Hyperkalemia

Hyperkalemia causes a number of affects on the EKG and can lead to fatal arrhythmias. There tends to be a progression of EKG changes, though the progression can occur incredibly rapidly. Predictors of adverse events (in order) are bradycardia, junctional rhythm, and a widened QRS. Almost all patients with adverse events have EKG abnormalities. Hyperkalemia is a sodium channel blocker and can cause right axis deviation. There have been descriptions about the potassium levels correlating with the 'steps' of hyperkalemia changes, though this is not reliable on an individual patient level. The 'steps' are:

peaked T waves
prolonged PR segment
loss of P waves
bizarre QRS complexes
sine wave

Peaked T waves are rather symmetric, tall, and 'pointy' T waves. They differ from hyperacute T waves in their thin and pointy morphology. Note that these T waves are close to, the same size as, or even bigger than some of the QRS complexes. Note also how flat the ST segment typically becomes with abrupt initiation of the T wave.

Hyperkalemia can cause a large variety of changes, however. It can cause various bradyarrhythmias and blocks as well. The wide QRS complexes can become >200ms, which is particular more towards a metabolic/toxicologic etiology of wide QRS complexes and not VT. As the QRS becomes more wide, development of extreme right axis deviation can occur (may also be seen with sodium channel blocker toxicity or severe acidosis). This wide variety of QRS altering changes can be confused with other etiologies, such as Brugada syndrome and OMI.

Slow junctional rhythm with peaked T waves

Brugada-like appearance, though resolved with administration of calcium

Examples:

Sine wave