Watch the following video for a demonstration of how to add obstructions to the original artery geometry using Ansys SpaceClaim.
Quick Summary:
Edit Model in SpaceClaim
File → SpaceClaim Options → Set Minimum Grid Spacing to 0.1mm
Place a point where you want the centroid of the obstruction located
Merge the surrounding faces using Repair → Merge Faces
Hide Artery
Sketch an ellipse on XZ plane
Major axis length (along Z): 12mm
Minor axis length (along X): 4mm
Pull → Select the Z axis → Click the → button
Move → Up to → Click on the Point from earlier
Unhide Artery and make sure ellipsoid is properly sized and positioned
Use Pull → Scale to resize the ellipsoid
Use Move to reposition the ellipsoid using the directional or orientational handles
Click Combine
Click the artery, then the ellipsoid (should result in three solids)
Delete or suppress all entities except the artery
Click Pull, click on the edge of the resulting depression and create a fillet
If you need to restart for any reason, simply CTRL + click the depression and the fillet and then click Fill (make sure you click the green checkmark that is on the screen)