A guidewire apparatus for use during percutaneous catheter interventions, such as angioplasty or stent deployment. A protection element comprising a filter or an occluder is mounted near the distal end of a steerable guidewire, which guides a therapeutic catheter. The guidewire apparatus comprises a hollow shaft movably disposed about a core wire and, optionally, a slippery liner interfitted there between. The shaft and core wire control relative displacement of the ends of the protection element, causing transformation of the protection element between a deployed configuration and a collapsed configuration.