Hypokalaemia
K + < 2.5 mmol/L:
- Prominent U wave develops with apparent prolongation of the QTc
- Flat or diphasic T waves
- ST segment depression
As K + falls further:
- PR interval prolongs
- Sinoatrial block may occur
Hyperkalaemia
As K + rises:
- Tall peaked T waves, best seen in precordial leads
- Prolongation of QRS duration
- Prolongation of PR interval
- Disappearance of P waves
- Wide bizarre diphasic QRS complexes (sine waves)
- Eventual asystole
