Cardiology: pre-excited atrial fibrillation: practice question

A General Medicine question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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General Medicine · Cardiology: pre-excited atrial fibrillation

Sample item

A 32-year-old man has had palpitations for 2 hours and is haemodynamically stable. The ECG shows an irregular wide-complex tachycardia at 210 per minute with varying QRS shapes. A previous resting ECG showed a short PR interval and a slurred upstroke at the start of the QRS. Which drug is most appropriate?

AIV digoxin loadingBIV procainamideCIV verapamilDIV adenosine bolus

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

B. IV procainamide

This is atrial fibrillation conducted over an accessory pathway. The pathway, not the AV node, must be slowed, so a drug such as procainamide is used (or cardioversion if unstable). AV nodal blockers can push more impulses down the pathway and precipitate ventricular fibrillation.

Option by option

A. IV digoxin loading
Digoxin shortens the refractory period of the accessory pathway and can speed the ventricular rate dangerously.
B. IV procainamide (correct)
Correct. Procainamide slows conduction and prolongs refractoriness in the accessory pathway.
C. IV verapamil
Verapamil blocks only the AV node, so more atrial impulses go down the pathway and ventricular fibrillation can follow.
D. IV adenosine bolus
Adenosine blocks the AV node and can trigger very rapid pathway conduction, so it is avoided in pre-excited fibrillation.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this General Medicine question

What is the answer to this General Medicine question?

The best answer is B, IV procainamide. This is atrial fibrillation conducted over an accessory pathway.

Why is "IV digoxin loading" not the answer?

Digoxin shortens the refractory period of the accessory pathway and can speed the ventricular rate dangerously.

Why is "IV verapamil" not the answer?

Verapamil blocks only the AV node, so more atrial impulses go down the pathway and ventricular fibrillation can follow.

Why is "IV adenosine bolus" not the answer?

Adenosine blocks the AV node and can trigger very rapid pathway conduction, so it is avoided in pre-excited fibrillation.

What concept does this question test?

It tests Cardiology: pre-excited atrial fibrillation in General Medicine. The pathway, not the AV node, must be slowed, so a drug such as procainamide is used (or cardioversion if unstable). AV nodal blockers can push more impulses down the pathway and precipitate ventricular fibrillation.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Cardiology: pre-excited atrial fibrillation?

For each disease know the classic presentation, the best test, and the first-line treatment. Then use the flashcards and the other General Medicine questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.