AVS may show immediate symptoms like rapid breathing, difficulty feeding, sweating, and signs of decreased blood flow to the body, as the heart struggles to meet oxygen demands once placental circulation is removed.
The definitive diagnosis and assessment of severity are confirmed using a standard echocardiogram, a non-invasive ultrasound of the heart. This technology provides detailed images of the aortic valve’s structure, measures the pressure gradient across the valve, and evaluates the function and thickness of the left ventricle.
Current Treatment Approaches
Management of congenital AVS depends on the severity of the obstruction and the patient’s symptoms. For mild cases, treatment involves careful, long-term monitoring by a pediatric cardiologist to track for any progression of the stenosis over time. Since the condition can worsen, regular follow-up is necessary to assess the strain on the left ventricle.
For moderate to severe stenosis, interventions are necessary to relieve the obstruction and protect the heart muscle. One common procedure is balloon valvuloplasty, a catheter-based intervention where a thin tube is guided to the heart and a balloon is briefly inflated across the narrowed valve to stretch the opening. This less-invasive method is often a temporary measure to improve blood flow.
Surgical options are often considered when the stenosis is severe or cannot be adequately addressed by catheterization. Open-heart surgery may involve repairing the malformed valve by separating fused leaflets or, in more complex cases, replacing the valve entirely. One specialized procedure is the Ross procedure, which involves replacing the diseased aortic valve with the patient’s own pulmonary valve, offering a durable solution that avoids the need for long-term blood-thinning medication. Even after successful intervention, patients require lifelong cardiology care to manage potential future issues, such as re-narrowing of the valve or issues with the replacement valve.