STEP 1 — MCQs (No Answers Here)

MCQ 1 — Major Determinants

Which of the following is NOT one of the three major variables determining the outcome after vascular occlusion?

a. Anatomy of vascular supply

b. Rate of occlusion

c. Tissue vulnerability to hypoxia

d. Patient age

e. All three above are the true determinants

MCQ 2 — Dual vs End-Arterial Supply

Which organ pair demonstrates strong resistance to infarction due to dual or parallel blood supplies?

a. Kidney and spleen

b. Lung and liver

c. Brain and spinal cord

d. Spleen and heart

e. Retina and pancreas

MCQ 3 — Vulnerable End-Arterial Organs

Arterial occlusion in which organs almost always causes infarction due to end-arterial circulation?

a. Liver and lung

b. Spleen and kidney

c. Hand and forearm

d. Heart and liver

e. Lung and small intestine

MCQ 4 — Coronary Collaterals

Which scenario BEST illustrates the role of rate of occlusion?

a. Sudden complete blockage of a coronary artery always prevented by collateral flow

b. Slow atherosclerotic narrowing allows collateral flow to enlarge and prevent infarction

c. Rapid occlusion improves perfusion by enhancing collateral resistance

d. Slow occlusion causes more ischemia than rapid occlusion

e. Collaterals do not exist in the coronary circulation

MCQ 5 — Dual Blood Supply Example

Which statement is correct?

a. Pulmonary infarction is common even when bronchial circulation is intact

b. Lung infarction requires compromise of both pulmonary and bronchial circulations

c. Liver has end-arterial supply and infarcts very easily

d. Hand and forearm infarct frequently due to single arterial channel

e. Portal vein blockage alone causes liver infarction

MCQ 6 — Tissue Sensitivity

Rank the tissues from most sensitive to least sensitive to ischemia:

1. Neurons
2. Myocardial cells
3. Fibroblasts

a. 3 → 2 → 1

b. 1 → 2 → 3

c. 2 → 1 → 3

d. 1 → 3 → 2

e. 3 → 1 → 2

MCQ 7 — Time to Irreversible Injury

At what time frame do neurons undergo irreversible damage?

a. 1 second

b. 3–4 minutes

c. 20–30 minutes

d. 1 hour

e. Several hours

MCQ 8 — Myocardial Cell Tolerance

Myocardial cells typically die after how long without adequate blood supply?

a. 1–2 minutes

b. 3–4 minutes

c. 10 minutes

d. 20–30 minutes

e. Several hours

MCQ 9 — Fibroblast Resistance

Fibroblasts in myocardium:

a. Die within minutes of ischemia

b. Die within 20 minutes, similar to myocytes

c. Remain viable for many hours of ischemia

d. Have identical sensitivity to neurons

e. Die immediately on occlusion

MCQ 10 — Most Important Factor

The single most important factor in determining whether vascular occlusion leads to infarction is:

a. Age of patient

b. Blood pressure

c. Anatomy of vascular supply

d. Presence of fever

e. WBC count

STEP 2 — Answers + Short Explanations

MCQ 1 — d

Three key determinants: anatomy, rate of occlusion, tissue vulnerability.

MCQ 2 — b

Lung (pulmonary + bronchial arteries) and liver (hepatic artery + portal vein) resist infarction.

MCQ 3 — b

Kidney and spleen = classic end-arterial organs → infarction is typical.

MCQ 4 — b

Slow atherosclerotic narrowing → collaterals enlarge → may prevent infarction.

MCQ 5 — b

Lung infarction requires compromise of both pulmonary and bronchial circulations.

MCQ 6 — b

Sensitivity:

Neurons (minutes) > Myocytes (20–30 min) > Fibroblasts (hours).

MCQ 7 — b

Neurons die after 3–4 minutes of ischemia.

MCQ 8 — d

Myocardial cells die in 20–30 minutes.

MCQ 9 — c

Fibroblasts can remain viable for many hours.

MCQ 10 — c

Anatomy of vascular supply is the most important determinant.

STEP 3 — HIGH-YIELD NOTES (Exam-Ready)

1. Three Determinants of Infarct Outcome

A. Anatomy of Vascular Supply — MOST IMPORTANT

• Determines whether alternate routes can compensate.
• Dual or parallel circulations protect against infarction:
• Lung: Pulmonary + bronchial arteries → infarct only if both compromised.
• Liver: Hepatic artery + portal vein → highly resistant.
• Hand & forearm: Parallel radial + ulnar arteries → resistant.
• End-arterial organs → high risk of infarction:
• Kidney
• Spleen

B. Rate of Occlusion — Determines Collateral Development

• Slow occlusion (e.g., gradual atherosclerosis):
• Allows time for collaterals to enlarge.
• Can completely prevent infarction even if artery becomes fully occluded.
• Example: Coronary circulation — interarteriolar anastomoses expand when one vessel narrows slowly.
• Sudden occlusion:
• No time for collateral adaptation.
• Produces ischemia → infarction.

C. Tissue Vulnerability to Hypoxia — Intrinsic Sensitivity

Different tissues tolerate ischemia differently:

• Explains why:
• Stroke develops rapidly after arterial occlusion.
• Myocardial infarction takes ~20 minutes of ischemia.
• Scar tissue fibroblasts survive long ischemic periods.

2. Clinical Implications

• Organs with dual supply ≠ infarct easily → lung, liver, forearm.
• Kidney and spleen infarct readily.
• Slow atherosclerotic narrowing may be silent because collaterals protect myocardium.
• Infarct severity depends on:
• Supply anatomy
• Speed of vessel occlusion
• Cell type vulnerability

3. Ultra-High Yield Lines for Exams

• “Anatomy of blood supply is the single most important factor determining infarction.”
• “Lung infarcts require compromise of BOTH pulmonary and bronchial circulations.”
• “Spleen and kidney = classic end-arterial organs → infarct with any arterial obstruction.”
• “Neurons die in 3–4 minutes; myocytes in 20–30 minutes; fibroblasts survive hours.”
• “Slow occlusion allows collateral development and may completely prevent infarction.”