鍵山 暢之, SHRESTHA Sirish

Nobuyuki KAGIYAMA, Sirish SHRESTHA

ウェストバージニア大学心臓血管センター

West Virginia University Heart and Vascular Institute

キーワード : sechocardiography, three-dimensional (3D) echocardiography, mitral regurgitation, mitral valve prolapse, mitral valve repair ・ transcatheter mitral valve repair

僧帽弁逆流（MR）は，先進国で最多の弁膜症の1つであり，心エコー図評価は，病変，重症度および治療適応を評価するのに不可欠な手段である．僧帽弁複合体の構造は複雑で，僧帽弁弁尖と僧帽弁輪のみでなく腱索，乳頭筋，左室壁も含まれ，MRは僧帽弁弁尖または腱索の器質性変化による一次性MRと，弁尖自体には異常のない二次性MRに分けられる．さらに二次性MRは乳頭筋および左室壁の偏位や機能不全などの左室に原因がある場合と，著明な僧帽弁輪拡大を中心とする左房に原因がある場合に大別される．一次性MRと対照的に，左室機能不全による二次性MRでは軽度の逆流も予後に関与するため注意が必要である．重症度評価は，外科的介入および経カテーテル的治療の適応判断に重要であり，心エコー図法によるMRの重症度評価は多数のパラメータを用いて行われる．しかし，どの手法も単独で十分な信頼性を有してはおらず，常に複数の手法を組み合わせることが推奨される．心エコー図にてMRの重症度の結論が出ない場合，磁気共鳴画像法（MRI）が有用な場合がある．重症度に加えて，僧帽弁逸脱による一次性MRでの病変局在や，左室の拡張/機能不全による二次性MRでの左室の大きさといった解剖学的情報は，治療方針決定に寄与する重要事項であり，経食道心エコー図法および3D心エコー図法は，これらの情報を得るのにも重要な手法である．また，近年隆盛の経カテーテル的治療でも，心エコー図法は手術やエンドポイントの指標として極めて重要な役割を果たす．本総説では MRの心エコー図評価の現行基準を包括的に要約する．

Mitral regurgitation (MR) is one of the most frequent indications for valve surgery in developed countries, and echocardiographic assessment is an essential tool to evaluate its etiologies, severity, and therapeutic indications. The mitral valve apparatus is a complex structure composed of several parts: apart from the mitral valve leaflets and annulus, it also includes the chordae tendineae, papillary muscles, and left ventricular (LV) wall. MR can be caused not only by organic changes of the mitral valve leaflets or chordae (primary MR) but also by extreme mitral annular enlargement or mitral leaflet tethering due to displacement and malfunction of papillary muscles and LV wall (secondary MR). In secondary MR with LV dysfunction, a milder degree of MR can be associated with adverse outcomes compared with primary MR. Grading the severity is the first step in evaluation of indication for surgical/transcatheter interventions. As such, there are several techniques to assess the severity of MR using echocardiography. However, none of the techniques is reliable enough by itself, and it is always recommended to integrate multiple methods. In cases where echocardiographic assessment of MR severity is inconclusive, magnetic resonance may be helpful. In addition to the severity, anatomical information, such as localization in primary MR due to mitral valve prolapse and LV size in secondary MR due to LV dilatation/dysfunction, is an important concern in presurgical echocardiography. Transesophageal echocardiography and three-dimensional echocardiography are key techniques for anatomical evaluation including mitral valve and LV volumes. In transcatheter intervention for MR, echocardiography plays a pivotal role as a guide for procedures and endpoints. In this review article, the authors provide a comprehensive summary of current standards of echocardiographic assessment of MR.