右室圧負荷は僧帽弁のtetheringを増悪させる : 内科的加療のみで軽快した重症僧帽弁狭窄兼閉鎖不全の1乳児例の考察

Mitral stenosis and regurgitation (MSR) induced by congenital mitral valve dysplasia generally necessitates surgical repair or valve replacement. Here we report the case of a female infant diagnosed with congenital MSR that improved with pharmacotherapy alone and without a mitral valve surgery. The patient was a 22-day-old girl diagnosed with severe MSR accompanied with over-systemic pulmonary hypertension (PH). She was treated with respiratory support using a high-flow nasal cannula; diuretics and digitalis were also administered. Unexpectedly, the patient’s MSR and PH alleviated, and surgery was avoided. Tethering of the mitral valve induced by left ventricular dilation is known to result in secondary mitral regurgitation in adult ischemic heart disease. We speculated that the underlying mechanisms of MSR in this case: were due to elevation of the right ventricular pressure caused by physiological and pathological PH, which is a result of papillary muscle displacement and tethering of the mitral valve. We consider this the reason for the appearance of MSR on admission. Differentiating functional MSR from organic MSR is crucial while making decisions regarding surgery.

先天性僧帽弁異形成症による僧帽弁狭窄兼閉鎖不全（MSR）は，通常外科的弁形成術が必要であり，術後の予後不良な疾患である．我々は内科的加療のみで軽快した乳児例を経験した．症例は日齢22の女児で，心雑音を契機に重度のMSRおよびoversystemicな肺高血圧（PH）と診断された．僧帽弁形成術も念頭に置き，High flow nasal cannula，利尿剤，ジギタリス製剤による治療を開始したところ，徐々にMSR，PH，呼吸循環動態は安定し，内服薬のみで退院が可能となった．成人では左室拡大に伴うtetheringのためにMR，MSRを呈する病態が報告されているが，本症例では元来存在した先天的僧帽弁異形成に加え，生理的・病的PHによる右室圧上昇に伴う左室の変形，乳頭筋の外側偏位，僧帽弁前後径の短縮によって僧帽弁のtetheringが増悪した結果，重度のMSRを呈していたと考えた．乳児期早期の僧帽弁手術適応を適切に診断するために，先天性僧帽弁異形成における器質的問題と機能的問題を鑑別する必要があると考えた．

© 2018 Japanese Society of Pediatric Cardiology and Cardiac Surgery