14. 小児狭小弁輪に対する大動脈弁再手術

Aortic Valve Reoperation in Small Aortic Annulus

先天性大動脈弁狭窄症（AS）の多くは加齢とともに徐々に病態が進行するが，一部は小児期に重症化する．新生児～小児期にかけて手術を要する重症大動脈弁狭窄症（critical AS）の約2/3は2尖弁であるが，交連の癒合がなくても弁尖の肥厚や異形成によって高度の狭窄をきたす場合があり，弁輪が狭小であることも少なくない．新生児や乳児のcritical ASに対する初回手術としては，弁輪の大きさが許容範囲であれば（おおむね－3 SD以内），直視下交連切開術が選択されることが多い．かつてはカテーテルを用いた経皮的大動脈弁切開術の優位性が謳われていたが，近年直視下交連切開術の安全性と有効性が見直され（手術死亡率3％以下，10年の再介入回避率約65％），確実な弁切開により多くの症例で再手術を学童期以降に持ち越すことができるようになった1）．

Pediatric patients with narrow aortic valve annulus are often forced to undergo repeated aortic valve surgery, and it is not uncommon to plan a treatment strategy from the beginning with the assumption of reoperation or staged surgery. This article describes the anatomical structure of the aorto-mitral curtain and presents an example case of the Yamaguchi method, a relatively infrequently performed aortic valve procedure, in anticipation of aortic annular enlargement as a third reoperation in a 15-year-old boy with critical aortic valve stenosis. In the Nicks procedure, the incision beyond the posterior annulus is limited to the fibrous tissue of the aorto-mitral curtain；in the Manouguian procedure on the other hand, the incision is extended beyond this point to the anterior leaflet of the mitral valve. In the Yamaguchi procedure, the Konno incision at the anterior annulus near the right-left commissure is added to the standard Nicks incision for posterior annular enlargement, and thus the narrow annulus is enlarged in two places using two separate patches. However, the anterior incision cannot be very deep because the area immediately below the anterior annulus is nearly muscular tissue. Usually the annulus is enlarged with four posterior pledgets and additional two anterior pledgets.