I. Classification
L. Contrast catheter: It is a thin hollow tubular structure with thin walls, and the end of the catheter can be connected to a syringe or high-pressure syringe. The catheter material mainly uses polytetrafluoroethylene, polyurethane, polyethylene or nylon, etc. The hydrophilic coating of the catheter increases the ability to follow up, and the mid-wire braiding structure of the tube wall increases the strength, folding resistance and torsional control of the catheter. The roles of contrast catheters are: injection of contrast agent to observe vessel morphology; pressure measurement to obtain hemodynamic information: transport and release of drugs or embolic materials; acting as a guiding catheter, etc. Contrast catheters are generally divided into non-selective contrast catheters and selective contrast catheters according to their use. The former are mainly pigtail catheters and tennis racket catheters, which are mainly used for non-selective imaging of large vessels (such as aorta, pulmonary artery, vena cava), and the multi-lateral holes at the distal end of the catheter allow high speed and high flow rate of contrast injection), and straight catheters with multiple side holes can also be classified as non-selective catheters for selective imaging of carotid artery, iliofemoral artery, inferior vena cava, etc., which can increase the flow rate and flow rate accordingly. Selective contrast catheters are available in a variety of shapes, including preformed catheters with a single bend and reverse bend, with a single end hole, for selective vascular cannulation and selective catheterization of specific aortic branches. Selective catheters typically have lower contrast flow and flow rates than non-selective catheters. Commonly used selective contrast catheters include Ve]al catheters (vertebral artery catheters), Headhunter catheters (Hunter head catheters), Simmon series catheters, Cobra catheters (Cobra catheters), Shepherd catheters (Shepherd catheters), Mikaelsson abdominal catheters, Bentson JB2 catheters, Vitek catheters Mani catheter, RDC catheter (renal double bend catheter), etc.
Catheter specifications are generally divided into outer diameter, commonly used for 4F-7F outside diameter, general imaging is generally used in small diameter catheters, usually 4F and 5F catheters. In addition to increasing the flow and flow rate of the contrast, the side port function is also contraindicated, especially in high-pressure injection contrast, to avoid high amplitude oscillation of the catheter to damage the vessel wall. The catheter length for abdominal aortic localization angiography is typically 60-80: while in the thoracic aorta and carotid region a catheter of 00-120 length is required for the door. Catheters should always be kept moist and should be flushed before entering the body: intermittent intraoperative flushing can extend the life and reduce the formation of blood clots at the catheter tip.
2.Guidance catheter: Guidance catheter is an important channel for interventional device delivery, with functions such as delivery, support, pressure measurement and contrast injection. The appropriate guiding catheter is an important guarantee for the successful completion of balloon dilation and stentoplasty. The guiding catheter is similar to but different from the contrast catheter in shape and knot. The special requirements are that the guiding catheter must have sufficient internal lumen to deliver the interventional device, and that the outer diameter of the catheter should not be too large to avoid complications at the puncture site. Therefore, the design, material selection, and structure of the guidewire catheter are more important than those of the imaging catheter because of its “small outer diameter and large inner lumen”, while taking into account the important properties of the guidewire catheter such as fracture resistance, torsional control, and support. Basic structure: The wall is composed of three layers, the outer layer is made of polyethylene, which determines the shape and hardness of the catheter and has a smooth outer surface to prevent intimal damage and thrombosis: the middle layer is a woven mesh of stainless steel wire, which is the backbone of the guidewire catheter and makes the catheter less likely to collapse and deform and resists fracture and transmits torsional control forces to the tip of the catheter: the inner layer is made of nylon or polytetrafluoroethylene for lubrication. Reduce the friction between the post-interventional device and the lumen of the guiding catheter, and prevent thrombosis.
The outer diameter of the guiding catheter: according to the size of the outer diameter is divided into 5F to 9F, the most commonly used outer diameter is 6F and 7F, while 8F is mainly used for carotid stents. Therefore, when dealing with lesions requiring strong support (e.g., type II or type III aortic arch during carotid stenting, severely twisted abdominal aorta during renal stenting) and more complex lesions requiring multiple devices (e.g., anastomotic balloon dilation at the opening or bifurcation) and special devices (e.g., cutting balloons and rotary grinding), large guiding catheters are the appropriate choice. The large OD guiding catheter is the appropriate choice for complex lesions requiring multiple devices (e.g., anastomotic balloon dilation of the opening or bifurcation) and special instrumentation (e.g., cutting balloons and rotary grinding). However, large OD guiding catheters also cause greater damage to the vessel and increase local complications at the puncture site.
3.Thrombolytic catheter: The standard thrombolytic catheter is a straight-ended multi-lateral hole catheter with a tip end hole that can be inserted into the thrombus through a guidewire. Both ends of the perfusion segment are marked with opaque X-rays to precisely show the length and location of the perfusion segment, and the side holes of the perfusion segment are mainly used to increase the contact area between the thrombolytic drug and the thrombus. The length of the perfusion segment ranges from F 5 to 20 cm, and the number of corresponding side holes varies from 10 to 20. The length of the perfusion segment that contacts the thrombus should be selected according to the length of the thrombus occlusion. During thrombolysis, the end hole is blocked by the guidewire, and the thrombolytic solution flows out through the side holes and penetrates evenly into the thrombus. The inner diameter is generally 3F, which can accommodate the perfusion guidewire to form a word axis system to expand the thrombolytic area.
Fogarty catheters are single-lumen or double-lumen balloon catheters, which are inserted through direct visual dissection of the peripheral vessels and traverse the thrombus to its distal end. Afterwards, the balloon is filled with physiological saline or dilute contrast and pulled back from the vascular incision to remove the thrombus. The disadvantage is the large amount of residual mural thrombus and the presence of severe endothelial injury.
Second, the use of principles
Currently, contrast catheters are mainly produced by Cordis, Cook, and Terumo companies, with the Codis catheter being the hardest and having good torque and maneuverability: the Terumo catheter is the softest and easy to complete selective intubation; the Cook catheter is between the two >. The Cook catheter is somewhere in between. The choice of the three is usually dependent on the experience and habits of the operator. Routine diagnostic angiography tends to use a 4F or 5F catheter with a 0.0335-inch guidewire. Off-catheter reductions are sufficient for multi-site treatment; the use of counter-anastomosis or spin-grinding techniques usually requires a 6F or larger catheter. The choice of catheter length depends on the access route and insertion site. The catheter must be of sufficient length to reach the target vessel and should be of adequate length outside the body to facilitate manipulation of the catheter: however, excessive catheter length can sometimes prevent manipulation of the catheter. Peripheral vascular disease differs from coronary artery disease in that multiple sites of elective cannulation are involved, and preoperative access should be planned and catheters of appropriate length should be selected. Typically, the femoral route is used to cannulate the superior aortic arch with a contrast catheter length between 90-120. For retrograde femoral route for renal artery cannulation and ipsilateral or contralateral iliofemoral artery cannulation, the catheter length ranges from 65-lOO cm. The cis-femoral route for ipsilateral infrapopliteal or even pedicled artery cannulation usually requires a catheter length of about lOO cm.
In general, the catheter should be matched to the diameter of the guidewire, and the catheter should be advanced along the guidewire while the guidewire is continuously pulled to ensure that the catheter does not continue to slide forward. Do not advance the catheter until the guidewire is straightened. When using a hydrophilic guidewire, the posterior end of the guidewire must be clamped to prevent the guidewire from sliding forward suddenly in the catheter. The catheter site should not be too far from the sheath in vitro, as this may cause the catheter and guidewire to bend.
When the catheter reaches the softer part of the guidewire, the catheter may retain its original shape, resulting in a significant reduction in advancement. At this point, the catheter should continue to be advanced so that the catheter always advances over the stiffer portion of the guidewire. If the catheter cannot be advanced along the stiffer portion of the guidewire, the arterial dilator should be advanced to continue to dilate the artery or replaced with a stiffer guidewire to provide additional support for the catheter. If the catheter becomes less propulsive after entering the vessel, consider replacing the guidewire with a stiffer one. If the catheter does not follow the guidewire into the lesion, it is possible that the disease itself is resistant, or that the stenotic lesion is so stenotic that the guidewire is blocking the remaining arterial access, or that the guidewire has entered the subintima.
III. Precautions.
1. The catheter should be flushed with heparin saline outside the body before entering the body to evacuate any solids and blood clots including air bubbles from the bladder lumen of the tube.
2. The catheter should be used with careful selection of the appropriate size, length and head shape based on the contrast site and experience.
3.When the guidewire is successfully placed through the vascular puncture site, careful finger pressure should be applied to the puncture site for arterial hemostasis before placing dilators, sheaths or placing catheters to stop bleeding, correct compression can effectively reduce the formation of hematoma at the puncture site;
4. Use mosquito forceps to dilate the epidermis to a suitable size to facilitate subsequent dilatation. Tensioner and catheter entry.
5. The dilator or catheter should be pushed into the vessel along the stiffer part of the guidewire.
6. Advance the catheter gradually under fluoroscopy, a few centimeters at a time;
7.Pay attention to the advancing resistance and feel during the catheter guidewire to avoid entering the subendothelial lamina channel;
8, the operation should intermittently pull the guidewire to prevent the guidewire and the catheter from advancing at the same time;
9.If the catheter needs to advance too far and is not easily put in place smoothly, it is usually due to the large friction force. In this case, it is necessary to place a long sheath, replace the rigid guidewire or choose another arterial puncture site;
10.The catheter should be intermittently flushed with heparin saline during in vivo operation to prevent micro-thrombosis of the vessel wall;
11.No substance (heparin saline and contrast medium) should be injected into the catheter until the outer end of the catheter has returned blood; under normal blood pressure, the catheter usually returns blood unless the tip of the catheter is embedded and adheres to the vessel wall;
12. The catheter tip should be adjusted under constant fluoroscopy prior to high pressure contrast injection to ensure that it is free of the vessel lumen, otherwise entrapment or perforation may be induced;
13.Before high pressure injection of contrast medium, the contrast medium should be pumped back to the injection syringe to avoid air bubbles entering the body at the interface between the syringe and the end of the catheter;
14.If the end of the catheter becomes knotted, use a stiffer guide wire to untie the knot through the catheter;
15, to determine the catheter is located in the lumen of the blood vessel in addition to the return of blood judgment, but also in vitro rotation of the catheter fluoroscopic observation of the catheter tip in the lumen of the free mobility;
16.When a small amount of contrast agent is injected, the contrast agent should be diluted by the rapid flushing of blood flow, rather than being retained in the vessel wall causing lamellar staining.
The catheter is located in the lumen of the free vessel;
17.After removal of the guidewire, if the position of the catheter tip is uncertain under fluoroscopy, a small amount of contrast agent can be injected to help visualize the catheter;
18.When withdrawing the catheter or exchange operation, the guidewire should be fixed in the original position and the catheter should be withdrawn at the same time; intermittent fluoroscopy should be used to check whether the guidewire is in the original position.