An illustrative mechanical thrombectomy system may comprise an outer catheter extending from a proximal end to a distal end and defining a first lumen extending therethrough and an inner sheath extending from a proximal end to a distal end and defining a second lumen extending therethrough. The inner sheath may be slidably disposed within the first lumen of the outer catheter. An inner shaft may be slidably disposed within the second lumen of the inner sheath and an expandable anchor mechanism may be coupled to the distal end region of the inner shaft. The expandable anchor mechanism may be configured to move between a collapsed delivery configuration and an expanded configuration.