心室中隔欠損の術前診断が困難であった右室二腔症

Double-chambered Right Ventricle with Difficult Preoperative Diagnosis of Ventricular Septal Defect in Adulthood

右室内腔の異常筋束によって右室が流入路側の高圧腔と流出路側の低圧腔に二分される右室二腔症は1），先天性心疾患の全症例の1.5～2.0％の発生頻度である2，3）．また，右室二腔症の80～90％は心室中隔欠損（ventricular septal defect：VSD）を合併するといわれており，孤立性右室二腔症はまれである2，3）．

Case 1 is a 65-year-old woman with right ventricular outflow tract stenosis due to dyspnea on exertion. Preoperative echocardiography revealed no shunt between the right and left ventricles. After resecting the right ventricular muscle bundle and weaning from cardiopulmonary bypass, transesophageal echocardiography confirmed a shunt between both ventricles. Right ventriculotomy under second cardiopulmonary bypass revealed a ventricular septal defect （VSD） that was closed with an expanded polytetrafluoroethylene patch.

Case 2 is a 58-year-old woman with a double-chambered right ventricle due to dyspnea on exertion. Preoperative echocardiography revealed a perimembranous VSD that coexisted；however, the VSD was completely covered by a membranous septal aneurysm, and no shunt appeared between both ventricles perioperatively. If right ventricular outflow tract stenosis/double-chambered right ventricle has been diagnosed in adulthood, the echocardiographic findings could have differed preoperatively and postoperatively. Combined use with other imaging modalities should improve the diagnostic accuracy of congenital heart disease.