Instrumentation for percutaneous delivery of blood filtration devices to atrial appendages includes a curved access sheath and a delivery tube. A compressed filter device attached to a tether wire is loaded in the delivery tube. The access sheath and the delivery tube can be mechanically locked and moved together to place the device in a suitable deployment position. The device is deployed by expelling it from the delivery tube either by retracting the delivery tube over the tether wire, or by moving the tether wire forward through the delivery tube. A filter membrane in the deployed device extends across the appendage ostium to filter blood flow through the ostium. The filter membrane is configured to present a flat surface to atrial blood flow past the ostium.