Giant negative T waves after treatment of severe hyperkalaemia

We present the case of a 79-year-old female with severe hyperkalaemia and severe prerenal insufficiency due to dehydration and nephrotoxic medications, including spironolactone. The ECG showed AV nodal rhythm and tented T waves. After treatment with fluids, insulin, polystyrene sulphonate and sodium bicarbonate, the serum potassium level and kidney function normalised. Several days later, she developed QT prolongation with giant negative T waves without signs of ischaemia. In this report, we review the effect of hyperkalaemia on cardiac ion channel function and the associated changes on the ECG. In addition, the causes and mechanisms of giant negative T waves are discussed.