It is common practice in the fields of angioplasty and atherectomy to insert catheters into the artery through a plastic sheath. These sheaths are typically made from PVC or an equivalent plastic and have a wall thickness which is typically 10 mils (1.0 mil equals 0.001 inches). One difficulty with existing sheaths is that they are so thin-walled and made from plastic so that they occasionally buckle or kink at the point where they enter into or bend in the femoral artery or where they pass through a highly curved section of an iliac artery.
It is also highly advantageous to make the sheath as thin-walled as is possible. The inner diameter of a sheath has a dimension which is controlled by the outside diameter of the catheter to be placed through it. The outside diameter of the sheath is then typically 20 mils greater than the inside diameter in order to provide a 10 mil wall of plastic which is necessary to give the sheath adequate strength. However, it would be highly advantageous to reduce the outside diameter of the sheath so as to minimize arterial distention thereby reducing the bleeding that occurs at the insertion site after the catheter and sheath are removed from the artery.
Because they are made from a thin-walled plastic, current sheaths are not significantly radiopaque. However, it would be highly advantageous to have a radiopaque sheath so that the placement of its distal end in a vessel could be easily ascertained by fluoroscopy.