Six simple steps for reading EKGs

By Michael Spinner

As with reading a chest X-ray, the key to reading EKGs is to have a systematic method that you follow each and every time. While there are a number of different methods out there, the following 6-step approach for reading EKGs is particularly easy and effective:


  1. Rate – is it slow, normal, or fast?


Slow/brady – HR <60 bpm (>5 large blocks between R waves)

Normal – HR 60-100 bpm (3-5 large blocks between R waves)

Fast/tachy – HR >100 bpm (<3 large blocks between R waves)

  1. QRS interval – is it narrow or wide?


Narrow – QRS interval <0.12 seconds (<3 small blocks)

Wide – QRS interval >0.12 seconds (>3 small blocks)


  1. Rhythm – is it regular or irregular?


Regular – RR interval is consistent throughout EKG strip

Irregular – RR interval is not consistent; may be further described as:

–regularly irregular (e.g. every other beat dropped in 2° heart block)

–irregularly irregular (e.g. no noticeable pattern as in atrial fibrillation)

–single irregularity (e.g. a single PAC or PVC but otherwise regular)


  1. P waves – are there P waves before each QRS?


  1. Axis – is it normal or deviated to the right or left?


Normal: positive in lead I, positive in aVF

Right deviation: negative in lead I, positive in aVF

Left deviation: positive in lead I, negative in aVF


  1. ST changes – is there ST elevation or depression? When reading a 12-lead EKG, practice looking for ST changes in the following groupings:


First, look at the lateral leads/CFX distribution – I, aVL, V5, V6

Second, look at the inferior leads/RCA distribution – II, III, aVF

Lastly, look at the anterior leads/LAD distribution – V1-V4


I           aVR       V1       V4

II          aVL        V2       V5

III         aVF        V3       V6


Although by no means comprehensive, following these six simple steps will help you to correctly identify the majority of arrhythmias and determine the presence of coronary ischemia or infarction. Indeed, the following six tachyarrhythmias are easily distinguished on the basis of the first four steps alone!


Tachyarrhythmia Rate QRS Rhythm P waves
Sinus tachycardia Fast Narrow Regular Yes
SVT (AVNRT) Fast Narrow Regular No
Atrial fibrillation Fast Narrow Irregular No
Atrial flutter Fast Narrow Regular Sawtooth
Ventricular tachycadia Fast Wide Regular No
Ventricular fibrillation Fast Wide Irregular No

Try practicing this 6-step method for reading EKGs on your cardiology and emergency medicine rotations. I hope it will serve you well!







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