His ECG reveals sinus rhythm with a rate of 88, a normal PR interval (0.14 seconds) and a QRS duration of 0.10 sec. The deep S waves in leads V1-V3 are suggestive of LVH. There is a prominent U wave that is seen best in leads V2-V5 and the QT/U interval is significantly prolonged (580 msec). Note that the amplitude of the U wave is equal to or exceeds that of the T wave in many leads. This tracing is highly suggestive of hypopotassemia and at the time it was recorded, the patient's serum potassium was 2.6 mM..