The allergic myocardial infarction dilemma: is it the anaphylaxis or the epinephrine?

We highlight two distinct cases of myocardial infarction occurring concurrently with anaphylaxis at our centre in Singapore. The first case had cardiac symptoms and electrocardiogram changes concomitant with his anaphylaxis presentation, suggestive of Kounis syndrome, while the second case presented with anaphylaxis and only developed cardiac symptoms and electrocardiogram changes after treatment with intramuscular epinephrine, suggestive of epinephrine-induced myocardial infarction. Both these conditions are uncommon and under-recognised, and we review the current literature to compare the similarities and differences in their clinical manifestations, pathophysiology, and management. Kounis syndrome occurs secondary to mast cell degranulation ultimately resulting in coronary vasospasm, platelet activation and inflammatory response, whereas epinephrine causes platelet aggregation. Therefore, treatment priorities of Kounis syndrome are treatment of allergy, treatment of vasospasm, and treatment with anti-platelet therapy and revascularization if coronary plaques are present. For epinephrine-induced myocardial infarction, after epinephrine treatment is discontinued, considerations in management are re-vascularisation or pharmacotherapy. Further research will help with better understanding of both conditions and formulation of clinical management guidelines.