PGCEE MDS 2022 : Most suitable antiarrhythmic drug for counteracting ventricular extrasystoles due to digoxin toxicity

 # The most suitable antiarrhythmic drug for counteracting ventricular extrasystoles due to digoxin toxicity is :

A. Lignocaine

B. Quinidine

C. Verapamil

D. Amiodarone

The correct answer is A. Lignocaine.

The primary treatment of digoxin toxicity is digoxin immune fab, which is an antibody made up of anti-digoxin immunoglobulin fragments. This antidote has been shown to be highly effective in treating life-threatening signs of digoxin toxicity such as hyperkalemia, hemodynamic instability, and arrhythmias. Fab dose can be determined by two different methods. First method is based on the amount of digoxin ingested whereas the second method is based on the serum digoxin concentration and the weight of the person.

Other treatment that may be used to treat life-threatening arrhythmias until Fab is acquired are magnesium, phenytoin, and lidocaine. Magnesium suppresses digoxin-induced ventricular arrhythmias while phenytoin and lidocaine suppresses digoxin-induced ventricular automaticity and delay afterdepolarizations without depressing AV conduction. In the case of an abnormally slow heart rate (bradyarrhythmias), Atropine, catecholamines (isoprenaline or salbutamol), and/or temporary cardiac pacing can be used.

USES OF LIDOCAINE

Lidocaine is safe if given by slow i.v. injection; is used to suppress VT and prevent VF. It is ineffective in atrial arrhythmias. Because of rapidly developing and titratable action it is a good drug in the emergency setting, e.g. arrhythmias following acute MI or during cardiac surgery. In acute MI, i.v. infusion of lidocaine can prevent VF, but a metaanalysis has shown that it fails to improve survival; may even increase short term mortality. Therefore, lidocaine is no longer administered prophylactically to all MI patients, but may be used in selected cases, and to treat ventricular arrhythmias when they occur. Efficacy of lidocaine in chronic ventricular arrhythmia is poor, but it suppresses VT due to digitalis toxicity, for which it is used because it does not worsen A-V block.