Читать книгу Interventional Cardiology - Группа авторов - Страница 137

Guidewires are required to cross the target lesion and to provide support for the delivery of balloons, stents, and other devices while at the same time minimizing the risk of vessel trauma. A guidewire needs to be steerable, visible, flexible, lubricious, and supportive. There is no single wire that has the perfect combination of all these characteristics. Variations in guidewire components have produced a wide range of wires suitable for different anatomies and lesion characteristics. Wire selection depends on which features are thought to optimally facilitate angioplasty for a given clinical and angiographic scenario.

Guidewires typically come in 180–195 cm length for rapid exchange (Rx) use. Long (300 cm) wires have become almost obsolete since the technique of balloon trapping has gained wide application to remove or insert OTW balloons or microcatheters. The only limitation of this technique is its inapplicability in very small guiding catheters (5 Fr) or when a guide extension is present (except Trapliner). Anyway, almost all wires (Abbott, Asahi, Terumo) have wire extensions that can be fixed at the distal end to increase wire length. Most wires (Abbott, Asahi, Terumo) anyway allow fitting at the distal end a dedicated extension wire. Finally, maintaining pressure with an Indeflator connected to the central lumen of the OTW microcatheter or balloon catheter allows flushing it out keeping the wire in place (Nanto technique).

Guidewires consist of a central core of stainless steel or nitinol alloy that makes up the proximal section of the wire, approximately 145 cm long, and which tapers toward a distal section measuring 35–40 cm. This distal segment has a further outer covering of either a fine coil spring consisting of tungsten, platinum, or stainless steel, or a polymer coating loaded with a material such as tungsten to improve radiopacity. The tip often has a lubricious coating that is either hydrophobic or hydrophilic (Figure 5.7). Using stainless steel as the core material improves the steerability and torque control, but steel wires can be deformed by tortuosity and cannot be reshaped. A nitinol core also offers excellent torque control, but the wire retains its shape better and can be reshaped if deformed. Increasing the core diameter increases shaft support (Figure 5.8). There is often a short transition zone between the tapered distal segment whereas some wires have a very gradually tapering central core, which tends to track better around tortuous anatomies and prolapse less when there is extreme angulation (Figure 5.8). Features of the functional design of guidewires are listed in Table 5.4. Guidewires can be classified into general purpose or “workhorse” and dedicated wires (Table 5.5).

Figure 5.8 The components of a rapid exchange balloon catheter.

Table 5.4 The selection of a guidewire depends on the characteristics required to deal with lesion complexity or particular vessel characteristics. The characteristics of guidewires can be altered by modifying specific components during the production process.

Flexibility	Flexible wires can better negotiate severe tortuosity or angulation without deformation.	Shaft core material (nitinol offers greater flexibility and shape retention), core thickness (thinner core = more flexible).
Support	Improved equipment delivery when hampered by angulation, tortuosity, lesion severity, calcification.	Shaft core material, core thickness.
Steerability is a function of:
Torque transmission	1 : 1 transmission of torque to the tip is the ideal.	Core materials are chosen for having good torque transmission, which is also improved by a thicker core with more gradual distal taper.
tip shape ability	Importance increases as lesion complexity increases.	Nitinol is more difficult to shape, but can be reshaped; steel is easier to shape but can be ruined by being deformed.
Lubricity	Can ease wire passage in tight, calcified, severely tortuous lesions.	Tip or distal segment coating with silicon, hydrophilic coating, or polymer coating: “plastic jacketed” wires are the most lubricious but also the most dangerous; when combined with a stiff tip long dissections can be inadvertently created:hydrophilic requires water for activationhydrophobic does not require water for activation, allows feedback from distal tip so that excessive friction when creating a subintimal dissection or going below stent struts can be detected.
Tendency to prolapse	Can be important when negotiating angles >75°	A gradually tapering core with a smooth transition toward the tip improves support and tracking around bends; abrupt tapers and floppy cores are more likely to prolapse.
Visibility	The level of visibility becomes more important in obese patients or when angled working views are required.	Lubricious polymer‐coated nitinol wires can be difficult to see, platinum, steel, or tungsten markers at distal tip.
Tactile feedback	Provides the operator with essential nonvisual information, allows “palpation” of the lesion at the distal wire tip.	Hydrophylic wires provide poor tactile feedback; hydrophobic wires provide more feedback.
Tip stiffness	A soft gentle tip is essential for all “workhorse” wires; to reduce the risk of vessel trauma; stiffer tips are required for dedicated CTO wires.	More gradual distal taper, distal core material (e.g. high tensile steel).

Table 5.5 Classification of guidewires.

Product name	Core material	Rail support	Radiopaque tip length (cm)	Tip type	Tip style	Tip tapering	Tip stiffness	Tip load (g)	Tip coating type
Workhorse wires
Hi‐Torque BMW Universal	Elastine Nitinol	Moderate	3	Polymer/ Spring coil	Shaping ribbon	Non‐tapered (0.014″)	Soft	0.7	Hydrophilic
ChoICE Floppy	Stainless steel	Light	3	Polymer/ Spring coil	Core‐to‐tip	Non‐tapered (0.014″)	Soft	0.8	Hybrid (distal 3 cm uncoated)
Runthrough NT	Stainless steel/ Nitinol	Light	3	Stainless steel coils	Shaping ribbon	Non‐tapered (0.014″)	Soft	1.0	Hydrophilic
Asahi Soft	Tru Torque Steel	Moderate	3	Spring coil	Core‐to‐tip	Non‐tapered (0.014″)	Soft	0.7	Hydrophobic
Hi‐Torque Floppy II	Stainless steel	Moderate	2/30	Spring coil	Shaping ribbon	Non‐tapered (0.014″)	Soft	0.4	Hydrophilic/hydrophobic
PROWATER (Rinato)	Tru Torque Steel	Moderate	3	Spring coil	Core‐to‐tip	Non‐tapered (0.014″)	Soft	0.8	Hydrophilic
Extra support wires
HT Iron Man	Stainless steel	Extra support	3	Spring coil	Core‐to‐tip	Non‐tapered (0.014″)	Soft	1.0	Hydrophobic
Grand Slam	Tru Torque Steel	Extra support	4	Spring coil	Core‐to‐tip	Non‐tapered (0.014″)	Soft	0.7	Hydrophilic
HT BHW	Elastine/ Nitinol	Extra support	4.5	Spring coil	Shaping ribbon	Non‐tapered (0.014″)	Soft	0.7	Hydrophilic
HT Extra S’Port	Stainless steel	Extra Support	3	Spring coil	Core‐to‐tip	Non‐tapered (0.014″)	Soft	0.9	Hydrophobic
Hi‐Torque Whisper ES	Durasteel	Extra Support	3	Polymer over coils	Core‐to‐tip	Non‐tapered (0.014″)	Soft	1.2	Hydrophilic
ChoICE Extra Support	Stainless steel	Extra Support	3	Polymer/Spring coils	Core‐to‐tip	Non‐tapered (0.014″)	Soft	0.9	Hybrid (distal 3 cm uncoated)
Lubricious/tortuous/subtotal/CTO lesions wires
Hi‐Torque Whisper LS	Durasteel	Light	3	Polymer over coils	Core‐to‐tip	Non‐tapered (0.014″)	Soft	0.8	Hydrophilic
Hi‐Torque Whisper MS	Durasteel	Moderate	3	Polymer over coils	Core‐to‐tip	Non‐tapered (0.014″)	Soft	1.0	Hydrophilic
Hi‐Torque Pilot 50	Durasteel	Moderate	3	Polymer over coils	Core‐to‐tip	Non‐tapered (0.014″)	Intermediate	1.5	Hydrophilic
Fielder/Fielder FC	Tru Torque Steel	Moderate	3	Polymer over coils	Core‐to‐tip	Non‐tapered (0.014″)	Soft	1.0/0.8	Hydrophilic
Fielder XT	Tru Torque Steel	Moderate	16	Polymer over coils	Core‐to‐tip	Non‐tapered (0.009″)	Soft	0.8	Hydrophilic
Sion	Tru Torque Steel	Moderate	3	Spring coil	Core‐to‐tip	Non‐tapered (0.014″)	Soft	0.7	Hydrophilic
Sion Blu	Tru Torque Steel	Moderate	3	Spring coil	Core‐to‐tip	Non‐tapered (0.014″)	Soft	0.5	Hydrophilic (except very distal tip)
Miracle 3/4.5/6/12	Tru Torque Steel	Moderate	11	Spring coil	Core‐to‐tip	Non‐tapered (0.014″)	Intermediate (3/4.5), Stiff (6/12)	3.0/4.5/ 6.0/12.0	Hydrophilic
Conquest	Tru Torque Steel	Moderate	20	Spring coil	Core‐to‐tip	Non‐tapered (0.014″)	Stiff	9.0	Hydrophobic
Conquest (Confianza) Pro	Tru Torque Steel	Moderate	20	Spring coil	Core‐to‐tip	Non‐tapered (0.014″)	Stiff	9.0	Hydrophilic (except very distal tip)
Conquest (Confianza) Pro 12	Tru Torque Steel	Moderate	20	Spring coil	Core‐to‐tip	Non‐tapered (0.014″)	Stiff	12.0	Hydrophilic (except very distal tip)
GAIA First	Stainless Steel	Moderate	15	Polymer over coils	Core‐to‐tip	Tapered (0.014–0.010″)	Soft	1.7	Hydrophilic
GAIA Second	Stainless Steel	Moderate	15	Polymer over coils	Core‐to‐tip	Tapered (0.014–0.011″)	Soft	3.5	Hydrophilic
GAIA Third	Stainless Steel	Moderate	15	Polymer over coils	Core‐to‐tip	Tapered (0.014–0.012″)	Soft	4.5	Hydrophilic

Workhorse guidewires typically have soft tips, but the amount of shaft support varies (Table 5.5). Although some wires have preshaped tips, the tip stiffness can be increased by heating it during the preshaping process and the standard (30 degrees, 2‐3 mm from the tip) angle may not match the anatomy. As a result, preshaping rarely offers an advantage except perhaps for polymer‐coated wires, which can be difficult to shape, or for CTO wires where a fixed more durable very small primary curve is preferable. Guidewire shaping can be achieved in many ways including curling the shaping ribbon of the wire over the side of the introducer needle, advancing the wire through the introducer tip and bending it gently outside of the introducer needle tip, or curling it with a finger. It does not matter which method is used to shape the wire tip, provided that it is done gently without damaging the wire. When shaping the tip of a wire, the primary curve should match the greatest angle to be negotiated, whereas the secondary curve is chosen to match the size of the vessel (Figure 5.9).

Figure 5.9 Distal tip styles and components contributing to the crossing profile of balloon catheters.

Polymer coated wires are not recommended as a first choice for general purpose use, because the highly lubricious tip can easily slip beneath a plaque and create a dissection during insertion. These wires also have a higher tendency to migrate distally and increase the risk of perforation, give less tactile feedback, and have lower visibility. Highly tortuous vessels require a flexible lubricious wire in the first instance (e.g. BMW Universal, WhisperMS, Choice floppy), which can then be exchanged via an OTW microcatheter for a more supportive wire (e.g. Choice extra support, Mailman, Ironman, Sion Blue ES, Grand Slam, Platinum Plus).

The handling characteristics of different wires vary substantially and even the same wire can have a very different “feel” under different circumstances. For example, wires frequently perform differently and offer different tactile feedback in more complex lesion subsets including those with diffuse disease with heavy calcification or angulation. Unexperienced operators often progress more confidently by becoming familiar with one workhorse wire used for most cases. Nitinol wires are more forgiving and can be reshaped. An important principle is never to push when the wire bends or buckles, but rather to withdraw and rotate before gently re‐advancing it. Learning how to exchange a wire using OTW microcatheters is an essential skill before tackling complex lesions. More complex angioplasty will also provide an opportunity to gain familiarity with an expanded range of wires.

Dedicated wires for treating CTO have stiffer tips. Tip stiffness is measured in grams of forward pressure required to flex the tip. Specialty wires are listed in Table 5.5 and are discussed in other chapters. Over the last two decades, technologies used for CTO recanalization have emerged with the production of wires specially developed to satisfy the demand of operators involved in this challenging field. The development of new interventional recanalization techniques has been followed by a concomitant increase in the number of specialized wires for specific applications.

The Sion and Suoh 03 wires are currently the gold standard for septal or epicardial collateral tracking, because of their unique trackability which enables the wire to follow most collateral bends. Using this innovative wires, epicardial connections are successfully utilized in almost 35% of retrograde cases in contemporary series from Japan [17,18]. It uses a composite core technology that includes multiple wire components to enhance durability and torque transmission. The tip of the Sion wire can be shaped and a larger than expected curve (70 degrees) near the tip (1 mm) is recommended and may need reshaping during the procedure. The Suoh 03 has a preshaped tip that surprisingly retains its shape through tortuous collateral tracking. These wires can be extremely helpful also outside the CTO field, for instance to gently regain the distal lumen in the presence of spontaneous or iatrogenic (post‐PCI) dissections. Polymer jacketed tapered soft guidewires (Fielder XTR, Sion Black) with composite core technology can greatly facilitate crossing subocclusive calcific lesions in tortuous arteries, overcoming the limitations of poor GC support. These wires should always be advanced over a microcatheter to increase support at the tip, when needed, and to exchange them after crossing with a workhorse wire using trapping.