Choice of Sheaths, Wires, and Catheters

Fig. 5.1

Components of a sheath (a): The sheath (straight arrow) is introduced into the blood vessel using an introducer (curved arrow) that snaps onto the hub of the sheath when fully inserted. The introducer is threaded over the wire placed into the vessel. Once the sheath is introduced into the vessel, the introducer can be removed by detaching at its cap end (asterisk) from the sheath hub. The hub of the sheath has an eyelet to enable it to be sutured to the skin. The sheath is connected to a continuous flush of heparinized saline via provided tubing (double arrow). The guidewire used to place the sheath into the artery is lying to the left, still within its plastic container tubing. The plastic introducer (dot) can be used to straighten the tip of the J-tipped wire, enabling easier insertion into the needle, or sheath. The sheaths are color coded for size. Additionally, the label (b) is designed to provide appropriate information at a glance. The label of the pictured sheath readily demonstrates that it is 6 Fr (arrow) in size, the length of the sheath is 10 cm (double arrow), and the provided guidewire is 0.035″ in thickness (curved arrow). However, the sheath can take a guidewire up to 0.038″ in thickness (asterisk). The expiry date is also indicated (black dot)

If anticipating intervention, use at least a 6 Fr sheath from the very outset. It is time-saving and often the same closure device (6 Fr) will be used if the sheath used is 5 Fr or 6 Fr.

In case of stroke, start off with a 7 or 8 Fr sheath.

In case the femoral artery is tortuous, using a longer sheath, e.g., 25 cm (Terumo^®, Pinnacle) instead of 10 cm, may help straighten out the artery.

Long Sheaths (90–100 cm)

Also called ‘Guiding sheaths,’ these may be needed for supporting the catheter in a tortuous vasculature where the catheter would otherwise drop out of, or cannot be placed in the target vessel, e.g., in older patients.

Shuttle ^® Sheath: One option is placement of shuttle^® sheath (Cook Medical Inc, Bloomington, IN). To do this:

Access is obtained using modified Seldinger technique (see Chap. 1) and an exchange length 0.035 glidewire is advanced into the descending aorta.
A shuttle sheath (e.g., 6 Fr) with its dilator inserted is threaded onto the glidewire and advanced to the descending aorta.
Ensure that the tip of the glidewire always leads once the sheath is within vasculature.
If the shuttle sheath needs to be positioned in a vessel other than aorta, then:
- Remove the dilator completely and thread a slip catheter (5.5 or 6.5 Fr for 6 Fr and 7 Fr shuttles, respectively; H1, JB1 or Simmons 2 shapes) over the glidewire and into the shuttle sheath.
- Advance the slip catheter over the glidewire and position it in the target vessel, e.g., CCA.
- Advance the shuttle sheath over the slip catheter to the target vessel.
- Remove the glidewire and slip catheter once the shuttle sheath has been appropriately positioned.

Special Considerations

Use a braided long sheath where the patient is positioned in a manner that is inconvenient for angiography, e.g., prone or three-quarter prone positioning in the operating room. A considerable length of the sheath remains outside to assist easy access. As the sheath is braided, it is less likely to kink if the patient is lying on it.
If the sheath needs to be left overnight, e.g., in case the patient is expected to return to the angio laboratory in a day or so, it should be completely secured, such that inadvertent accidents involving removal, disconnection, or injections into it do not occur. If a microcatheter has also been left in place, e.g., when administering tPA into a sinus, both sheath and microcatheter should be protected to prevent accidental retraction, disconnection, or accidentally pushing the microcatheter forward.
If a long sheath was used, consider exchanging it for a short sheath, if the sheath is to be left in situ overnight.

Table 5.1 shows examples of commonly used sheaths.

Table 5.1

Examples of commonly used sheaths, available sizes, lengths, and wire compatibility

Brand	Size (Fr)	Length (cm)	Wire (in.)
Pinnacle^®, Terumo	4, 5, 6, 7, 8, 9, 10, 11	10, 25	0.035
Super ArrowFlex^®, Arrow International	5, 6, 7, 8, 9, 10, 11	11, 24, 45, 65, 90	0.035
Shuttle Select Sheath™, Cook Medical	5, 6, 7	90	0.038

The most commonly used sizes and length are shown in bold

Wires

Guide wires

Terumo ^®Front Angled Glidewire (0.035″, 150 cm): Our preferred wire in navigating the arch and neck vasculature. Compared to others, it is easier to manipulate and has a hydrophilic coating that remains lubricious within the catheter.

Use of coated wires through the percutaneous access needle should be avoided, as withdrawing coated wires may shear the coating at the needle’s tip.

Bentson ^®Wire (0.035″, 150 cm): An uncoated, braided stainless steel wire. Its straight shape may be advantageous when avoiding inadvertent selection of splanchnic or renal arteries from the aorta. However, remember to shape the tip to give it an angle (e.g., 45°) if intended for selective catheterization off the aortic arch. Otherwise, it will be difficult to manipulate. Bentson wire may be used as the primary choice in certain situations requiring frequent femoral artery access, e.g., patients receiving intra-arterial chemotherapy, where placement of sheath is avoided to minimize trauma to arteries accessed repeatedly over a short course of time. A Bentson^® wire is advanced through the needle used to gain arterial access. The coating of a Glidewire^® may be damaged and shorn during movement directly through the needle. This is not a problem with Bentson wires due to the lack of such coating.

Stiff Wires

A stiff wire may be needed in situations where more support is necessary, e.g., during advancing a catheter with stent or angioplasty balloon. Options include the stiff Glidewire^® or an Amplatz^® wire may also be used. These less flexible wires are less prone to deformation while advancing rigid devices around vascular curves and may serve to straighten tortuous anatomy to improve navigation.
Do not cross a severely stenosed segment with a large or stiff wire as it may injure plaque. A good strategy is to cross the lesion using a soft microwire and microcatheter [e.g., use a Prowler^® 10 microcatheter (Cordis Endovascular) with a Transend Microguidewire (Stryker Neurovascular, Fremont, CA)]. Once the catheter is distal to the lesion, switch to an exchange length stiffer microwire. As an example, this situation may arise during treatment of severe carotid stenosis, in which case, if need, perform an angioplasty to enable usage of larger wires and catheters.

Exchange Length Wires

Used to maintain access in a catheterized vessel and enable catheter exchange in a vessel that has proven difficult to catheterize. It must be roughly twice the length of the catheter being removed, usually 200–300 cm in length. This allows the operator to maintain wire access at the distal end of the catheter and to always have direct contact with the wire outside the patient as the catheter is removed.

Table 5.2 shows examples of guidewires.

Table 5.2

Examples of guidewires, available types, lengths, diameter, and tip shape

Brand	Types	Length (cm)	Diameter (in.)	Tip shape
Glidewire ^®, Terumo	Standard	150	0.032	Angle; straight
		120^a, 150, 180, 260	0.035
		120^a, 150, 180, 260	0.038
		150	0.035, 0.038	J-Tip
	Shapeable	150, 180	0.035	Shapeable
	Shapeable	150	0.038	Shapeable
	Stiff	80^a, 150, 180, 260^b	0.035, 0.038	Angle; straight
Bentson^®, Cook Medical	TFE-coated stainless steel	145, 180, 200	0.035	Straight/shapeable
	TFE-coated stainless steel	145	0.025, 0.032, 0.038
	TFE-coated stainless steel with heparin coating	80, 145, 180, 200	0.035
	TFE-coated stainless steel with heparin coating	145, 260	0.038
Amplatz^®, Cook Medical	Stiff	145, 180, 260^b	0.035, 0.038	Straight/shapeable

The kind most commonly used by us is highlighted in bold

^aAvailable only in angle tip

^bAvailable only in 0.035 diameter

Shaping a Wire

Usually, a gentle 45º angle to the guidewire or microwire suffices. They also come pre-shaped. However, the wire may require shaping specifically to address the peculiarities of vasculature or location of the lesion. The technique is as follows:
- Using a mandrel soaked in normal saline, hold the distal portion of the wire intended for shaping between the forefinger and thumb, pinching the wire against the mandrel (or other shaping device such as hemostat).
- Slide the mandrel toward the wire tip maintaining the finger pinch on the wire and mandrel. This motion is similar to curling ribbon on a package wrapping.
- The wire may be bent to create a tighter curve.
- A second curve in the reverse direction just proximal to the first may create a shepherd’s hook shape useful in access acute vascular takeoffs such as the anterior cerebral artery from the internal carotid.