The electrocardiogram can pick up all sorts of electrolyte abnormalities. The most common abnormalities revolve around high and low levels of potassium and calcium. Magnesium derangements typically have nonspecific findings. How do you keep things straight? To make things more complicated, multiple electrolyte derangements can occur at the same time, making ECG interpretation challenging.
Thanks to Dr. Steve Field (Resident at Resurrection EM program) for the idea and card on electrolytes and ECG changes. Also take a look at Life In the Fast Lane’s extensive review of ECG abnormalities and their causes.
PV Card: ECG Manifestations of Electrolyte Imbalance
Adapted from 
Go to ALiEM (PV) Cards for more resources.
- Diercks D, Shumaik G, Harrigan R, Brady W, Chan T. Electrocardiographic manifestations: electrolyte abnormalities. J Emerg Med. 2004;27(2):153-160. [PubMed]