Percutaneous Transluminal Coronary Angioplasty (PTCA) procedures begin with accessing a major artery. As these arteries provide critical blood supply to the body, a conventional incision would be life threatening. In 1953 Swedish radiologist Dr. Sven-Ivar Seldinger developed a procedure to limit the risk of accessing a major artery. With some variation, this procedure is used today to begin PTCA procedures.
The Seldinger technique uses a hollow needle to puncture the skin and access the femoral (leg) or radial (arm) arteries. A guidewire, with an outside diameter closely matching the inside diameter of the hollow needle, is quickly inserted through the needle and into the blood vessel. This limits blood loss from the needle puncture. Once the wire is in the blood vessel, the needle is removed.
A dilator and sheath are then placed over the wire and inserted into the blood vessel. The dilator is a tapered tube, on the inside of the two-component set, which is designed to gradually expand the opening upon insertion. It is typically made of a moderately rigid and low friction polyethylene.
The outer tube, known as a sheath, follows the dilator into the expanded blood vessel opening. Once in position, the dilator and guidewire are removed. The sheath remains and is used to introduce catheters or other devices into the blood vessel. For this reason, the entire set of components is often referred to as an ‘introducer kit.’
Sheaths are short, thin-walled tubes, typically constructed from Fluorinated Ethylene Propylene extrusions and low-friction coatings (e.g., hydrophilic). These tubes are sufficient to accommodate the largest diameter catheter anticipated for the PTCA procedure. A hemostasis valve is attached on the end of the sheath, outside the body, so that catheters and guidewires can be exchanged without blood loss. A flushing side port near the valve allows for pressure monitoring, delivery of fluids or drugs and blood withdrawal, if required.