急性前壁梗塞における下壁誘導ST変化の意義—前下行枝の大きさと下壁領域の虚血との関係についての検討

Significance of inferior ST segment changes in acute anterior myocardial infarction:Relationship between the distribution of left anterior descending artery and concomitant ischemia of the inferior wall

　〔目的・方法〕初回急性前壁梗塞にて冠動脈血栓溶解療法に成功した23例を，前下行枝の大きさより，心尖部を越えて下壁に達しているかどうか，および側副血行路の有無で3群に分け，下壁誘導（II，III，aV_F）ST変化の意義を検討した。下壁領域の虚血の有無は，左室造影・²⁰¹Tl心筋シンチグラフィーより評価し，また，側壁誘導のST変化との関連性についても検討した。〔結果〕下壁誘導のST低下は，前下行枝の大きさが長くても心尖部までで下壁には達しない群に多く認められ，それは下壁領域の虚血のためではなく，前胸部誘導（V_1-4）と側壁誘導（1，aV_L）のST上昇の鏡像としてのreciprocalな変化であることを示唆した。下壁誘導のST上昇は，心尖部を越えて下壁に達する大きな前下行枝をもち，かつ前下行枝への側副血行路発達不良群に多く認められ，下壁領域の虚血の反映を示唆した。

The significance of inferior ST segment changes was studied in 23 patients with acute anterior myo-cardial infarction by the distribution of the left anterior descending artery (LAD) after percutaneous transluminal coronary recanalization. In 9 patients (Group A) LAD suppied the anterior wall of the left ventricle up to or including the apex but did not reach the inferior wall; in 8 patients (Group B) it continued beyond the apex onto the inferior wall of the left ventricle with welldeveloped collateral circulation; in 6 patients (Group C) it continued beyond the apex onto the inferior wall of the left ventricle with less-developed or no collateral circu-lation. Thallium-201 scintigraphy and contrast left ventriculography showed that inferior myocardial ischemia was significantly more prominent in Group C than Group A. These results were consistent with coronary anatomy. Inferior ST segment was significantly more depressed in Group A with no concomitant inferior wall ischemia, than in Group C with concomitant inferior wall ischemia (maximal inferior ST segment change:-1.7±1.1;0.8±1.7 mm, respectively; p＜0.02). In Group A inferior ST segment was depressed in all 6 patients with lateral ST segment elevation, but it was depressed in only one of 3 patients with no lateral ST seg-ment change. Lateral ST segment elevation tended to cause inferior ST segment depression. This study indicates that the inferior ST segment changes in patients with acute anterior myocardial infarction depend on concomitant ischemia of the inferior wall of the left ventricle by the distribution of LAD and the lateral ST segment changes.