中隔に限局した急性心筋梗塞の1例

A Case of Pure Septal Myocardial Infarction

　症例は67歳，男性．胸痛を主訴に来院した．心電図上，V_1〜3のST上昇，I,aV_L，V_5,6の陰性T波を認め，心臓超音波検査で，中隔基部に限局した壁運動低下を認めた．緊急冠状動脈造影で左右冠状動脈本幹には有意狭窄はなく，第一中隔枝にのみ90％狭窄を認め，左室造影で中隔基部に限局した壁運動低下を示した．発症11日目の²⁰¹Tl心筋シンチグラムでも中隔基部に限局した欠損像を認めたことより，中隔梗塞と診断した．心電図経過ではV_1,2のR波減高と既存の左軸偏位の消失を認めた．本症例および過去の報告例の心電図学的検討より，V₁のQS型，V_5,6のq波消失，心室内伝導障害の出現および急性期のV_1〜3に限局したST上昇が中隔梗塞を示唆する所見であったが，確定診断には²⁰¹Tl心筋シンチグラムが必須と考えられた．

A 67-year old man was admitted to our hospital with the chief complaint of prolonged chest pain. On admis-sion, an electrocardiogram showed ST elevation in V_1~3 and T wave inversion in I, aV_L, V_5,6 Echocardiography showed hypokinesis at the base of the interventricular septum. The emergent coronary angiography demon-strated 90% narrowing in the first septal branch which suggested an infarct-related artery. The left ventriculo-graphy also showed hypokinesis in its septal wall. The ²⁰¹Tl SPECT imaging taken on the 11th hospital day also revealed a defect at the base of the interventricular septum. Therefore, we made a diagnosis of a pure septal myocardial infarction. An electrocardiogram on the 11th hospital day showed decreased R wave ampli-tude in V_1~2 and disappearance of pre-existing left axis deviation. We assessed the characteristics of electrocardiographic findings for predicting a pure se-ptal myocardial infarction from findings in this case as well as from the previous reports. QS pattern in V₁, disappearance of septal Q wave in V_5,6 appearance of intraventricular conduction disturbance, and ST eleva-tion in V_1~3 at the acute phase are probably finding suggestive of a pure septal infarction. ²⁰¹Tl imaging is still most essential for the definitive diagnosis of septal infarction.