<prompt> The first change takes place in ECG in hyperkalemia isTall T waveShort PR intervalProlong QT intervalWidening of QRS complex  <response>: A Tall T wave Effects of Hyperkalemia on the ECG: Serum potassium 5.5 mEqL is associated with repolarization abnormalities: Peaked T waves usually the earliest sign of Hyperkalaemia Vital for assessing the physiologic significance of the hyperkalemia ECG findings generally correlate with the potassium level, but potentially life-threatening arrhythmias can occur without warning at almost any level of hyperkalemia In patients with organic heart disease and an abnormal baseline ECG, bradycardia may be the only new ECG abnormality ECG changes have a sequential progression, which roughly correlate with the potassium level Early ECG changes of hyperkalemia, typically seen at a serum potassium level of 5.5-6.5 mEqL, include the following: Tall, peaked T waves with a narrow base, best seen in precordial leads Shortened QT interval ST-segment depression At a serum potassium level of 6.5-8.0 mEqL, 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 mEqL, the ECG shows the following: Absence of P wave Progressive QRS widening Intraventricularfascicularbundle branch blocks Progressively widened QRS eventually merges with the T wave, forming a sine wave pattern. Ventricular fibrillation or asystole follows. 