I. Superior vena cava obstruction syndrome Superior vena cava obstruction syndrome is a group of clinical symptoms caused by significant narrowing or obstruction of the superior vena cava or bilateral cephalic veins, characterized by swelling of the face, neck and arms, often accompanied by dyspnea, telescopic breathing, nausea, cough and formation of lateral circulation in the chest, and sometimes headache, dizziness and even syncope can occur. Its etiology is mostly caused by malignant tumors of the chest and mediastinum, and its prognosis is poor. Without timely and effective treatment, life-threatening complications, such as laryngeal or cerebral edema, can occur. The efficacy of radiotherapy and chemotherapy is slow, while stent placement provides rapid relief of symptoms. Indications It is generally accepted that patients with superior vena cava syndrome with the following conditions should be considered for interventional treatment. 1.Patients with rapid disease progression and significant venous return obstruction, especially those with respiratory distress and intracranial hypertension symptoms, who need timely release of obstruction. 2.Patients with superior vena cava syndrome have poor effect of regular radiotherapy and chemotherapy and other anti-tumor treatment. 3.Patients who have entered the advanced stage of tumor and are physically unable to tolerate radiotherapy and chemotherapy as well as surgical opportunities combined with superior vena cava syndrome. Contraindications If there is no iodine or anesthetic allergy and serious infection, there is generally no absolute contraindication. For those with well established collateral circulation and no obvious clinical symptoms or signs, intervention is not required. Preoperative preparation In addition to identifying the cause of obstruction, enhanced CT or MR should be performed to identify the site of superior vena cava obstruction, the degree and length of obstruction, and the establishment of collateral circulation. Patient preparation 1. routine blood, clotting time, INR, liver and kidney function, electrolytes, electrocardiogram, etc. 2. local anesthetic and iodine allergy test 3. preoperative explanation of the condition, treatment and possible complications with the family, and signing of the surgical protocol 4. preoperative fasting for 4 hours, and preoperative sedation. Technical operation 1.Venous access The femoral vein is usually used, if it is difficult to operate, the internal jugular vein can also be used, while the subclavian vein or even the axillary vein is also an optional route. 2.Vena cava angiography and pressure measurement The catheter is passed through the stenotic segment with the help of a guidewire and enters the distal end of the superior vena cava. The site of obstruction, the degree and length of stenosis, and the presence of thrombosis are observed on imaging and manometry. If no thrombus is found, balloon dilation will be performed directly; if there is thrombosis, thrombolysis will be performed first. 3.Balloon dilation Before the proposed balloon dilation, systemic heparinization should be given according to the patient’s weight. The balloon of suitable size for the diameter of the blood vessel should be selected, and the expansion can be performed from small to large. The pressure of the expanded balloon should not be too large to prevent the rupture of the blood vessel, resulting in bleeding, shock or even death. 4.Stent implantation The diameter of the stent should be 10% larger than the normal SVC diameter, and the length should be 1~2 cm beyond the upper and lower part of the stenosis. After the release of the stent, if the stent is not fully expanded, no further treatment can be done, and the stent itself can be gradually expanded to the ideal diameter by the tension of the stent. 5. Review imaging Observe the stent position, the opening of the superior vena cava, and the spillage of contrast agent to ensure that the vessel is not ruptured and bleeding, and then measure and record the values. Postoperative treatment Routine observation of vital signs. Antimicrobial prophylaxis for 3 days, subcutaneous injection of low molecular heparin sodium 5000 U once/12 h for 3 d, oral warfarin and aspirin, and monitoring of coagulation time (PT), activated prothrombin time (APTT) and INR (controlled at 2.0-3.0) for 3-6 months. Complications and their prevention and control Serious complications of interventions for superior vena cava syndrome are rare. Complications such as stent migration, stent obstruction, pulmonary embolism, vessel rupture, and even pericardial tamponade can theoretically occur with stent implantation in the superior vena cava, but similar complications have not been reported clinically. Other uncommon complications include fever, infection at the puncture site, and transient pain during balloon expansion. Efficacy evaluation The vast majority of clinical symptoms resolve within the first 24-72 hours, but restenosis or occlusion is often associated with the treatment of the primary disease, but some patients have thrombosis due to suboptimal anticoagulation therapy, so regular anticoagulation should be administered within the first 3 months if not contraindicated.