Cardiac mechanics: pressure-volume loop: 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 · Cardiac mechanics: pressure-volume loop

Sample item

On a left ventricular pressure-volume loop, a sudden rise in aortic pressure (increased afterload) is imposed with unchanged preload and contractility. Which change occurs in the next beats?

AEnd-systolic volume decreases with unchanged stroke volumeBStroke volume decreases and end-systolic volume increasesCEnd-diastolic volume falls with unchanged end-systolic volumeDStroke volume increases and end-systolic volume decreases

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

The answer and the reasoning

B. Stroke volume decreases and end-systolic volume increases

A higher afterload means the ventricle must reach a higher pressure before the aortic valve opens, so the loop becomes taller and narrower. The ventricle ejects less before reaching its end-systolic pressure-volume line, so stroke volume falls and end-systolic volume rises. The increased residual volume then raises preload on subsequent beats, partly restoring output through the Frank-Starling mechanism.

Option by option

A. End-systolic volume decreases with unchanged stroke volume
End-systolic volume rises, not falls, when afterload increases.
B. Stroke volume decreases and end-systolic volume increases (correct)
Correct. Higher afterload reduces ejection and leaves a larger end-systolic volume.
C. End-diastolic volume falls with unchanged end-systolic volume
End-diastolic volume is unchanged initially, and end-systolic volume rises.
D. Stroke volume increases and end-systolic volume decreases
These changes occur with increased contractility, not afterload.

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 B, Stroke volume decreases and end-systolic volume increases. A higher afterload means the ventricle must reach a higher pressure before the aortic valve opens, so the loop becomes taller and narrower.

Why is "End-systolic volume decreases with unchanged stroke volume" not the answer?

End-systolic volume rises, not falls, when afterload increases.

Why is "End-diastolic volume falls with unchanged end-systolic volume" not the answer?

End-diastolic volume is unchanged initially, and end-systolic volume rises.

Why is "Stroke volume increases and end-systolic volume decreases" not the answer?

These changes occur with increased contractility, not afterload.

What concept does this question test?

It tests Cardiac mechanics: pressure-volume loop in Physiology. The ventricle ejects less before reaching its end-systolic pressure-volume line, so stroke volume falls and end-systolic volume rises. The increased residual volume then raises preload on subsequent beats, partly restoring output through the Frank-Starling mechanism.

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 Cardiac mechanics: pressure-volume loop?

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.