急性後下壁心筋梗塞に対するt-PA静注直後に左前下行枝の閉塞を認めた1例

A Case of Acute Occlusion of the Left Anterior Descending Artery following Thrombolytic Therapy for Acute Inferoposterior Myocardial Infarction

　急性後下壁心筋梗塞に対する血栓溶解療法直後に左前下行枝の閉塞を来した稀な症例を報告する．症例は59歳，男性．胸部圧迫感と心電図上II,III,aV_F，V₅，V₆のST上昇とI,aV_LのST低下を認め，急性心筋梗塞の診断でalteplase（t-PA）2,400万単位を点滴静注した．点滴終了から45分後，再び症状出現し，V₁からV₄のSTが上昇した．緊急冠動脈造影では左前下行枝（LAD）＃7に完全閉塞，左回旋枝（LCX）＃13に90％狭窄，右冠動脈（RCA）＃3に75％狭窄を認めた．＃7，＃13に対しPTCAを施行して，それぞれ30％，50％狭窄にまで改善した．発症4日目の心筋dualシンチグラムの所見は，前壁中隔，心尖部および後下壁の梗塞として矛盾はなかった．本症例はt-PAにより最初の梗塞責任血管であるRCAの再開通を認めた後にLADの完全閉塞がみられたが，その発症機序として心筋梗塞発症時の凝固能亢進，t-PAによる凝固能亢進，冠攣縮の関与など複数の原因が考えられた．

We report a rare case of acute myocardial infarction with occlusion of LAD following intravenous throm-bolytic therapy with t-PA for RCA which was initially suspected as the infarct-related artery. A 59 year-old man presented with chest oppression. ECG revealed ST elevation in leads II, III. aV_F, V₅, and V₆; and STdepression in leads I and aV_L. Intravenous throm-bolytic therapy (t-PA 2,400x10⁴I.U.) brought his chest oppression under control. At 45 minutes after the therapy, ECG showed ST elevation in leads V_1-4 with chest oppression. Emergent CAG demonstrated total occlusion of LAD-Segment 7,90% stenosis of LCX-Segment 13, and 75% stenosis of RCA-Segment 3. After PTCA was performed on the lesions of LAD and LCX, stenosis of the LAD lesion decreased to 30%, and the LCX lesion to 50%. Myocardial dual scintigram on the 4th day of admission showed findings compatible with infarctions of the anteroseptal wall, apex, and infer-oposterior wall. In this case, we speculate that the RCA lesion which was suspected as the initial infarct-related artery was recanalized by t-PA, but the LAD lesion occluded. We considered hyper-coagulability at the onset of myocardial infarction, hyper-coagulability due to t-PA itself, coronary vasospasm, and other unknown factors as the mechanism (s) involved in this case.