Pulmonary stenosis (PS) is a heart condition where the pulmonary valve, which controls blood flow from the heart’s lower right chamber to the lungs, is narrowed. This narrowing restricts blood flow to the lungs for oxygenation, forcing the right ventricle to work harder to push blood through the obstruction. PS is most often present at birth, making it a common congenital heart defect. Whether PS can resolve on its own depends almost entirely on its initial severity and the specific anatomical structure of the valve.
Defining the Types and Severity of Stenosis
Pulmonary stenosis is primarily categorized by the location of the narrowing. The vast majority of cases occur directly at the valve itself (valvular stenosis). Less common forms involve obstruction below the valve (subvalvular) or above it in the pulmonary artery (supravalvular). While most cases are congenital, PS can rarely be acquired later in life due to issues like rheumatic heart disease or carcinoid syndrome.
The severity of pulmonary stenosis is determined by measuring the pressure difference, or gradient, across the narrowed area. This measurement is performed using Doppler echocardiography, which calculates the gradient in millimeters of mercury (mmHg) by assessing blood flow velocity. A gradient below 36 mmHg is considered mild stenosis, meaning the heart faces little extra strain. Moderate stenosis is defined by a gradient between 36 and 64 mmHg. A reading above 64 mmHg signifies severe stenosis, indicating a significant obstruction that places considerable stress on the right side of the heart.
When Stenosis Stabilizes or Improves
True spontaneous resolution, where the narrowed valve returns to a normal structure, is rare in congenital pulmonary stenosis. Stability and a measurable decrease in obstruction are common, particularly in mild cases. This improvement often occurs because the fixed size of the valve opening becomes less restrictive as a child grows and heart structures enlarge.
Patients with mild pulmonary stenosis often show a decrease in their pressure gradient over time, with some studies reporting elimination of the measurable gradient in about 30% of cases. This natural course is favorable for patients diagnosed after infancy. Mild cases diagnosed in infants require careful monitoring, however, as a small percentage (about 15%) can progress to moderate or severe stenosis within the first two years of life, requiring intervention.
For individuals with moderate or severe pulmonary stenosis, spontaneous improvement is unlikely; the condition is more likely to remain stable or worsen. When obstruction is significant, prolonged high pressure causes the right ventricle muscle to thicken (hypertrophy). If left uncorrected, this can eventually lead to heart muscle damage and right-sided heart failure. This progression necessitates medical intervention, as the heart cannot indefinitely compensate for the increased workload.
Treating Severe Pulmonary Stenosis
When pulmonary stenosis is moderate to severe, or if a patient shows symptoms like shortness of breath or fainting, a procedure is necessary to relieve the obstruction. The first-line treatment for typical valvular PS is Balloon Valvuloplasty (BPV). This minimally invasive, catheter-based intervention avoids open-heart surgery by accessing the heart through a blood vessel, typically in the groin.
During BPV, a thin tube with a balloon tip is guided across the narrowed pulmonary valve. The balloon is briefly inflated, splitting the fused valve leaflets (commissures) and widening the valve opening. This action immediately reduces the pressure gradient across the valve, lowering the strain on the right ventricle and restoring blood flow to the lungs.
Intervention is generally recommended for asymptomatic patients when the peak pressure gradient exceeds 60 mmHg, or for symptomatic patients when the gradient is greater than 50 mmHg. While BPV is highly effective, open-heart surgery remains an option for complex cases, such as those involving a poorly formed (dysplastic) valve or when other defects require simultaneous repair. The goal is to relieve obstruction and prevent damage.
Life After Diagnosis or Intervention
Long-term follow-up with a cardiologist is required, regardless of whether the stenosis was managed conservatively or required intervention. This specialized care ensures stable heart function and allows for the early detection of potential late complications. Routine echocardiograms monitor the pressure gradient and assess the health and size of the right ventricle.
The long-term prognosis after successful intervention is excellent, allowing many patients to lead full and active lives. A common consequence following BPV or surgical repair is pulmonary regurgitation (a mild leakiness of the valve). While a small leak is tolerated, a significant leak can cause the right ventricle to enlarge and may eventually necessitate a pulmonary valve replacement, often decades later. Physical activity restrictions are minimal for those with mild, stable stenosis or those successfully treated for moderate or severe stenosis.