Cardiovascular system: pulsus paradoxus mechanism: practice question

A Physiology 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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Physiology · Cardiovascular system: pulsus paradoxus mechanism

Sample item

In a patient with cardiac tamponade the systolic pressure falls by more than 10 mmHg during inspiration. Which mechanism contributes most to this?

AInterventricular interdependence, as right ventricular filling restricts left ventricular fillingBA rise in aortic afterload from lung expansionCVagal slowing of the heart rate during inspirationDA fall in right ventricular preload because intrathoracic pressure drops

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

The answer and the reasoning

A. Interventricular interdependence, as right ventricular filling restricts left ventricular filling

Inspiration increases venous return to the right heart. In tamponade the pericardium is filled with fluid, so the total volume of the heart is fixed, and the expanded right ventricle bulges the septum into the left ventricle and limits its filling. Left stroke volume and systolic pressure then fall.

Option by option

A. Interventricular interdependence, as right ventricular filling restricts left ventricular filling (correct)
Correct. A fixed pericardial space makes right and left filling compete.
B. A rise in aortic afterload from lung expansion
Lung expansion does not raise aortic afterload to this extent.
C. Vagal slowing of the heart rate during inspiration
Sinus arrhythmia changes rate but does not explain the stroke volume fall seen here.
D. A fall in right ventricular preload because intrathoracic pressure drops
Inspiration increases, not decreases, right ventricular preload.

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 Physiology question

What is the answer to this Physiology question?

The best answer is A, Interventricular interdependence, as right ventricular filling restricts left ventricular filling. Inspiration increases venous return to the right heart.

Why is "A rise in aortic afterload from lung expansion" not the answer?

Lung expansion does not raise aortic afterload to this extent.

Why is "Vagal slowing of the heart rate during inspiration" not the answer?

Sinus arrhythmia changes rate but does not explain the stroke volume fall seen here.

Why is "A fall in right ventricular preload because intrathoracic pressure dr…" not the answer?

Inspiration increases, not decreases, right ventricular preload.

What concept does this question test?

It tests Cardiovascular system: pulsus paradoxus mechanism in Physiology. In tamponade the pericardium is filled with fluid, so the total volume of the heart is fixed, and the expanded right ventricle bulges the septum into the left ventricle and limits its filling. Left stroke volume and systolic pressure then fall.

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 Cardiovascular system: pulsus paradoxus mechanism?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology 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.