複合座標系による虚血性心疾患における左室局所収縮能の定量評価

Quantitative analysis of left ventricular wall motion with the combined co-ordinate system

はじめに

　シネアンギオグラフィによる左室各領域収縮能の診断は，最も直接的な左室機能判定法として虚血性心疾患の診断上極めて重要と考えられているが^1〜5,8），その方法は従来より検者の主観に基づく定性診断が主流を占めており，客観的定量診断法の確立が待たれているところである。しかしながら心収縮各相におけるフレームの重ね合わせの方法^6），収縮能を表現する座標系とパラメーターの選択^7）が未だ諸家の間で一致をみず，このことが定量診断法の普及の障害となっていると考えられる。このたび筆者らは，心基部は左室長軸に垂直方向の，一方心尖部は左室長軸中点から放射方向の2種からなる複合座標系を考案し，虚血性心疾患患者44名と健常対照群12名とにおいて，この座標系から得られた諸指標を冠病変の有無ならびに重症度との関連において検討し，興味ある知見を得たので報告する。

In order to assess deteriorated contractility of ischemic myocardium, quantitative analysis of regional left ventricular contraction was performed by means of the combined co-ordinate system, which involves the rectangular co-ordinates in the basal segments and the radial co-ordinates in the apical segments. End-diastolic and end-systolic silhouettes were realigned as both the center of the aortic root and the long axsis of the left ventricle were superimposed, correcting for descent of the aortic valve and rotation of the apex.

All of the 26 patients with myocardial infarction (12 patients with anterior MI, 6 patients with inferior MI, and 8 patients with both anterior and inferior MI), who had been evaluated to have aneurysm and/or akinesis in the infarcted segmants, had remarkably lower value for regional mean percent shortening in association with the site of infarction than 12 control subjects.

In the 12 patients, who had severe (≧99%) stenosis only in the left coronary artery without any evidence of infarction (LCA group), PSI (2)+PSI (3), the index for contractility of the anterior wall, was significantly (p<0.05) higher than those with anterior MI and was significantly (p<0.001) lower than the control subjects, whereas there was no difference in PSI (6)+PSI (7), which is the index for contractility of the inferior wall, between LCA group and the control subject. On the contrary, in the 6 patients, who had severe (≧99%) stenosis only in the right coronary artery with no evidence of infarction (RCA group), in whom no abnormal wall motion was detected by qualitative analysis, PSI (6)+PSI (7) was significantly (p<0.05) higher than those with inferior MI and was significantly (p<0.001) lower than the control subjects. For PSI ratio (=PSI (2)+PSI (3)/PSI (6)+PSI (7)), which repre-sents relative contractility of the anterior wall compared with that of the inferior wall, all of the patients with anterior MI had values lower than 1.1 in contrast to the patients with inferior MI all of whom had values higher than 1.2, suggesting that PSI ratio may be a usefull index with exellent sensitivity and specificity for diagn-osis of the site of myocardial ischemia.

In summary we conclude that the combined co-ordinate system has an efficiency to detect not only definitely abnormal contractility of the myo-cardium with infarction but also slightly decre-ased amplitude of the motion of that without infarction.