Which of the following 9 patients had hyperkalemia? Can you estimate how high their serum potassium was based on the ECG? Jesse MacLaren guides us through 9 ECGs underscoring the fact that while the ECG cannot rule out hyperkalemia, significant hyperkalemia often produces ECG changes in the heart rate (bradycardia, junctional rhythm), electrical conduction (PR prolongation or loss of P waves, QRS prolongation, pacemaker delays), and ST/T waves (Brugada phenocopy, peaked T waves that are narrow/pointy) that can be easily recognized. He suggests when you might pull the trigger on giving empiric calcium treatment based on the ECG finding in this month's ECG Cases...