Pulmonary Site Bioprosthesis: Failure at 15 Years
A 20-year-old woman, born with pulmonary atresia, intact interventricular septum, and slightly reduced right ventricle (RV), presented with mild shortness of breath and loss of energy. She had been palliated with a central shunt and a closed pulmonary valvotomy as a newborn. The repair was completed 5 years later by the replacement of her pulmonary valve with a 21-mm Ionescu-Shiley low-profile pericardial bioprosthesis (ISLP), enlargement of the right ventricle outflow tract (RVOT) with a pericardial patch, and closure of the central shunt and atrial septal defect. At age 18, she developed RVOT stenosis, which was treated with an RVOT stent. The following year, MRI showed small proximal right and left pulmonary arteries (12 mm and 11 mm, respectively) with mild to moderate turbulence in the main pulmonary artery and preferential flow to the left pulmonary artery. A transthoracic echocardiogram showed persistent elevation of RV systolic pressure >70 mm Hg (mean transvalvular gradient of 30 mm Hg), severe pulmonary regurgitation, and moderate tricuspid regurgitation. Despite this, the patient remained asymptomatic. At age 21, repeat MRI and transthoracic echocardiogram indicated increasing RVOT stenosis and valve replacement was recommended (Figure 1). She underwent replacement of the pulmonary prosthesis with a 27-mm pulmonary homograft. The homograft’s opened pulmonary artery branches were used to enlarge the openings of her right and left pulmonary arteries. After bypass, the RV pressure measured 31/3 mm Hg. The patient made an uneventful recovery.
A large strip of ventricular outflow tract and prosthetic valve removed by electrocautery at surgery was examined. The ISLP pericardial valve showed stiffened, fixed cusps with marked host tissue overgrowth (pannus) on the sewing ring, stent posts, and both flow and nonflow surfaces on all 3 cusps (Figure 2). The pannus extended to and covered the free margins in 2 of the leaflets and came close to the free margin in the third. All 3 cusps were retracted and fixed in place by the pannus, creating a fixed stenotic triangular orifice with a maximum dimension of the orifice of 1.3 cm. Histological sections showed the pericardial leaflet tissue to be structurally unremarkable and folded in an “accordion pleat pattern” covered by pannus, causing the leaflets to be nonfunctional and the valve incompetent. Pannus was comprised of fibrous tissue, cells with the features of smooth muscle cells (vimentin and smooth muscle actin positive), and lined by endothelial cells (Figures 3 and 4⇓). Within the fibrous connective tissue, blood vessels were rare. Macrophages and leukocytes could not be detected by immunostaining (CD 68 and CD 45, respectively) and stains for microorganisms were negative.
The editor of Images in Cardiovascular Medicine is Hugh A. McAllister, Jr, MD, Chief, Department of Pathology, St Luke’s Episcopal Hospital and Texas Heart Institute, and Clinical Professor of Pathology, University of Texas Medical School and Baylor College of Medicine.
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