About Pediatric Valve Disease: Understanding the most common malformations

Aortic Valve

The most common aortic valve lesion in childhood is aortic stenosis. Left ventricular outflow tract (LVOT) obstructive lesions account for approximately 6 percent of cases of congenital heart disease in children. Obstruction can occur at the valve (valvar), below the valve (subvalvar), or above it (supravalvar). 

The most common form of LVOT obstruction in children is valvar aortic stenosis (AS), accounting for as many as 71 to 86 percent of patients. In most cases of valvar AS, systemic blood pressure and cardiac output remain normal because of a compensatory elevation in left ventricular (LV) systolic pressure and total cardiac work. More severe disease in childhood, however, is not uncommon, and approximately 10 percent of patients develop heart failure during the first year after birth. Of these, approximately two-thirds become symptomatic by two months of age, and most will have symptims before six months. Infants with critical AS, the most severe form, present with signs of severe heart failure or cardiogenic shock in the neonatal period or shortly thereafter, following closure of the ductus arteriosus. 

Definitive therapy consists of reducing the degree of valvar stenosis. The initial treatment can be balloon valvuloplasty or surgery. However, patients who develop severe aortic regurgitation (AR) following balloon dilation will require surgical treatment. Valve intervention in the neonatal period commonly requires further intervention as the patient ages and grows; eventually some valves will need to be replaced.

Pulmonary Valve

Pulmonary valve stenosis (PS) is a common congenital heart defect, occurring in 6 to 8 out of every 10,000 live births and is characterized by obstruction in blood flow from the right ventricle (RV) to the pulmonary arteries.

PS can occur in isolation or be associated with other types of cardiac defects. Valvar stenosis is the most common type of PS, and is typically characterized by fused or absent commissures with thickened leaflets of the pulmonary valve. Severe PS is associated with RV hypertrophy and infundibular muscle hypertrophy, which can cause further dynamic obstruction below the pulmonary valve during RV contraction. 

Critical PS is the most severe case of valvar PS, resulting in an inadequate pulmonary blood flow. As a result, survival for affected infants is dependent upon maintaining a patent ductus arteriosus for pulmonary blood flow. Dysplastic pulmonary valves are another form of valvar PS and are less common. These valves are often irregular, with prominent leaflet thickening leading to a small (hypoplastic) valve annulus and reduced mobility. This anatomic variant is associated with Noonan syndrome. 

Pulmonary valve regurgitation is often secondary to the malformation tetralogy of Fallot. Repair of this condition in infancy typically leaves the pulmonary valve incompetent and years later this incompetence causes dilation and damage to the right ventricle. 

Tricuspid Valve

Ebstein anomaly is a congenital malformation that is characterized primarily by abnormalities of the tricuspid valve and right ventricle. The clinical presentation of Ebstein anomaly varies widely, ranging from the critically ill neonate to the asymptomatic adult, depending upon the degree of anatomic abnormality. The estimated risk of Ebstein anomaly in the general population is 1 in 20,000 live births, with no predilection for either gender. 

Clinically the anomaly may be fatal in utero or shortly after birth if severe cardiomegaly and heart failure are present. Children and adults with marked tricuspid leaflet displacement may have severe regurgitation, right-sided heart failure, elevated right atrial pressures, and significant cyanosis due to right-to-left interatrial shunting with or without functional/anatomic pulmonary valve atresia. In contrast, patients with mild apical displacement and mild dysfunction of the tricuspid valve (mild tricuspid regurgitation) may remain asymptomatic through adulthood or present in adulthood with arrhythmia or paradoxical embolic event. 

Contemporary repair techniques focus on a cone-type of reconstruction. This includes mobilization of all available valve leaflets and joining them to result in 360 degrees of leaflet tissue that is re-anchored at the level of the true annulus. The atrialized right ventricle is vertically plicated. Several other repair techniques, involving annuloplasty and/or ventricular plication, have also been described and used. If tricuspid repair is not possible and the patient has reached adult size, tricuspid valve replacement may be necessary. A biologic prosthesis is usually chosen because of the high incidence of thrombosis with a mechanical prosthesis placed in the right heart, particularly when the right ventricular function is poor.

Mitral Valve

Mitral stenosis (MS) is a condition characterized by obstruction of blood flow across the mitral valve from the left atrium to the left ventricle. The mechanical obstruction leads to increases in pressure within the left atrium, pulmonary vasculature, and right side of the heart. Most cases of MS are caused by rheumatic heart disease and congenital malformations (including parachute mitral valve). If untreated, MS often progresses to significant symptoms (eg, difficulty breathing and fatigue) and serious complications (eg, pulmonary edema, systemic arterial embolism, pulmonary hypertension, and death). Medical therapy can relieve symptoms but surgical or percutaneous intervention is required to relieve the obstruction to flow. 

Mitral regurgitation (MR) is a relatively common valvular disorder that can progress to ventricular decompensation and the need for mitral valve surgery. Congenital causes of MR include cleft mitral valve, which may be isolated or associated with other anomalies. MR is a common complication following atrioventricular canal defect repair, particularly in patients with preoperative MR. The only effective treatment is surgical valve repair or valve replacement.