Deep venous thrombosis (DVT) is a disease caused by abnormal blood clotting in the deep veins of the lower extremities, blocking blood return and causing swelling, pain, and dysfunction in the lower extremities. DVT and PE together are called venous thromboembolism (VTE), and if DVT is not effectively treated in the early acute stage, thrombus mechanization often leaves venous insufficiency, which is called post-thrombotic syndrome (PTS).
I. Interventional treatment of lower extremity deep vein thrombosis
I. Pathological typing of DVT
1, according to the location: (1) peripheral type: deep vein thrombosis below the lower segment of superficial femoral vein; (2) central type: iliofemoral vein thrombosis; (3) mixed type: whole lower limb deep vein thrombosis.
According to the severity: (1) common type DVT; (2) severe DVT: 1 femoral cyanosis: severe lower limb deep vein stasis; 2 femoral leukomalacia: with persistent arterial spasm.
Second, the clinical staging of DVT
Clinically, DVT is divided into (1) acute stage: within 14 d after onset; (2) subacute stage: 15-28 d after onset; (3) chronic stage: 28 d after onset; (4) sequelae stage: symptoms of PTS appear; (5) acute attack in chronic stage or sequelae stage: in chronic stage or sequelae stage, another attack.
At present, the main methods of interventional treatment for DVT are: transcatheter thrombolysis, mechanical thrombectomy, balloon angioplasty (PTA) and stent placement.
The interventional treatment of DVT should be considered from four aspects: safety, timeliness, comprehensiveness and long-term. (1) Safety: The placement of vena cava filter before the intervention of long segment acute thrombosis can effectively prevent pulmonary artery embolism. The use of mechanical thrombus removal and/or transcatheter pharmacological thrombolysis can significantly reduce the dosage of anticoagulants and thrombolytic agents and reduce the complications of visceral bleeding. (2) Timeliness: Once acute DVT is clearly diagnosed, it is advisable to make interventional treatment as soon as possible to shorten the course of the disease, improve the rate of complete lumen recanalization, avoid or reduce venous valve adhesions, reduce the incidence of valve insufficiency and thrombosis recurrence, and try to prevent the course of the disease from entering the chronic phase and the sequelae phase. (3) Comprehensive: Several interventional methods are often used for the comprehensive treatment of DVT, such as catheter aspiration, mechanical ablation and other interventional thrombus removal on the basis of transcatheter thrombolysis for acute thrombus; for DVT with iliac vein compression syndrome or with iliac vein occlusion, PTA and stent placement can be used in combination to rapidly restore blood flow and improve the efficacy of interventional treatment. (4) Long-term: After comprehensive interventional treatment, it is advisable to continue anticoagulation for more than 6 months and regular follow-up and review to reduce the recurrence of DVT.
Indications and contraindications
I. Transcatheter thrombolytic therapy
1.Indications: (1) Acute DVT; (2) Sub-acute DVT; (3) Acute attack of DVT in chronic phase or post-acute phase.
2, Contraindications: (1) history of cerebral hemorrhage and/or surgery within 3 months, history of gastrointestinal and other internal bleeding and/or surgery within 1 month; (2) more serious infection in the affected limb; (3) acute iliac-femoral vein or total lower limb deep vein thrombosis with a large amount of free thrombus in the vessel lumen without inferior vena cava filter placement; (4) refractory hypertension (blood pressure >180/110 mm Hg); (5) choose cautiously for patients over 75 years old.
II. Mechanical thrombectomy
Mechanical thrombectomy includes the use of large lumen catheter aspiration and thrombus ablation device to remove thrombus.
1. Indications: (1) acute DVT; (2) subacute iliofemoral vein thrombosis.
2, contraindications: (1) chronic DVT; (2) post-acute DVT; (3) infrapopliteal DVT.
PTA and stent placement
1. Indications: (1) severe compression of the iliofemoral vein without acute thrombosis (Cockett syndrome or May-Thurner syndrome); (2) severe stenosis and occlusion of the iliofemoral vein left after catheter thrombolysis and thrombectomy; (3) severe stenosis of the common femoral vein when the morphology and blood flow of the femoral vein are normal; (4) severe stenosis of the short segment of the femoral vein in the chronic phase (recommended for simple PTA).
Contraindications: (1) stenosis and occlusion of long segment of femoral vein; (2) incomplete mechanized recanalization of femoral vein; (3) acute thrombosis of long segment of iliofemoral vein without inferior vena cava filter placement.
Preoperative preparation
1.Physical examination: Observe, measure and record the skin color, superficial vein exposure and blood return direction, skin temperature and limb circumference of both lower limbs and perineum and inguinal area.
2.Laboratory examination: plasma D-dimer measurement; coagulation function measurement: detection of prothrombin time (PT) and international normalized ratio (INR), fibrinogen (FIB), activated partial thromboplastin time (APTT), thromboplastin time (TT).
3.Doppler ultrasonography has high sensitivity and specificity in diagnosing DVT, and combined with pressurized ultrasound imaging, it can be used as screening and dynamic monitoring of DVT.
4.Compliance venography: It is still the “gold standard” for the diagnosis of DVT. The detection rate of iliac vein thrombosis can be improved by increasing the rate of contrast injection through dorsalis pedis or saphenous vein puncture with indwelling needle.
5.Lower extremity vein CTA: Multi-row CT angiography (MSCTA) can evaluate the compression of the iliac veins while detecting DVT.
6.Lower extremity vein MRA: High-field MRA can assess the time of thrombosis (embolism age), and also can assess the iliac vein compression.
The above items 4-6 can be used according to the specific situation.
7.Anticoagulation therapy: low molecular heparin and warfarin are commonly used, and common heparin and warfarin can also be applied.
Operation steps
I. Transcatheter thrombolytic therapy
Urokinase is generally used as the thrombolytic agent, and the commonly used dose is 20~1 million U/d. The catheter is usually kept for no more than 7 days.
1.Cathodic thrombolysis: (1) puncture and cannulation through the affected N vein to the iliofemoral vein and retain the catheter for thrombolysis; (2) puncture and cannulation through the affected femoral vein to the iliac vein and retain the catheter for thrombolysis.
2.Reverse thrombolysis: (1) cannulation through the femoral vein on the healthy side to the iliofemoral vein on the affected side and retain the catheter for thrombolysis. (2) Intubate through the internal jugular vein to the iliofemoral vein on the affected side and retain the catheter for thrombolysis.
(3) Transarterial cannulae for paracrine thrombolysis: (1) Cannulate through the femoral artery on the healthy side to the iliofemoral artery on the affected side, and retain the catheter for thrombolysis. (2) Thrombolysis is performed through the femoral artery on the affected side with a tube in the distal femoral artery on the same side.
For acute thrombosis confined to the middle or upper femoral vein, paralleling thrombolysis via N vein puncture is recommended; for acute thrombosis of deep veins in the whole lower extremity, retrograde thrombolysis or paralleling thrombolysis via arterial retention tube is recommended.
Second, mechanical thrombectomy
1.Transcatheter aspiration: Use 8-12 F catheter sheath and guiding tube, insert along the guiding wire to the thrombus, and repeatedly aspirate with 50 ml or 30 ml syringe.
2.Thrombus ablation to remove the thrombus: Place a 7-8 F catheter sheath, insert a 4-5 F general contrast catheter, inject contrast agent to understand the location and extent of the thrombus, and then use a guide wire with the catheter to pass through the thrombus. The thrombus ablator is slowly inserted through the catheter sheath and advanced to the near thrombus under fluoroscopic surveillance, and the thrombus ablator is activated for thrombus removal.
PTA and stent placement
1.PTA: (1) For obstruction of the common iliac vein and superior external iliac vein, the recommended access is through the ipsilateral femoral vein. (2) For obstruction involving the inferior external iliac vein, common femoral vein and superior femoral vein, ipsilateral N vein puncture access is recommended. (3) A balloon catheter with a diameter of 10-12 mm is recommended for iliac vein angioplasty; a balloon catheter with a diameter of 8-10 mm is recommended for common femoral vein and femoral vein angioplasty. (4) It is recommended to use a pressure pump to fill the balloon until the balloon naming pressure is maintained for 1 to 3 min.
(2) Stenting: (1) Stenting of the iliofemoral vein is recommended after balloon angioplasty. (2) Self-expanding stents of 12-14 mm in diameter are recommended for stenting of the common iliac vein and upper external iliac vein. (3) Self-expanding stents of 10-12 mm in diameter are recommended for stenting of the inferior external iliac vein and common femoral vein.
Precautions
I. Transcatheter thrombolytic therapy
1.If thrombus exists in the lower femoral vein and N vein, transcatheter thrombolysis is generally not recommended to avoid aggravation of thrombus in the femoral N vein due to the damage of transcatheter thrombus. In this case, retrograde cannulation through the femoral vein on the healthy side or the internal jugular vein to the femoral N vein of the affected limb or intravenous thrombolysis through arterial cannulation is preferred.
2.When performing arterial cannulation for intravenous thrombolysis in the whole lower limb deep vein thrombosis, the position of the catheter head should be determined according to the plane of thrombus involvement. When there is thrombus in both the iliofemoral vein and the deep vein of the lower extremity, the catheter head can be placed in the common iliac artery on the affected side. When the drug passes through the internal iliac artery and the deep femoral artery, it can act on the thrombus in the internal iliac vein, the deep femoral vein and its branches to obtain better therapeutic effect.
3. The dosage of anticoagulant and thrombolytic agent should not be too large in order to avoid or reduce bleeding complications. Regular testing of coagulation function will help to adjust the dosage of drugs reasonably. In a few cases, the coagulation function test results of patients are not consistent with clinical manifestations. Patients have developed hematuria or blood in the stool, but the coagulation function test can still be within the normal range. At this time, the dosage of anticoagulation and thrombolytic drugs should be adjusted in a timely manner according to the clinical situation.
4.Transcatheter thrombolysis of lower extremity deep vein thrombosis is only one of the comprehensive interventional treatment methods. For the acute thrombosis in the iliofemoral vein, early combination with mechanical thrombectomy often can significantly improve the efficacy and shorten the course of the disease.
Second, mechanical thrombectomy
1.Thrombus aspiration: (1) A constant negative pressure must be maintained during aspiration to minimize the chance of dislodging the embolus. (2) Blood loss is often caused by thrombus aspiration, so the blood loss should be strictly controlled and should not exceed 200 ml each time.(3) When thrombus aspiration is proposed for patients with deep vein thrombosis in the lower extremities, it is recommended to preposition the inferior vena cava filter to prevent pulmonary artery embolism. (4) For residual lumen stenosis >30% after thrombectomy, especially in iliac veins, other interventions may be considered in combination. (5) Thrombus aspiration must be combined with anticoagulation and thrombolytic therapy, which can improve the efficacy and reduce the recurrence of thrombosis.
(2) Thromboablation thrombectomy: Before thromboablation thrombectomy for lower extremity deep vein thrombosis, inferior vena cava filter can be placed according to the situation to prevent lethal pulmonary embolism.
Third, PTA and stent placement
1.After DVT by catheter thrombolysis, mechanical thrombus ablation or balloon angioplasty, if the lumen is open, the wall is smooth, the density of intra-luminal contrast is uniform, and there is no obvious residual stenosis, stent placement is not possible.
2, stent placement is usually located in the iliac vein and the common femoral vein, the superficial femoral vein has more valves in the middle and lower section, and stent placement is not suitable to prevent the occurrence of venous insufficiency. Transarticular stents should be carefully selected.
The diameter of the stent should be 1 to 2 mm larger than the diameter of the adjacent normal vein, and the length should be sufficient to completely cover the stenotic segment. When the lesion involves the confluence of the common iliac vein, the proximal end of the stent should extend about 3 mm into the inferior vena cava; long stents should be used as much as possible to reduce overlap in long segments of the lesion.
4. Adequate heparinization should be maintained during stent placement.
Postoperative treatment
1. During interventional thrombolytic therapy and after interventional thrombectomy, PTA and stent placement, the affected limb should be elevated horizontally by 30 cm or 20° to facilitate the blood return and swelling of the affected limb.
2. 2 to 3 d after intravenous or intra-arterial retention catheter thrombolysis, patients may develop mild fever. The fever may be caused by the dissolution of the thrombus, or the retained catheter itself may be a source of heat, or both.
3.Check and treat other diseases that may cause hypercoagulable state, such as certain malignant tumors, connective tissue diseases and antiphospholipid thrombosis syndrome, easy embolism, etc.
4. Take oral anticoagulants for at least 6 months after iliofemoral vein stent placement. If restenosis or occlusion is found in the stent and the patient develops symptoms such as swelling of the lower limbs, it is advisable to perform in-stent intervention again in a timely manner.
Complication prevention and control
1. Bleeding and hemolysis: During anticoagulation and thrombolysis, signs of subcutaneous, mucosal and visceral bleeding should be closely observed. If patients have neurological symptoms, cerebral hemorrhage should be considered first, anticoagulation and thrombolytic drugs should be stopped immediately, and emergency cranial CT examination is recommended to clarify the diagnosis. If there is bleeding, additional hemostatic drugs can be used. For those with large bleeding, puncture and drainage or surgical decompression and hematoma removal are feasible.
2. Vascular wall injury: catheters, guidewires, thrombus removal devices and balloons can cause vascular wall injury. If contrast retention or diffusion is found in the tissue interstitial space, it can be identified as vessel wall injury or rupture. When catheter guidewires are used to probe through narrow or occluded veins, it is advisable to use a softer, ultra-smooth guidewire whenever possible. After a normal catheter has been passed through a long segment of occlusion, it is advisable to exchange it for a thrombolytic catheter for imaging to confirm that the catheter is located in the true lumen for safety. When vascular wall injury is found, the lower extremity part can be taken to stop bleeding by local pressure on the body surface, and the iliac vein can be taken to temporarily seal the balloon, and if necessary, implantation of overlapping stent can be considered.
3, residual thrombus and thrombus recurrence: Thrombolytic therapy and transcatheter thrombectomy are often difficult to completely remove the thrombus in the venous lumen. The recurrence of thrombus is mostly related to the hypercoagulable state of blood caused by the underlying lesion, incomplete treatment and intravenous injury during treatment. After interventional operation, subcutaneous injection of low molecular heparin is recommended; after that, it is recommended to adhere to oral anticoagulant for more than six months and adjust the dose of anticoagulant timely under the monitoring of coagulation function.
4.PE: PE should be considered if patients have symptoms such as dyspnea, cyanosis, chest tightness, cough and hemoptysis, shock, and decreased oxygen saturation during pharmacological thrombolysis, thrombectomy or PTA, etc. Before the intervention, for those who have fresh thrombus or floating thrombus in the inferior vena cava and iliofemoral vein, placing inferior vena cava filter to block the dislodged thrombus is an effective method to prevent PE. Once PE occurs, comprehensive interventional treatment can be chosen according to the specific situation.
5. Vascular obstruction and restenosis after PTA and stenting: If the swelling and pain in the lower limbs do not decrease or the symptoms recur or worsen after PTA and stenting, acute thrombosis should be considered. Intraoperative and postoperative anticoagulation, local thrombolytic therapy with retained catheter after PTA and stent placement can reduce the incidence of acute thrombosis. long-term oral anticoagulation is recommended after PTA and stent placement to reduce the incidence and extent of restenosis.
Clinical application of inferior vena cava filter insertion and removal
Inferior Vena Cava Filter (IVCF) is a device designed to prevent pulmonary artery embolism caused by dislodged emboli in the inferior vena cava system.
The clinical manifestations of pulmonary embolism are sudden onset of chest pain, chest tightness, dyspnea and cyanosis, and shock in severe patients, with a mortality rate of 30%. Acute massive pulmonary embolism is a common cause of sudden death in patients. In the United States, the annual incidence of pulmonary embolism is 600,000 cases/year, and the morbidity and mortality rate is 25%-30% (150,000-200,000). In China, with the rapid increase of thrombotic and cardiovascular diseases, the incidence of pulmonary embolism has also been increasing. The data of 900 consecutive autopsies in Fu Wai Hospital confirmed that pulmonary embolism above the pulmonary segment accounted for 11% of cardiovascular diseases.
The embolus of pulmonary embolism is 75%-90% from the thrombus in the deep veins of the lower limbs and pelvic plexus. Previously, to prevent or reduce the occurrence of pulmonary embolism, ligation of the inferior vena cava or weaving of a filter mesh with sutures within the inferior vena cava was commonly used to block thrombi dislodged from the inferior vena cava system. The first filters used in clinical practice had to be inserted through a venous incision. After more than 40 years of continuous improvement, the variety of filters has increased and the filtration effect has improved, significantly reducing the incidence of pulmonary artery embolism. On the other hand, complications such as inferior vena cava obstruction due to long-term placement of filters have gradually attracted clinical attention. Currently, filters can be divided into three categories: temporary filters, permanent filters, and removable filters (also known as temporary and permanent dual-use filters).
Indications and contraindications of inferior vena cava filter placement
I. Indications for inferior vena cava filter insertion
(A) Absolute indications.
1.Patients with pulmonary embolism or inferior vena cava or iliofemoral N vein thrombosis have one of the following conditions: (1) contraindications to anticoagulation; (2) complications such as bleeding during anticoagulation; (3) recurrence of pulmonary embolism even after adequate anticoagulation and various reasons for not achieving adequate anticoagulation.
2.Pulmonary artery embolism and the presence of lower extremity deep vein thrombosis at the same time.
3.Free thrombus or massive thrombus in iliac, femoral vein or inferior vena cava.
4, Diagnosis of easy embolism and repeated pulmonary artery embolism.
5.Acute lower limb deep vein thrombosis, who want to perform transcatheter thrombolysis and thrombus removal.
(B) Relative indications
Mainly for prophylactic filter placement, which should be selected with caution.
1.Severe trauma with or likely to occur lower extremity deep vein thrombosis, including: (1) closed craniocerebral injury; (2) spinal cord injury; (3) multiple long bone fractures or pelvic fractures of the lower extremities, etc.
2.Critical cardiopulmonary reserve with lower extremity deep vein thrombosis.
3, chronic pulmonary hypertension with hypercoagulable state.
4, Patients with high risk factors, such as long-term limb braking, intensive care patients.
5.Old age, long-term bed-ridden with hypercoagulability.
II. Contraindications for inferior vena cava filter insertion
1.Absolute contraindication: chronic inferior vena cava thrombosis, severe stenosis of inferior vena cava.
2.Relative contraindications: (1) severe large pulmonary embolism, the condition is dangerous and life threatening; (2) with bacteraemia or toxemia; (3) minors; (4) the diameter of inferior vena cava exceeds or is equal to the maximum diameter of the spare filter.
C. Indications for inferior vena cava filter removal
1.Temporary filter or removable filter.
2.The time period after filter placement does not exceed the period specified in the instructions.
3.Confirmed by imaging that there is no free floating thrombus or fresh thrombus in N, femoral, iliac veins and inferior vena cava, or the thrombus in the above mentioned vessels disappears after treatment.
4.Patients who no longer need filter protection after other treatments after prophylactic filter placement.
Contraindications for inferior vena cava filter removal
1.After permanent filter placement.
2.The removable filter placement time has exceeded the period specified in the instructions.
3.Confirmed by imaging that there is still free floating thrombus or more fresh thrombus in N, femoral, iliac vein and inferior vena cava.
4.Patients with existing pulmonary artery embolism or at high risk of pulmonary artery embolism (such as easy embolism).
Preoperative preparation
1.Ultrasound and/or angiography of the affected limb: to understand the scope, degree and nature of DVT. Enhanced CT and CTA examination if necessary to clarify the pulmonary artery embolism.
2.Coagulation function and liver and kidney function measurement.
3.Sign informed consent: introduce the indications, operation procedure, complications and their management of filter placement or removal to the patient and family members, and sign the informed consent for the operation.
4.Prepare the equipment and drugs needed for the procedure: Prepare the inferior vena cava filter and delivery device or the interventional equipment needed for filter removal. Heparin sodium injection (12500 U/pc) 1~2pcs, contrast 50~100 ml, thrombolytic agent such as urokinase 200~1 million U and various emergency drugs. Prepare and set up the cardiac monitor, oxygen, suction device for backup.
Operation steps
Before placing and removing the inferior vena cava filter, you should read the product instructions in detail, because the operation methods vary from manufacturer to manufacturer and from product to product.
I. Commonly used inferior vena cava filters at present
1.Temporary inferior vena cava filter: usually placed through the right internal jugular vein, the filter is connected to the indwelling tube, and the upper end of the indwelling tube is connected to the olive-shaped anchor cable buried under the skin. When the filter needs to be removed, a small incision is made under local anesthesia to detach the anchor cord, and the anchor cord, indwelling tube and filter are withdrawn together.
2.Permanent inferior vena cava filter: (1) SNF: can be placed by femoral vein, internal jugular vein, subclavian vein or anterior elbow vein on both sides; (2) TEF: can be placed by femoral vein, internal jugular vein or anterior elbow vein on both sides. (3) LP-VTF: It can be placed through both femoral veins, or through the right internal jugular vein or both subclavian veins.
3.Removable inferior vena cava filter: this type of filter can be removed within a specified time after placement, or can be left in place to make it a permanent filter. (1) GTF: It can be inserted through both femoral veins or internal jugular vein. As a temporary filter, it can be removed by a special retrieval device via the internal jugular vein within 12 days after insertion. (2) OEF: OEF can be inserted in the same way as TEF and can be removed within 12 d after insertion via the femoral vein on one side by a goose neck or other collaterals combined with a guide tube. (3) ZQL removable vena cava filter: This filter can be inserted through the right internal jugular vein or both femoral veins, and the insertion method is similar to that of 2 Z-shaped stents, and it can be removed through the right internal jugular vein within 2 weeks after insertion, and the removal method is the same as that of GTF. (4) Aegisy removable filter: This filter can be inserted through both femoral veins, and it can be removed through the femoral vein within 2 weeks after insertion, and the removal method is the same as that of OEF.
Inferior vena cava filter insertion steps
1.Selecting the access: inferior vena cava filter is usually inserted through the femoral vein on the healthy side, but when there is thrombus in both iliofemoral veins or thrombus exists in the inferior vena cava, it can be inserted through the internal jugular vein or the anterior elbow vein on one side.
2.Inferior vena cava angiography: All inferior vena cava filters must be placed with inferior vena cava angiography to understand the morphology of the inferior vena cava, such as the diameter of the inferior vena cava, the presence of vascular curvature, intraluminal thrombus, anatomical variations (duplicated inferior vena cava, left inferior vena cava, etc.), etc.
3.Determine the position of the opening of both renal veins: the filter is usually placed in the inferior vena cava below the lower edge of the opening of the renal vein, but if there is thrombus in the inferior vena cava at the level of the renal vein or 4 cm below it at the time of imaging, the filter should be placed above the level of the renal vein.
4.Selection of filter: The selection of filter should be based on the patient’s age, disease duration, inferior vena cava morphology and diameter, thrombus size and free degree. Temporary or removable filters are recommended for young patients and fresh or short thrombi; removable or permanent filters are recommended for deep vein thrombi longer than 20 cm or all lower limbs.
5.Placement operation: first place the filter delivery sheath, then slowly feed the filter through the delivery sheath, after repeatedly checking the position of the renal vein under X-ray fluoroscopy, slowly withdraw the delivery sheath until the filter pops open and is released.
6. Inferior vena cava angiography review: After the filter is placed, angiography review will be performed to observe the form of the filter, whether there is tilt and angle of tilt, and the distance between the apex of the filter and the renal vein. For the removable filter, the distance between the filter removal hook and the wall of inferior vena cava should be carefully observed and analyzed, if the distance is >5 mm is more ideal, it indicates a high success rate of removal.
Three, inferior vena cava filter removal steps
1.Determine the way of filter removal: the removable filter should be removed via femoral vein or internal jugular vein according to the position of the filter removal hook.
2.Inferior vena cava angiography: temporary or removable filters should be ultrasound or angiography of lower limb veins and inferior vena cava before removal to assess the risk of filter removal. If there is still more free thrombus in the lower extremity veins and/or inferior vena cava, for temporary filters, the time of filter placement can be extended appropriately, and replacement with removable filters or permanent filters can also be considered; for removable filters, the removal can be abandoned to make them permanent.
3.Take out the filter: For the temporary filter, the retention tube connected with the filter can be pulled out of the body directly. For removable filters, they must be removed by special recovery sheaths, guide tubes, goose neck traps or trilobular traps.
4.Check the filter: observe whether the filter is intact, whether it is broken; the amount and nature of the thrombus in the filter, and if necessary, take the specimen for pathological examination.
5.Review of inferior vena cava angiography: after removing the filter, review the angiography to observe whether the inferior vena cava wall is smooth, whether the inferior vena cava blood flow is smooth, whether the contrast agent is retained, and evaluate whether there is damage to the inferior vena cava wall.
Precautions
1.When selecting the filter, temporary or removable filter should be chosen as much as possible to reduce the probability of inferior vena cava obstruction caused by long-term placement of the filter.
2.If ultrasound or imaging is performed before removing the retrievable filter, if more fresh thrombus is still found in the inferior vena cava, the plan to remove the filter should be abandoned to avoid fatal pulmonary artery embolism during the filter removal.
3.If the removable filter is placed for more than the specified period, it is generally not advisable to remove it to avoid the difficulty of removing it and the damage of the inferior vena cava intima caused by tearing off the new endothelium covering the filter.
4.If the removable filter hook is embedded in the endothelium of the inferior vena cava, it is very difficult to remove the filter. Preoperative angiographic evaluation is particularly important, and if necessary, multi-angle inferior vena cava angiography can be performed.
5.Under no circumstances should the filter be forcibly pulled out to avoid laceration of the inferior vena cava wall which may lead to hemorrhage.
Postoperative treatment
1.After the inferior vena cava filter is inserted, anticoagulation, thrombolysis, mechanical thrombus removal and other comprehensive treatments are appropriate. This can shorten the course of disease and improve the success rate of treatment on the one hand, and prevent or reduce the occurrence of inferior vena cava obstruction on the other hand.
2.For patients with pulmonary artery embolism, after the placement of inferior vena cava filter, active treatment of pulmonary artery embolism should be carried out in order to open the pulmonary artery, relieve the patient’s symptoms and prevent the occurrence of pulmonary hypertension and pulmonary heart disease.
3. For patients with permanent filter placement (including removable filters not removed), if there is no contraindication to anticoagulation, long-term oral anticoagulants such as warfarin sodium tablets are recommended, and coagulation function should be reviewed regularly and warfarin dosage should be adjusted to maintain INR values between 2,0 and 3,0.
4. A follow-up visit should be made once at 1, 3 and 6 months after filter insertion, with abdominal X-ray and a cis-flow inferior vena cava angiography and/or ultrasonography at 6 months after filter insertion, and once a year thereafter. The main observation of the follow-up visit is the shape and position of the filter and the inferior vena cava blood flow.
Complications and their prevention
I. Inferior vena cava obstruction
It often occurs when a large amount of thrombus is dislodged and caught in the filter, and it may also be caused by filter-induced inferior vena cava thrombosis and obstruction of inferior vena cava blood flow, which is clinically manifested as inferior vena cava obstruction syndrome. For patients with hypercoagulable state, intensive anticoagulation is required after filter placement. The treatment of symptomatic inferior vena cava obstruction is the same as the interventional treatment of lower limb deep vein thrombosis.
Recurrent pulmonary artery embolism
Pulmonary embolism recurrence can occur at any time after filter insertion. Most cases are due to persistent hypercoagulability, dislodgement of the thrombus at the top of the filter, and reduced filtration due to deformation or tilting of the filter. Adherence to anticoagulation may avoid or reduce the probability of recurrent pulmonary embolism. The management of pulmonary embolism recurrence is the same as the treatment of pulmonary embolism.
Three, filter displacement
When the filter is displaced downward, it is mostly of no clinical significance. Occasionally, a filter displaced to the iliac vein or misplaced in the iliac vein may cause iliac vein obstruction. When the filter is displaced to the right heart, it may cause serious arrhythmia. Familiarity with the properties of various filters and the maximum diameter of the applicable vena cava can help reduce the incidence of filter displacement. If a filter displacement that can cause clinical symptoms is found, the filter can be removed or repositioned by interventional methods, or removed by surgery if it is not effective.
Filter fracture
Filter fracture is rare. If the filter fracture does not cause dislodgement and wandering, the filter position is stable, and other complications such as puncture of blood vessels will not occur, the filter can be closely and regularly observed under the premise of standard anticoagulation; otherwise, the filter should be removed by interventional or surgical procedures.
V. Filter legs penetrating the vessel wall
This condition is often due to pulsation of the abdominal aorta. Chronic inferior vena cava wall perforation usually does not cause hemorrhage and often does not require treatment; if it is accompanied by retroperitoneal bleeding, it can be treated conservatively or surgically depending on the degree of bleeding; if it causes perforation of the abdominal aorta and intestinal wall injury, surgical treatment is usually required.
Evaluation of efficacy
The index for evaluating the effectiveness of inferior vena cava filter placement is the incidence of pulmonary artery embolism. It is generally accepted that the incidence of pulmonary embolism after inferior vena cava filter placement is about 2 to 5, because most pulmonary embolisms after filter placement are asymptomatic and difficult to diagnose. Therefore, the incidence of pulmonary embolism after filter placement is actually higher than this value.
The comprehensive treatment of inferior vena cava filter placement, retrieval and deep vein thrombosis was performed in 85 cases in our hospital, and 85 cases were successful, with no acute pulmonary embolism in one patient. Inferior vena cava filter placement is minimally invasive, has low surgical risk, and can be tolerated by patients. After the operation with intravenous thrombolysis, the swelling of the affected limb can disappear rapidly for patients with acute thrombosis.
At present, some hospitals in the province have carried out inferior vena cava filter placement, but almost no filter can be recovered again. At the same time, our department can perform interventional thrombus removal measures such as transcatheter thrombolysis, catheter aspiration and mechanical ablation immediately after inferior vena cava filter placement; for DVT patients with iliac vein compression syndrome or iliac vein occlusion, PTA and stent placement are used in combination to rapidly restore blood flow. In patients with iliac vein compression syndrome or DVT with associated iliac vein occlusion, a combination of PTA and stenting was used to rapidly restore blood flow, and the filter was retrieved when the time was right. Good results were achieved through comprehensive treatment of 85 patients.
Summary
Although the indications for inferior vena cava filter placement are still debated, it is well established that filters can reduce the incidence of pulmonary embolism. The use of temporary and removable filters is recommended to minimize complications associated with long-term filter placement. The use of filters should be chosen appropriately for different situations and purposes.