Gd造影MRIによる回旋枝急性心筋梗塞の診断—核医学的検査との比較検討

The Usefulness of Gd-DTPA Enhanced MRI in the Diagnosis of Acute Myocardial Infarction due to Left Circumflex Coronary Artery Disease:Comparison with radionuclide imaging

　回旋枝急性心筋梗塞8例を対象として，回旋枝領域の急性心筋梗塞診断におけるGd造影MRIの有用性を検討した．入院時の心電図は8例中4例において急性心筋梗塞に特徴的な所見が認められず，心電図検査のみでは梗塞領域を正確に判定できなかった．全症例に対してspin echo法によるGd-DTPA造影MRIを施行し，全症例で梗塞部位が高信号領域として描出された．8例中7例において²⁰¹Tl，^99mTc-pyrophosphateによるDual SPECTを併せて施行した．Dual SPECTが施行されなかった1例は，入院時に急性心筋梗塞の診断がなされず，発症2週間後にMRIを用いて回旋枝心筋梗塞の診断を得た症例である．MRIにおける高信号領域とPYPの集積部位はよく一致した．緊急冠動脈造影において冠動脈狭窄を認めない症例が1例認められ，また回旋枝と前下行枝に狭窄を有する2枝病変症例が1例認められた．これらの2症例では冠動脈造影からは梗塞責任血管の診断が得られず，Gd造影MRIならびにDual SPECTを用いて回旋枝領域の急性心筋梗塞と診断した．以上より，Gd造影MRIは回旋枝の急性心筋梗塞の描出に優れるとともに，梗塞領域の把握に有用な診断法であることが示された．

We studied 8 patients with acute myocardial infarc-tion (AMI) due to occlusion of the left circumflex coronary artery (LCX). We evaluated the usefulness of Gd-enhanced MRI for detecting acute LCX myocardial infarction in these patients. Electrocardiograms record-ed on admission revealed nonclassic pattern of AMI in 4 patients. Therefore, it was difficult to predict the exact location of the infarcts from the electrocardio-gram alone. All patients underwent Gd-DTPA enhan-ced MRI with spin echo sequence. MRI clearly visual-ized the infarcts as a high signal intensity area after administration of Gd-DTPA in each case. Seven out of 8 patients also underwent dual isotope single photon emission computed tomography (SPECT) with ²⁰¹Tl and ^99mTc pyrophosphate (PYP). The other patient did not undergo PYP SPECT, because the diagnosis of AMI was not made until MRI disclosed the infarcts of LCX territory two weeks after the onset of AMI. There was a good correlation between the location of the high signal intensity area on MRI and the location of PYP accumulation. Emergency coronary angiography showed a normal coronary artery in one patient. In another patient, the angiography revealed two-vessel disease involving LCX and the left anterior descending coronary arteries. The diagnosis of LCX-related AMI was made from the findings of Gd-enhanced MRI and dual SPECT in both cases. In conclusion, Gd-enhanced MRI is able to correctly detect and locate LCX-related AMI as a positive image.