Indications.
Inferior vena cava filter placement is indicated for.
1, Patients with pulmonary artery embolism who are contraindicated for anticoagulation therapy and/or who develop complications.
2, Patients with pulmonary artery embolism who have failed anticoagulation therapy.
3.Patients with deep vein thrombosis who have a greater likelihood of complicating pulmonary embolism.
4.Patients with a history of pulmonary artery embolism or those who are intended or proposed for surgical removal.
Contraindications.
Patients with severe hematological disease, pulmonary fibrosis, pulmonary embolism caused by pulmonary insufficiency, pulmonary artery embolism caused by dislodgement of right heart embolus during cardiac disorders, etc.
Preparation.
1, routine heart, liver, kidney function and blood and urine routine.
2, Chest plain film, radionuclide lung scan.
3.Pulmonary arteriogram with measurement of pulmonary artery pressure and oxygen saturation.
4.Both lower extremity venography to clarify whether there is thrombosis in the lower extremity veins.
5.Preparation of supplies
(1)Puncture and vena cava angiography catheter, etc.
(2) Various types of filters and their delivery systems.
Methods
The methods and procedures depend on the different types of vena cava filters used.
1.Bird’s nest type filter
(1)The inferior vena cava is firstly made by puncture cannula through femoral vein or right internal jugular vein to understand the width of inferior vena cava, location of renal vein opening and vascular anatomy for reference when releasing the filter.
(2) After imaging, withdraw the contrast catheter, insert a 12F catheter sheath along the guidewire, withdraw the guidewire, and insert a loading catheter equipped with a bird’s nest filter through the catheter sheath so that the catheter tip is located at the level below the opening of both renal veins.
(3) Under television surveillance, the delivery guidewire is held stationary, and the loading catheter is slowly retracted along the delivery guidewire, and when its caudal end is retracted to the delivery guidewire mark, i.e., the first pair of legs of the filter is seen to open in a “V” shape, the delivery guidewire is gently pushed forward so that the “hooks” at the top of the two legs The “hooks” at the top of the two legs are fixed by embedding them into the walls of both sides of the inferior vena cava.
(4) Continue to retract the loading catheter, releasing the thin strip of wire and coiling it in a mesh-like pattern within the lumen of the inferior vena cava. Continue to retract the loading catheter while slowly pushing the delivery guidewire forward so that the 2nd pair of legs enters the inferior vena cava and opens in an inverted “V” shape. Gently pull down on the delivery guidewire so that the “hooks” of the legs are embedded in both walls of the vena cava.
(5) Rotate the delivery guidewire counterclockwise for 10-15 turns and gently pull to detach the delivery guidewire from the attachment of the filter.
(6) After taking an abdominal plain film to understand the condition of the filter, the delivery guidewire and loading catheter together with the catheter sheath can all be withdrawn. The puncture site is hemostatic and bandaged.
2.Günther Tulip filter
(1) After successful puncture through the femoral vein (using model GTCFS-45-FEM), the puncture tract is dilated with dilators, the catheter sheath is inserted along the guidewire to the appropriate position in the inferior vena cava, the guidewire is returned, and inferior vena cava angiography is performed to understand the position of the opening of both renal veins.
(2) The loading catheter with the filter is inserted into the catheter sheath so that the end of the catheter sheath is about 6 or 5 cm away from the mark on the back of the loading catheter, keeping the tip of the catheter sheath below the opening of both renal veins. At this point, the “hook and loop” at the top of the filter is located just above the tip of the sheath.
(3) Slowly retract the catheter sheath until the end of the sheath recedes to the marker where the catheter was loaded. At this point, the main part of the filter “hook and loop” leaves the sheath and sits in the vena cava, with the main part of the filter slightly distended, but with the lower metal fixation point of the filter still attached to the tip of the loading catheter.
(4) A vena cava angiogram is performed to approve the position of the filter. When satisfied, the red bolt at the posterior part of the loading catheter is rotated half a turn to loosen it, and then the red bolt is pulled downward to separate the filter from the loading catheter and release it completely into the inferior vena cava.
(5) Repeat the inferior vena cava angiography to understand the position and expansion of the filter in the vena cava, and then remove the tube when satisfied. The puncture site is hemostatic and bandaged.
Attachment: ①If the puncture route is via the internal jugular vein, the GTCFS-80-JUG filter is used and released according to the operation steps of the GTCFS-80-JUG. ②Whether using the GTCFS-45-FEM or GTCFS-80-JUG filter, if it is not satisfactory after implantation, it can generally be recovered within 10 d via the internal jugular vein puncture route with the GuntherTulip recovery device (GTRS-100).
Precautions
1. Preoperative inferior vena cava angiography is very important. Its main objectives include ① to clarify the site of the opening of both renal veins, so that the filter can be accurately positioned when implanted and prevent misplaced implantation and blockage of the opening of the renal vein or the opening of the hepatic vein. ② To understand the presence or absence of thrombosis in the inferior vena cava and its location. Generally, the filter should be implanted below the renal vein as a rule, but if there is thrombus above the renal vein, it should be implanted above the renal vein. ③To know whether there is any anatomical variation in the inferior vena cava and renal vein, which is important to determine the positioning of the implanted filter and the implantation method. ④Measure the width of inferior vena cava in order to choose a filter of suitable size to prevent the filter from being too small and dislodging after implantation and entering the right atrium, right ventricle or even the pulmonary artery causing serious consequences. Therefore, during the inferior vena cava angiography, a metal marker ruler is placed under the patient’s spine for accurate positioning of the renal vein and accurate measurement of the diameter of the inferior vena cava.
In a few patients, after implantation of the filter, the legs of the filter puncture the wall of the inferior vena cava and cause perforation, but usually this does not cause serious complications.
3.Other things such as thrombosis at the puncture site and arteriovenous fistula can occur in a few patients, especially through the femoral vein route.
4.There are many types of filters available in the market, and the operator should be very familiar with the structure, characteristics and release methods of these filters in order to ensure the success of the operation.