When Allergy Strikes the Heart: Kounis Syndrome and Cardiac Arrest

Introduction: Kounis syndrome is an acute coronary syndrome precipitated by allergic or hypersensitivity reactions and mediated by the release of inflammatory substances that affect the coronary circulation. In spite of increasing awareness of this syndrome, it remains underdiagnosed, particularly in young patients without conventional cardiovascular risk factors. Case description: We report the case of a patient with recurrent Kounis syndrome presenting with two distinct acute coronary syndromes within one month, initially classified as myocardial infarction with nonobstructive coronary arteries and subsequently recognised after angiographic documentation of transient coronary vasospasm. A 28-year-old man with a history of non-steroidal anti-inflammatory drug (NSAID) hypersensitivity presented with acute chest pain shortly after NSAID intake. Electrocardiography showed ischemic changes, and cardiac biomarkers showed a modest elevation. Coronary angiography revealed severe, reversible multivessel coronary artery spasm in the absence of structural coronary disease, consistent with type I Kounis syndrome. During the procedure, the patient developed ventricular fibrillation, successfully treated with electrical defibrillation and intracoronary nitrates. Left ventricular function fully recovered, and the patient was discharged with strict avoidance of NSAIDs. Subsequent allergological evaluation confirmed NSAID hypersensitivity. Conclusion: This case highlights that type I Kounis syndrome may present as a severe acute coronary syndrome complicated by malignant ventricular arrhythmias. A careful allergological and pharmacological history is essential for accurate diagnosis, guide management, and prevent recurrent potentially fatal events. Learning points: Kounis syndrome should be considered in young patients presenting with acute coronary syndromes and non-obstructive coronary arteries, especially when symptoms occur after exposure to drugs or allergens.Type I Kounis syndrome, despite the absence of structural coronary artery disease, may be complicated by life-threatening ventricular arrhythmias, underscoring that it is not always a benign condition.A detailed allergological and pharmacological history is crucial in patients with suspected myocardial infarction with nonobstructive coronary arteries to avoid misdiagnosis, prevent repeated exposure to triggering agents such as non-steroidal anti-inflammatory drugs, and guide appropriate multidisciplinary management.