While cardiac toxicity due to chemotherapeutic agents is rare, it is a major cause of mortality. The most frequent cardiac toxicity is myocardial cell damage and particularly left ventricular ejection fraction reduction, which is due to anthracycline, progresses irreversibly to cardiac failure. However in trastuzumab associated cardiotoxicity, contractility dysfunction occurs in myocytes and the reduction of ejection fraction is reversible, since there is no cell damage. This cardiotoxicity which is due to transtuzumab is quite rare and although more rarely, it may also develop in patients using lapatinib through a similar mechanism. Nevertheless, cardiac arrhythmia without a left ventricular dysfunction is not reported in the literature. In this article, we aimed to present an electrocardiography confirmed supraventicular tachycardia attack which had developed after the first dose of lapatinib in a metastatic breast cancer patient. We want to discuss the development of an isolated supraventricular tachycardia, without a left ventricular dysfunction, in patients who do not have a history of hypertension, cardiac disease or any sign of cardiotoxicity, through using the cardiotoxicity related information in the literature.

Keywords: lapatinib, trastuzumab, antiHer2 treatment, cardiotoxicity, arrhythmia, tyrosine kinase inhibitors