Haemodynamics: pulmonary embolism and infarction: practice question

A Pathology 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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Pathology · Haemodynamics: pulmonary embolism and infarction

Sample item

A medium-sized pulmonary artery embolus in a previously healthy adult usually does not cause lung infarction, but the same embolus in a patient with chronic left heart failure often does. What best explains the difference?

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

The answer and the reasoning

B. Bronchial arterial collateral supply keeps the segment viable unless raised venous pressure or poor systemic flow compromises it

The lung has a dual blood supply from the pulmonary and bronchial arteries, and alveoli also receive oxygen from air. Occlusion of a medium-sized branch therefore rarely infarcts normal lung. In left heart failure, congestion and low bronchial arterial flow remove this reserve, and a haemorrhagic, wedge-shaped infarct results.

Option by option

  • A. Emboli in healthy lungs are lysed within seconds, but fibrinolysis is impaired in heart failure

    Emboli are not lysed within seconds, and impaired fibrinolysis is not the explanation for the susceptibility of congested lungs.

  • B. Bronchial arterial collateral supply keeps the segment viable unless raised venous pressure or poor systemic flow compromises it (correct)

    Correct. The bronchial collateral supply is the safeguard that fails in congestion.

  • C. Pulmonary arteries anastomose freely with one another, so any occlusion is bypassed

    Medium-sized pulmonary branches are largely end-arteries and do not bypass an occlusion by anastomoses.

  • D. The lung parenchyma has such a low oxygen requirement that it tolerates ischaemia indefinitely

    Lung tissue is not metabolically inert, and it does infarct when collateral flow fails.

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 Pathology question

What is the answer to this Pathology question?

The best answer is B, Bronchial arterial collateral supply keeps the segment viable unless raised venous pressure or poor systemic flow compromises it. The lung has a dual blood supply from the pulmonary and bronchial arteries, and alveoli also receive oxygen from air.

Why is "Emboli in healthy lungs are lysed within seconds, but fibrinolysis is…" not the answer?

Emboli are not lysed within seconds, and impaired fibrinolysis is not the explanation for the susceptibility of congested lungs.

Why is "Pulmonary arteries anastomose freely with one another, so any occlusi…" not the answer?

Medium-sized pulmonary branches are largely end-arteries and do not bypass an occlusion by anastomoses.

Why is "The lung parenchyma has such a low oxygen requirement that it tolerat…" not the answer?

Lung tissue is not metabolically inert, and it does infarct when collateral flow fails.

What concept does this question test?

It tests Haemodynamics: pulmonary embolism and infarction in Pathology. Occlusion of a medium-sized branch therefore rarely infarcts normal lung. In left heart failure, congestion and low bronchial arterial flow remove this reserve, and a haemorrhagic, wedge-shaped infarct results.

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 Haemodynamics: pulmonary embolism and infarction?

Learn each disease as a bundle: cause, key histology, markers, and the clinical hallmark. Then use the flashcards and the other Pathology 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.