Excerpt from Pulmonic Valvular Stenosis

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Background

Until the 1950s, isolated pulmonary stenosis was considered to be a rare congenital abnormality.¹ A review of the literature in 1949 yielded just 68 cases. However, as physiologic testing has improved, this condition has been more frequently recognized.

Pulmonary valve stenosis (PVS) is described as those lesions that collectively are associated with obstruction to right ventricular outflow. PVS may be valvular, subvalvular, or supravalvular. PVS is the cause of isolated right ventricular outflow obstruction in 80% of cases.²

Pathophysiology

The pulmonic valve develops between the 6th and 9th week of gestation. Normally, the pulmonic valve is formed from 3 swellings of subendocardial tissue called the semilunar valves. These tubercles develop around the orifice of the pulmonary tree. The swellings are normally hollowed out and reshaped to form the 3 thin-walled cusps of the pulmonary valve.

Failure to develop normally can result in the following malformations: fusion of 2 of the cusps, 3 leaflets that are thickened and partially fused at the commissures, or a single cone-shaped valve. In Noonan syndrome, tissue pads within the sinuses interfere with the normal mobility and function of the valve.

The most common pathology is valvular pulmonic stenosis, which accounts for more than 80% of cases of pulmonary stenosis. Most cases are isolated valvular conditions, but they may be associated with a ventricular septal defect or secondarily lead to right ventricular infundibular hypertrophy.³

Isolated infundibular or subvalvular pulmonic stenosis is less common and is usually associated with a ventricular septal defect.

Most cases are congenital and sporadic. PVS is not understood to have significant inheritance, but its concordance among siblings is higher than would be expected. Rarely, pulmonic stenosis is associated with recessively transmitted conditions such as Laurence-Moon-Biedl syndrome. Isolated pulmonic stenosis has been reported in association with trisomy 21, and infundibular stenosis has been associated with trisomy 18, 15, and 13. In patients with Noonan syndrome, pulmonic stenosis, classically with dysplastic valves, can be present. Additionally, in the congenital rubella syndrome, supravalvular pulmonic and pulmonary artery branch stenoses are frequently present.

Acquired valvular disease is rare. The two most common etiologies are carcinoid and rheumatic fever.

Frequency

United States

PVS accounts for 10% of cases of congenital heart disease. Prevalence of pulmonary stenosis is 8-12% of all congenital heart defects. Isolated PVS with intact ventricular septum is the second most common congenital cardiac defect. PVS may occur in as many as 30% of all patients with congenital heart disease when associated with other congenital cardiac lesions.

Mortality/Morbidity

Much of what is known about the morbidity and mortality of PVS comes from the Natural History Study of Congenital Heart Defects and the Second Natural History Study of Congenital Heart Defects. The Natural History Study of Congenital Heart Defects included an initial cardiac catheterization and then follow-up for events over an 8-year period. The Second Natural History Study of Congenital Heart Defects reported on 16-27 years of follow up from the same cohort. The studies demonstrated that adverse outcomes directly relate to the right ventricular systolic pressure gradient.

• Mild (<50 mm Hg) PVS is well tolerated. Trivial differences were noted in the frequency of electrocardiographic abnormalities, exercise tolerance, echocardiographic findings, and adverse cardiac outcomes for those with pressure gradients less than 50 mm Hg. Of these patients, 94% were asymptomatic, without cyanosis or congestive heart failure.^{4, 5}
• Moderate to severe PVS (>50 mm Hg) can be associated with decreased cardiac output, right ventricular hypertrophy, early congestive heart failure (CHF), and cyanosis.
• The impact of this valvular lesion on pregnancy and fetal outcomes has not been rigorously studied. A case-control study of 17 patients in 2007 suggested that there is no adverse impact on either the mother or the fetus.⁶

Sex

The male-to-female ratio is approximately 1:1.

Age

PVS most commonly presents in newborns. It can be asymptomatic for years.

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