重症感染性心内膜炎に併発した細菌性脳動脈瘤の1例

A Case of Bacterial Aneurysm Complicated by Severe Infectious Endocarditis

Ⅰ．はじめに

　細菌性脳動脈瘤は感染性心内膜炎を有する患者に合併することが多く^2,5,15,17)，破裂した場合に致死的になる確立が高いとする報告があるが^1,2,8,15,16)，治療方針および重症感染性心内膜炎を有する場合の開心術のタイミングについて統一した見解がないのが現状である^{1-4,7,8,15-17,23)}．今回われわれは，重症感染性心内膜炎の患者において早期に未破裂細菌性脳動脈瘤を診断し，心臓血管外科で僧帽弁置換術を先行させた後，頻回な画像観察と抗生剤の長期投与で動脈瘤の消失を確認した1例を経験したので報告する．

　We report a case of bacterial aneurysm complicated by severe infectious endocarditis. A 34-year-old man developed idiopathic fever and general fatigue persisting for a month. He was admitted to our institution, and examinations revealed severe bacterial endocarditis with vegetation at the mitral valve and mitral incompetence. Right after admission, he suddenly developed acute cardiac infarction and cardiac arrest due to occlusion of the coronary artery by emboli from vegetation of the mitral valve. After achieving a good recovery, magnetic resonance (MR) imaging demonstrated an unruptured bacterial aneurysm at the distal branch of the left middle cerebral artery (MCA) supplying the left parietal lobe 5 days after admission, and T2^＊ weighted images demonstrated multiple signal loss lesions, which were suspected of being thrombosed bacterial micro-aneurysms or micro-vasculitis. Although there was a risk of aneurysm rupture, we decided to proceed with mitral valve replacement by an artificial heart valve made of carbon, and repeatedly observed an unruptured bacterial aneurysm by serial MR imaging and angiography. Due to the preceding cardiac surgery, we were able to completely cure the severe infection and prevent new embolic showers. Under administration of antibiotics, the bacterial cerebral aneurysm did not increase over a period of 4 weeks, and finally the aneurysm disappeared about 6 weeks after admission. Although the timing of treatment of an unruptured bacterial aneurysm and cardiac surgery for infectious endocarditis associated with a bacterial cerebral aneurysm are controversial, we think that proceeding with cardiac surgery and observing the unruptured bacterial aneurysm by repeated MR imaging and angiography under administration of antibiotics was an appropriate strategy in this case.