Pulmonic Valvular Stenosis

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Pulmonic Valvular Stenosis

Introduction

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 ce-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.

Clinical

History

History of a heart murmur since birth

Acyanosis

Dyspnea

Fatigue

Dizziness or syncope, occasionally

Chest pain

Physical

Physical examination findings correlate with the severity of right ventricular outflow obstruction.

The first heart sound is normal and followed by a systolic ejection

click. The systolic ejection click is variable with respiration and

louder on expiration. It is loudest over the left upper sternal border.

Patients with dysplastic valves may not have a systolic ejection click.

The second heart sound is split. This is due to delayed closing of the

pulmonic valve at the end of systole. The pulmonic component of the

second heart sound may be diminished in intensity.

Systolic ejection murmur (crescendo-decrescendo), grade 2-5/6, is

audible at the left upper sternal border, transmitting into the back

and posterior lung fields. The murmur is heard best in the 1st to 3rd

intercostal spaces.

Severity of valvular disease is related directly to the intensity and

duration of the murmur. When severe, murmur extends into diastole

(beyond the second heart sound).

Hepatosplenomegaly may develop in cases of CHF.

Severe PVS is associated with tricuspid insufficiency and may be

associated with elevated central venous pressure, hepatosplenomegaly, a

pulsatile liver, jugular venous pulsations, and hepatojugular reflux.

Murmur of peripheral pulmonary stenosis (commonly encountered in

neonates) is a grade 2/6 systolic murmur that radiates into the

posterior lung fields.

Pathology of peripheral pulmonic stenosis is secondary to the acute

angular takeoff of the branch pulmonary arteries from the main

pulmonary arteries specific to a neonatal anatomy. This condition and

associated murmur usually resolve spontaneously in the first month of

life.

Myocardial infarction of hypertrophied right ventricle may occur.

Prominent A wave of the jugular venous pulse is observed.

Tricuspid regurgitation occasionally is present.

The murmur usually radiates to the clavicles, the suprasternal area,

and left neck. Radiation down the left sternal border is less common.

Causes

PVS primarily results from a maldevelopment of the pulmonic valve

tissue and the distal portion of the bulbus cordis. One maldevelopment

is characterized by fusion of leaflet commissures, resulting in a domed

appearance to the valve. Other etiologies result in dysplastic valves,

which do not open and close normally.

Coexisting cardiac malformations (eg, ventricular septal defect, atrial

septal defect, patent ductus arteriosus) may complicate the anatomy,

physiology, and clinical picture.

Aberrant flow patterns in utero also may be associated, in part, with maldevelopment of the pulmonary valve.

Rubella embryopathy may cause PVS.

Family history is a mild risk factor.7

Cases have been reported in the setting of Mayer-Rokitansky-Kuster-Hauser syndrome.8-- Carol in ILMom to , 8 DSMy problem is not how I look. It's how you see me.Join our Down Syndrome information group -

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