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
A 78-year-old man with advanced renal disease has the ECG shown in Figure below (lead II). What is the diagnosis? 
Select and explain. 
A. hyperkalemia, B. hypercalcemia, C. hypernatremia, D. pericarditis
A: hyperkalemia
Answer: A: hyperkalemia 
Explanation: No atrial activity is detected. The ventricular rate is slightly irregular. Beat number 4 is a ventricular premature contraction. The T waves are tall and markedly peaked. This type of T wave is characteristic of hyperkalemia, as is absence of visible atrial activity.The potassium level was 8.2mmol/L.