Hypercalcaemia

This teaches the importance of making sure that each ECG has an ST segment.

In hypercalcaemia, there is none, so the J point merges with the T wave and there is no flat bit (ST segment) in between.




This is because phase 2 (aka PLATEAU phase) of the action potential is shortened.



So, 0 is blast-off/depolarization (Sodium channels open)
1 is the notch (sodium channels close)
2 is plateau (calcium channels open, outward potassium channels open)
3 is repolarization (calcium channels close, potassium channels stay open)
4 is rest/electrically neutral