Technical Information

The following information is provided for reference only in the design and specification of medical guidewires.

The typical access and interventional guidewire is constructed with an outer spring coil welded to an inner member, either a ribbon wire, core wire or both.

Guidewires with diameters over 0.032” are usually constructed using an inner ribbon wire (sometimes called a safety wire) that is welded to both ends of the coil to provide longitudinal integrity. The core wire in this case would be welded at the proximal end and would terminate prior to the distal weld. Guidewires with diameters less than 0.032” typically do not have enough room for both the ribbon wire and the core wire. As a result the core wire only is used and it is welded at both the proximal and the distal end to provide longitudinal integrity in the smaller diameter guidewires. This design can also be applied to guidewires above 0.032" diameter without loss of strength or structural integrity.

The body flexibility of a guidewire is determined by the material used, the diameter of the wire used to make the outer coil, the diameter of the core wire and the coil tension. Tip flexibility is primarily based on the coil tension and the design of the core wire taper grind configuration: i.e. the taper diameter, length of the taper and number of ground tapers incorporated in the design.

Access and interventional guidewires can be produced in an infinite number of lengths and diameters and they are usually specified using inches for diameter and centimeters for length.

Guidewire diameters are typically 0.018”, 0.021”, 0.025”, 0.032”, 0.035” and 0.038” although any diameter can be produced to properly interface with the corresponding catheter. The typical length for an access wire is 45 cm and 70 cm while the interventional wires are generally 150 cm and 260 cm, however, any length variation up to approximately 500 cm can be manufactured depending on the application requirement.

Another design option is the creation of a flexible tip at one or both ends of the guidewire; a single distal guidewire has a flexible taper at one end only while the double distal guidewire has a flexible taper at both ends of the guidewire.

Access and interventional guidewires are also manufactured in both straight and “J” configurations. The J typically has a 3 mm radius and looks like a shepherds hook. The J can be "finger" straightened for easy insertion but returns to the J shape once in the vasculature to help negotiate placement in tortuous vasculature.

Although the most common J radius is 3 mm other designs incorporate radii as small as 1.5 mm and as large as 15 mm.

Often the double distal design will incorporate a J tip at one end and a straight tip at the other to facilitate user preference in a single guidewire.

The longer interventional guidewires are generally coated with PTFE (poly tetra fluoro ethylene) which is a lubricous plastic similar to the non stick coatings used in cookware. The industry standard color is green. Originally PTFE coated wires were made by spraying the plastic over the finished wire, however, the current state of the art is to use wire pre‐coated with the PTFE. This design provides a smoother surface and better material adhesion as well as better flexibility and movement of the J tip; spray coating fills in the gaps between the coils increasing stiffness and impeding the straightening of the J tip.

Interventional wires are also available in a movable core configuration versus the fixed core design. In this case the main coil spring body is welded to a ribbon wire at both the distal and proximal ends. The core wire, typically incorporating a PTFE coating for lubricity, has a short spring section with the same outer diameter as the main body spring welded in place at the proximal end. The core wire is then inserted into the main body spring. During use the core can be retracted by the physician to provide a variable flexible length at the distal tip which can be straight or with a J radius.

Other variations of the standard guidewire are also available and include the Amplatz, Rosen, Bentson and Mandrel type guidewires.

The Amplatz guidewire utilizes a flat wire versus a more traditional round wire in the manufacture of the coil thereby reducing the cross sectional area of the coil in the final guidewire assembly. This design also tends to employ a larger diameter core wire which provides more body stiffness than can be achieved in a standard round wire coil design of similar diameter.

The Bentson type guidewire design typically has a longer taper length then a standard interventional guidewire providing an extra long flexible tip.

The Rosen design has a more traditional taper length with the “J” formed into a very tight, nearly circular, distal tip.

Mandrel guidewires are, as the name infers, built using a mandrel for the guidewire body. The distal end is tapered to provide the flexibility required for tracking through the vasculature and a spring coil is welded or bonded to the tapered end. This design provides the maximum amount of body stiffness per the cross sectional area.

Standard guidewire tolerances:

Coil Spring Outer Diameter: + 0.000”/‐ 0.001”
Length: +/‐ 1.0 cm
J Radius: +/‐ 0.5 mm
Wire Diameter: +/‐ 0.0002”

Materials:

Ascent Medical Corporation uses ASTM grade 304 Vacuum Arc Re‐melted (VAR) stainless steel in the construction of its guidewires. The VAR process typically improves the purity and homogeneity of the metal and yields a more uniform chemistry with minimal voids and contaminants.

Tensile Strength:

The industry standard minimum break strength for access and interventional guidewires is detailed in Annex H of the test standard - BS EN ISO 11070: 1999. The requirements are dependent on the diameter but equate to the following:

Diameters from 0.021” - 0.0295" (0.55 - 0.75 mm) - have a minimum break of 1.1 pounds (5 Newton's) Diameters greater than 0.0295" (0.75 mm) - have a minimum break of 2.25 pounds (10 Newton's)

Each guidewire produced by Ascent Medical Corporation is proof loaded to verify proper attachment of the ribbon and/or core wire to the proximal and distal ends of the guidewire coil.

Back to Top