A collapsible and deployable filter for blocking debris and passing blood in a blood vessel in a patient's body, the filter including； a framework of a flexible material, constructed to have a radially compressed state, in which the framework is radially compressed by radial deforming forces, and a radially expanded state to obdurate an artery； and a flexible filter material secured to said framework and having pores dimensioned to prevent the passage of debris therethrough while allowing the passage of blood. The filter has, in the radially expanded state of the framework, a generally conical or frustoconical form with a large diameter end, a small diameter end opposite to the large diameter end, and a side surface extending between the ends. The filter has an opening that is free of filter material at the small diameter end or in the side surface.
