REGULAR WIDE QRS TACHYCARDIAS

Regular wide QRS tachycardias are ventricular until proved otherwise. Regular wide QRS supraventricular tachycardias are uncommon.

Refer all cases after resuscitation and stabilisation.

Emergency DC cardioversion is mandatory with a full protocol of Cardiopulmonary resuscitation (CPR).

GENERAL MEASURES

CPR.

If no cardiac arrest:

DC cardioversion, 200 J, after sedation with:

• Diazepam, IV, 10–20 mg. o If 200 J fails, use 360 J.

 If cardiac arrest: 

Defibrillate (not synchronised).

MEDICINE TREATMENT

Caution

Never give verapamil IV to patients with a wide QRS tachycardia.

DC cardioversion is first line therapy for regular wide QRS tachycardias. Drugs are needed if ventricular tachycardia (VT) recurs after cardioversion, or spontaneous termination.

• Amiodarone, IV, 5 mg/kg infused over 30 minutes. Follow with:
• Amiodarone, oral, 800 mg daily for 7 days.
  • Then 600 mg daily for 3 days. o Titrate to maintenance dose of 200–400 mg daily.

Precautions:

• If on warfarin, halve the dose of warfarin and monitor INR closely, until INR is stable.
• Avoid concomitant digoxin. o Monitor thyroid function every 6 months as thyroid abnormalities may develop.
• Ophthalmological examination every 6 months.

OR

Only in haemodynamically stable patients:

• Lidocaine (lignocaine), IV, 50–100 mg (1–2 mg/kg) initially and at 5 minute intervals if required to a total of 200–300 mg. Thereafter, for recurrent ventricular tachycardia only:
• Lidocaine, IV infusion, 1–3 mg/minute for 24–30 hours.

Lidocaine will only terminate ± 30% of sustained ventricular tachycardias, and may cause hypotension, heart block or convulsions.

For emergency treatment of ventricular tachycardia, DC cardioversion is first-line therapy, even if stable.

SUSTAINED (>30 SECONDS) IRREGULAR WIDE QRS TACHYCARDIAS

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 beats per minute, treat as for atrial fibrillation. Narrow QRS complex (supraventricular) tachydysrhythmias. If the rate is >170 beats per minute, 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 drugs.

Verapamil and digoxin may precipitate ventricular fibrillation by increasing the ventricular rate.