Mastering Medical
USMLE Step 1 · Cardiovascular

Infantile/preductal coarctation vs Adult/postductal coarctation

How to tell Infantile/preductal coarctation and Adult/postductal coarctation apart when a board question makes them look alike.

Fastest separator

Preductal coarctation presents as ductal-dependent neonatal shock; postductal presents later with arm-leg pressure gradient and collaterals.

Side by side

Infantile/preductal coarctationAdult/postductal coarctation
Key clue

Neonate worsens when ductus closes because lower-body perfusion is ductal-dependent.

Older child or adult with arm hypertension, weak femoral pulses, collateral intercostal flow, and rib notching.

Mechanism

Narrowing proximal to the ductal insertion makes systemic perfusion dependent on PDA flow.

Narrowing distal to the ductal region allows collateral vessels to develop over time.

Labs and tests

Ductal closure shock, lower-body cyanosis, or prostaglandin responsiveness points preductal disease.

Rib notching, radiofemoral delay, and upper-lower BP gradient point postductal disease.

The trap

Weak femoral pulses can appear in both, but timing and ductal dependence separate them.

Watch it explained

In the rapid reviewCongenital Heart Defects for USMLE Step 1: ASD, VSD, Tetralogy & More
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The repair move

For coarctation, ask age first, then whether the ductus is helping or collaterals are helping.

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Core

A neonate develops shock and lower-body cyanosis when the ductus arteriosus closes. Coarctation is proximal to the ductal insertion and systemic flow depends on ductal patency. Which pattern is this?

Show answer and explanation

Answer: A. Infantile/preductal coarctation. Infantile/preductal coarctation presents early and may depend on PDA for lower-body perfusion.

Why the other choices are tempting

  • B. Adult/postductal coarctation presents later with upper-extremity hypertension and collateral circulation.
  • C. PDA alone causes continuous machinery murmur and bounding pulses.
  • D. Aortic regurgitation causes wide pulse pressure and early diastolic murmur.
  • E. TOF causes cyanotic spells and RV outflow obstruction.

Flashcards

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What is the fastest separator for Infantile/preductal coarctation vs Adult/postductal coarctation?

Preductal coarctation presents as ductal-dependent neonatal shock; postductal presents later with arm-leg pressure gradient and collaterals.

What clue should make you choose Infantile/preductal coarctation?

Neonate worsens when ductus closes because lower-body perfusion is ductal-dependent.

Quick answers

What is the fastest way to tell Infantile/preductal coarctation from Adult/postductal coarctation?

Preductal coarctation presents as ductal-dependent neonatal shock; postductal presents later with arm-leg pressure gradient and collaterals.

What is the key clue for Infantile/preductal coarctation?

Neonate worsens when ductus closes because lower-body perfusion is ductal-dependent.

What is the key clue for Adult/postductal coarctation?

Older child or adult with arm hypertension, weak femoral pulses, collateral intercostal flow, and rib notching.

What is the common trap with Infantile/preductal coarctation vs Adult/postductal coarctation?

Weak femoral pulses can appear in both, but timing and ductal dependence separate them.