Chapter 10 Pulmonary Valve in Health and Disease

The pulmonary valve is the smallest valve in the body and, in keeping with its size, plays a relatively uncommon role in adult cardiology. Despite the limited involvement of the pulmonary valve in adult cardiac disorders, it is important to review the clinical situations for which pulmonary valve pathology is present. Pulmonic stenosis rarely is identified in adulthood and is a problem much more frequently identified and treated in pediatric patients. Mild to moderate pulmonary regurgitation is, of course, common and normal in adults.

The most common cause of significant pulmonary regurgitation (defined as more than moderate pulmonary regurgitation) in adults is pulmonary hypertension from any cause, with or without dilation of the pulmonary valve ring. Like the tricuspid valve, the pulmonary valve typically becomes incompetent when exposed to high pressure. Less common causes of pulmonary valve regurgitation include infectious endocarditis, carcinoid syndrome, and tumor infiltration of the valve (e.g., papillary fibroelastoma).¹^–⁵ Pulmonary hypertension can be primary or secondary; the most common secondary cause is left-sided heart failure. Pulmonary artery dilation also can ultimately result in valve ring dilation. Causes of pulmonary artery dilation include connective tissue diseases such as Marfan syndrome, Ehler-Danlos syndrome, systemic lupus erythematosus, and scleroderma. Idiopathic dilation of the pulmonary artery is a clinically described phenomenon. This entity typically is seen in older women and can result in severe pulmonary regurgitation. In the patient population at Harborview Medical Center, infective endocarditis with destruction of the valve is a not-infrequent cause of pulmonary regurgitation. The fact that we have identified several cases of pulmonary valve endocarditis in recent years is notable because the overall incidence of pulmonary valve endocarditis is quite low—estimated to be as low as 2% at autopsy series and clearly less common than tricuspid valve endocarditis.⁶ Indeed, between 1960 and 1999, only 36 cases of pulmonic valve endocarditis were reported in structurally normal hearts.⁷ Transesophageal echocardiography (TEE) undoubtedly has improved the diagnostic yield of pulmonic valve endocarditis compared with transthoracic echocardiography (TTE), but the true incidence remains uncertain.^8,⁹ Congenital absence of the pulmonary valve can be seen in association with tetralogy of Fallot or accompanying a congenital ventricular septal defect (VSD) and less commonly with atrial septal defect (ASD), coarctation of the aorta, or tricuspid atresia.¹⁰ In practice, the valve leaflets are rudimentary and dysplastic rather than completely absent.¹¹ Isolated dysplastic pulmonary valve is rare and much less common than when seen in association with the previously named defects.

Three-dimensional echocardiography (3DE) of the pulmonary valve is very difficult to perform by TTE in adults, just as imaging the pulmonary valve by two-dimensional echocardiography (2DE) typically is challenging.¹² The limitation typically is ultrasound penetration due to interference from lung tissue. A clear rule of thumb regarding 3DE imaging is that if the 2DE image is poor, the 3DE image is likely to be poor or worse. Figures 10-1 and 10-2 show a TTE image in the parasternal short-axis view with the pulmonic valve adjacent to the aortic valve in 2D (Video 10-1) and 3D (Video 10-2). The pulmonic valve is seen in the longitudinal view, and typically only one, or at best two, of the valve leaflets is identified. Not infrequently, the subcostal view can come in handy for viewing the pulmonary valve with surface imaging. Figure 10-3 and Video 10-3 show subcostal views of the pulmonary valve by 2DE and 3DE.

Figure 10-1 Two-dimensional transthoracic echocardiography image of a normal pulmonary valve, pulmonary artery, and pulmonary artery bifurcation (see Video 10-1).

Figure 10-2 Three-dimensional (3D) image obtained from the transthoracic parasternal short-axis view of the pulmonary valve (PV), pulmonary artery (PA), and pulmonary artery bifurcation. Most notably for the pulmonary valve, the 3D image loses some of the distinguishing characteristics of the various structures compared with the two-dimensional view. The benefit of depth in this case is offset by the limited ultrasound penetration allowed by transthoracic imaging (see Video 10-2).

Figure 10-3 Two-dimensional (A) and three-dimensional (B) transthoracic echocardiography images by the subcostal view showing the pulmonary valve (arrow), pulmonary artery, and pulmonary artery bifurcation (see Video 10-3).

Case 1

The first case is an example of detection of a pulmonary embolus using TTE. In this case, there is a saddle embolus. Figure 10-4 and Video 10-4 show 2D views in the parasternal long-axis and apical four-chamber view of a patient who presented with dyspnea and hypotension. The right ventricle is dilated and markedly hypocontractile. McConnell’s sign is present, with severe right ventricular dysfunction that spares the apex. Figures 10-5 and 10-6 and Videos 10-5 and 10-6 show examples of an embolus at the bifurcation of the pulmonary artery, hence a “saddle embolus.” The right ventricular dilation and severe systolic dysfunction are emphasized even more with injection of saline contrast into the right ventricle (see Figure 10-6; Video 10-7).