This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S., Subject name: Medicine
ECG finding in Hypokalemia is 
Select and explain. 
A. Absent P wave, B. Prominent U wave, C. ST elevation, D. T wave tnting
B: Prominent U wave
Answer: B: Prominent U wave 
Explanation: (Prominent 'U' wave): (439-Davidson 21st)HyperkalemiaHypokalemia1. Earliest changes increased T wave amplitude**- Early changes flattening or inversion of T wave **2. Prolong PR interval and QRS duration- Prominent 'U' wave**3. AV conduction delay, loss of P wave- ST segment depression, prolong QU interval4. Sin wave pattern** (progressive widening of the QRS complex merging with T wave)- Prolonged PR interval, decreased voltage and widening of the QRS complex** Prolong QT interval - Hypocalcemia, SAH** Short QT interval - Hypercalcemia, digitalis glycosides