宇都 俊紀¹, 岩川 幹弘², 田端 強志¹, 佐々木 健¹, 高橋 憲子¹, 蓮沼 絵里香¹, 本村 昇³, 塩屋 雅人³, 蛭田 啓之⁴, 木下 利雄²

Toshinori UTO¹, Masahiro IWAKAWA², Tsuyoshi TABATA¹, Takeshi SASAKI¹, Noriko TAKAHASHI¹, Erika HASUNUMA¹, Noboru MOTOMURA³, Masato SHIOYA³, Nobuyuki HIRUTA⁴, Toshio KINOSHITA²

¹東邦大学医療センター佐倉病院生理機能検査部, ²東邦大学医療センター佐倉病院循環器センター, ³東邦大学医療センター佐倉病院心臓血管外科, ⁴東邦大学医療センター佐倉病院病理診断科

¹Department of Clinical Physiology, Toho University Medical Center Sakura Hospital, ²Department of Cardiovascular Center, Toho University Medical Center Sakura Hospital, ³Department of Cardiovascular Surgery, Toho University Medical Center Sakura Hospital, ⁴Department of Pathology, Toho University Medical Center Sakura Hospital

キーワード : right-sided infective endocarditis（RSIE）, tricuspid valve endocarditis, tricuspid regurgitation, <i>Staphylococcus lugdunensis</i>

症例は60代男性．1か月間持続する発熱を主訴に前医を受診．前医の経胸壁心臓超音波検査（以下，TTE）では異常所見は指摘されず，CT検査で肺炎および肺塞栓像を認めた．抗菌薬投与による内科的治療が開始されたが，奏功しないため当院に紹介となった．当院で施行したTTEで三尖弁前尖に付着する可動性に富む構造物を認め，軽度の三尖弁閉鎖不全症（以下，TR）を伴っていた．経食道心臓超音波検査では，TTE同様の所見に加え，三尖弁中隔尖の弁尖肥厚像と接合不全に伴う軽度から中等度のTRを認めた．入院第1病日と第2病日の血液細菌培養検査からStaphylococcus lugdunensisが検出され，三尖弁位感染性心内膜炎と診断された．抗菌薬投与による内科的治療で炎症反応は低下傾向にあり，解熱していたが，第7病日に再度発熱した．経過観察のために施行したTTEでは，疣腫の増大とTRの増悪がみられた．起炎菌が判明後，抗菌薬を変更したが，炎症反応の改善が乏しく鎮静化しなかった．疣腫が大きく，新規の肺塞栓症発症リスクや薬剤抵抗性も考慮し，第10病日に疣腫切除術および三尖弁形成術が施行された．術後の経過は良好であり，TRの増悪や疣腫再発は認めなかった．TTEは感染性心内膜炎において，新規病変の検出だけでなく，既知の病変の経過を非侵襲的に評価でき，特に本症例においては，外科的治療介入時期を検討する上で有用であった．

The patient, a male in his sixties, had been diagnosed with pneumonia and pulmonary embolism at a previous hospital, and despite receiving antibiotic treatment, his fever persisted, so he visited our hospital. On admission, transthoracic echocardiography（TTE）revealed a mobile vegetation on the anterior leaflet of the tricuspid valve. Blood cultures identified Staphylococcus lugdunensis（S. lugdunensis）, confirming the diagnosis of right-sided infective endocarditis（RSIE）. Treatment with antibiotics continued for more than a week, but the inflammatory reaction and fever did not improve. Moreover, follow-up TTE showed a slight increase in the size of the vegetations and worsening of tricuspid regurgitation. RSIE accounts for approximately 5-10％ of all IE cases. Additionally, tricuspid valve IE constitutes 80-90％ of RSIE cases. S. lugdunensis is highly toxic, comparable to Staphylococcus aureus, and requires caution. From the ESC guidelines（revised 2023）, commonly accepted indications for surgical treatment of RSIE in patients receiving antibiotic treatment are :（i）Right ventricular dysfunction secondary to acute severe tricuspid regurgitation unresponsive to diuretics.（ii）Respiratory failure requiring ventilatory support after recurrent pulmonary emboli.（iii）Large residual tricuspid vegetation（>20 mm）after recurrent pulmonary emboli.（iv）Patients with simultaneous involvement of left-heart structures（Class Ⅰ）. In addition, surgery should be considered in patients with RSIE on appropriate antibiotic treatment who present with persistent bacteremia/septicemia after at least 1 week of appropriate antibiotic treatment（Class Ⅱa）. In the present case, vegetectomy and tricuspid valvuloplasty were performed for RSIE, and the patient had a favorable outcome. In patients with IE, TTE can be used to noninvasively evaluate the position and size of the vegetation, the extent of infection in the surrounding tissue, and the presence or absence of worsening valvular regurgitation. In this case, TTE was particularly useful in considering the timing for surgical intervention.