Supraventricular arrhythmias (atrial tachycardia, flutter, AVNRT, AVRT)

1. Big picture

Supraventricular tachycardias (SVTs) are tachyarrhythmias that originate above the His bundle: atria, atrioventricular (AV) node, or accessory pathways. In exams, they usually present as sudden palpitations with a regular narrow QRS tachycardia.

The practical approach is:

Tachycardia on ECG
↓
Is the patient unstable?
    Yes → synchronized electrical cardioversion
    No  → assess QRS width and rhythm regularity
↓
Regular narrow QRS SVT
↓
Vagal maneuvers → adenosine → AV nodal blocker / cardioversion
↓
Recurrent symptomatic SVT
↓
Electrophysiology study + catheter ablation

The most important exam distinction is:

| Rhythm | Mechan