In an ECG tracing, how much time is represented by 5mm on the horizontal axis?

In an ECG tracing, the horizontal axis represents time, and the standard calibration is that 1 millimeter (mm) on the tracing corresponds to 0.04 seconds (40 milliseconds). Therefore, when you have a measurement of 5 mm on the horizontal axis, you multiply the measurement in mm by the time per mm.

Calculating it:

5 mm x 0.04 seconds/mm = 0.20 seconds.

This means that 5 mm represents 0.20 seconds in an ECG tracing, which is consistent with the typical standards used in interpreting ECGs. Understanding this measurement is vital for accurately analyzing the timing of the cardiac cycle as depicted in an ECG. This ability to interpret the temporal relationships between various components of the ECG is essential for diagnosing and managing various cardiac conditions.