人工弁に生じた血栓により急性心筋梗塞を来した１例

A Case of Acute Myocardial Infarction due to a Thrombus having developed in the Artificial Valve

要旨

　患者は74歳，女性．1987年4月に某病院で大動脈弁置換術を施行され，以後は近医で加療されていた．2002年9月に施行した弁透視では人工弁の開放は良好で，経食道エコーでも弁周囲に血栓は認めなかった．2003年2月に右後頭葉腫瘍と未破裂脳動脈瘤が発見され，手術を前提に抗凝固療法は緩和されていた．2003年4月に突然の胸痛を自覚し救急受診した．以前より，心電図は広範囲の誘導でST低下を認めていたが，その程度が増悪しており，急性冠症候群の診断下に入院となった．経過観察したが，翌日にCK値の上昇を認めたため心臓カテーテル検査を施行した．大動脈造影では左冠動脈に病変は認められなかったが，人工弁上部に弁の動きに同調して可動する造影剤の停留を認めた．造影CTでは人工弁上部に造影欠損を認め，経食道エコーでは可動性の血栓が確認された．人工弁機能不全と判断し，緊急手術を施行したところ，左冠動脈入口部を閉塞する巨大血栓が確認され，左室の心尖部は暗赤色で瘤化していた．抗凝固療法の緩和によって人工弁に血栓が生じ，急性心筋梗塞を発症したものと考えられた．

Summary

　This is a case of a 74-year-old woman, who underwent aortic valve replacement(AVR) in 1987 and has been treated at another hospital. Fluoroscopy was performed in September, 2002 showed good opening of the artificial heart valve, and a transesophageal echocardiogram(TEE) showed no thrombus in the tissue surrounding the valve. In April, 2003, the patient experienced an abrupt development of chest pain and underwent emergency treatment. There was exacerbation of decreased ST, which was detected by comprehensive-lead electrocardiography. The patient was diagnosed as having acute coronary syndrome and hospitalized for course observation. On the following day, she showed an increased CK level and consequently underwent cardiac catheterization. On aortagraphy, the left coronary artery exhibited no stenosis, but there was retention of contrast medium moving in coordination with the movement of the valve in a region above the valve. CT with contrast medium exhibited contrast defect in the region above the valve, and TEE showed a moving thrombus. The patient was diagnosed with artificial valve insufficiency and underwent emergency surgery. A giant thrombus closing the inlet of the left coronary artery was found. The apex of the left ventricle was aneurismal and was colored dark red. The patient probably developed acute myocardial infarction secondary to a thrombus having formed in the artificial valve.