How to Read EKG Voltage

An electrocardiogram (EKG) strip measures two values: time and amplitude. Read from left to right, it depicts a wave formation over a specific amount of time. Examining the EKG strip from bottom to top evaluates the voltage of the waveforms. Voltage and amplitude are two terms that can be used interchangeably; however, it is more accurate to say amplitude than voltage. Amplitude is the measurement of how strong the electrical impulse is from heartbeat to heartbeat.

Things You'll Need

• Pre-existing EKG tracing Diagram of cardiac wave formations Ruler or calipers Pen and notebook paper

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Instructions

Measuring Time

• 1

  Begin by laying the EKG tracing strip out flat.

• 2

  Examine the EKG strip. The strip is segmented into a series of square blocks.

• 3

  Differentiate the bold line boxes from the regular weight line boxes. Each bold box measures 0.20 when reading the EKG strip from left to right or from bottom to top.

• 4

  Notice that the bold line blocks contain 25 individual smaller boxes. These smaller boxes measure .04 when reading the EKG from left to right or from bottom to top.

• 5

  Record the waveform values over time at this step, if desired, before calculating the amplitude values.

Measuring Amplitude

• 6

  Choose a measuring tool, either calipers or a ruler, and locate the waveform on the EKG in which you need to find the voltage or amplitude value.

• 7

  Begin measuring the waveform from where it begins a positive (upward) deflection from the isoelectric line.

• 8

  Measure the height of the waveform amplitude by counting the amount of large boxes from the beginning of the positively deflected waveform.

• 9

  Determine if the amplitude of the wave begins at the bottom of a bold box and terminates at the top of another bold box. If this is the case, you are done with the amplitude measurement. Record the value at this time in millimeters.

• 10

  Determine if the amplitude of the wave begins on a smaller size box inside a bold box or ends on a smaller size box. If this is the case, count each of the smaller boxes from the isoelectric line to the top of the measured waveform. Record the value at this time in millimeters.