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How to read EKG printouts

Updated July 20, 2017

An EKG, also known as an electrocardiogram (ECG), generates a graphic representation of the cardiac cycle. An EKG measures the contraction and relaxation of the heart's activity. Electrodes, which are placed on the body's surface, pick up the heart's activity and carry the heart's impulse to a continuous running graph. Interpreting an EKG's cardiac activity should be left to medical professionals. However, with the correct instruction, anyone can read and interpret an EKG printout.

Obtain EKG graphic printout.

Inspect EKG printout. EKG results are plotted on graph paper. The graph is designed with 5mm squares in bold, and 1mm squares that are situated within the 5mm squares. On the horizontal axis, each 5mm square represents 0.2 second. The 1mm squares represents 0.04 second. An EKG result that is not plotted on graph paper cannot be read properly.

Determine the points that spike above, or below the horizontal waveform on the EKG. Normal heart activity will show 5 points that spike above, or below the horizontal plane. The points of each spike are plotted in sequence with P, Q, R, S and T. The first spike in the reading is labelled P. The last spike in the reading is labelled T. In the case of abnormal heart activity, soft curves may be displayed rather than sharp, pointed spikes. In this case, find the peak of each curve and label accordingly.

Find the P wave. The P wave represents the beginning of atrial contraction.

Find the QRS complex. The QRS complex consists of three points and represents the ventricle changing its normal electrical charge immediately before ventricular contraction.

Find the T wave. The T wave is the last point on the complex and represents the ventricle returning to its normal electrically charged state.

Determine the heart rate. The heart rate is calculated by counting the number of 5mm squares between two succeeding QRS complexes, and dividing that number into 300.

Determine the P, Q, R, S and T locations on the graph. Normal sinus rhythm will consistently show sharp, upright P waves.

Use the 1mm squares on the graph to measure the length of time between the P-R waves. Normal sinus rhythm occurring in the P-R waves should measure between 0.12 to 0.20 second.

Measure the length of time between the Q, R and S wave. Normal sinus rhythm occurring in the QRS complex should measure between 0.4 to 0.10 second.

Calculate the heart rate by counting the number of 5mm squares between two succeeding QRS complexes, and dividing that number into 300. A normal heart rate is between 60 to 100 beats per minute.

Things You'll Need

  • EKG printout
  • Pencil/pen
  • Calculator
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About the Author

Jeremy Heck has been working as a freelance writer since 2004. Publications include, "Dangerous Ammonia Levels in Humans & Animals," "How to Brew Sierra Beer," and "Skin Irritation in Pugs." He received his B.A. in English from the University of California, Davis in 2004.