The intramyocardial dissecting haematoma is an unusual rupture of the left ventricular wall, complicating acute myocardial infarction. The mechanism is an hemorrhagic dissection among the spiral myocardial fibres creating a neocavitation limited by the myocardium. It appears in 9% of left ventricular wall ruptures, complicating acute myocardial infarction. Diagnosis is often difficult and in most of the cases it is post-mortem. We present the case report of a 69 year old patient who suffered a posterolateral acute myocardial infarction treated with primary PTCA/Stent plus AAS, clopidogrel, unfractioned heparin bolus and GP IIb- IIIa inhibitors. In the following few hours he suffered this unusual form of cardiac rupture that took him into cardiogenic shock and finally led to his death. The pathophysiology, diagnosis and management of this lethal complication of acute myocardial infarction (90% mortality in the medically treated group) which is only effectively treated by surgery are also reviewed.