Abstract: A patient with atrial fibrillation admitted for an elective electrical cardioversion. He was given an amiodarone bolus that triggered Kounis syndrome with cardiac arrest (CA) and refractory shock needing mechanical support with ECMO and refractory hypoxemia that improved with inhaled nitric oxide. Allergy to amiodarone was later confirmed.IntroductionAtrial fibrillation is the most common supraventricular arrhythmia. Some studies revealed benefits in maintaining sinus rhythm in patients with AF, especially in young patients (1). Electrical cardioversion is an option when pharmacological cardioversion fails.Kounis syndrome (2) is a rare disease that consists of an allergic coronary syndrome, it usually presents as an ST-segment elevation acute coronary syndrome. It requires emergent coronary angiography with intracoronary vasodilators infusion and angioplasty if required. We present an unusual form of Kounis Syndrome triggered by endovenous amiodarone that underwent with cardiorespiratory arrest and refractory shock due to the vasospasm. In this situation mechanical circulatory support with ECMO was necessary to ensure tissue perfusion. Specifically, in the in-hospital cardiac arrest, ECMO implantation is an expanding therapy and is showing promising results.