A 64-year-old man with heart failure is recently started on 80 mg/day of furosemide. He now feels weak and tired, but notes that his heart failure symptoms have improved. There is no change in his urine output and he gets a good diuretic response every time he takes his furosemide.Select the characteristic ECG findings.

Hypokalemia results in prolongation of the QU interval. The delayed repolarization in hypokalemia is best expressed at QU rather than QT prolongation since it can be difficult to separate the T wave from the U wave. In severe cases, the ST segments become depressed. Quinidine, even in therapeutic doses, can cause similar ECG findings. This is felt to be a risk factor for ventricular arrhythmias, including Torsades des pointes.