“Blocking potassium channels is precarious—a little blockade helps prevent arrhythmia, but too much can cause a lethal brand of ventricular tachycardia known by its French name “torsades de pointes,” or twisting of the points, due to its distinct appearance on the ECG. It is a malignant arrhythmia because it can lead to sudden death. This severe downside, along with the fact that most potassium blockers profoundly slow the heart rate, makes these drugs of little use to the athlete with AF.”