Trastuzumab, a humanized monoclonal antibody targeting the HER2 receptor used in treatment for metastatic breast cancer, is a typical biological agent associated with cardiac toxicities such as decreased left ventricular ejection fraction, particular in combination with anthracycline.[5,24] While lapatinib, a tyrosine kinase inhibitoralso targeting HER2, has been associated with QTprolongation.[3] As a chimeric mouse/human antibody, cetuximab showed transient and reversible effects on TNI ultra and ECG in our study. The gene discussed is ERBB2; the disease is breast cancer.