I47.0-2/I47.9
These tachycardias are usually due to atrial fibrillation with bundle branch block, or pre-excitation (WPW syndrome).
If the QRS complexes have a pattern of typical right or left bundle branch block, with a rate <170 bpm, treat as for atrial fibrillation. See : Narrow QRS complex (supraventricular) tachycardias.
If the rate is >170 bpm, and/or the complexes are atypical or variable, the likely diagnosis is WPW syndrome with atrial fibrillation, conducting via the bypass tract. Treat with DC conversion.
Do not treat with medication.
Verapamil and digoxin may precipitate ventricular fibrillation by increasing the ventricular rate.
If in doubt as to the nature of a tachycardia, and in all patients with haemodynamic compromise, DC cardioversion under IV sedation is the safest option.
DC cardioversion, 200 J, after sedation with:
- Midazolam, IV, 1–2.5 mg, administered over 2-3 minutes.
- Monitor and repeat dose after 2-3 minutes, as necessary.
- If 200 J fails, use 360 J.