A method and apparatus for thrombectomy with partial dissolving by streptokinase or the like, wherein a catheter set with a sheath having two open lumens extending in parallel over most of the length of the sheath. The lumen are distal-parallel to one another and issue proximally under a finite angular alignment. The first lumen takes up virtually the entire cross-sectional area of sheath, while the second lumen is much narrower and is constructed in a widened area of the wall of the first lumen. A safety change wire is adapted to be accommodated in the second lumen.
