Tamoxifen-induced QT interval prolongation.

We report on a case of tamoxifen-induced QT interval prolongation in a 56-year-old-female patient with hormone-dependent carcinoma of the right breast, stage T2N0M0, grade 3 and HER-2 negative. Partial mastectomy with axillary lymph node excision was performed in July 2007 with adjuvant hormonal and radiation therapy. This case highlights the risk of tamoxifen causing depression of electrical impulse in the sino-atrial node, leading to symptomatic sinus bradycardia with prolonged QT interval. It indicates the necessity of regular monitoring of patients undergoing tamoxifen treatment. ECG should be performed not only before and after, but also during treatment. with an average duration of treatment of 5 years, we would advise an annual ECG for asymptomatic patients. In the presence of symptomatic sinus bradycardia, constant monitoring is necessary. We also highlight potential drug interactions, between tamoxifen and acitretin and the need to be aware of drugs which may induce QT interval prolongation.