Tall 'T' waves are seen in-

Clinical features Mild to moderate hyperkalaemia (< 6.5 mmol/L) is usually asymptomatic. More severe hyperkalaemia can present with progressive muscular weakness, but sometimes there are no symptoms until cardiac arrest occurs. The typical ECG changes are shown on page 347. Peaking of the T wave is an early ECG sign, but widening of the QRS complex presages a dangerous cardiac arrhythmia. However, these characteristic ECG findings are not always present, even in severe hyperkalaemia. Ref Davidson 23rd edition pg 363