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.

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Anatomy · Thorax: conduction system

Sample item

During catheter ablation for an atrioventricular nodal re-entry tachycardia, the operator targets the slow pathway low in the right atrium while avoiding the compact node. Between which landmarks is the node found?

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

The answer and the reasoning

D. Tendon of Todaro, septal tricuspid leaflet and coronary sinus ostium (triangle of Koch)

The atrioventricular node lies in the triangle of Koch at the base of the interatrial septum, bounded by the tendon of Todaro, the attachment of the septal leaflet of the tricuspid valve and the ostium of the coronary sinus. Slow pathway ablation is done at the inferior (coronary sinus) end of the triangle. Excess energy near the apex can cause complete heart block.

Option by option

  • A. Moderator band, anterior papillary muscle and pulmonary valve

    The moderator band and papillary muscle are in the right ventricle, away from the AV node.

  • B. Crista terminalis, sulcus terminalis and Eustachian valve

    The crista terminalis region relates to the sinoatrial node and the Eustachian valve is at the IVC, not the node.

  • C. Fossa ovalis, superior vena cava and right atrial appendage

    These landmarks lie in the upper right atrium and do not define the AV node.

  • D. Tendon of Todaro, septal tricuspid leaflet and coronary sinus ostium (triangle of Koch) (correct)

    Correct. The triangle of Koch locates the AV node.

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.

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Questions about this Anatomy question

What is the answer to this Anatomy question?

The best answer is D, Tendon of Todaro, septal tricuspid leaflet and coronary sinus ostium (triangle of Koch). The atrioventricular node lies in the triangle of Koch at the base of the interatrial septum, bounded by the tendon of Todaro, the attachment of the septal leaflet of the tricuspid valve and the ostium of the coronary sinus.

Why is "Moderator band, anterior papillary muscle and pulmonary valve" not the answer?

The moderator band and papillary muscle are in the right ventricle, away from the AV node.

Why is "Crista terminalis, sulcus terminalis and Eustachian valve" not the answer?

The crista terminalis region relates to the sinoatrial node and the Eustachian valve is at the IVC, not the node.

Why is "Fossa ovalis, superior vena cava and right atrial appendage" not the answer?

These landmarks lie in the upper right atrium and do not define the AV node.

What concept does this question test?

It tests Thorax: conduction system in Anatomy. Slow pathway ablation is done at the inferior (coronary sinus) end of the triangle. Excess energy near the apex can cause complete 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.