Abstract
Kounis syndrome is an allergic acute coronary syndrome (ACS) characterised by coronary artery spasm, plaque erosion/rupture or stent thrombosis caused by mast cell and other interacting cell activation. Although intracoronary imaging modalities can detect those ACS mechanisms, Kounis syndrome due to plaque rupture has rarely been reported using intracoronary imaging. We present the case of a woman in her 70s who developed Kounis syndrome as a result of plaque rupture detected with optical coherence tomography (OCT). She had non-ST-segment elevation ACS as a result of anaphylaxis to cefazolin. Coronary angiography revealed severe stenosis in the left anterior descending artery; angiographically undetectable plaque rupture was detected using OCT. OCT also revealed intraplaque neovascularisation, suggesting that the culprit plaque had been vulnerable. OCT can aid in understanding the underlying mechanisms of Kounis syndrome.