<prompt> All of the following are the electrocardiographic features of severe hyperkalemia except-Peaked T wavesPresenceof U wavesSine waves patternLoss of P waves  <response>: Effects of hyperkalaemia on the ECG Serum potassium 5.5 mEqL is associated with repolarization abnormalities: Peaked T waves usually the earliest sign of hyperkalaemia Ref Harrison 20th edition pg 1456 Serum potassium 6.5 mEqL is associated with progressive paralysis of the atria: P wave widens and flattens PR segment lengthens P waves eventually disappear Serum potassium 7.0 mEqL is associated with conduction abnormalities and bradycardia: Prolonged QRS interval with bizarre QRS morphology High-grade AV block with slow junctional and ventricular escape rhythms Any kind of conduction block bundle branch blocks, fascicular blocks Sinus bradycardia or slow AF Development of a sine wave appearance a pre-terminal rhythm Serum potassium level of 9.0 mEqL causes cardiac arrest due to: Asystole Ventricular fibrillation PEA with bizarre, wide complex rhythm Warning! In individual patients, the serum potassium level may not correlate closely with the ECG changes. Patients with relatively normal ECGs may still experience sudden hyperkalaemic cardiac arrest. Ref Davidson 23rd edition pg 463 