Guide wires are essential tools in interventional cardiology and radiology, acting as the vanguard in navigating complex vasculature to reach target lesions or vessel segments. Once in place, they serve as rails, allowing larger catheters to be advanced to the treatment site with greater ease and precision. Understanding the design and function of these wires is crucial for effective and safe procedures.
Many common guidewires are designed to aid the placement of balloon dilatation catheters during percutaneous transluminal coronary angioplasty (PTCA) and percutaneous transluminal angioplasty (PTA). PTCA is performed in the coronary arteries, whereas PTA is performed in other arteries. The performance of a guidewire is usually defined by pushability, steerability, torque, and radiopacity.
Core Construction and Braiding in Guidewires
Guidewires come in two primary configurations: solid steel or nitinol core wires, and solid core wires wrapped in a smaller wire coil or braid. The use of coiled or braided wires offers enhanced flexibility, pushability, and resistance to kinking. For example, some of Boston Scientific’s guidewires use a nitinol tube with micro-cut slots instead of braided wire. This improves torque control.
Nitinol wire, used independently or braided with stainless steel, improves flexibility, allowing the wire to return to its original shape after traversing tortuous vessel segments. Guidewires commonly feature a flexible tip and a stiffer body, facilitating easy navigation while providing good pushability.
Coatings and Visibility
To enhance performance, some wires are coated with polymers such as silicone or polytetrafluoroethylene (PTFE) to increase lubricity. Hydrophilic coatings reduce friction during deployment, enabling easier movement within tortuous vessels. Radiopaque markers, such as gold bands or platinum wires, are frequently incorporated to improve visibility during fluoroscopic X-ray imaging.
The tips of guidewires are available in various configurations, including “J” curves, angled tips, and straight tips, to aid navigation through diverse vessel anatomies.
Dimensions and Recent Advances
Guidewire diameters are measured in thousandths of an inch, typically ranging from 0.014 to 0.038 inches. Lengths vary from 80 to 450 cm.
Recent innovations in guidewire technology include the Boston Scientific Journey guidewire. It’s a 0.014-inch wire designed for treating arteries below the knee and features a micro-cut nitinol sleeve. This design provides efficient transmission of torque energy for more precise control, along with enhanced durability and tactile response. Another is Terumo’s Glidewire Advantage peripheral guide wire, launched in September 2009, is a single wire that enables the operator to cross the lesion and deliver interventional devices. The device is a combination of Terumo’s Glidewire construction on the distal 25 cm with a unique spiral PTFE coating on the proximal end
Volcano introduced an improved fractional flow reserve (FFR) guide wire called PrimeWire Prestige pressure guide wire to speed treatment of multivessel disease. It combines FFR with a guide wire designed to reduce the number of catheters needed.
Conclusion
In summary, while not all guide catheters utilize wire braiding, it is a common and effective design choice to achieve the necessary flexibility, pushability, and kink resistance for successful navigation through complex vascular systems. Understanding the nuances of guidewire design, including the presence or absence of wire braiding, is essential for interventional specialists.
