D3.308 - Kounis Syndrome: the allergic myocardial infarction

Background: Kounis syndrome is defined as the ocurrence of acute coronary syndrome (ACS) in the context of an allergic reaction, mediated by mast cell degranulation and platelet activation. Although rare, it is potentially life-threatening and should be considered in patients presenting with chest pain during anaphylaxis, with Hymenoptera stings reported as a possible trigger. A multidisciplinary collaboration between cardiology and allergology is essential for both allergy and ischemia management.

Case report: We report the case of a 68-year-old man with a history of non–ST-segment elevation myocardial infarction (NSTEMI) treated with percutaneous coronary intervention (PCI) and drug-eluting stent implantation in the left anterior descending artery (LAD) in 2022, hypertension, dyslipidemia and diabetes mellitus, for which he was under polypharmacy. He presented to the Emergency Department of his local hospital with generalized pruritus, lip edema, oropharyngeal tightness and syncope approximately 10 minutes after a wasp sting. Upon recovery of consciousness in the pre-hospital setting, he developed precordial chest pain. On admission, ECG and transthoracic echocardiography showed acute myocardial ischemia with moderately reduced ventricular function, and troponin T increased to 8,624 ng/L. Standard cardiac and supportive therapy was initiated as well as intravenous corticosteroid and clemastine. He was transferred to the intermediate cardiology unit for emergent coronary angiography in the context of anterior STEMI. Angiography demonstrated intra-stent LAD occlusion with extensive thrombus. Successful reperfusion of the proximal/mid LAD was achieved, with no significant residual stenosis. Dual antiplatelet therapy was initiated and an epinephrine autoinjector was prescribed at discharge on allergology recommendation. The clinical presentation was consistent with Kounis syndrome type III. The patient was referred for allergological evaluation, which confirmed wasp sensitization by specific IgE as well as positive skin prick and intradermal testing. Given the severity of the reaction, the case was discussed within the multidisciplinary team and pre-treatment with omalizumab prior to venom immunotherapy (VIT) was recommended and is currently pending approval.

Discussion: Kounis syndrome remains underdiagnosed and should be considered in any ACS accompanied by allergic manifestations. This case highlights the complex interplay between allergic and cardiovascular mechanisms and underscores the importance of early recognition, as management differs from conventional myocardial infarction, requiring simultaneous treatment of both cardiac ischemia and the allergic response. For patients with Hymenoptera venom-induced Kounis syndrome, VIT represents the only disease-modifying intervention to prevent recurrent systemic reactions and subsequent cardiac events. When performed in specialized centers with appropriate surveillance, VIT demonstrates a favorable safety profile. Increasing awareness of this syndrome is essential to improving patient outcomes and preventing recurrences.