An unexpected ECG finding

A woman in her 60s presented to hospital for a second cycle of postoperative adjuvant chemotherapy with docetaxel and cyclophosphamide, having received her first cycle 19 days previously. She had received a diagnosis of left breast cancer six weeks earlier, for which she had undergone modified radical mastectomy. She had no other medical history.

Results of cardiac function tests (electrocardiogram (ECG), troponin I, brain natriuretic peptide (BNP), and transthoracic echocardiogram) were in the normal range on all evaluations at the start of her first cycle of chemotherapy. Before starting the second cycle, she underwent an ECG (fig 1) as standard procedure in the oncology clinic. Abnormal findings were seen on the ECG. The patient did not report any chest pain. Repeat troponin I and BNP test results were within normal ranges and repeat transthoracic echocardiogram showed normal biventricular functions with a left ventricular ejection fraction of 62% (no change from before) and no …