僧帽弁位異種生体弁の石灰化狭窄を呈した小児例

抄録

A three year-old girl with atrial septal defect, mitral regurgitation and pulmonary edema underwent suture closure of the atrial septal defect and mitral valve replacement with a 23 mm Hancock xenograft on an emergency basis. Relief of symptom was remarkable. Two years later, a grade 2/6 diastolic rumbling murmur was noted at the apex, but her physical activity was normal. She started to have symptom after acute onset of pneumonia 3 years after operation. She was admitted with the diagnosis of mitral stenosis and congestive heart failure 3 years and 4 months after operation. The chest X-ray film showed cardiomegaly (CTR 63%) and pulmonary venous congestion. Echocardiography failed to demonstrate any significant pathology of the porcine xenograft. Cardiac catheterization revealed typical mitral stenosis. The mitral valve area was 0.34cm^2 and the left ventricular ejection fraction was 0.43. The left atrium and the pulmonary artery were dilated. Because of progressive symptom, surgical intervention was indicated. At re-operation, two of the three leaflets of the porcine xenograft were heavily calcified and not mobile, the remaining leaflet was mobile without significant calcification. The porcine xenograft was replaced with a 27mm Bjork-Shiley mitral prosthesis. The patient could not be weaned off bypass because of severe left ventricular failure. Recently, increasing number of reports dealt with high incidence of calcification of the porcine xenograft in children. The increased calcium turnover in children, along with relatively low blood flow through the mitral valve, immunological reaction and fatigue are considered as causes of calcification. Since porcine xenograft posseses high possibility of malfunction in early stage, its application on children should be avoided.