Mitral regurgitation due to papillary muscle dyssynchrony during trastuzumab treatment

Trastuzumab is a monoclonal antibody used for the treatment of metastatic breast carcinoma in women whose tumors overexpress the human epidermal growth factor receptor-2. Although trastuzumab is generally well tolerated, cardiac toxicity has occurred as a rare but potentially serious complication that limits its use in some patients. In this study, we detected new-onset mitral regurgitation in trastuzumab-treated patients. To our knowledge, there is no report or survey on new-onset mitral regurgitation during this treatment. We discussed the possible reasons for this newly described side effect of the drug in the light of left ventricular longitudinal global strain and papillary muscle dyssynchrony of the patient by detecting two-dimensional speckle tracking echocardiography.