Why do you need to know about the generation of electrical activity in a cell and the effect of electrolytes on the electrocardiogram (ECG) or rhythm strip? Because, before you can understand what a rhythm strip does, you need to know how it gets its information. Electrolytes are the means by which the cell develops “electricity.” You also need to know about electrolytes because imbalances can cause life-threatening problems. For example, if you knew that peaked, sharp T waves were a sign of hyperkalemia (elevated potassium), or that a prolonged QT interval could be a sign of hypocalcemia or hypomagnesemia, you might avert a serious arrhythmia. It takes only minutes in some cases to go from peaked T waves to asystole. (By the way, pacers do not work in hyperkalemia!) A little knowledge about electrolytes and their effects on the ECG patterns can save the patient—and you.
To understand why the ECG is altered by an electrolyte abnormality, we will review the way in which the myocardial cell becomes polarized and depolarized, and the biochemical mechanisms that allow the cell to contract. We will try to make the concepts as painless as possible, so bear with us. This is intended to be only a very basic discussion of the topic, which you can supplement with a good physiology textbook as needed.