What does the vertical axis on an EKG graph represent?

The vertical axis on an EKG graph represents gain or amplitude. This indicates the strength of the electrical signals being recorded from the heart. Specifically, the height of the waves (P, QRS complex, T wave) corresponds to the voltage or electrical activity produced by the heart's depolarization and repolarization processes. This measurement provides important information about how strongly the heart is contracting and can help identify various cardiac conditions.

The other aspects of the EKG, such as the representation of time, heart rate, and electrical conduction, are denoted differently. Time is represented on the horizontal axis, where each small square indicates a specific duration, helping to assess the timing of the heart's electrical activity. Heart rate can be derived from the distance between the peaks of the waves in a given time interval, but it is not specifically represented on the vertical axis. Electrical conduction relates to the pathway of the electrical impulses through the heart, but this is not measured by the amplitude shown vertically on the graph.