1.Discussion on the treatment method of acute deep vein thrombosis
The main hazards of acute lower limb deep vein thrombosis are pulmonary embolism causing pulmonary hypertension or patient’s death, venous obstruction and valve destruction causing distant venous insufficiency, therefore, correct and timely treatment in the acute stage can reduce the occurrence of pulmonary embolism and deep vein thrombosis sequelae, and the treatment methods include anticoagulation, thrombolysis and surgical thrombus removal.
The literature reports that only 6% of patients with acute lower extremity DVT under traditional anticoagulation therapy have their thrombus dissolved within 10 days, and 40% of patients have possible spread of thrombus in the lower extremity. 5-year follow-up shows that 95% of patients have muscle pump failure in the affected extremity and destruction of the proximal DVT valve.
In 1980, the National Institutes of Health suggested that thrombolytic therapy could be the basic treatment for acute deep vein thrombosis and pulmonary embolism, and the follow-up results showed that thrombolytic therapy was superior to anticoagulation alone in all aspects. In particular, the use of interventional means to insert a thrombolytic catheter into the thrombus for direct intraluminal thrombolysis has yielded encouraging results in restoring patency of the deep venous trunk and preserving the deep venous valves. Although surgical thrombectomy also has a high effect on restoring the patency of the deep venous trunk and preserving the deep venous valves, it is clinically used for the treatment of femoral white (cyanotic) swelling and patients with contraindications to anticoagulation and thrombolysis because of its high trauma and high intraoperative bleeding, and animal experiments have proved that the destruction of venous endothelial cells by surgical thrombectomy is much greater than that by thrombolytic therapy.
At present, thrombolysis combined with anticoagulation has become the main means of clinical treatment for acute lower limb deep vein thrombosis.
2.Advantages and indications of direct thrombolysis by catheterThrombolytic catheter
It is inserted directly into the thrombus site, and urokinase is continuously pushed by micro-pump to maintain high local drug concentration, so that the thrombus can be dissolved rapidly, which can better preserve the proximal deep vein valve of the affected limb and reduce the occurrence of lower limb deep vein valve insufficiency.
Secondly, dissolving as much thrombus as possible can make the trunk vein as smooth as possible and open a large number of side branches, improve venous reflux and reduce venous pressure, relieve the symptoms of distension and edema, and help restore the muscle pump function.
The literature confirms that anticoagulation with direct catheter thrombolysis is superior to anticoagulation alone in both near and long-term clinical outcomes. Most data suggest that direct catheter thrombolysis is effective only for central iliofemoral vein thrombosis, especially with the Unifuse catheter, whose unique structure allows adequate and prolonged contact of the thrombolytic drug with the thrombus to achieve a good thrombolytic effect.
We found that direct thrombolysis with catheters, especially with the UniFus catheter, has good efficacy in patients with central and mixed types, as long as the onset of thrombosis is within 5-7 days. In this group of 36 patients, the treatment results showed that the swelling symptoms of the affected limbs improved significantly after thrombolysis, and the follow-up results before and after thrombolysis and greater than 6 months showed that the venous patency score decreased, the difference in venous patency was significant, and the long-term deep venous valve preservation rate and the average venous patency improvement achieved more satisfactory results.
3.The choice of thrombolytic drugs and dose
Urokinase for injection, streptokinase and recombinant t-PA are the main thrombolytic drugs used clinically for the treatment of acute lower limb deep vein thrombosis. Streptokinase is less commonly used in clinical practice due to the high incidence of bleeding and allergic reactions to the drug.
Urokinase and recombinant t-PA are reported to have good clinical efficacy and low bleeding complications, and there is no significant difference in efficacy and complications, while in China, the cost difference between the two therapeutic doses is tens of times, therefore, we think that urokinase is a wiser choice as a drug for direct thrombolysis by catheter.
Regarding the dose of the drug, the literature reports vary, with foreign reports reporting an average total dose of 4.9 million IU, and small doses have also been reported. Domestic reports use doses of 200,000-500,000 IU/day for 3-5 days. The average dose of the total course of treatment in our patients is 152.30±79.06 million IU on average. Due to the use of catheter thrombolysis for local treatment, the total dose is reduced, the incidence of systemic bleeding complications is greatly reduced, and the safety is significantly increased.
4.The route and method of direct thrombolysis
The route of catheter direct thrombolysis for the treatment of lower limb deep vein thrombosis is closely related to the effect and complications of thrombolytic therapy. The commonly used routes are: internal jugular vein, femoral vein, N vein, saphenous vein and other routes. The consequences of internal jugular vein placement for thrombolysis are more serious if bleeding complications occur. The rest of the sites do not cause serious consequences. The site of insertion depends on the venous cascade angiography and DSA of the affected limb, and can also be placed by Duplex ultrasound-guided puncture, which must enable the thrombolytic catheter to be inserted directly into the thrombus, so that the direction of the injected thrombolytic drug is as much as possible consistent with the direction of venous blood flow.
The current clinical use of thrombolytic therapy is a special catheter with a guidewire and a long segmental lateral hole in the front, especially the specialized Unifuse catheter for thrombolysis. The central guidewire not only plays a supporting role when the catheter is inserted, which is easy to insert into the thrombus and block the top hole of the catheter, so that the injected thrombolytic drug only gushes out from the lateral fissure of the catheter, which increases the range of contact between the thrombolytic drug and the thrombus, and enables the observation of the thrombolytic effect by catheterography and easy adjustment of the catheter position.
During thrombolysis, we injected 200,000-250,000 IU into the thrombolytic catheter by micro-pump in the first 1/2-1 hour, and continued to push 40,000 IU/hour thereafter. We use 1 million IU for the first time, and every 500,000 IU of urokinase via the thrombolytic catheter once thereafter to observe the effect of thrombolysis and adjust the position of the thrombolytic catheter.
In our opinion, thrombolysis should be terminated in the following cases: continuous patency of the main veins above the N vein, no progress of thrombolysis in two imaging results, and peripheral blood fibrinogen content <1.0g/L.
5.Use of vena cava filter
Pulmonary embolism is a serious complication of acute lower extremity deep vein thrombosis.William reported that 46-60% of pulmonary embolism is associated with limb vein thrombosis.Eicheter was the first to use inferior vena cava filter placement to prevent fatal pulmonary embolism caused by lower extremity deep vein thrombosis in clinical practice in 1968, thus reducing its occurrence.Decousus randomized 400 cases of lower extremity deep A prospective study of 400 randomized patients with lower extremity deep vein thrombosis who were placed with an inferior vena cava filter found that 80% of mortality in patients without an inferior vena cava filter was associated with pulmonary embolism, whereas mortality in patients with an inferior vena cava filter was not associated with pulmonary embolism.
What’s more, when a catheter is inserted directly into a venous thrombus for local thrombolysis, the insertion operation and the ease of disintegration and dislodgement of the thrombus during thrombolysis both increase the risk of pulmonary embolism. Basically, the catheter thrombolysis treatment reported in China is also accompanied by the placement of inferior vena cava filter. Therefore, we suggest that if a catheter is used for direct thrombolysis of acute lower extremity deep vein thrombosis, placement of an inferior vena cava filter is necessary to prevent pulmonary embolism due to the disease itself and the dislodgment of the thrombus during the operation and treatment.