Question

In post-ductal coarctation of the aorta, collaterals may be formed by all of the following, except:

• A. Vertebral artery
• B. Suprascapular artery
• C. Subscapular artery
• D. Posterior intercostal artery

Hint:

Collaterals link subclavian branches to the intercostals; which option heads to the brain instead of the chest wall?

Answer 1

The Correct Option is A

Note on the key: The recalled paper printed no answer for this item. The medically correct answer is determined below from the anatomy of the collateral circulation.

Step 1: In post-ductal coarctation, the narrowing lies distal to the left subclavian artery. Blood must bypass the obstruction to reach the descending aorta. The collaterals connect branches arising above the coarctation (mainly from the subclavian arteries) with branches that join the descending aorta below the coarctation (chiefly the posterior intercostal arteries).

Step 2: The main pathway uses the anterior intercostal branches of the internal thoracic artery and the branches of the subclavian artery (including the costocervical trunk, the lateral thoracic and the scapular anastomosis). Blood flows back through the posterior intercostal arteries into the descending aorta below the block. This rib-notching anastomosis is the hallmark.

Step 3: The scapular anastomosis (suprascapular and subscapular arteries, both ultimately fed from the subclavian/axillary system) carries blood toward the posterior intercostals, so the suprascapular artery (B), the subscapular artery (C) and the posterior intercostal arteries (D) are all genuine collateral channels.

Step 4: The vertebral artery passes upward into the skull to supply the brain; it does not contribute to the chest wall collateral pathway that bypasses an aortic coarctation. It is therefore the exception.

Answer: A. Vertebral artery