Pulmonic Stenosis

Introduction
Background

Pulmonic stenosis (PS) refers to a dynamic or fixed anatomic obstruction to flow from the right ventricle (RV) to the pulmonary arterial vasculature. Although most commonly diagnosed and treated in the pediatric population, individuals with complex congenital heart disease and more severe forms of isolated PS are surviving into adulthood and require ongoing assessment and cardiovascular care.
Pathophysiology
PS can be due to isolated valvular (90%), subvalvular, or peripheral (supravalvular) obstruction, or it may be found in association with more complicated congenital heart disorders. The characteristics of the various types of PS are described in this section.

Valvular pulmonic stenosis

Isolated valvular PS comprises approximately 10% of all congenital heart disease. Typically, the valve commisures are partially fused and the 3 leaflets are thin and pliant, resulting in a conical or dome-shaped structure with a narrowed central orifice. Poststenotic pulmonary artery dilatation may occur owing to "jet-effect" hemodynamics.

Alternatively, approximately 10-15% of individuals with valvar PS have dysplastic pulmonic valves. These valves have irregularly shaped, thickened leaflets, with little, if any, commissural fusion, and they exhibit variably reduced mobility. The leaflets are composed of myxomatous tissue, which may extend to the vessel wall. The valve annulus is usually small, and the supravalvular area of the pulmonary trunk is usually hypoplastic. Poststenotic dilatation of the pulmonary artery is uncommon. Approximately two thirds of patients with Noonan syndrome have PS due to dysplastic valves.

A bicuspid valve is found in as many as 90% of patients with tetralogy of Fallot, whereas it is rare in individuals with isolated valvar PS.

With severe valvular PS, subvalvular right ventricular hypertrophy can cause infundibular narrowing and contribute to the right ventricular outflow obstruction. This often regresses after correction of valvular stenosis.

With severe PS and decreased right ventricular chamber compliance, cyanosis can occur from right-to-left shunting if a concomitant patent foramen ovale, atrial septal defect, or ventricular septal defect is present.

Subvalvular pulmonic stenosis

Subvalvular PS occurs as a narrowing of the infundibular or subinfundibular region, often with a normal pulmonic valve. This condition is present in individuals with tetralogy of Fallot and can also be associated with a ventricular septal defect (VSD).

Double-chambered right ventricle is a rare condition associated with fibromuscular narrowing of the right ventricular outflow tract with right ventricular outflow obstruction at the subvalvular level.

Peripheral pulmonary stenosis

Peripheral pulmonary stenosis (PPS) can cause obstruction at the level of the main pulmonary artery, at its bifurcation, or at the more distal branches. PPS may occur at a single level, but multiple sites of obstruction are more common. PPS may be associated with other congenital heart anomalies such as valvular PS, atrial septal defect (ASD), VSD, or patent ductus arteriosus (PDA); 20% of the patients with tetralogy of Fallot have associated PPS.

Functional or physiologic PPS is a common cause of a systolic murmur in infants. It occurs in both premature and full-term infants; with time, the pulmonary artery grows, and the murmur usually disappears within a few months.

Poststenotic dilatation occurs with discrete segmental stenosis but is absent if the stenotic segment is long or if the pulmonary artery is diffusely hypoplastic.

PPS is associated with various inherited and acquired conditions including rubella and the Alagille, cutaneous laxa, Noonan, Ehlers-Danlos, and Williams syndromes.

Frequency
United States

PS is a common form of congenital heart disease that occasionally is diagnosed for the first time in adulthood. Isolated valvular PS comprises approximately 10% of all congenital heart disease.
Mortality/Morbidity

Except for critical stenosis in neonates, survival is the rule in congenital PS.

The long-term course of patients with mild PS is indistinguishable from that of the unaffected population. Mild PS does not tend to progress in severity; rather, pulmonic valve orifice size usually increases with body growth. However, untreated severe PS may result in outflow obstruction that progresses over a period of years; 60% of patients with severe PS require intervention within 10 years of diagnosis.

Sex

A slight female predominance exists.
Clinical
History
Most children and adults with mild-to-moderately severe pulmonic stenosis (PS) are asymptomatic.
Those with severe PS may experience exertional dyspnea and fatigue.
In extremely rare cases, patients present with exertional angina, syncope, or sudden death.
Peripheral edema and other typical symptoms occur with right heart failure.
Cyanosis is present in those with significant right-to-left shunt via a patent foramen ovale, atrial septal defect, or ventricular septal defect.
Physical
A precordial heave or a palpable impulse from the RV along the left parasternal border may suggest severe PS. In the left upper sternal border, a systolic thrill may be palpable at the level of the second intercostal space.
In valvular PS, auscultation reveals a normal S1 and a widely split S2, with a soft and delayed P2. Valvular PS typically causes a systolic crescendo-decrescendo ejection murmur in the left upper sternal border that increases with inspiration and radiates diffusely.
In patients with pliable valve leaflets, a systolic ejection click may precede the murmur, distinguished from aortic ejection sounds by its increased intensity on expiration and softening on inspiration. As the severity of PS increases, the ejection murmur increases in intensity, its duration prolongs, and its peak becomes more delayed. No ejection click is heard when dysplasia or severe leaflet thickening immobilizes the valve leaflets, or if the stenosis is above or below the pulmonic valve.
The murmur of PPS may be continuous, softer, and higher pitched.
Mild-to-moderately severe desaturation or frank cyanosis may be noted with right-to-left shunting through a patent foramen ovale, atrial septal defect, or ventricular septal defect.
Causes
See Pathophysiology.

Other forms of acquired pulmonic stenosis
PS is a rare manifestation of rheumatic heart disease, and it follows involvement of the mitral and aortic valves.
Carcinoid may result in development of myxomatous plaques in the RV outflow tract, with distortion and constriction of the pulmonic ring, as well as fusion or destruction of pulmonary valve leaflets, resulting in both stenosis and regurgitation.
Rarely, cardiac tumors can grow on or into the RV outflow tract and cause flow obstruction.
Sinus of Valsalva aneurysms and aortic graft aneurysms are extracardiac entities that can cause PS by external compression.

http://emedicine.medscape.com/article/157737-overview