An Unusual Presentation of QT Prolongation

A 55-year-old woman with a history of chronic bronchitis, Clostridium difficile colitis, and alcohol and tobacco abuse was admitted with altered mentation, hyponatremia, and necrotizing right-upper-lobe pneumonia. She was started on cefepime and vancomycin; metronidazole was added for colitis. A resting electrocardiogram (ECG) showed sinus tachycardia with a QS pattern in the precordial leads, normal intervals, and small T-wave inversions in leads V5 and V6. Four days later, significant changes in her baseline telemetry rhythm prompted a repeat 12-lead ECG; the patient's pulse rate was 75 beats/min with a QT interval of 720 ms and QTc of 746 ms (Fig. 1). Her troponin T level was