6 Stages to Analyse ECG Rhythm

This simple technique can be used to analyse a rhythm strip.

  • Stage 1: Is there electrical activity?

    If you cannot see any electrical activity, check your patients’ pulse, if no pulse follow life support algorithm.

    If there is a pulse, then check your monitor leads are all connected.

  • Stage 2: What is the ventricular rate?

    Calculate the rate using the R waves that occur within 30 large squares (6 seconds) and multiply by 10.

    This method works if the rhythm is regular or irregular.

  • Stage 3: Is the ventricular activity regular or irregular?

    To decide if a patient’s heart rate is regular, measure the distance between two consecutive R waves (R-R interval) and compare it to the other R-R intervals on the strip.

    TOP TIP – mark a few R-R intervals on a blank piece of paper and move it along the strip. If the rhythm is regular, the subsequent R waves should match the marks.

    Irregular rhythms are broadly divided in two categories:

    • Irregularly irregular – disorganised with no pattern.

    • Regularly irregular – the irregularity has a pattern to it.

  • Stage 4: Narrow or broad QRS?

    • A narrow QRS complex is when the width of the QRS is <0.12s (3 small squares)

    • A broad QRS complex is when the width of the QRS is >0.12s (3 small squares)

    Narrow complex QRS will happen when the electrical impulse is conducted down through the bundle of His and through the purkinje fibres to the ventricles.

    A broad QRS may originate from the myocardium of the ventricles and spread slowly across the myocardium. This can also be the case in bundle branch block – when there may be rapid conduction through the intrinsic conduction system in one ventricle and then spread to the other ventricle through the myocardium.

  • Stage 5: Is atrial activity present?

    Atrial activity can be represented by a P wave.

    If atrial activity is present, describe it. Look at the shape and direction of the P wave. In atrial flutter, you may see a ‘saw tooth’ pattern along the isoelectric line which is generally regular.

    Occasionally it can be challenging to identify as the P wave can be obscured by QRS or T waves. For example in atrial fibrillation (AF) it will not be possible to see P waves due to the random depolarization in both atria, but you may notice P waves in some of leads on a 12 lead ECG.

  • Stage 6: Does atrial activity relate to ventricular activity?

    When there is atrial activity present, describe how it relates to the ventricular activity (QRS).

    For example, is every P wave followed by a QRS complex?

    Is the interval between them regular (PR interval) or is there variation?

    When there is no relationship between atrial activity and ventricular activity this can be called atrioventricular dissociation.