Which of the following defines In-stent Restenosis (ISR)?

• A. Less than 30% stenosis
• B. Stenosis greater than 50% within the stent
• C. Stenosis less than 50% within the stent
• D. No stenosis observed

Answer: (B)

In-stent restenosis (ISR) is characterized by the re-narrowing of an artery at the site of a previously placed stent, and it is typically defined as having significant stenosis within the stent. Specifically, the criterion for ISR is set at greater than 50% stenosis.

This definition is crucial because it helps clinicians evaluate the efficacy of stent placement and determine the appropriate management for patients who may experience this complication. Greater than 50% stenosis indicates a clinically significant narrowing that may lead to symptoms or decreased blood flow, necessitating further intervention.

Understanding this definition aids in differentiating between varying degrees of arterial narrowing post-stent placement, which is important for patient monitoring and treatment planning. The other options either denote levels of stenosis that do not meet the criteria for ISR or suggest no significant abnormality.