I. Structure and basic characteristics of guidewires The basic characteristics of guidewires include guidewire stiffness, maneuverability, flexibility and smoothness. Understanding the existing design and basic structure of the guidewire helps to select the appropriate guidewire to complete the procedure.
1.Structure
The basic structure of a guidewire consists of a stiff inner spool and a tightly wound outer spring coil. The internal axis of the guidewire is called the spool, which ensures the hardness of the guidewire, which tapers toward the tip, making the tip softer. The outside of the spool is made of a stainless steel spring coil. The guide wire contains a thin safety wire that connects the shaft wire to the tip of the external spring ring to prevent separation. The wire is usually coated with a hydrophilic polymer, such as PTFE, to increase its smoothness. This property facilitates guidewire advancement and catheter/guide wire exchange.
The shape of the head of the guidewire plays a major role in its passage performance. A “J” shaped head is the least traumatic and is less likely to cause entrapment or perforation, but this shape makes it difficult to pass through severely stenotic lesions. The head of the guidewire can be shaped to the desired shape, and the shaped head allows easy access to the branch vessels. The guidewire is equipped with a twisting device that provides a 1:1 rotation ratio.
2. Classification
According to the shape of the head end, the guidewire can be divided into different types such as “J” shaped head, straight head, and angled head. According to the diameter of the guide wire can be divided into 0.035 inch, 0.038 inch, 0.018 inch, and 0.014-0,018 inch micro-guide wire, etc. According to the role of the guide wire can be divided into puncture guide wire, selective guide wire for guide wire, etc.. Each type of guidewire has different length specifications (such as 80cm. 145cm. 180cm. 260cm. 300cm, etc.). The standard length of cross-Q guidewire is 145cm to 300cm. 145cm long guidewire can be used to deliver catheter for routine imaging. 180cm long guidewire is used for aortic bifurcation for hill-turning operation and can deliver catheter to the contralateral superficial femoral artery. 260-300cm long guidewire is used for long distance operation such as aortic arch, carotid angiography and aortic stent placement.
(Bentson guidewires (Cook, Inc., U.S.A.) are an ideal choice, with a soft tip, a toughened body, a diameter of 0.035 inch, and a standard length of 145 cm, with special Longer guidewires are also available for special lesions.
(2) The selective guidewire has good maneuverability and is coated with a hydrophilic surface. Hydrophilic coated guidewires are useful when passing through stenotic or irregular lesions, where they can follow the blood flow path. Hydrophilic-coated guidewires are very smooth when exposed to water, giving the operator the impression that the guidewire will slide forward during manipulation, when in fact it is very stable. When it is necessary to exchange different catheters through hydrophilic guidewires, it is best to choose a stiffer guidewire that does not slide easily.
(3) Exchange guidewires have a strong inner core and are therefore stiffer than other guidewires. The use of a cross-Q guidewire will ensure a safe operation. If the access to the endoluminal device is tortuous or if the device is large, then an exchange guidewire should be considered. Amplatz, Rosen and Lunderquist are some of the more suitable exchange guidewires. Stiffened guidewires should not be used during initial passage through the lesion because of the potential for damage to the vascular lumen. Stiffened guidewires can be very helpful when performing complex endoluminal maneuvers such as complex, multi-stent revascularization or release of the graft vessel.
II. General principles of guidewire manipulation
Manipulation of the guidewire should begin with a clear interrelationship between the head end of the guidewire and the lesion site under fluoroscopic imaging. Patiently observe the morphological changes of the guidewire in the vascular lumen and its route of travel.
1. Soak the guidewire with heparin saline to make the guidewire function better. The guidewire with hydrophilic coating must be soaked in heparin saline before use. When each exchange of the guidewire is completed, wipe the guidewire with heparin saline.
2. Increase the stiffness of the soft tip of the puncture guidewire so that it can pass smoothly through the puncture needle and through the arterial access point.
3. Standard, non-flexible guidewire tips can be shaped with fingers and hemostatic forceps to make the tip curved.
4.If the guidewire cannot pass through the puncture needle, it should be replaced promptly.
If the tip of the guidewire is close to the lesion but has not yet passed through the lesion, fluoroscopy must be performed intermittently to ensure that the tip of the guidewire has not migrated or impinged on the lesion. Blind delivery of the guidewire may lead to vascular damage.
6. If the guidewire is bent a few centimeters at a time, the delivery device may be difficult and the guidewire must be replaced. Do not apply force to the guidewire.
7.When the tip of the guidewire touches the lesion, the operator must be alert.
8.When using selective guidewires, it is best to use a twisting device. The torsion device provides a 1:1 rotation ratio for the guidewire.
9.When exchanging the guidewire and catheter, the guidewire is kept flat and tightened externally to prevent relaxation and advancement of the guidewire in the catheter.
10.When delivering the intraluminal treatment device through the guidewire, the position of the guidewire must be clarified first.
11.When operating the hydrophilic guidewire, the guidewire should be fixed (with the thumb and index finger) to prevent the guidewire from sliding forward or backward.
12.After withdrawing the guidewire, the guidewire should be rotated to its original state to prevent confusion on the instrument table. Place a piece of gauze on the guidewire outside the body to prevent the guidewire from slipping under the operating table.
13. If the guidewire is contaminated, the operator must use a new guidewire for the operation. If the end of the guidewire is contaminated, the end of the guidewire can be removed, but the original position of the guidewire is still maintained.
14. The placement of catheters or sheaths can increase the support and pushing force of the guidewire.
Third, the general principle of choosing a guidewire
The appropriate guidewire should be selected before the operation begins, and it should be clear that if this guidewire does not solve the problem, what should be done next. A 0.035-inch guidewire is generally preferred. The common guidewire used for coronary interventions is the 0.014 guidewire. Primary branch vessels such as the carotid, renal, cervical, and distal lower extremity arteries can be treated with both types of guidewires, but the technical trend is to attempt silicone revascularization of all branch arteries with 0.014 guidewires. 0.014-inch guidewires are more commonly used in conjunction with single-track systems for branch arteries.
When selecting the length of the guidewire, the length of the guidewire inside the patient must reach and exceed the lesion to ensure that the exchange catheter can reach the lesion; the length of the guidewire outside the patient must ensure that it can support the longest catheter and that the tail of the guidewire extends beyond the catheter after catheter introduction to facilitate the operator’s manipulation of the guidewire. The length of the guidewire usually ranges from 145 cm to 300 cm, with the option of longer guidewires when dealing with specific lesions. Monorail systems require less extracorporeal guidewire length than coaxial systems because the length of the guidewire within the catheter of a monorail system is only a small fraction of the overall catheter length, usually 20 cm to 30 cm.