Why introducers are needed
The classic Seldinger technique involved introducing a catheter directly into a vessel over a guidewire. Today, this approach is practically obsolete due to high trauma: introducing an instrument "directly" often leads to vessel wall injury, hematoma formation at the puncture site, and local thrombosis.
Today, before any catheter insertion and angiography, an introducer must be placed. It serves as a safe gateway for all other instruments.
Characteristics and labeling
Introducers are selected individually for each procedure. They differ in several parameters:
- Size: measured on the French (F) scale.
- Length.
- Manufacturing material.
- Presence of a hemostatic valve, which prevents backflow of blood.
- Type of coating.
- Presence of a radiopaque tip for precise positioning under fluoroscopic guidance.
A specific feature of labeling is that the size of an introducer in F does not indicate its own outer diameter, but rather the outer size of the catheter it can accommodate. That is, if you need to use a 6-F catheter, a 6-F introducer is the ideal fit.
Guidewires
Guidewires are introduced into the vessel through the introducer. They can be basic (providing rigid support for diagnostic angiography) or specialized (e.g., for crossing chronic total occlusions).
Key characteristics of guidewires:
- Material: most commonly stainless steel.
- Coating: may be polytetrafluoroethylene (PTFE)-coated or uncoated, and can also be heparin-coated.
- Tip: straight flexible (floppy tip) or J-shaped.
- Sizes: length ranging from 80 to 450 cm, diameter measured in thousandths of an inch (0.014, 0.018, 0.035, 0.038).
Hydrophilic guidewires (hydrophilic-coated) require special attention. They slide easily and penetrate the smallest branches, but due to the risk of vessel perforation, they must be used exclusively under fluoroscopic guidance (fluoroscopic guidance).
Diagnostic catheters
Passed through the introducer over a guidewire. They are divided into two types:
- Pig-tail (flush catheters). They feature side holes and are placed in the aorta. They can withstand high pressure (900 psi) and high contrast injection rates (40 ml in 2 seconds) while maintaining a stable position.
- Selective catheters. Required to access the ostia of aortic branches (renal artery, etc.). They have a single end-hole and are often equipped with a radiopaque tip.
All diagnostic catheters feature braiding (braiding). This provides support and transmits the surgeon's finger rotation to the catheter tip in a 1:1 ratio. The most common size for such catheters is 5 F.
Puncture closure devices
After removing the introducer, the puncture site must be closed. This is especially important for patients on anticoagulants.
By design, closure devices (closure devices) are classified into:
- External (plug or clip outside the vessel).
- Combined (anchor inside, plug outside).
- Suturing devices (deploying sutures).
If the puncture hole size is greater than 8 F, the use of suturing devices is mandatory. The success rate of device deployment is over 97%, and major complications (aneurysms, large hematomas) are rare—around 1.3%.
Briefly: answers to topical questions
What types of selective catheters exist for catheterization of aortic branches?
The provided materials do not describe specific types of selective catheters, but their general characteristics are provided.
- Selective catheters are designed for selective placement into the ostia of aortic branches (e.g., renal artery, celiac trunk).
They typically have only a single end-hole at the tip and are sometimes equipped with a radiopaque marker. Like all diagnostic catheters, they feature braiding for a 1:1 torque transmission ratio, allowing for precise control, and their standard size is 5 F.
Class and exam questions
What does the 6-F marking on an introducer mean?
It means that a catheter with an outer size of 6-F will pass freely through this introducer.
What is the danger of hydrophilic guidewires?
They are extremely slippery and can easily damage or perforate a vessel, which is why they are used only under continuous fluoroscopic guidance.
Which closure device should be used for a puncture larger than 8 F?
In this case, it is mandatory to use closure devices that place sutures on the vessel wall.
What else to study on this topic
- Technique of ultrasound guidance during common femoral artery puncture
- Differences in catheter braiding technology among various manufacturers
- Features of antegrade and retrograde access (failure and complication statistics)
- Principles of guidewire selection for chronic total occlusions (CTOs)
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