## **Core Concept**
Digitalis-induced ventricular arrhythmias are a serious side effect of digitalis therapy, which can be life-threatening if not managed promptly. Digitalis toxicity can cause various arrhythmias due to its effect on the heart's electrical conduction system. The management of digitalis-induced ventricular arrhythmias requires careful consideration of the underlying mechanism.

## **Why the Correct Answer is Right**
The correct answer, **Lidocaine (or lignocaine)**, is a class Ib anti-arrhythmic drug that is particularly effective in treating ventricular arrhythmias caused by digitalis toxicity. Lidocaine works by blocking sodium channels, which helps to stabilize the cardiac membrane and reduce the automaticity of ventricular myocytes. Unlike other anti-arrhythmic drugs that can further depress the AV node or worsen the arrhythmia, lidocaine has a minimal effect on the AV node and is therefore safe to use in digitalis-induced arrhythmias.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Phenytoin is an antiepileptic drug that can also be used for certain types of arrhythmias but is not the first choice for digitalis-induced ventricular arrhythmias due to its side effect profile and less efficacy compared to lidocaine.
- **Option B:** Propranolol is a beta-blocker that can actually worsen digitalis toxicity by further depressing the AV node and increasing the risk of heart block.
- **Option D:** Atropine is used to treat bradycardia and heart block associated with digitalis toxicity but is not effective in treating ventricular arrhythmias.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that in digitalis-induced ventricular arrhythmias, the treatment often involves discontinuing the digitalis and administering **lidocaine** as a first-line treatment. Additionally, it's crucial to correct any underlying electrolyte imbalances, particularly potassium and magnesium levels, as these can contribute to digitalis toxicity.

## **Correct Answer:** . Lidocaine