The presentation depends on age, degree of obstruction, and the ability of the right ventricle to compensate. Mild pulmonary valve stenosis may produce no symptoms and be discovered because of a systolic ejection murmur at the upper left sternal border. The murmur is a clue to turbulent forward flow; it does not establish severity. Echocardiography does that. As obstruction progresses, the right ventricle works against a fixed outlet. Older children and adults may report exertional dyspnea, reduced exercise tolerance, fatigue, chest discomfort, presyncope, or syncope. These symptoms arise when the right ventricle cannot increase pulmonary blood flow adequately during exertion. Severe obstruction can raise right-sided pressure enough to promote right-to-left flow through a patent foramen ovale or atrial septal defect. The result is cyanosis: deoxygenated blood bypasses the lungs and enters systemic circulation. Cyanosis in a patient with pulmonary stenosis is therefore a warning that the physiology may be more serious than an isolated murmur. Advanced right-sided pressure overload may produce raised jugular venous pressure, hepatomegaly, peripheral edema, worsening tricuspid regurgitation, or atrial arrhythmias. These are not early findings. Their...