Pulmonic valve disease in adults

Background

PS is usually an isolated lesion; it occurs in approximately 8% to 10% of congenital heart disease cases and is the most common form of right-sided obstruction. The pulmonic valve is often dome shaped in systole with a narrow central opening and leaflet fusion; it can be calcified in older adults.

Pulmonic valve dysplasia is a less common form of PS; leaflets are thickened and poorly mobile, and there is no commissural fusion. It can be associated with a hypoplastic annulus and supravalvular PA narrowing. Dysplastic pulmonic valves are more often found in the setting of other cardiac and noncardiac anomalies. Unicuspid and bicuspid pulmonic valves rarely occur in isolation; they are usually found in complex congenital heart disease conditions such as TOF ( Fig. 24.1 ). PS is associated with genetic syndromes, including Noonan, Alagille, and Williams syndromes, and with congenital rubella ( Table 24.1 ).

Valvular PS can be accompanied by aneurysmal dilation of the PA, with the poststenotic jet favoring the left PA. However, the degree of PA dilation is not necessarily related to the severity of PS. Most patients do not require operative repair unless there is PR resulting in RV dilation or symptoms attributable to compression of adjacent structures. The risk of dissection or rupture in the absence of pulmonary hypertension, left-to-right shunting, or connective tissue disorder is low, and conservative management is appropriate.

Clinical presentation and assessment

Most patients with PS are asymptomatic and come to attention when a murmur is auscultated. Symptoms rarely occur in childhood but become more common with age and severity of disease. Symptoms of moderate to severe PS include exercise intolerance and dyspnea resulting from inadequate augmentation of cardiac output with exertion and can progress to frank right-sided heart failure if not addressed. Exertional chest discomfort can arise from relative RV ischemia or coexistent coronary atherosclerosis. Rarely, patients can experience syncope or even sudden death due to ischemia from decreased myocardial perfusion of a hypertrophied RV and resultant arrhythmia. Desaturation can result from right-to-left shunting across an atrial-level communication, such as an atrial septal defect or patent foramen ovale.

Physical examination findings in the adult with valvular PS depends on the severity of the stenosis and any associated lesions. In mild PS, the jugular venous waveforms are normal, and the precordium is quiet. A systolic crescendo-decrescendo murmur is heard in the pulmonic position; it increases with inspiration and usually ends in mid-systole but can extend further with increasing severity of obstruction. There may be a pulmonic ejection click that decreases with inspiration. The second heart sound (S ₂ ) is usually split.

In severe PS, the jugular venous pressure can be elevated with a prominent a wave. There may be an RV lift and a loud, harsh ejection murmur with associated thrill that radiates to the back. The degree of S ₂ splitting is proportional to the degree of stenosis; it may be widely split and fixed. However, the pulmonic (P ₂ ) component of the S ₂ may be reduced or absent in severe stenosis, which can make splitting difficult to appreciate. A right-sided fourth heart sound (S ₄ ) gallop may be auscultated.

The electrocardiogram (ECG) of PS is often normal in cases of mild disease, but with increasing severity the axis rotates rightward and features of RV hypertrophy and right atrial enlargement emerge. The chest radiograph typically demonstrates an enlarged main PA. The cardiac silhouette and vascularity are often normal in mild to moderate PS, but with severe PS cardiomegaly, right atrial enlargement, and decreased pulmonary vascular markings are seen ( Fig. 24.2 ).

Echocardiography is considered the mainstay of imaging valvular PS ( Fig. 24.3 ). The definition of severe valvular PS according to the 2018 American Hospital Association (AHA)/American College of Cardiology (ACC) guidelines for the management of adults with congenital heart disease is a maximum velocity (V _max ) greater than 4 m/s or a peak instantaneous gradient greater than 64 mmHg, whereas mild PS is defined as a V _max lower than 3 m/s or a peak instantaneous gradient lower than 36 mmHg ( Table 24.2 ).

Physiologic conditions that alter flow across the pulmonic valve affect the accuracy of gradient calculation by the modified Bernoulli equation. For example, if there is severe RV systolic dysfunction, the RV cannot generate sufficient pressure to overcome significant PS, yielding a peak instantaneous gradient that underestimates the true severity of the stenosis. Similarly, left-to-right flow across a septal defect or concomitant PR increases flow across the pulmonic valve, thereby increasing the transpulmonary gradient and overestimating the severity of pulmonic valve stenosis. Long-segment stenosis and serial obstructions (i.e., associated subvalvular PS and/or supravalvular PA stenosis) are other conditions in which Doppler-derived gradients are less reliable.

Peak instantaneous gradients measured by echocardiography overestimate peak-to-peak gradients in the catheterization laboratory and may be exaggerated by the effects of sedation. RV systolic pressure estimates based on tricuspid regurgitation peak velocity, qualitative assessment of septal position, and degree of RV hypertrophy can provide additional information on PS severity. Correlation between the Doppler gradient derived by echocardiography and clinical findings is recommended.

If there is a question, the gold standard in assessing the severity of valvular PS is cardiac catheterization, during which hemodynamic data, including pressure gradient across the pulmonic valve, RV systolic pressure compared with systemic pressure, and right-sided filling pressure, are obtained. In patients with normal cardiac output, mild stenosis is defined as a gradient lower than 35 to 40 mmHg or an RV pressure less than one half of the systemic pressure. Moderate stenosis is a gradient between 40 and 60 mmHg with RV pressure between one half and three fourths of the systemic pressure. Severe PS is defined as a gradient greater than 60 mmHg or an RV pressure equal to or greater than three fourths of the systemic pressure.

Angiography can demonstrate the morphologic characteristics of the pulmonic valve, including leaflet thickening, mobility and excursion, and leaflet tethering, as well as associated lesions, including annular hypoplasia, infundibular obstruction, and distal main or branch PA stenosis.

There are mixed data on the accuracy of peak instantaneous gradients derived by echocardiography compared with gradients obtained by invasive cardiac catheterization for PS. Some studies have demonstrated excellent correlation with peak-to-peak gradients, ^, whereas others have shown that peak instantaneous gradients overestimate peak-to-peak gradients but are comparable to catheter-derived maximal instantaneous gradients. ^, Mean Doppler gradients have the best correlation with peak-to-peak gradients in isolated and complex valvular PS.

Management and outcomes

Progression of mild PS is unusual after early childhood. The Second Natural History Study of Congenital Heart Defects demonstrated comparable survival rates for patients with mild PS and the general population, regardless of a medical or surgical management strategy, with most patients being asymptomatic. Those with a gradient between 25 and 49 mmHg had a 20% chance of needing an intervention, and most of those with gradients equal to or greater than 50 mmHg had progressive stenosis and required intervention.

Indications for intervention in valvular PS are summarized in Table 24.3 . Successful percutaneous balloon valvuloplasty was initially reported in 1982, and it is the treatment of choice for classic domed valvular PS ( Fig. 24.4 ). The mechanism for relief of stenosis is commissural splitting, and the outcomes are usually excellent. ^, Moreover, although the outcomes are not as optimal as with classic domed PS, balloon valvuloplasty may provide some degree of relief for dysplastic pulmonic valves and is a reasonable first-line option.

TABLE 24.3

Recommendations for Intervention in RVOT Obstruction, Pulmonic Valve Stenosis, and Supravalvular Pulmonary Stenosis.

A large, multicenter registry of 533 patients followed for a median of 33 months (range, 1 month to 8.7 years) after balloon valvuloplasty showed that 23% had suboptimal results, defined as a residual gradient of 36 mmHg or greater or repeat balloon valvuloplasty or surgical valvotomy. Predictors of suboptimal outcome included earlier study year of intervention, higher residual postprocedural gradient, and unfavorable valvular anatomy. Long-term outcomes were reported for 139 patients who underwent balloon valvuloplasty with a median follow-up of 6 years (range, 0–21 years); reintervention was required in only 9.4% of patients, mostly for restenosis. Mild PR is common, but moderate or greater PR can occur after balloon valvuloplasty and was observed in up to 60% of patients after a median follow-up of 15.1 years (range, 10.1–26.3 years). ^,

Surgical relief of PS involves commissurotomy or valvotomy by an incision through the pulmonary trunk using an open or closed technique. Valvectomy is reserved for situations in which simple valvotomy is inadequate (i.e., dysplastic pulmonic valves). A transannular patch using autologous pericardium may be required to enlarge the annulus and supravalvular area. Outcomes of surgical valvotomy have demonstrated excellent survival rates of 90% to 96% up to 40 years after surgery but with a significant incidence of PR necessitating repeat surgical intervention (e.g., pulmonic valve replacement [PVR]) later in life.

Worsening of infundibular obstruction after relief of valvular PS by surgical valvotomy or balloon valvuloplasty is well documented, but this improves over time with regression of RV hypertrophy. ^, PR is not uncommon, especially after surgical intervention for valvular PS, and indications for PVR in cases of severe PR after surgical valvotomy are not well established. PVR may be appropriate in the setting of progressive RV dilation and dysfunction. ^, Management of residual PR is discussed later (see Tetralogy of Fallot ).