Pulmonary Valve Stenosis (PS)

Overview and Natural History

Pulmonary valve stenosis (PS) is most commonly a congenital entity. The pulmonary valve may be dysplastic, thickened and/or tethered causing restriction of the flow of blood from the right ventricle to the main and branch pulmonary arteries. This ultimately results in the reduction of flow of blood to the lungs.  There are varying degrees of severity from very mild to severe disease.

It may present as a newborn in the form of critical pulmonary stenosis, when the ductal flow is critical to maintain adequate pulmonary perfusion. Closure of the duct leads to inadequate pulmonary perfusion and desaturation that is not responsive to oxygen. It may also present later in infancy as a murmur that grows louder with age, heard as a harsh ejection systolic crescendo-decrescendo murmur loudest over the left upper sternal border, and associated with an ejection click. It may extremely rarely present as sudden collapse, if an occult pulmonary valve stenosis lead to progressive right ventricular hypertrophy and sudden loss of cardiac output.

Epidemiology

Isolated pulmonary valve stenosis is found in 8-10% of patients with congenital heart disease. About 1-2% of the siblings of patients with pulmonic stenosis will also have congenital heart disease.

Genetics

Syndromic associations include Noonan’s syndrome and LEOPARD syndrome. These patients have a genetic mutation causing dysplastic valve leaflets with myxomatous tissue which has not undergone the normal organization and resorption to lead to thin valve leaflets

Types

Valvar pulmonary stenosis can be classified based on the nature of the valve and the physical cause of the stenosis. The stenotic valve can be unicuspid, bicuspid or tricuspid with thickened leaflets.

Valvar pulmonic stenosis can also be classified by the presence or absence of associated stenosis in the subvalvar or supravalvar region. The subvalvar stenosis can be due to the muscle bundle proliferation in a pressure-overloaded right ventricle. The supravalvar stenosis is more commonly associated with a syndrome like Noonan, or as a part of a lesion complex like tetralogy of Fallot.

Hemodynamics

The obstruction to the outflow of blood from the right ventricle adds a pressure load to the right ventricle. As a neonate this obstruction may be underestimated by the velocity across the valve, as the pulmonary vascular resistance and hence the pulmonary pressures are still high. However as the pulmonary vascular resistance drops with age and is at its nadir around 6-10weeks of age, the velocity of blood across the stenotic valve becomes higher.

The right ventricular hypertrophy leads to diastolic dysfunction of the ventricle, and can manifest as hepatomegaly or raised jugular venous pressure. In the absence of intervention it would lead to high right atrial pressures and right to left shunting at any atrial septal communication, leading to cyanosis. Due to the higher right ventricular pressures, the interventricular septal configuration would be abnormal and lead to decrease in the efficiency of contraction of the left ventricle as well due to the ventriculo-ventricular interactions.

Goals of Echocardiography Exam

  • Pressure gradient across the pulmonary valve – calculated using the Bernoulli’s equation with the peak velocity of flow across the valve. This can underestimate the obstruction in the setting of high pulmonary vascular resistance or pulmonary hypertension
  • Right ventricular pressure – based on the tricuspid regurgitation velocity, or the orientation of the interventricular septum, or direction of shunting at an atrial septal communication or a patent ductus arteriosus if present
  • Right ventricular systolic and diastolic dysfunction – using TAPSE or tissue Doppler imaging
  • Morphology of the pulmonary valve – number of leaflets, dysplastic appearance, doming of leaflets in systole. Also, presence of post-stenotic dilation is typical for isolated valvar pulmonic stenosis
  • Associated presence of subvalvar pulmonary stenosis – by using pulse wave Doppler along
  • Associated presence of supravalvar stenosis

Grading Severity of Pulmonary Stenosis by Spectral Doppler

  Mild Moderate Severe
Peak Velocity (m/s) <3 3-4 >4
Peak Gradient (mmHg) <36 36-64 >64

 

References:

Eidem BW, O’Leary PW, Cetta F, et al. Echocardiography in Pediatric and Adult Congenital Heart Disease. Wolters Kluwer 2015: 250-262

Burch M, Sharland M, Shinebourne E, Smith G, Patton M, McKenna W. Cardiologic abnormalities in Noonan syndrome: phenotypic diagnosis and echocardiographic assessment of 118 patients. J Am Coll Cardiol. 1993;22:1189–1192.

Lima OC, Sahn DJ, Valdes-Cruz LM, Goldberg SJ, Barron JV, Allen HD, Grenadier E. Noninvasive prediction of transvalvular pressure gradient in patients with pulmonary stenosis by quantitative two-dimensional echocardiographic Doppler studies. Circulation. 1983;67:866–871

Baumgartner H, Hung J, Bermejo J, et al. Echocardiographic Assessment of Valve Stenosis: EAE/ASE Recommendations for Clinical Practice. Eur Jour of Echo. 2009;10:1-25.