僧帽弁後尖形成術後の遺残逆流

Residual Mitral Regurgitation after Repair for Posterior Leaflet Prolapse；Importance of Preoperative Anterior Leaflet Tethering

僧帽弁後尖逸脱症に対する形成術式は，弁尖切除・縫合と人工腱索再建の二つに大別され，それぞれ良好な成績が報告されている．Braunberger, Carpentierは切除・縫合を主体とした形成術後20年の再手術回避率が96.9％1），Davidらは人工腱索による後尖形成術後18年の再手術回避率が95％以上であった2）と報告している．またCastilloらは，連続744例の僧帽弁形成術（うち後尖単独病変は75％）の形成完遂率は99.9％，術後7年の逆流再発回避率は91％と報告しており3），後尖形成術式はほぼ確立されているといっても過言ではない．

Background：Carpentier’s techniques for degenerative posterior mitral leaflet （PML） prolapse have been established with excellent long-term results reported. However, residual mitral regurgitation （MR） occasionally occurs even after a straightforward repair, though the involved mechanisms are not fully understood. We sought to identify specific preoperative echocardiographic findings associated with residual MR after a PML repair.

Methods and Results：We retrospectively studied 117 consecutive patients who underwent a primary mitral valve repair for isolated PML prolapse including a preoperative three-dimensional transesophageal echocardiography （3D-TEE） examination. Eleven had residual MR after the initial repair, of whom 7 required a corrective second pump run, 4 underwent conversion to mitral valve replacement, and 1 developed moderate MR within 1 month. Their preoperative parameters were compared with those of 105 patients who had an uneventful mitral valve repair. There were no hospital deaths. Multivariate analysis identified preoperative anterior mitral leaflet （AML） tethering angle as a significant predictor for residual MR ［odds ratio （OR） 6.82, 95％ confidence interval （CI） 1.8～33.8, p＝0.0049］. Receiver operator characteristics curve analysis revealed a cut-off value of 24.3° （area under the curve 0.77）, indicating that AML angle predicts residual MR. In multivariate regression analysis, smaller anteroposterior mitral annular diameter （p＜0.001） and lower left ventricular ejection fraction （p＝0.002） were significantly associated with higher AML angle, while left ventricular and left atrial dimension had no significant correlation.

Conclusions：AML tethering in cases of PML prolapse has an adverse impact on early results following mitral valve repair. The findings of preoperative 3D-TEE are important for consideration of a careful surgical strategy.