VVIペースメーカー植え込み例に発症した急性心筋梗塞の1例

A Patient with VVI Pacemaker Subjected to Acute Myocardial Infarction with Congestive Heart Failure

　われわれはペースメーカー植え込み例で心筋梗塞を発症し，梗塞範囲は小範囲ながら心不全を合併した症例を経験した．症例は72歳，男性．主訴は呼吸困難，下肢倦怠感．5年前，当院で永久ペースメーカー（VVI）植え込み術を受けていた．入院時理学所見上III音および胸部両下肺野にて湿性ラ音を聴取し，心電図は完全左脚ブロック型でV₃—V₅にST-T変化を認めた．軽度のCPKの上昇，軽度の低酸素血症，心エコー図では心尖部のhypokinesisがみられたことから心不全を合併した心筋梗塞と診断された．ペースメーカー挿入例で心筋梗塞を合併することは稀ではないものの，その診断は心電図のみでは時に困難である．本症例の梗塞領域は小範囲と推測されたが心不全を合併した．その機序の一つとして心室ペースメーカーによる非生理収縮様式の寄与が推測され，VVIペースメーカー植え込み例の心筋梗塞の診断には左室機能の低下を重視するべきと思われた．

A 72 year-old male in whom a VVI pacemaker had been implanted was admitted to our hospital because of dyspnea on slight exercise and leg fatigue. His electrocardiography showed the complete LBB pattern and slight changes in ST segment at V_3-5. The III sound and a fine moist rale were audible at the apex of the heart and at bilateral lower lung fields. The serum level of CPK was slightly elevated (the peak CPK: 169, normal range＜115IU/dl) and mild hypoxia was detect-ed by blood gas analysis. Echocardiography revealed apical hypokinesis. Based on these findings, the patientwas diagnosed as having acute myocardial infarction (AMI) with congestive heart failure, although the infar-cted size was suspected to be small. The persistant defect on exercise ²⁰¹Tl scintigraphy before his dis-charge was small at the apex, which was consistent with the serum and echocardiographic findings.

This case suggested to us that it is difficult to diag-nose ischemic heart disease in patients with a VVI pacemaker. In addition, such patients may easily com-plicate heart failure due to the non-physiological pat-tern of LV contraction.