Guidewire technology over the past decade has greatly improved and most companies offer a comprehensive collection of various wires with different properties to help interventional cardiologists reach their vascular target in a timely, accurate and safe manner.
Many interventional cardiologists prefer to use the same guidewires on which they trained as fellows. It’s partly comfort for how the guidewire feels in their hands, but it’s also about success: why fix what isn’t broken?
There are many design options for wires. The core is usually ground to a taper towards the end for the tip to attach. In some wires, the core extends up to the tip. In others, the tip is made of a different material. If the core starts tapering more towards the tip, the wire as a whole becomes more rigid, steerable and torquable. The opposite happens when the core tapers more proximally, allowing for a longer tip. The core may be continuous or joined. Joined transitions are more prone to prolapse when moving the wire back and forth.
All wires have tradeoffs, such as more or less tactile sensation, rigidity, flexibility and durability. It is important for interventional cardiologists to understand the different nuances of available wires and to use them to better facilitate the procedure.
“The so-called workhorse wires steer, torque and shape very well,” says William L. Lombardi, MD, medical director of the cardiac catheterization laboratories, St. Joseph Hospital in Bellingham, Wash. “There are subtle differences between them, but generally what you’ve trained on is what you use.”
Guidewires can be coated with a hydrophobic or hydrophilic polymer. A hydrophobic wire repels water, giving the interventionalist a stronger tactile sensation. A hydrophilic coating attracts water, making the delivery smoother, but with less tactile sensation. Extra care has to be taken with hydrophilic wires so as not to perforate a vessel or dislodge parts of a lesion.
“With regard to all wires, in general, we try to use the least aggressive wire we can while still achieving some degree of support. The optimal wire is one that doesn’t cause damage if it gets into a spot where you can’t see,” says Morton Rinder, MD, an interventional cardiologist at St. Luke’s Hospital and St. John’s Mercy Medical Center, St. Louis.
Workhorse wires, such as the HT Balance Middleweight, or BMW (Abbott Vascular), Cougar (Medtronic), IQ (Boston Scientific) and Stabilizer (Cordis), are used for the majority of cases, but there are specialty wires that could be used more often but are not, says Lombardi, mostly because workhorse wires perform so well. Nevertheless, he laments “the lack of education about the distinctive specialty wires.”
Although a workhorse wire has its benefits, there are several reasons why it won’t get the job done, such as lesion characteristic, vessel tortuosity or location. “In those situations, you may want to use another wire with distinct properties to help facilitate the interventions,” says Lombardi.
One of the first things to look for in tough situations is a stiffer wire, one that offers more support. The hydrophobic Grand Slam (Abbott), for example, allows for extra support and tactile sensation for navigating tortuous vessels and delivering devices. The hydrophilic Mailman (Boston Scientific), on the other hand, will give the interventionalist a different “feel” while navigating through tortuosity and deploying stents or balloons. Specialty wires can be used as the primary wire or as a “buddy” wire, a second wire that adds support to the first.
Michael Jones, MD, medical director of the Baptist Heart and Vascular Institute at Central Baptist Hospital in Lexington, Ky., turns to the Venture Catheter (St. Jude Medical) in tough situations. The Venture, a small catheter that fits into the catheters that are used to deliver 0.014-inch guidewire, allows interventionalists like Jones to “direct—and more importantly, redirect—the tip.”
Jones says it was more common for interventions to fail 15 or 20 years ago. “Today, failure rate is probably under 1 percent, given the improved guidewire technology and stent and balloon platforms.” But the main advantage of a “bailout” wire, or in this case, catheter, is that the procedure can be completed faster, with less contrast and radiation exposure, and with fewer complications. In fact, Jones will often start with the Venture, rather than