Congenital aortic valve stenosis is the inborn obstruction of blood flow through the aortic valve, most often associated with abnormal valve morphology: aortic bicuspid or unicuspid valve. It can be associated with other cardiac malformations and the condition, in the majority of cases, becomes symptomatic sooner or later. Critical congenital aortic valve stenosis should be addressed immediately.
Congenital aortic valve stenosis patients could rapidly develop heart failure symptoms, such as tachypnea, deficient feeding, unsatisfactory ponderal curve, and decreased urine output. These become worse every day, as the patency of ductus arteriosus decreases. If the valvular stenosis is not critical, children remain asymptomatic for a period of time and the suspicion is raised by clinical examination performed for other conditions. It is estimated that less than 15% of patients are symptomatic before they reach the age of one year  . However, congenital aortic valve stenosis patients may have certain complaints, such as asthenia, excessive sleeping, decreased exercise tolerance, presyncope, syncope, dyspnea, and chest pain. Sudden death during strenuous activities may be the first manifestation of congenital aortic valve stenosis.
In severely ill newborns, a murmur may not be audible or may be low grade and not accompanied by a thrill because of the low cardiac output. Clicks are also absent, because of the decreased mobility of the valve. In these patients, presentation resembles a sepsis case. Affected patients have symmetrically decreased or absent peripheral pulses and low peripheral perfusion, they are tachycardic, tachypneic, and dyspneic. If the stenosis is not critical, the patient is likely to be sent to a consultation with a pediatric cardiologist because an intense systolic murmur is heard.
Congenital aortic valve stenosis may be accompanied by aortic regurgitation. In this case, a balloon dilatation should not be performed. In cases where regurgitation is absent, this procedure may alleviate symptoms , but the valve may become stenotic again after a while or regurgitation may follow dilatation  .
In older children, the clinical diagnosis is easier to establish and is based on findings like a harsh systolic crescendo-descrescendo ejection murmur that peaks in mid-systole in the aortic auscultation area, which is more intense and longer if the valve is severely stenotic. A suprasternal thrill is often found. The murmur radiates to the neck and is better heard in a forward leaning, squatting or left decubitus position. The aortic component of the second heart sound is more or less delayed, depending on the severity of the obstruction, sometimes leading to a paradoxically split second heart sound. Left ventricular hypertrophy is suggested by the presence of the fourth heart sound or an increased apical impulse.
Workup should include a thoracic radiography, that may reveal the presence of cardiomegaly and pulmonary venous congestion in critical congenital aortic valve stenosis. The ascending aorta may be dilated. The diagnosis is established by echocardiography. Two-dimensional echo will characterize valve anatomy as well as the number and mobility of leaflets. Moreover, it will measure the size of the valvular ring. It is also important to describe the presence of associated abnormalities and characterize the left ventricular function. Continuous and pulsed Doppler echocardiography will determine the transvalvular maximum and mean gradient, thus establishing disease severity and need for effort restriction , assuming that left ventricular function is not compromised. Associated severe aortic regurgitation will lead to an overestimation of gradients by this imaging method . It is important while measuring gradients to pay an attention to the angle between the jet flow and ultrasound beam (they should be parallel) . Color Doppler will reveal a turbulent flow across the valve. Transesophageal echocardiography is rarely necessary and only applicable to adolescents and adults. Exercise testing is used for risk stratification and an assessment regarding the surgical intervention. Three-dimensional echocardiography, if available, is a useful tool in congenital aortic valve stenosis , allowing precise valve and volumes measurement and characterization of subvalvular membranes, if present .
The electrocardiogram could reveal left ventricular hypertrophy, left bundle branch block, ST segment depression, and negative T waves . Diffuse T-wave and ST-segment changes suggest severe stenosis .
Holter monitoring may demonstrate the presence of ventricular arrhythmias. Magnetic resonance imaging is used in patients with poor acoustic windows and is also useful in acknowledging the presence of endocardial fibroelastosis  .