Cardiovascular: coronary steal: 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: coronary steal

Sample item

During a dipyridamole stress perfusion scan, a patient with a 90% stenosis of one coronary artery develops chest pain and a reversible perfusion defect in that territory. What is the mechanism?

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

The answer and the reasoning

C. Adenosine dilates normal coronary arteries, diverting flow away from the maximally dilated stenotic territory

Dipyridamole blocks adenosine reuptake, raising its level and dilating resistance vessels. Vessels beyond a critical stenosis are already maximally dilated and cannot respond, while normal beds dilate and draw blood away, lowering perfusion pressure in the stenotic bed (coronary steal). This produces a defect that identifies significant disease.

Option by option

  • A. Dipyridamole increases myocardial oxygen demand by raising heart rate and contractility

    Dipyridamole stress is a vasodilator test; it does not rely on higher demand as in exercise or dobutamine.

  • B. Dipyridamole causes coronary vasospasm in the stenotic vessel

    The drug works by vasodilation, not by inducing spasm.

  • C. Adenosine dilates normal coronary arteries, diverting flow away from the maximally dilated stenotic territory (correct)

    Correct. Vasodilation of normal beds diverts flow from the fixed, already dilated stenotic territory.

  • D. Dipyridamole blocks platelet aggregation and causes distal embolisation

    The antiplatelet effect is unrelated to the perfusion defect, which is haemodynamic.

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 Physiology question

What is the answer to this Physiology question?

The best answer is C, Adenosine dilates normal coronary arteries, diverting flow away from the maximally dilated stenotic territory. Dipyridamole blocks adenosine reuptake, raising its level and dilating resistance vessels.

Why is "Dipyridamole increases myocardial oxygen demand by raising heart rate…" not the answer?

Dipyridamole stress is a vasodilator test; it does not rely on higher demand as in exercise or dobutamine.

Why is "Dipyridamole causes coronary vasospasm in the stenotic vessel" not the answer?

The drug works by vasodilation, not by inducing spasm.

Why is "Dipyridamole blocks platelet aggregation and causes distal embolisati…" not the answer?

The antiplatelet effect is unrelated to the perfusion defect, which is haemodynamic.

What concept does this question test?

It tests Cardiovascular: coronary steal in Physiology. Vessels beyond a critical stenosis are already maximally dilated and cannot respond, while normal beds dilate and draw blood away, lowering perfusion pressure in the stenotic bed (coronary steal). This produces a defect that identifies significant disease.

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: coronary steal?

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.