Pulmonary stenosis
Aetiology
The most common aetiology of pulmonary stenosis (PS) is congenital PS which can be isolated or associated with other congenital abnormalities.
The PS may occur on a normal tricuspid valve, bicuspid, unicommissural or acommissural valve or the valve can be dysplastic.
Acquired PS is less common.
Common causes of pulmonary stenosis are summarized in a table below (Image 1).
Clinical presentation
Mild and moderate PS is usually asymptomatic.
Patients may present with:
- fatigue
- dyspnea
- exertional presyncope or syncope
- symptoms of right sided heart failure once the the PS reaches severe grade
Auscultation
Systolic crescendo–decrescendo murmur can be heard in the pulmonic position and increases with inspiration and usually ends in mid-systole in mild stenosis but can extend further with increasing severity of obstruction.
Mild PS typically has a murmur of grade 3 or lower with moderate to severe stenosis characterized by grade 4 or higher with right ventricular lift and associated thrill which radiates to the back. The murmur may be soft if there is associated right heart failure and low cardiac output.
ECHO diagnosis
Echocardiography plays a major role in diagnosis and assessment of PS. It can be used to identify the cause of the PS and can detect additional anomalies such as right ventricular hypertrophy.
Pulmonic stenosis especially when severe may be associated with:
- right ventricular hypertrophy
- eventually right ventricular enlargement
- right atrial enlargement
The parasternal long-axis and subcostal long-axis views are often best in assessing RV hypertrophy.
The normal thickness of the RV is 2–3 mm but given the difficulties in estimating thickness, a thickness of >5 mm is usually considered abnormal.
RV enlargement is typically assessed in the apical or subcostal four-chamber view.
Severity of PS
The severity of PS is graded based on transpulmonary pressure gradient. The estimation of the systolic pressure gradient is derived from the transpulmonary velocity flow curve using the simplified Bernoulli equation ΔP=4v2.
Pulsed-wave Doppler may be useful to detect the sites of varying levels of obstruction in the outflow tract and in lesser degrees of obstruction may allow a full evaluation of it.
Image 2 Severity of pulmonary stenosis
Video 1 Moderate PS with mild pulmonary valve insufficiency, PSAX at the level of the great vessels - on the left side of the picture is a 2D view of the PV and on the right Colour Doppler is applied. Increased velocities across the pulmonic valve and a small regurgitant jet is visualized.
https://echocardia.com/en/searchassist.html#s=Pulmonary%20valve%20stenosis%20&ps=2466&pa=284&f=1-1-1-2-1-4-6+3.mp4&browse=284
Video 2 Mild PS caused by external compression, PSAX view at the aortic level - a mediastinal tumour is seen compressing the RVOT, PV and PA. On the right, Colour Doppler is applied to visualize increased velocities across the pulmonic valve.
From:https://echocardia.com/en/searchassist.html#s=Pulmonary%20valve%20stenosis%20&ps=2433&pa=279&f=1-1-1-2-1-4-6+4.mp4&browse=279
Video 3 Mild supravalvular pulmonary valve stenosis, PSAX view
From:https://echocardia.com/en/searchassist.html#s=Pulmonary%20valve%20stenosis%20&ps=2466&pa=281&f=1-1-1-1-1-4-6+2.mp4&browse=281
Image 4 Mild PS due to external compression, PSAX view CW Doppler measurement - peak velocity 1,65 m/s and peak gradient reaching 18,6 mmHg.
From:https://echocardia.com/en/searchassist.html#s=Pulmonary%20valve%20stenosis%20&ps=2433&pa=279&f=1-1-1-4-1-4-6.png&browse=279
Image 5 Severe PS, CW Doppler measurement in PSAX view - dense CW waveform with peak velocity reaching over 4 m/s in a patient with severe PS. Also note PV max 66.13 mmHg.
From: https://www.echopedia.org/index.php?title=Pulmonary_Stenosis
Other diagnostic methods
Cardiac CT is excellent for assessing anatomy, particularly of the branch pulmonary arteries where echocardiography is inadequate.
CMR is useful for assessing anatomy and for quantification of PR as well as RV size and function and is considered the imaging modality of choice for these reasons.
Cine imaging, phase contrast techniques and MR angiography allow for more precise quantification compared with echocardiography. CMR is well suited for the evaluation of right ventricular volumes and function given that geometry of the right ventricle is better viewed in three dimensions.
Historically, cardiac catheterization was the gold standard for diagnosing PS but now no longer required for diagnostic purposes
Management
There is currently no standard medical management for patients with PS. If symptoms of right heart failure are present it may be reasonable to consider the use of diuretics. The natural history of mild PS is typically benign.
Those patients with low gradients in childhood almost never require intervention in early adulthood and had equivalent survival to those without PS.
Most patients with severe PS require intervention. Indications for intervention are summarized in the table below (Image 6).
Ruckdeschel E, Kim YY Pulmonary valve stenosis in the adult patient: pathophysiology, diagnosis and management Heart 2019;105:414-422.
1) Transcatheter therapy
The method of choice is percutaneous balloon valvuloplasty during which commissural splitting is performed. When balloon valvuloplasty is not sufficient, surgical intervention can be considered.
More recently, transcatheter pulmonary valve implantation (The Melody valve) has been used instead of the surgical option with the same indication criteria.
Image 7 Melody valve
From: TPV Systems - Melody TPV Ensemble II Delivery System | Medtronic
2) Surgery
Surgical relief of pulmonic stenosis involves commissurotomy or valvotomy via an incision through the pulmonary trunk using an open or closed technique.
Valvectomy is reserved for situations in which simple valvotomy is inadequate, that is, dysplastic pulmonic valves. A transannular patch using autologous pericardium may be required to enlarge the annulus and supravalvar area.
Outcomes of surgical valvotomy demonstrate excellent survival but there is a significant incidence of PR necessitating repeat surgical intervention such as pulmonary valve replacement (PVR) later in life.
References
- Ruckdeschel E, Kim YY Pulmonary valve stenosis in the adult patient: pathophysiology, diagnosis and management Heart 2019;105:414-422.
- Zipes, Peter Libby, Robert O. Bonow ; founding editor and online editor Eugene Braunwald. Braunwald's Heart Disease : a Textbook of Cardiovascular Medicine. Philadelphia, PA :Elsevier/Saunders, 2015
- Stout KK, Daniels CJ, Aboulhosn, JA, Bozkurt B, Broberg CS, Colman JM, Crumb SR, Dearani JA, Fuller S, Gurvitz M, Khairy P, Landzberg MJ, Saidi A, Valente AM, Van Hare GF. 2018 AHA/ACC guideline for the management of adults with congenital heart disease: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Circulation. 2019;139:e637–e697. doi: 10.1161/CIR.0000000000000602.
- Baumgartner H, Hung J, Bermejo J, Chambers JB, Evangelista A, Griffin BP, Iung B, Otto CM, Pellikka PA, Quiñones M; American Society of Echocardiography; European Association of Echocardiography. Echocardiographic assessment of valve stenosis: EAE/ASE recommendations for clinical practice. J Am Soc Echocardiogr. 2009 Jan;22(1):1-23; quiz 101-2. doi: 10.1016/j.echo.2008.11.029. Erratum in: J Am Soc Echocardiogr. 2009 May;22(5):442. PMID: 19130998.
