A male patient in his early 60s was referred to the cardiology department for evaluation of a persistent apical ventricular thrombus following a myocardial infarction. Transthoracic echocardiography could not rule out the presence of an apical thrombus, leading to the intravenous administration of the contrast agent sulphur hexafluoride (SonoVue). The patient quickly exhibited signs of anaphylaxis accompanied by haemodynamic shock, resulting in cardiac arrest. He was successfully resuscitated with no significant secondary neurological impairment. According to the European Medicines Agency, anaphylactic reactions to the contrast agent sulphur hexafluoride (SonoVue) occur in approximately 1 in 10 000 cases. To our knowledge, this represents the first case of hypersensitivity to sulphur hexafluoride (SonoVue) confirmed by positive in vitro testing.