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?
✅ Correct Answer:
E. Lidocaine
📚 Expert Detailed Answer and Rationale:
- E. ✅ Lidocaine – Class IB antiarrhythmic agent. Effective for post-MI ventricular arrhythmias. Targets rapidly depolarizing and ischemic ventricular fibers while sparing normal tissue. Rapidly dissociates from sodium channels, especially in ischemic myocardium.
- A. Adenosine ❌ – Slows AV nodal conduction; used for paroxysmal supraventricular tachycardia, not ventricular arrhythmias.
- B. Digoxin ❌ – Increases vagal tone; slows AV conduction; indicated for supraventricular arrhythmias, not ventricular arrhythmias.
- C. Diltiazem ❌ – Class IV calcium channel blocker; used for atrial arrhythmias, rate control; not first-line for ventricular arrhythmias.
- D. Ibutilide ❌ – Class III drug; terminates atrial flutter/fibrillation; risk of torsades de pointes; not for ischemic ventricular arrhythmias.
- F. Metoprolol ❌ – Beta-blocker; protective post-MI but not primary therapy for acute ischemic ventricular arrhythmias.
- G. Procainamide ❌ – Class IA; targets open-state sodium channels; higher proarrhythmic risk than lidocaine; not preferred post-MI.
🧠Educational Objective / 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.
🩺 Clinician’s Challenge:
Why are class IB antiarrhythmics preferred over class IA agents for acute ischemic ventricular arrhythmias in post-MI patients?
0 Comments