Pulmonic Valvular Stenosis

Pulmonic valvular stenosis, sometimes referred to simply as pulmonic stenosis, is a narrowing of the opening through the pulmonic valve, the group of three leaflets that separate the right ventricle from the pulmonary trunk, or within the general vicinity of this valve.  The most common cause of this restricted opening is congenital malformation (born with the condition), either as an isolated finding or as part of a more complex congenital heart defect.1  An example of this latter group is its inclusion as one of the four components of Tetralogy of Fallot, the most common cyanotic (impaired circulation of oxygen that leads to decreased delivery of this vital gas to the organs, leading to a bluish tinge to the lips and skin, among other complications) cardiac condition.  Two-thirds of patients with Noonan syndrome (an autosomal dominant condition characterized by a short stature, abnormal facial appearance, and chest deformities, along with congenital heart defects) will have pulmonic stenosis.2,3  The most common acquired condition resulting in this valvular condition occurs with carcinoid heart disease, in which white plaques stick to the thin leaflets, eventually restricting their movement and narrowing the effective opening to the pulmonary vasculature.1

Pulmonic stenosis accounts for approximately 10 percent of cases of congenital heart disease; this number may be skewed and underestimated owing to a large percentage of patients tending to be asymptomatic until adulthood.2  This valvular pathology can be categorized by its location in relation to where the valve is positioned.4  If the narrowing actually involves the valve itself, the defect is termed valvular stenosis, with etiologies including the aforementioned congenital defect as well as the systemic effects of cancers (carcinoid heart syndrome) and damage to the leaflets due to bacterial endocarditis.  More than 90% of cases of pulmonic stenosis arise from the valvular level.3  Narrowing that is focused within the main pulmonary artery, just beyond the valve, is termed supravalvular stenosis; causes of this form of the defect include a continuum of anomalies ranging from discrete stenosis to widespread underdevelopment of the pulmonary trunk to mechanical compression of the vessel by a nearby tumor.4  The third variation involves narrowing within the right ventricular outflow tract (also known as the infundibulum); it is deemed subvalvular or infundibular, with etiologies including Tetralogy of Fallow and tumor compression.  A final, most severe, form of the disease involves a complete absence of the pulmonic valve, termed pulmonic atresia; in these patients, maintenance of the ductus arteriosus is paramount for blood flow entering the pulmonary vasculature and ensuring some degree of oxygenation.

Most individuals who have isolated pulmonic stenosis tend to be asymptomatic.1  When patients with this valvular anomaly do develop clinical manifestations, it typically is a result of concomitant pulmonic regurgitation (where the valve fails to close properly and allows leaking of blood from the pulmonary arteries backward into the right ventricle during diastole) or pulmonary hypertension (elevated pressures within the pulmonary vasculature owing to a wide range of causes).  Common symptoms expressed by patients include gradually worsening exertional difficulty breathing, chest pain, and fatigue, with the intensity of onset directly related to the increasing pressure gradient across the diseased valve.  Right ventricular hypertrophy (thickening of the heart muscle) arises in an attempt to generate greater contractile force to push blood through the narrowed valvular opening.  This compensatory mechanism is only effective at overcoming the increased resistance to forward propulsion of blood (termed “afterload”) to a certain point, with subsequent diastolic (the phase of the cardiac cycle involved with ventricular filling and relaxation) compliance being compromised.5  Ultimately, systolic contractions are impaired and right heart failure ensues, manifested by venous congestion with jugular venous distention (backfilling of blood into the neck veins), ascites (fluid accumulation within the abdominal cavity), enlargement of the liver and spleen, and peripheral edema.  In the setting of an intra-cardiac shunt (e.g., atrial septal defect, ventricular septal defect), cases of significant restriction lead to decreased access to the pulmonary vasculature and ventricular contraction will propel the blood through the path of least resistance (through the shunt, with minimal blood entering the pulmonary vasculature) and into the left side of the heart, potentially leading to decreased blood oxygen levels (hypoxemia) and cyanosis.6  This can be further worsened by compression of the coronary arteries during systolic contractions by the massive right ventricular mass and the increased oxygen demands of the myocardium, resulting in ischemia (condition in which the tissues fail to receive adequate oxygen).5

As is prudent with most congenital heart anomalies, women who are of child-bearing age with pulmonic stenosis should consider the risks associated with becoming pregnant.  As an isolated abnormality, most women can carry a child to term without compromise from the narrowed valve.  In one study, 11 patients with various NYHA functional classes were followed; all proceeded with their pregnancies without complication, but two remained stable, with one digressing from functional class I to class II and one going from class II to class III transiently.7  Also of note, there was no statistically significant correlation between the neonatal outcomes and the degree of valvular stenosis in the mother.  This study does not take into account, however, cases where pulmonic stenosis is a part of a more complex congenital defect.

Evaluation of the severity of pulmonic stenosis can be performed using a right heart catheter, such as a Swan-Ganz catheter.  By measuring the gradient across the lesion, one can classify the degree of obstruction, assuming that forward cardiac output is preserved.3  If the peak systolic transvalvular pressure gradient is 50 mmHg or less, such a stenosis would be considered as mild.  Gradients in the range of 50 to 80 mmHg typify moderate stenosis, while measurements in excess of 80 mmHg define severe cases.  These measurements can by made either in the cardiac catheterization laboratory as part of a right heart catheterization study or at the bedside within the critical care unit.  The central venous waveform, also evaluated via the above catheter, yields a prominent a wave with otherwise normal waveform characteristics.1 

Physical examination of patients with pulmonic stenosis tends to reveal evidence of right heart enlargement.  There is commonly a prominent “a” wave noted during evaluation of the jugular venous patterns, owing to forceful right atrial contraction against a stiffened, noncompliant right ventricle.8  A pronounced palpable impulse over the right side of the sternum correlates with right ventricular hypertrophy.  The murmur of pulmonic stenosis occurs during systole, has a crescendo-decrescendo characteristic (gets louder, then tapers off), and is best auscultated at the left upper sternal border.  The second heart sound typically is split, with the degree of splitting proportional to the degree of valvular narrowing.1  Further auscultation over the left upper sternal border may reveal an ejection click resulting from abrupt leaflet opening or from dilation of the main pulmonary artery.8

Echocardiography is a very useful modality for imaging various aspects of pulmonic stenosis.  This allows for evaluation of the lesion's morphology and location, the pressure gradient across this region, and computing the orifice area.9  One can also determine the compensatory effects of this condition on the right side of the heart (such as right ventricular hypertrophy, right atrial enlargement, and venous congestion).  Aspects of more complex congenital defects can be evaluated, such as the ventricular septal defect and overriding aorta found in Tetralogy of Fallot.  Cardiac catheterization, in the form of a right heart study, can is recommended for adolescents and young adults with echocardiographic evidence of significant pressure gradients (peak velocities exceeding 3 meters per second), as well as in those who are deemed to be ideal candidates for balloon valvuloplasty.1

Other means of evaluations reveal nonspecific findings.  Electrocardiography can be used to demonstrate the right ventricular strain due to compensatory hypertrophy (thickening of the heart muscle); other findings include right bundle branch block, right axis deviation, and possibly right atrial enlargement.1  Chest radiography may show nonspecific enlargement of the right ventricle and pulmonary arteries (due to associated pulmonary regurgitation).  One of the best indicators of pulmonic stenosis via chest radiography is dilation of the main pulmonary artery (noted due to both valvular narrowing and pulmonary hypertension).

Management is dependent on the severity of the stenosis and its location, as well as the presence of other congenital malformations.  Mild cases of narrowing usually involve very slow progression of the disease and the compensatory effects on the heart and therefore do not require treatment.3  The most common method of relieving moderate to severe cases of stenosis is through the use of balloon valvuloplasty, utilizing specialized catheters to position a noncompliant balloon across the narrowing and then forcing the fused leaflets apart during inflation.  This method of valvular repair has consistently proven beneficial, with decreases in right ventricular systolic pressure, pulmonary transvalvular and peak-to-peak systolic pressure (the primary ones used to determine stenosis severity) noted in a majority of patients undergoing this procedure.10  All of the patients in Boshra’s study had symptom improvement and there was no significant morbidity or mortality noted. Surgical replacement of the diseased valve is rarely necessary, occurring typically from severe malformation of the valve’s leaflets or if there is already significant valvular insufficiency (as balloon valvuloplasty almost invariably creates some degree of such valve leakage).2  Although many patients who undergo valvuloplasty will have persistent right-to-left shunting of blood and continued hypoxemia, over the course of 3 to 6 months, ventricular hypertrophy regression and shunting will typically diminish to less clinically significant levels.11

Neonatal patients found to have severe pulmonic stenosis should receive a prostaglandin E1 infusion in order to keep the ductus arteriosus open (this conduit normally closes within approximately 7 days following birth) in order to reduce resistance and thus ensure blood flow into the pulmonary vasculature.6  Some patients with pulmonic valve issues may need lifelong endocarditis prophylaxis prior to dental or invasive procedures, regardless of if valvuloplasty is performed or not; however, the incidence of such valvular infection is low and prophylactic antibiotics is considered by some as controversial and unnecessary.8

Prognosis in patients with pulmonic stenosis is dependent on the severity of the condition and whether balloon valvuloplasty has been performed or not.  In cases of mild disease, prognosis is considered excellent with greater than 90 percent living more than 20 years after diagnosis.2  By comparison, patients with severe disease have a mortality rate approaching 60 percent within 10 years if no intervention is performed.  These patients have significant improvement in these statistics following valvuloplasty or valve replacement.

References and Further Reading:

1.                  Crawford, M.H. (2009).  Current Cardiology Diagnosis & Treatment, 3rd ed.  Lange Medical Books / McGraw-Hill, New York, et al.

2.                  Brickner, M.E. (2000).  "Congenital Heart Disease in Adults (First of Two Parts)."  New England Journal of Medicine, 342 (4), 256-263.

3.                  Lilly, L.S. (2007).  Pathophysiology of Heart Disease:  A Collaborative Project of Medical Students and Faculty, 4th ed.  Lippincott, Williams, & Wilkins, Baltimore and Philadelphia.

4.                  Weissman, N.J. & Adelmann, G.A. (2004).  Cardiac Imaging Secrets.  Hanley & Belfus, Philadelphia.

5.                  Russell, I.A., Rouine-Rapp, K., Startmann, G., & Miller-Hance, W.C. (2006).  “Congenital Heart Disease in the Adult:  A Review with Internet-Accessible Transesophageal Echocardiographic Images.”  Anesthesiology & Analgesia, Vol. 102, 694-723.

6.                  Peacock, W.F. & Tiffany, B.R. (2006).  Cardiac Emergencies.  McGraw-Hill, New York, et al.

7.                  Hameed, A.R. (2007).  "Effect of Pulmonary Stenosis on Pregnancy Outcomes – A Case-Control Study."  American Heart Journal, Vol. 154(5), 852-854.

8.                  Wu, J.C. & Child, J.S. (2004).  "Common Congenital Heart Disorders in Adults."  Current Problems in Cardiology 2004, 29, 641-700.

9.                  Otto, C. M. (2007).  The Practice of Clinical Echocardiography, 3rd ed.  Saunders / Elsevier, Philadelphia.

10.              Boshra, H. (2011).  "Balloon Pulmonary Valvuloplasty in Adults with Congenital Valvular Pulmonary Stenosis."  Heart Mirror Journal from Affiliated Egyptian Universities and Cardiology Centers, Vol. 5(1), 288-292.

11.              Taeusch, H.W., Ballard, R.A., & Gleason, C.A. (2005).  Avery's Diseases of the Newborn, 8th ed.  Elsevier, Philadelphia.


 Contributor:

Sean M. Hancock, RDCS (AE), RCS, RCSA, RCIS, CCT

Staff Echo Sonographer and Clinical Educator

Cardiac Study Center, Puyallup, WA

September 2012