Thorax: persistent left superior vena cava: 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: persistent left superior vena cava

Sample item

A cardiac catheter passed through the left subclavian vein in a young man enters a vessel that descends in front of the left lung root and ends in the posterior atrioventricular groove. Where does this anomalous left-sided channel drain?

ARight brachiocephalic vein at the cardiac baseBCoronary sinus, which opens into the right atriumCLeft atrium, through the pulmonary veinsDInferior vena cava below the diaphragm

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

The answer and the reasoning

B. Coronary sinus, which opens into the right atrium

A persistent left superior vena cava is the remnant of the left anterior cardinal vein (left common cardinal vein). It runs in front of the left lung root and enters the dilated coronary sinus, so blood still reaches the right atrium and the anomaly is usually harmless unless the sinus is unroofed.

Option by option

A. Right brachiocephalic vein at the cardiac base
A normal left brachiocephalic vein crosses to the right, but this persistent channel descends rather than crossing.
B. Coronary sinus, which opens into the right atrium (correct)
Correct. The persistent left superior vena cava empties into the coronary sinus and so reaches the right atrium.
C. Left atrium, through the pulmonary veins
Drainage into the left atrium would be a right-to-left shunt and is not the usual course.
D. Inferior vena cava below the diaphragm
The left-sided channel runs in the thorax and has no connection with the inferior vena cava below the diaphragm.

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 B, Coronary sinus, which opens into the right atrium. A persistent left superior vena cava is the remnant of the left anterior cardinal vein (left common cardinal vein).

Why is "Right brachiocephalic vein at the cardiac base" not the answer?

A normal left brachiocephalic vein crosses to the right, but this persistent channel descends rather than crossing.

Why is "Left atrium, through the pulmonary veins" not the answer?

Drainage into the left atrium would be a right-to-left shunt and is not the usual course.

Why is "Inferior vena cava below the diaphragm" not the answer?

The left-sided channel runs in the thorax and has no connection with the inferior vena cava below the diaphragm.

What concept does this question test?

It tests Thorax: persistent left superior vena cava in Anatomy. It runs in front of the left lung root and enters the dilated coronary sinus, so blood still reaches the right atrium and the anomaly is usually harmless unless the sinus is unroofed.

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: persistent left superior vena cava?

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.