Guidewires: To Treat It, You have to Reach It
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| Hi-Torque Balance guidewire from Abbott Vascular |
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.”
‘Bailout’ 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 waiting for trouble to arise.
James T. DeVries, MD, an interventional cardiologist at Dartmouth-Hitchcock Medical Center in Lebanon, N.H., estimates that he might want to start with a wire that has more support in 25 percent of cases. “Today’s devices are easier to deliver than those from five or 10 years ago. Consequently, there is not as great a need for support wires,” he says.
Sometimes the choice of wires depends on the patient population. In the Northeast where DeVries is located now, the patients tend to be older, have very calcified and less compliant vessels, making it more challenging to deliver devices. When he was in New Orleans, the general population tended to be younger, in their 50s, with a lot of plaque burden, but not necessarily the same degree of dense calcification. “The strategies I employed were different for these different regions,” he says.
Cath lab managers should understand physician preferences in regards to workhorse wires. They should try to minimize the number of wires that do the same things. For routine coronary interventions, three to five wires is enough to get through 95 percent of the cases. “For CTOs, you will need at least 10 wires to ensure you cover all the eventualities and issues,” says Lombardi.
Cardiologists agree that comfort plays a big role in guidewire selection. Of course, it has to get the job done, but many interventionalists talk about guidewires as if they were extra appendages on their body. “They become very much a part of what you do. You trust that wire and you try not to deviate,” says Rinder. “New wires are an unknown and the last thing you want to do is use a wire that isn’t what you thought it was and get into trouble.”
| Peripheral Interventions |
| In the areas of the iliac and subclavian arteries, Morton Rinder, MD, an interventional cardiologist in St. Louis, likes the Wholey (Covidien) series of wires. “They have good tip steerage and the wire transitions into a much stiffer portion so you can deliver peripheral devices more easily,” he says. While he mostly limits himself to the subclavian and iliac arteries, he will venture below the leg on occasion. When those cases arise, he uses “a more aggressive wire, one with a stiffer, hydrophilic coating that can pound through the occlusions.” For these situations, he likes Terumo wires. |