Subpulmonary stenosis

Subpulmonary stenosis is a congenital heart defect characterized by the narrowing (stenosis) of the area below the pulmonary valve, which is one of the four valves in the heart. This condition impedes the heart's ability to pump blood from the right ventricle into the pulmonary artery, which carries blood to the lungs for oxygenation. Subpulmonary stenosis is a form of right ventricular outflow tract obstruction (RVOTO), which can occur in isolation or as part of more complex congenital heart diseases such as Tetralogy of Fallot.

Causes and Pathophysiology

Subpulmonary stenosis results from abnormal development of the heart and great vessels during fetal life. The exact cause is often unknown, but it can be associated with genetic conditions or environmental factors affecting fetal development. The stenosis is typically caused by a narrowing of the muscular or infundibular region below the pulmonary valve. This narrowing can increase the workload on the right ventricle, leading to hypertrophy (thickening of the heart muscle) and potentially compromising blood flow to the lungs.

Symptoms

Symptoms of subpulmonary stenosis can vary widely depending on the severity of the obstruction. Mild cases may be asymptomatic and go undetected until later in life. More severe forms can present in infancy or early childhood with symptoms such as:

• Shortness of breath
• Fatigue
• Cyanosis (a bluish tint to the skin, indicating decreased oxygenation)
• Heart murmur
• Poor weight gain in infants
• Exercise intolerance

Diagnosis

Diagnosis of subpulmonary stenosis typically involves a combination of physical examination, where a heart murmur may be detected, and imaging studies. Echocardiography is the primary diagnostic tool, providing detailed images of the heart's structure and function, including the presence and severity of stenosis. Other diagnostic procedures may include:

• Electrocardiogram (ECG) to assess heart rhythm
• Cardiac MRI for detailed anatomical information
• Cardiac catheterization to measure pressures within the heart chambers and great vessels

Treatment

Treatment for subpulmonary stenosis depends on the severity of the condition and the presence of associated congenital heart defects. Mild cases may require no immediate treatment but regular monitoring to assess changes in the condition. Moderate to severe cases may require intervention to relieve the obstruction and improve blood flow to the lungs. Treatment options include:

• Balloon valvuloplasty, a catheter-based procedure to widen the narrowed area
• Surgical repair to remove the obstruction or reconstruct the affected area
• In cases associated with complex congenital heart defects, more comprehensive surgical correction of the defects may be necessary

Prognosis

The prognosis for individuals with subpulmonary stenosis varies depending on the severity of the obstruction and the presence of other heart defects. With appropriate treatment, many patients can lead normal or near-normal lives. Ongoing cardiac care and monitoring are essential to manage potential long-term complications, such as arrhythmias or heart failure.