Acute coronary syndromes exhibit rapid and variable ischemic dynamics, with consecutive electrocardiographic changes, sometimes in the absence of angina.We report the case of a 50 year-old man, admitted for suspected angor de novo, asymptomatic upon admission, and with a normal electrocardiogram. After a few hours, the repeated electrocardiogram displays biphasic T waves in V2–V4, in the absence of symptoms, and then marked ST elevation in the same territory, without chest pain. The patient is transferred with a STEMI diagnosis, and the coronary angiography documents a critical sub-occlusive stenosis in the proximal segment of the left anterior descending artery (LAD), for which a drug-eluting stent is inserted, with a favourable evolution.Wellens syndrome is defined by characteristic electrocardiographic changes of T waves in leads V2–V4, occurring in the context of unstable angina, usually without pain. They express a critical stenosis in the proximal LAD artery. Recognition of the Wellens syndrome is crucial, as these “pre-infarction” changes tend to evolve, sometimes rapidly, to an extensive anterior myocardial infarction. The rapid and unpredictable ischemic electrocardiographic changes make this case remarkable, as they occur in an asymptomatic patient with unstable angina (angor de novo), thus underlining the need for careful supervision in such patients.