Introduction to Arrhythmias

Author(s)	J.S.S.G. de Jong
Moderator	J.S.S.G. de jong
Supervisor
some notes about authorship

Morphologic criteria to differentiate between SVT vs. VT in a wide complex tachycardia. This is part of the wide complex tachycardia flowchart

Arrhythmias (non-normal heart rhythms) can be a challenge to understand, but with a systematic approach, diagnosis is often less difficult than it may appear at first.

A good stepwise approach to interpret the heart rhythm is to follow these steps:

• What is the ventricular heart rate?
  • >100 bpm = tachycardia
  • <60 bpm = bradycardia
  • are there extra beats? -> Ectopic Beats
• Cherchez le P, French for find the P waves.
  • Do you see P waves? Leads II and V1 are often most suitable to find P waves.
  • What is the rate of the P waves?
  • What is the P wave morphology?
• What is the relationship between P waves and QRS complexes?
  • Is there a 1:1 relation between P waves and QRS complexes? If not there may be AV dissociation due to a Ventricular Arrhythmias or AV block
  • Is every P wave followed by a QRS complex? And every QRS preceded by a P wave?
  • What is the PR interval and does it change?
• What is the QRS width?
  • If the QRS < 120ms (i.e. a narrow complex), then it is either a sinus arrhythmia, supraventricular rhythm or a junctional tachycardia. In tachycardias, this flowchart will lead to the right diagnosis.[1]
  • If the QRS > 120ms it is either a ventricular tachycardia or a supraventricular rhythm with additional bundle branch block. This is a challenging difficulty in arrhythmia diagnosis, therefore a flowchart might help, which incoporates the Brugada criteria for VT.[2] Another method to discriminate VT from SVT has been proposed by Vereckei et al.[3] In the editorial on that paper an excellent review is given on the subject by Dendi and Josephson.[4]
• What is the Heart Axis and did it change?
  • If the heart axis turns significantly when compared to the heart axis during sinus rhythm a ventricular origin of the rhythm is more likely.
• What is the clinical setting?
  • A wide complex tachycardia in a hemodynamically unstable 70-year-old man with previous myocardial infarction should be considered a ventricular tachycardia until proven otherwise
  • A wide complex tachycardia in a 24-year-old woman with recurrent spells of tachycardia that respond to vagal maneuvers is most likely an AVNRT with aberrant conduction.

References

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