3．左心低形成症候群

Current Surgical Treatment for Patients with Hypoplastic Left Heart Syndrome, from the Viewpoint of Emergent Operation

左心低形成症候群（hypoplastic left heart syndrome：HLHS）は，胎生期に卵円孔の狭窄や僧帽弁の狭窄・閉鎖により左室を通過する血流が減少して左室が小さくなり，それに伴い大動脈弁が狭窄ないしは閉鎖する疾患である．上行大動脈の径は大動脈弁の通過血流量に規定され細くなり，大動脈弁閉鎖の場合は動脈管から大動脈弓を通過した逆行性の冠状動脈血流分のみで外径2 mm程度となる．また僧帽弁狭窄と大動脈弁閉鎖が合併した場合は，左室に流入した血液の行き場がなくなり左室冠状動脈瘻を形成する．これらの解剖学的特徴により，右室が体心室となる動脈管依存性体循環が完成される．

The treatment of hypoplastic left heart syndrome has improved dramatically with the development of treatment strategies due to improved understanding of hemodynamics, improved surgical methods, and the widespread use of fetal diagnosis. However, cases of early closure of the foramen ovale require emergency surgery immediately after birth, and further improvement of treatment results is needed. The right ventricular pulmonary artery shunt reported from Japan is well known worldwide and has greatly contributed to improved outcomes up to six months after the Norwood procedure. Also contributing to the improved results of the Norwood procedure is the widespread use of bilateral pulmonary artery banding to avoid palliative open heart surgery in the neonatal period. Although this method is widely used in Japan, there is still room for improvement in such areas as postoperative left pulmonary artery stenosis and aortic arch reconstruction after stenting of the ductus arteriosus. Now that the results of the Norwood procedure have stabilized, there is a need to improve treatment methods to establish a better Fontan circulation in the future.