Trastuzumab is a recombinant humanized monoclonal antibody used for the 
treatment of advanced breast cancer. It improves survival and increases response 
to chemotherapy. The major side effect of trastuzumab is cardiotoxicity 
manifesting as a reduction in left ventricular systolic function, either 
asymptomatic or with signs and symptoms of heart failure. Although reversible in 
most cases, cardiotoxicity frequently results in the discontinuation of 
trastuzumab. The objective of this review is to summarize facts about 
trastuzumab-induced cardiotoxicity and to highlight the areas of future 
investigations. We searched PubMed for trials involving trastuzumab used as an 
adjuvant therapy for breast cancer, including the metastatic breast cancer 
setting, and focused on cardiotoxicity.