General Principles of Endovascular Therapy: Guidewire and Catheter Manipulation

Historical Background

The age of endovascular therapy began with Dr. Sven Seldinger’s publication in 1953 of his technique for vascular access over a wire. The field expanded rapidly with subsequent seminal publications, including those by Dr. Charles Dotter, an American radiologist, in 1964 that demonstrated a technique to cross an atherosclerotic lesion. Indeed, Dotter was the first to describe flow-directed balloon catheterization, the double-lumen balloon catheter, the safety guidewire, and the “ J ” tipped guidewire. In his angiography laboratory in Oregon, Dotter and his technicians were the first to make wire guides and produced Teflon catheters using a blowtorch. These pioneering endeavors set the stage for Andreas Gruntzig, who developed the technique of balloon angioplasty, as well as Julio Palmaz, who designed the first balloon expandable stent in 1985.

Without first obtaining the basic skills of wire and catheter selection and manipulation, the interventionist cannot be successful with endoluminal therapies. To that end, the following text describes the basic concepts of selecting and utilizing various catheters and guidewires.

Guidewire Selection

Guidewires are available in many sizes, shapes, and compositions, which are dictated by their intended purpose ( Table 4-1 ). Their diameters are measured in inches, with standard sizes on which current endovascular platforms are based, including 0.035-, 0.018-, and 0.014-inch guidewires. Guidewire length is chosen based on the sum of the distance from the site of vascular entry to the site of intervention and the device platform, such as an over-the-wire or monorail system.

Guidewires are composed of a nonhydrophilic metal but may be coated with a hydrophilic polymer film that once moistened affords a low friction surface. The hydrophilic coating can be on a portion of the tip or on the entire guidewire shaft. Hydrophilic guidewires should not be used for initial arterial entry because of the risk of shearing off the film coating with the beveled edge of the entry needle, as well as an increased risk of subintimal dissection. Aside from the guidewire type and diameter, other important characteristics include radiopacity; flexibility; “torquability” or “steerability,” which reflects the capacity to turn the guidewire tip; “trackability,” or the ability to pass the wire into the target vessel once the tip is engaged within the vessel orifice; and tip shape, which may be straight, angled, or J shaped ( Fig. 4-1 ).

Many guidewires have gradations of diameter and flexibility, and familiarity should be sought with the transition points along a given guidewire. The degree of flexibility along a guidewire has implications for both its trackability and its torquability. In addition, guidewires with various tip weights are available, with a heavier tip associated with decreased flexibility that may improve the ability of the wire to cross a dense, heavily calcified plaque.