An intravascular filter device (10) having a flexible arm (20) which comprises a portion of an alarm system for detecting filling or plugging of the filter by captured emboli is described. The flexible arm may be made of ferromagnetic material, a magnet, or have at its tip a magnet (24) which, as it moves under systolic and diastolic pressures, generates a signal detectable by an electrical sensor or a magnetometer. The signals from each of a pair of artery filters may be measured and compared to determine whether one filter is plugged. A system for detection and a method of use are also provided.
