Method of operating a microvalve protection device

A method of infusing a therapeutic agent into a fluid-filled vessel during a procedure, comprising:

• a) providing a device having,
• i) a catheter having a proximal end, a distal end, and a lumen, and
• ii) a valve coupled to said distal end of said catheter, said valve comprising,
• A) a plurality of elongate first filaments each having a diameter of 0.025 mm to 0.127 mm, said first filaments extending in a braided formation and having a proximal end, a distal end, and a length extending therebetween,
• said proximal ends secured relative to each other, said first filaments along said lengths distal of said proximal ends not bonded to each other such that said first filaments are movable relative to each other,
• said valve fully collapsible into an undeployed state, and expandable from said undeployed state into a radially-expanded deployed state by a spring bias of said first filaments,
• wherein in said deployed state said first filaments cross one another at an angle of 100° to 150°;
• and
• B) a filter integrated with said first filaments, said filter formed by electrostatically depositing or spinning polymeric second filaments onto said first filaments, said filter defining a pore size preventing passage of the therapeutic agent;
• b) inserting the device into the vessel such that said valve dynamically responds to the relative fluid pressures located both (i) downstream said valve and (ii) upstream said valve, all while said valve is located within said vessel;
• and
• c) infusing the therapeutic agent through said catheter and into the vessel through the catheter at an infusion pressure.

A method of infusing a therapeutic agent into a blood-filled vessel during a procedure, the vessel having a blood flow with upstream and downstream directions, the blood having proteins, said method comprising:

• a) providing a device having,
• i) a catheter having a proximal end, a distal end, and a lumen, and
• ii) a filter valve coupled to said distal end of said catheter, said filter valve defining pores with a pore size preventing passage of the therapeutic agent;
• b) inserting said device into the vessel;
• and
• c) infusing the therapeutic agent at a first infusion pressure through said catheter and into the vessel,
• wherein said first infusion pressure causing said filter valve to open across said vessel to prevent reflux of the therapeutic agent in the upstream direction past said filter valve, wherein at the first infusion pressure the proteins in the blood adhere to the filter valve and create a barrier to passage of blood through said pores of said filter valve in the upstream direction past said filter valve;
• and
• d) infusing the therapeutic agent a second infusion pressure through said catheter and into the vessel,
• wherein said second infusion pressure is greater than said first infusion pressure, and at said second infusion pressure the proteins in the blood are at least partially removed from said pores of said filter valve to permit passage of blood through said pores of said filter valve in the upstream direction past said filter valve while preventing reflux of the therapeutic agent in the upstream direction past said filter valve.