We report a 54-year-old woman with an stage IIA (T2N0M0) RE and RP negative and 
HER2-positive ductal invasive breast cancer who developed a reversible 
cardiotoxicity associated with chemotherapy. After surgery, she received four 
cycles of doxorubicin and cyclophosfamide. Later, she used paclitaxel and 
trastuzumab. At the 7th cycle of trastuzumab, she had symptoms of heart failure 
with left ventricle ejection fraction = 59%. Trastuzumab dosage was reduced in 
25%, and heart function progressively improved. Two years after her discharge, 
the patient remains asymptomatic. Systolic function of the left ventricle was 
normal before the initial dosis of trastuzumab, but significantly worsened 
following the beginning of drug administration. Moreover, a clear improvement of 
heart function was observed soon after the daily dose of trastuzumab was 
reduced. Better knowledge of risk factors for cardiotoxicity related to 
chemotherapy, and longstanding surveillance with serial echocardiograms can 
avoid more severe cardiotoxicity by chemotherapy.