Thorax: conduction system: practice question

A Anatomy 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.

Try it

Anatomy · Thorax: conduction system

Sample item

A surgeon closes a perimembranous ventricular septal defect through the right atrium. After surgery the patient develops complete heart block. Which conduction structure runs along the posteroinferior rim of the defect and was most likely injured?

ADistal right bundle branch in the septomarginal trabeculaBSubendocardial Purkinje network of the left ventricular apexCSinoatrial nodeDAtrioventricular bundle (bundle of His)

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

The answer and the reasoning

D. Atrioventricular bundle (bundle of His)

The bundle of His penetrates the fibrous skeleton, runs along the lower border of the membranous septum and divides into bundle branches at the top of the muscular septum. Sutures placed at the posteroinferior rim of a perimembranous defect can damage it and cause heart block.

Option by option

A. Distal right bundle branch in the septomarginal trabecula
The distal right bundle branch runs toward the apex, away from the defect rim.
B. Subendocardial Purkinje network of the left ventricular apex
The apical Purkinje network lies far from the septal rim and is not injured by this repair.
C. Sinoatrial node
The sinoatrial node lies at the junction of the superior vena cava and right atrium, far from the defect.
D. Atrioventricular bundle (bundle of His) (correct)
Correct. The AV bundle runs on the rim of the membranous septum, where stitches are placed.

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 Anatomy question

What is the answer to this Anatomy question?

The best answer is D, Atrioventricular bundle (bundle of His). The bundle of His penetrates the fibrous skeleton, runs along the lower border of the membranous septum and divides into bundle branches at the top of the muscular septum.

Why is "Distal right bundle branch in the septomarginal trabecula" not the answer?

The distal right bundle branch runs toward the apex, away from the defect rim.

Why is "Subendocardial Purkinje network of the left ventricular apex" not the answer?

The apical Purkinje network lies far from the septal rim and is not injured by this repair.

Why is "Sinoatrial node" not the answer?

The sinoatrial node lies at the junction of the superior vena cava and right atrium, far from the defect.

What concept does this question test?

It tests Thorax: conduction system in Anatomy. Sutures placed at the posteroinferior rim of a perimembranous defect can damage it and cause heart block.

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 Thorax: conduction system?

Learn every nerve by its route, its muscles and what a lesion looks like at the bedside. That one habit answers a large share of questions. Then use the flashcards and the other Anatomy 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.