Tu, CM et al. Trastuzumab (Herceptin)-associated cardiomyopathy presented as new onset of complete left bundle-branch block mimicking acute coronary syndrome: a case report and literature review. Am J Emerg Med. 2009 Sep;27(7):903.e1-3.
The clinically most important side effect of Herceptin is cardiotoxicity, which is reported in 2.6% to 4.5% of patients receiving trastuzumab alone and in as many as 27% of patients when trastuzmab is combined with an anthracycline in metastatic disease.