Anticancer chemotherapy continues to advance. One of the new therapeutic orientations is the targeting of receptors which regulate the tumoral activity of the malignant cells. Trastuzumab is the prototype of these new chemotherapeutic agents. It is a monoclonal antibody directed against a tyrosine kinase receptor related to the EGF (Epidermal Growth Factor): the HER receptor. This receptor is also present in myocardial cells. Blockade of this myocardial receptor could cause severe cardiotoxicity about which some information is available but which continues to pose many problems. This data should be known as cardiologists will be consulted before the prescription of Trastuzumab and could also be confronted by these cardiotoxic effects. Precise physiopathological explanations have already been published from experimental studies which show the deleterious effects of the suppression of certain HER receptors on the heart. These studies not only explain all the clinical signs of Trastuzumab's cardiotoxicity but also suggest ways of preventing and treating some of these cases of cardiac failure.