Early isonitrile SPECT in acute myocardial infarction: feasibility and results before and after fibrinolysis

Early 99Tcm-labelled methoxy-isobutyl-isonitrile (MIBI) SPECT was performed in 14 patients with suspected acute myocardial infarction (AMI). The radiopharmaceutical was administered immediately upon admission to the intensive care unit and before any diagnostic confirmation. Then, if decided, thrombolytic therapy was started. Cardiac imaging was performed 1 h later, and as there is no significant re-distribution, the pictures still showed the pre-treatment MIBI uptake. In three cases acute myocardial infarction was not confirmed. For one of them, the result was normal and this patient was ultimately considered to have had a transient ischaemic event. The two other cases had acute chest pain with a previous history of myocardial infarction (MI) and a pathological MIBI SPECT. In the 11 cases with confirmed first AMI significant perfusion defect was seen. For every patient a new MIBI injection with a control SPECT was repeated 72 h after admission. Eight patients were seen 1 h 15 min to 3 h 15 min after the onset of chest pain and had thrombolytic therapy. Defects were always in agreement with coronary angiography and 2D echocardiography performed in the same period. After thrombolysis, control SPECT showed no recovery in three cases, partial recovery in four, and nearly complete recovery in one. Using this technique, it was then possible to get high quality myocardial perfusion imaging without delaying treatment of AMI. This preliminary series suggests that MIBI SPECT may be useful in accurately showing the size and location of the immediate perfusion defect, and in assessing the response to emergency therapy of AMI, especially thrombolysis.