In hyperkalamia-

Hyperkalemia is defined as a plasma potassium level of 5.5 mM, Early ECG changes of hyperkalemia, typically seen at a serum potassium level of 5.5-6.5 mEq/L, include the following: Tall, peaked T waves with a narrow base, best seen in precordial leads Shoened QT interval ST-segment depression At a serum potassium level of 6.5-8.0 mEq/L, the ECG typically shows the following: Peaked T waves Prolonged PR interval Decreased or disappearing P wave Widening of the QRS Amplified R wave At a serum potassium level higher than 8.0 mEq/L, the ECG shows the following: (reference : harrisons principles of internal medicine,19E, page 308,310) Absence of P wave Progressive QRS widening Intraventricular/fascicular/bundle branch blocks Ref Davidson 23rd edition pg 364