What best describes stent underexpansion and why it is problematic?

• A. Incomplete stent expansion against the vessel wall, increasing risk of restenosis and stent thrombosis; corrected with post-dilation using noncompliant balloons.
• B. Overexpansion against the vessel wall leading to rupture.
• C. Complete expansion with no risk.
• D. Stent underexpansion is unrelated to restenosis.

Answer: (A)

Stent underexpansion means the stent doesn’t fully press against the vessel wall, leaving areas where the struts aren’t apposed to the intima. This creates zones of malapposition and disturbed flow, which promote neointimal hyperplasia and increasing the risk of restenosis. It also leaves a thrombogenic surface that can lead to stent thrombosis, especially under high shear conditions.

The way to address this is post-dilation with a noncompliant balloon. These balloons resist further stretching as you apply more pressure, allowing you to press the stent firmly against the vessel wall at the intended diameter without overexpanding the vessel itself. Achieving full expansion and proper apposition reduces both restenosis and thrombosis risk.

The other statements don’t fit because overexpansion can rupture the vessel, complete expansion with no risk is not realistic, and underexpansion is indeed related to restenosis.