Method and device for filtering body fluid

A method of protecting a patient from embolization during a percutaneous procedure at a treatment site within a vessel comprising:

• introducing a first elongate member into the vessel at a vessel access location, the first elongate member having an expandable filter carried on a distal portion thereof;
• introducing a second elongate member into the vessel at the vessel access location, the second elongate member having an expandable treatment device carried on a distal portion thereof;
• advancing the first elongate member through the vessel to position the expandable filter downstream of the treatment site;
• advancing the second elongate member through the vessel to position the expandable treatment device within the treatment site;
• expanding the expandable filter within the vessel;
• expanding the treatment device radially outwardly at the treatment site, embolic particles released from the treatment site being prevented from flowing distally through the vessel by the expanded filter;
• removing the second elongate member from the vessel;
• after the second elongate member has been removed from the vessel, introducing a distal end of an elongate retrieval member into the vessel, the elongate retrieval member having a lumen sized to receive the first elongate member;
• advancing the elongate retrieval member through the vessel over the first elongate member to retrieve the expandable filter;
• and
• removing the elongate retrieval member, first elongate member and expandable filter from the vessel.