Pulmonary stenosis Q22.1

Pulmonary valve stenosis was first described in detail by Morgagni in 1761. A more detailed description - especially of the anatomical pathology - was given by Meckel in 1871, and in 1888 Fallot developed the first clinical classification of the cyanotic form (Golla 2009).

Pulmonary valve stenosis (PS) is either:

• a narrowing of the unicuspid, bicuspid, tricuspid or dysplastic valve opening (valvular stenosis)
• a narrowing of the RV outflow path (subvalvular stenosis)
• or the pulmonary artery (supravalvular stenosis - central or peripheral) (Wilkenshoff 2008; Erdmann 2006).

Valvular stenosis results in a restriction of valve mobility, which in turn leads to a reduction of the valve's opening area and thus to an obstruction of the forward blood flow (Herold 2018).

Normally PS is a congenital vitium (Kasper 2015). Acquired pulmonary stenosis is a rarity (Krakow 2005).

The risk of recurrence in siblings is about 2.9%, the risk if the mother herself suffers from a congenital heart defect is about 4% - 6.5% and if the father suffers from it is about 2% (Apitz 1998).

Of all congenital heart valve defects, the valvular PS accounts for approx. 8 % - 12 %, the sub- and supravalvular PS for approx. 2 % - 3 % each. The gender ratio between male and female is balanced (Erdmann 2006).

Among the congenital heart defects, PS as an isolated form or as combined vitium accounts for approx. 25 % - 30 % of all congenital heart defects (Riecker 1993).

Stenosis can occur in isolation or, more rarely, in the context of complex heart defects such as tetralogy of Fallot, VSD, complete transposition of the large vessels, double outlet right ventricle. Relatively often it occurs in the context of syndromes (such as Noonan syndrome, William Beuren syndrome, etc.) or rubella embryopathy (Erdmann 2006).

In the very rare cases of acquired pulmonary valve stenosis, this can be caused by:

• rheumatic fever
• Carcinoid syndrome (Pinger 2019)

Pathophysiology: Due to the obstruction of the outflow tract there is a pressure load on the right ventricle which finally leads to a concentric hypertrophy of the ventricle - especially in the area of the infundibulum and the anterior wall (Cracow 2005). The prestenotic pressure is increased and the poststenotic pressure can be normal to slightly decreased (Erdmann 2006).

Due to compensatory hypertrophy of the right ventricle, cardiac output can usually be maintained for years. In the case of moderate or severe pulmonary stenosis, however, the HMV is already reduced at rest and without simultaneous right ventricular failure, which leads to a compensatory increase in peripheral oxygen depletion. Under exertion, an adequate increase in the cardiac output is no longer possible due to the obstruction, and this leads to a sharp increase in the arteriovenous oxygen difference with an increase in heart rate and a simultaneous decrease in stroke volume without an increase in right-atrial pressure (also known as congestive heart failure [Krakow 2005]).

The hypertrophy of the right ventricle also causes a compliance disorder of the ventricle with an increase of the right ventricular filling pressure, which in the further course also causes a hypertrophy of the right atrium [Krakow 2005].

Mild to moderate PS is usually asymptomatic and is often only discovered by chance - e.g. when a previously auscultated heart murmur is clarified (Kasper 2015).

If symptoms occur in the further course, these are:

• Dyspnea, initially especially under stress
• early physical fatigue
• Vertigo (only rarely)
• Syncopes (also only rarely)
• sudden cardiac death (extremely rare) (Dörfler 2015)
• Stenocardia (Herald 2018)
• Cyanosis (can occur in critical pulmonary stenosis or pulmonary atresia with simultaneous right-left shunt) (Pinger 2019)
• Angina pectoris- symptomatology with very pronounced obstruction due to the disproportion between oxygen demand and oxygen supply (Kasper 2015)

Echocardiography: Echocardiography is usually sufficient for diagnosis (Pinger 2019). In 2-D echo, the anatomy and function of the pulmonary valve can be assessed, as well as the width of the pulmonary annulus and the pulmonary artery, and the size and function of the right heart (Herold 2018). In Doppler, gradient quantification (see w. below), estimation of right ventricular and pulmonary artery pressures, and graduation of any concomitant pulmonary valve regurgitation are performed (Herold 2018).

Transesophageal echocardiography can visualize the right ventricular outflow tract and any infundibular hypertrophy that may be present (Kasper 2015)

Classification of the severity of stenosis according to EAE / ASE 2009 into mild, moderate or severe:

• mild-grade PS:
  • Peak velocity < 3.0 m/ sec
  • peak gradient < 36 mmHg
• moderate PS:
  • Peak velocity 3,0 - 4,0 m/ sec
  • Peak gradient 36 - 64 mmHg
• high-grade PS:
  • Peak velocity > 4,0 m/ sec
  • Peak gradient > 64 mmHg

Gradient setting can be unreliable, so always determine RV pressure as well (measured via tricuspid regurgitation [Herold 2018]).

Chest X-ray: As long as the right ventricle is compensated, the X-ray may be unremarkable. If myocardial insufficiency is present, the following changes may then be seen:

• the right ventricle is bordering the cardiac waistline
• both the right atrium and the right ventricle may be enlarged
• the retrosternal space is narrowed
• there is a prominent pulmonary arch (due to poststenotic dilatation of the pulmonary artery)
• there is NO hyperperfusion of the lung (in contrast to shunt vitia such as ventricular septal defect = VSD, atrial septal defect = ASD, etc. ) (Pinger 2019)

Cardio- MRI or CT: These examinations are the method of choice to visualize peripheral pulmonary stenosis or pulmonary dilatation (Pinger 2019).

Otherwise, this allows:

• the graduation of the pressure
• planimetry of the pulmonary valve
• exact localization of the stenosis
• visualization of any ectasia of the pulmonary arteries
• quantification of the function of the right ventricle and volumes are possible
• statements can be made about pulmonary perfusion (Herold 2018).

Coronary angiography: It is not usually necessary to perform coronary angiography (Pinger 2019). However, indications for it may be:

• an adequate diagnosis is not possible due to poor sonic patency
• a catheter intervention planned anyway
• in case of known CHD
• in case of associated anomalies (Herold 2018).

Lapp (2013) recommends catheterization in patients with sonographic suspicion of moderate or severe pulmonary stenosis and a pressure gradient of > 50 mmHg.

Note: If possible, invasive diagnostics should be performed in valvuloplasty readiness (Lapp 2013).

The severity of the stenosis can be calculated using coronary angiography (Herold 2018). This pressure measurement should be taken above and below the pulmonary valve. Care should also be taken to ensure that a dynamic component of the pressure gradient is present. The mean gradient measured sonographically correlates better with the peak-to-peak gradient in cardiac catheterization than with the maximum pressure gradient in ultrasound (Kasper 2015). The following classification has proven useful (Lapp 2013):

• Severity I (insignificant)
  • systolic pressure gradient: < 25 mmHg
  • valve opening area: 1.0 - 2.0 cm2 / m2
• Severity II (mild)
  • systolic pressure gradient: 25 - 49 mmHg
  • valve opening area: 0.5 - 1.0 cm2 / m2
• Severity III (moderate)
  • systolic pressure gradient: 50 - 79 mmHg
  • valve opening area: 0,25 - 0,5 cm2 / m2
• Severity IV (severe)
  • systolic pressure gradient: > 80 mmHg
  • valve aperture area: < 0.25 cm2 / m2

Inspection / Palpation

• the patient is primarily acyanotic
• peripheral cyanosis is found at low minute volume
• a central cyanosis with right-left shunt in the area of the atria
• a systolic buzzing may be present on the left parasternal side
• lifting pulsations above the lower left sternal border are possible
• signs of right heart failure may be detectable (edema of the dependent body parts, jugular venous congestion, liver enlargement, in later stages also ascites and pleural effusion possible) (Kasper 2015)

auscultation:

I. in valvular stenosis:

• normal louder 1st heartbeat;
• The 1st heart sound is followed by the so-called early systolic pulmonary ejection click, which in a mild to moderate stenosis is clearly heard from the 1st heart sound. The ejection click represents a right-sided heart murmur; its intensity decreases inspiratory; this is related to the fact that the pulmonary valve opens prematurely due to the increased end-diastolic right ventricular pressure; with increasingly high PS, the ejection click moves closer and closer to the 1st heart sound until it can no longer be distinguished from it (Kasper 2015)
• A systolic crescendo-decrescendo heart murmur with a maximum point above the 2nd or 3rd ICR on the left side with conduction to the back (auscultation between the scapulae)
• the 2nd heart sound is widely split (due to the late closing of the pulmonary valve) and has a silent pulmonary valve component (Herold 2018)
• on the right side a 4th heart sound can be auscultated; with a light valvular PS (RV- pressure up to 60 mmHg) this is still missing; with a medium-heavy PS (RV- pressure between 60 mmHg - 120 mmHg) it can be auscultated quietly and with a heavy PS (RV- pressure > 120 mmHg) it can be heard loud (Franke 1984)

II. in subvalvular stenosis:

• the early systolic pulmonary ejection click following the 1st heartbeat is missing
• there is also a systolic expulsion sound, the point of which is maximum but somewhat lower

III. in supravalvular stenosis:

• the early systolic pulmonary ejection click following the 1st heartbeat is also missing
• the systolic expulsion noise is present, but the pointum maximum is somewhat higher

IV. for peripheral stenosis:

• also here the early systolic pulmonary ejection click following the 1st heartbeat is missing
• there are systolic vascular sounds in the periphery, some of which are perceived as continuous noise

ECG:

As long as the pressure in the right ventricle is < 60 mmHg, the ECG is mostly inconspicuous (Pinger 2919). In case of a higher degree of stenosis there are:

• P- dextrocrimal
• Signs of right ventricular hypertrophy (change of position type with axial deviation to the right, Sokolow- Lyon index as a sign of right ventricular hypertrophy ( RV1 +SV5/6 > 1.05 mV) etc.)
• (in-) complete right thigh block
• possible atrial arrhythmias (Pinger 2019)

The treatment options for pulmonary valve stenosis consist of

• I. Balloon valvuloplasty / Stent implantation
• II Operation

The indications for the treatment are:

• symptomatic patients (stress dyspnea, presyncope, syncope, angina pectoris, etc.)
• the maximum peak-to-peak gradient is > 50 mmHg
• if there is more than half-systemic pressure in the right ventricle (note, however, that the pressure in the right ventricle is lower in heart failure)
• Atrial flutter or other relevant arrhythmias
• Associated ventricular septal defect or atrial septal defect, especially in the presence of a re- li shunt
• possibly also if the patient wants to do competitive sports or if a pregnancy is planned
• for persistent arterial hypertension or a pressure gradient of 30 mmHg - 40 mmHg (Lapp 2013).

• I. Balloon valvuloplasty / Stent implantation
  • Balloon valvuloplasty is now the treatment of choice for valvular, supravalvular and subvalvular / peripheral stenosis. There are good results both in the short-term and long-term course. The restenosis rate is < 5 %. In case of central or peripheral pulmonary artery stenoses, an additional combination with stent implantation is possible.
  • In patients with dysplastic or calcified pulmonary valves, the decision on therapy should be made together with cardiac surgeons and interventional cardiologists. Balloon dilatation with stent implantation could possibly offer an alternative here as well (Lapp 2013).
• II Operation
  • The operation is an option especially for patients with infundibular / subclavicular stenosis, patients with dysplastic valves and also for those with an anomaly requiring surgery. With open valvulotomy (possibly with patch plastic) the 25-year survival rate is 93 % with a reinvention rate of 15 % (Pinger 2019).
  • Indication for the surgical treatment is:
    • Existing right ventricular obstruction with a Doppler peak gradient > 64 mmHg (peak velocity > 4 m/s); also independent of any existing symptoms, of normal function of the right ventricle and if otherwise no valve replacement would be necessary
    • after ineffective balloon valvuloplasty in asymptomatic patients, surgical correction should be performed as soon as the systolic pressure in the right ventricle is > 80 mmHg (Vmax above tricuspidalis > 4.3 m/s).
    • Patients with a peak gradient < 64 mmHg should then be operated on,
      • if they become symptomatic or
      • have limited function of the right ventricle, or
      • relevant arrhythmias exist or
      • with a right-left shunt over a ventricular septal defect or atrial septal defect
      • Patients with peripheral pulmonary stenosis - also independent of any existing symptoms - in whom there is a lumen constriction > 50 % and a systolic pressure of > 50 mmHg in the right ventricle and / or relevant changes in lung perfusion

Natural course

The following applies to spontaneous progress without surgical treatment:

• almost all children with congenital PS reach adulthood (exception: children with critical PS)
• the mean age of death in older studies is about 26 years
• the spontaneous course depends on:
• the initial severity of the stenosis (initially mild stenoses usually show less progression)
• the adaptability of the right ventricle
• the progress of the project
• an initially high-grade valvular stenosis may show fibrosis in the course of the disease; however, this rarely develops in adulthood
• subvalvular or infundibular stenoses are particularly prone to progression
• from the 4th decade of life onwards, calcifications of the valve can occur
• as the gradient increases, right ventricular hypertrophy may increase, which can then lead to infundibular stenosis
• Consecutive right heart failure is found in severe stenoses
• in persistent Foramen ovale a right-left shunt can occur due to the stretching of the right atrium which is overloaded by the volume
• Occurrence of endocarditis (but this is rarely the case)

The causes of death in the spontaneous course are:

• right heart failure
• sudden cardiac death induced by increasing and permanent stress (Herold 2018)

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