5th May 2025

Regular narrow-complex tachycardias

For patients who are haemodynamically stable and have a regular narrow-complex tachycardia, follow the steps below:

1. Attempt vagal manoeuvres. This can be sufficient to cardiovert the patient back to sinus rhythm.
2. If unsuccessful and there is no evidence of a pre-excitation syndrome (e.g. WPW), give adenosine under direct ECG monitoring. The doses are 6mg rapid IV bolus, then 12mg if unsuccessful, then 18mg if unsuccessful.
3. If unsuccessful, give verapamil or beta-blocker (metoprolol is the drug of choice in acute situations due to its fast onset of action)
4. If ineffective, attempt DC cardioversion as above (note atrial flutter is unlikely to chemically cardiovert and will often need DC cardioversion if treatment of underlying causes is unsuccessful).

Patients with a pre-excitation syndrome such as Wolff-Parkinson-White should not be given digoxin or verapamil, as these can provoke fatal arrhythmias through blockade of the SA node, encouraging conduction down the aberrant pathway.. If cardioversion is unsuccessful, patients should be referred for consideration of radio-frequency ablation of their aberrant conduction pathway.

Table 4: Vaughan-Williams classification of anti-arrhythmic drugs.