A 53-year-old male complaining of chest pain was admitted to our hospital with suspected acute myocardial infarction (AMI). Emergent coronary angiography (CAG) determined a totally occluded middle right coronary artery (RCA). Thrombus aspiration was conducted, followed by intravascular ultrasound (IVUS) imaging. Diffuse intima plus media thickness was identifed at the obstruction site and a thrombus was observed proximally to the occlusion site on IVUS. Following isosorbide dinitrate (ISDN) administration, dilatation of the RCA was confrmed. IVUS study indicated the luminal dilatation was achieved by the release of the diffuse intima plus media thickening. Of note, plaque volume showed no signifcant difference after administration of ISDN at any vessel site. These results clearly show that luminal dilatation and vessel dilatation were achieved from the redistribution of plaque volume (intima plus media). A follow-up CAG showed no signifcant stenosis in the RCA. After a provocation test using methylergometrine maleate, the RCA was totally occluded at the very site of the initial event. The involvement of vasospasm as a cause of AMI in the present case was doubly confirmed with characteristic IVUS images of vasospasm in the acute phase and with a provocation test at follow-up.
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