This involves accessing the venous system by placing a catheter into a vein in the groin and guiding it through the veins by using fluoroscopic imaging until it is located next to the PE in the lung circulation. Medication that breaks up blood clots is released through the catheter so that its highest concentration is directly next to the pulmonary embolus. CDT is performed by  interventional radiologists or vascular surgeons, and in medical centers that offer CDT, it may be offered as a first-line treatment. Catheter-based ultrasound-assisted thrombolysis is being investigated.The use of thrombolysis in non-massive PEs is still debated. Some have found that the treatment decreases the risk of death and increases the risk of bleeding including intracranial hemorrhage. Others have found no decrease in the risk of death. Inferior vena cava filter
There are two situations when an inferior vena cava filter is considered advantageous, and those are if anticoagulant therapy is contraindicated (e.g. shortly after a major operation), or a person has a pulmonary embolus in spite of being anticoagulated. In these instances, it may be implanted to prevent new or existing DVTs from entering the pulmonary artery and combining with an existing blockage. In spite of the devices theoretical advantage of preventing pulmonary emboli, there is a lack of evidence supporting its effectiveness.Inferior vena cava filters should be removed as soon as it becomes safe to start using anticoagulation. Although modern filters are meant to be retrievable, complications may prevent some from being removed.
Alterations in blood flow: immobilization (after surgery, long-haul flight), injury, pregnancy (also procoagulant), obesity (also procoagulant), cancer (also procoagulant)
Factors in the vessel wall: surgery, catheterizations causing direct injury ("endothelial injury")
Factors affecting the properties of the blood (procoagulant state):
Estrogen-containing medication (transgender hormone therapy, menopausal hormone therapy and hormonal contraceptives)
Genetic thrombophilia (factor V Leiden, prothrombin mutation G20210A, protein C deficiency, protein S deficiency, antithrombin deficiency, hyperhomocysteinemia and plasminogen/fibrinolysis disorders)
Acquired thrombophilia (antiphospholipid syndrome, nephrotic syndrome, paroxysmal nocturnal hemoglobinuria)
Cancer (due to secretion of pro-coagulants)Although most pulmonary embolisms are the result of proximal leg deep vein thrombosis (DVTs), there are still many other risk factors that can also result in a pulmonary embolism. Risk factors include:
Varicose veins caused by vascular damage
Pulmonary hypertension
Diabetes
Traumatic hip fractures that immobilize the patient
Joint fixation (primarily in the legs)

Underlying causes
After a first PE, the search for secondary causes is usually brief. Only when a second PE occurs, and especially when this happens while still under anticoagulant therapy, a further search for underlying conditions is undertaken. This will include testing ("thrombophilia screen") for Factor V Leiden mutation, antiphospholipid antibodies, protein C and S and antithrombin levels, and later prothrombin mutation, MTHFR mutation, Factor VIII concentration and rarer inherited coagulation abnormalities. Diagnosis
To diagnose a pulmonary embolism, a review of clinical criteria to determine the need for testing is recommended.