Restenosis is the re-narrowing of a blood vessel after it has been treated to remove a blockage. This condition often occurs after procedures like angioplasty or the placement of a stent, which are designed to improve blood flow. Despite these interventions, scar tissue can form, leading to a return of the blockage. The process of restenosis can limit the effectiveness of these treatments and may require additional procedures to restore proper blood flow. Factors contributing to restenosis include the type of stent used, the patient's overall health, and the specific characteristics of the blood vessel involved.