It is easy to be confused by the variable terminology used for tachycardias arising above the ventricles: the term supraventricular tachycardias (SVT) could be applied to all such arrhythmias, including atrial fibrillation and flutter.

It is often used as an overall label for patients with narrow complex tachycardias who have not yet been fully assessed. In common parlance in the UK, the term includes all atrial and junctional tachycardias but excludes atrial fibrillation.

Atrial flutter is a specific type of re-entry tachycardia closely linked to atrial fibrillation but will be covered here with other re-entry tachycardias.

Narrow complex tachycardias are always supraventricular because a normal QRS width indicates that conduction is down the bundle of His in the normal antegrade manner. Sometimes SVT can present as a broad complex tachycardia, if ventricular depolarisation is triggered by antegrade conduction down an accessory pathway, or in the presence of pre-existing bundle branch block.

Learning Bite

Narrow complex tachycardias are always supraventricular but not all supraventricular tachycardias are narrow complex.

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