The Human Circulatory System

Pulmonary valve stenosis

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Pulmonary valve stenosis

Pulmonary valve stenosis is a heart valve disorder that involves the pulmonary valve.

This is the valve separating the right ventricle (one of the chambers in the heart) and the pulmonary artery. The pulmonary artery carries oxygen-poor blood to the lungs.

Stenosis, or narrowing, occurs when the valve cannot open wide enough. As a result, less blood flows to the lungs.

Stenosis of the pulmonary valve or right ventricular (RV) infundibulum increases the resistance to RV outflow, raises the RV pressure, and limits pulmonary blood flow. Pulmonic stenosis is often congenital and associated with other cardiac lesions. Pulmonary blood flow preferentially goes to the left lung in valvular pulmonic stenosis. In the absence of associated shunts, arterial saturation is normal. Peripheral pulmonic stenosis can accompany valvular pulmonic stenosis and may be part of a variety of clinical syndromes, including the congenital rubella syndrome.

Patients who have had the Ross procedure for aortic valve disease (transfer of the pulmonary valve to the aortic position with a homograft pulmonary valve placed in the pulmonary position) may experience noncongenital postoperative pulmonic valvular or main PA stenosis due to an immune response in the homograft. RV outflow obstructions can also occur when there is a conduit from the RV to the pulmonary artery (PA) that becomes stenotic from degenerative changes over time or when there is degeneration of a bioprosthetic replacement pulmonary valve.

Symptoms and Signs

Mild cases of pulmonic stenosis are asymptomatic; moderate to severe pulmonic stenosis may cause symptoms of dyspnea on exertion, syncope, chest pain, and eventually RV failure.

On examination, there is often a palpable parasternal lift due to right ventricular hypertrophy (RVH) and the pulmonary outflow tract may be palpable if the PA is enlarged. A loud, harsh systolic murmur and occasionally a prominent thrill are present in the left second and third interspaces parasternally. The murmur radiates toward the left shoulder due to the flow pattern within the main PA and increases with inspiration.

In mild to moderate pulmonic stenosis, a loud ejection click can be heard to precede the murmur; this sound decreases with inspiration as the increased RV filling from inspiration prematurely opens the valve during atrial systole when inspiratory increased blood flow to the right heart occurs. The valve excursion during systole is thus less with inspiration than with expiration, and the click is therefore less audible with inspiration. This is the only right-sided auscultatory event that decreases with inspiration. All of the other auscultatory events increase with the increased right heart output that occurs with inspiration. In severe pulmonic stenosis, the second sound is obscured by the murmur and the pulmonary component of S2 may be diminished, delayed, or absent. A right-sided S4 and a prominent a wave in the venous pulse are present when there is RV diastolic dysfunction or a c-v wave may be observed in the JVP if tricuspid regurgitation is present.

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Pulmonary valve regurgitation is relatively uncommon in primary pulmonic stenosis and may be very difficult to hear, as the gradient between the reduced PA diastolic pressure and the elevated RV diastolic pressure may be quite small (low-pressure pulmonary valve regurgitation).

Diagnosis

Echocardiography/Doppler is the diagnostic tool of choice, can provide evidence for a doming valve versus a dysplastic valve, can determine the gradient across the valve, and can provide information regarding subvalvular obstruction and the presence or absence of tricuspid or pulmonic valvular regurgitation. Mild pulmonic stenosis is present if the peak gradient by echocardiography/Doppler is less than 30 mm Hg, moderate pulmonic stenosis is present if the peak gradient is between 30 mm Hg and 60 mm Hg, and severe pulmonic stenosis is present if the peak gradient is greater than 60 mm Hg or the mean gradient is greater than 40 mm Hg. A lower gradient may be evident if there is RV dysfunction. Catheterization is usually unnecessary for the diagnosis; it should be used only if the data are unclear or in preparation for either percutaneous intervention or surgery

ECG and Chest Radiography: Right axis deviation or RVH is noted; peaked P waves provide evidence of right atrial (RA) overload. Heart size may be normal on radiographs, or there may be a prominent RV and RA or gross cardiac enlargement, depending on the severity. There is often poststenotic dilation of the main and left pulmonary arteries. Pulmonary vascularity is usually normal, although there tends to be preferential flow to the left lung.

Treatment

Class I (definitive) indications for intervention include all symptomatic patients and all those with a resting peak-topeak gradient greater than 60 mm Hg or a mean greater than 40 mm Hg, regardless of symptoms. Percutaneous balloon valvuloplasty is highly successful in domed valve patients and is the treatment of choice. Surgical commissurotomy can also be done, or pulmonary valve replacement (with either a bioprosthetic valve or homograft) when pulmonary valve regurgitation is too severe or the valve is dysplastic.

Pulmonary outflow tract obstruction due to RV to PA conduit obstruction or to homograft pulmonary valve stenosis can often be relieved with a percutaneously implanted pulmonary valve (both the Medtronic Melody valve and the Edwards Sapien XT valve have been FDA approved). Percutaneous pulmonary valve replacement is also FDA approved for those with conduit stenosis or following the Ross procedure. Percutaneous valve replacements have also been performed off-label for native pulmonary valve disease.

Endocarditis prophylaxis is unnecessary for native valves even after valvuloplasty unless there has been prior pulmonary valve endocarditis (an unusual occurrence). It should be used if surgical or percutaneous valve replacement has occurred. There appears to be more pulmonary valve endocarditis following percutaneous pulmonary valve replacement with the Melody valve than expected, and this is being closely monitored by the FDA.

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