habt,   Thanks for your question.    A stent is a device that is placed within a coronary artery to keep this blood vessel open.  It is used when blockages develop in the arteries that can result in chest pain and heart attacks.  Once the blockages are identified, a catheter with a balloon tip is placed across the blockage and then inflated.  This opens up the vessel by compressing fatty buildup (the blockage) against the vessel wall.  Once opened, the stent is then inserted across this site and once deployed, the stent opens up (like a spring) and keeps the vessel open.    Because blood thinners are used during this procedure, it is less likely to develop a clot during the procedure, but still possible.  Blood thinners are usually maintained in an oral form after the procedure to help prevent the formation of clot.  The stent will be covered with a membrane of tissue within a month, and once formed, also cuts down on the likelihood of clot formation.  Some people develop excess scar tissue on the stent which can lead to restenosis (blockage recurrence).  This can be treated with radiation therapy.  To avoid this, some stents (DES - drug eluding stents) have a medication embedded within them to help prevent this scar tissue formation.   So, the answer to your question is yes, it is possible to form a clot during placement of a stent, but unlikely due to use of intravenous blood thinners during the procedure. To help prevent clot after the procedure, blood thinners are maintained orally.   I hope this information has been helpful.  Best wishes.   Martin Cane, M.D.