Thorax: right atrium and ablation: 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: right atrium and ablation

Sample item

A patient with typical atrial flutter undergoes catheter ablation of a narrow strip of tissue that forms the slow-conduction limb of the re-entry circuit. Which pair of landmarks bounds this strip in the right atrium?

AThe inferior vena cava orifice and the tricuspid valve annulusBThe superior vena cava orifice and the fossa ovalisCThe crista terminalis and the right atrial appendageDThe coronary sinus orifice and the left atrial appendage

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

The answer and the reasoning

A. The inferior vena cava orifice and the tricuspid valve annulus

Typical flutter circulates around the tricuspid annulus, and the cavotricuspid isthmus lies between the inferior vena cava orifice (with Eustachian ridge) and the tricuspid annulus, passing near the coronary sinus ostium. A linear ablation across it blocks the circuit. The crista terminalis is the posterolateral boundary between the smooth and rough parts of the atrium.

Option by option

A. The inferior vena cava orifice and the tricuspid valve annulus (correct)
Correct. The isthmus runs between the IVC orifice and the tricuspid annulus, and ablating it interrupts the flutter circuit.
B. The superior vena cava orifice and the fossa ovalis
The superior vena cava orifice and fossa ovalis lie in the upper and septal part of the atrium and are not part of the flutter isthmus.
C. The crista terminalis and the right atrial appendage
The crista terminalis and right atrial appendage are not the isthmus; the crista forms a conduction barrier at the lateral wall.
D. The coronary sinus orifice and the left atrial appendage
The left atrial appendage lies in the left atrium, not in the right atrial circuit.

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 A, The inferior vena cava orifice and the tricuspid valve annulus. Typical flutter circulates around the tricuspid annulus, and the cavotricuspid isthmus lies between the inferior vena cava orifice (with Eustachian ridge) and the tricuspid annulus, passing near the coronary sinus ostium.

Why is "The superior vena cava orifice and the fossa ovalis" not the answer?

The superior vena cava orifice and fossa ovalis lie in the upper and septal part of the atrium and are not part of the flutter isthmus.

Why is "The crista terminalis and the right atrial appendage" not the answer?

The crista terminalis and right atrial appendage are not the isthmus; the crista forms a conduction barrier at the lateral wall.

Why is "The coronary sinus orifice and the left atrial appendage" not the answer?

The left atrial appendage lies in the left atrium, not in the right atrial circuit.

What concept does this question test?

It tests Thorax: right atrium and ablation in Anatomy. A linear ablation across it blocks the circuit. The crista terminalis is the posterolateral boundary between the smooth and rough parts of the atrium.

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: right atrium and ablation?

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.