CHECK

Clinical Scenario

A 49-year-old woman presents to the emergency department with squeezing chest pain and profuse sweating lasting for the past 2 hours. Her medical history is notable for type 2 diabetes mellitus, controlled with diet. Electrocardiogram (ECG) shows ST-segment elevation in leads I, aVL, and V1–V4. She is immediately taken to the cardiac catheterization laboratory, where complete occlusion of the left anterior descending coronary artery is identified. The blockage is successfully treated with percutaneous coronary intervention and stent placement. However, following the procedure, she develops recurrent and sustained ventricular arrhythmias. She is managed with an antiarrhythmic agent that selectively targets rapidly depolarizing and ischemic ventricular myocardial fibers, with minimal effects on normal ventricular tissue.

👉 Question:

Which of the following drugs was most likely administered?

A. Adenosine

B. Digoxin

C. Diltiazem

D. Ibutilide

E. Lidocaine

F. Metoprolol

G. Procainamide

✅ Correct Answer:

E. Lidocaine.

📚 Expert Rationale

E. ✅ Lidocaine – A Class IB antiarrhythmic agent. It is highly effective for treating ventricular arrhythmias that occur after a myocardial infarction (MI). Its mechanism involves selectively targeting rapidly depolarizing and ischemic ventricular muscle fibers while having minimal effect on normal heart tissue. It quickly detaches from sodium channels, a key feature of its action in the ischemic myocardium.

A. Adenosine ❌ – Primarily slows conduction through the AV node. It's the drug of choice for paroxysmal supraventricular tachycardia (PSVT), not ventricular arrhythmias.

B. Digoxin ❌ – Works by increasing vagal tone, which slows AV conduction. It is indicated for supraventricular arrhythmias (like atrial fibrillation) and not for ventricular arrhythmias.

C. Diltiazem ❌ – A Class IV calcium channel blocker. Used for atrial arrhythmias and rate control, it is not a first-line agent for ventricular arrhythmias.

D. Ibutilide ❌ – A Class III drug used to terminate atrial flutter and fibrillation. It carries a significant risk of causing torsades de pointes and is not suitable for ischemic ventricular arrhythmias.

F. Metoprolol ❌ – As a beta-blocker, it is protective after an MI but is not the primary therapy for managing acute, ischemia-induced ventricular arrhythmias.

G. Procainamide ❌ – A Class IA agent that targets open-state sodium channels. It has a higher risk of causing new arrhythmias (proarrhythmic risk) compared to lidocaine and is therefore not preferred post-MI.

🧠 High-Yield Points

• Lidocaine selectively binds inactivated sodium channels and rapidly dissociates.
• Highly effective for acute ischemia-induced ventricular arrhythmias post-MI.
• Minimal effect on normal ventricular tissue, reducing proarrhythmic risk.

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