Pulmonary embolism is a clinical syndrome caused by obstruction of the pulmonary arterial system by endogenous or exogenous emboli, resulting in dysfunction of the pulmonary circulation. Although the causes of pulmonary embolism include pulmonary thrombosis embolism (PTE), fat embolism, amniotic fluid embolism, and air embolism, more than 99% of pulmonary embolism in clinical practice is pulmonary thrombosis embolism.
Since pulmonary embolism usually has no specific clinical manifestations, it has a high rate of underdiagnosis, misdiagnosis and mortality. Currently, there are many treatment methods for pulmonary embolism, such as anticoagulation, thrombolysis, interventional therapy, and surgical embolization, while anticoagulation is the most necessary basic measure for all patients with pulmonary embolism, and thrombolysis is the main elective treatment. In this paper, we will focus on how to select the right patient for thrombolysis in acute pulmonary embolism, how to choose the right drug and its dose, how to improve the success rate of thrombolysis, and several other issues that must be concerned.
1.Selection of thrombolytic therapy for acute pulmonary embolism
1.1 Indications for thrombolytic therapy of acute pulmonary embolism:
For patients with high-risk acute pulmonary embolism, the ESC and AHA/ADA guidelines unanimously recommend thrombolytic therapy, while for intermediate-risk patients, thrombolytic therapy is still controversial. However, a series of studies have shown that pulmonary hypertension due to residual pulmonary artery thrombosis is closely related to the long-term prognosis and quality of life of patients. Therefore, thrombolytic therapy is needed for some patients with intermediate-risk pulmonary embolism. Our clinical practice experience is that for patients with large pulmonary thrombus and right heart failure caused by pulmonary hypertension, patients with pulmonary embolism involving more than two lobes of the lung, and patients with pulmonary embolism accompanied by massive thrombus in the deep veins of the lower extremities, thrombolytic therapy should be actively performed to dissolve pulmonary artery thrombus and relieve pulmonary hypertension as much as possible, and dissolve limb vein thrombus to improve patients’ quality of life and long-term prognosis.
1.2 Contraindications to thrombolytic therapy for acute pulmonary embolism:
The main contraindications to thrombolytic therapy are patients at risk of intracranial hemorrhage, gastrointestinal hemorrhage, and major bleeding from other important sites. Therefore, it is extremely important to perform bleeding risk assessment before thrombolytic therapy. The main risk factors for major bleeding include.
(1) Advanced age, especially age 75 years or older;
(2) Previous gastrointestinal bleeding, especially if not systematically treated;
(3) Recent history of cerebral infarction or cerebral hemorrhage;
(4) Recent post-surgical or traumatic history;
(5) Other serious acute and chronic diseases;
(6) Combination of antiplatelet drugs;
(7) Poorly controlled anticoagulation;
(8) severe hepatic or renal insufficiency.
For the above bleeding risks to be dynamically assessed, we have three patients with acute large pulmonary embolism within 3 days after surgery, due to local bleeding or hematoma formation at the surgical site, through several days of observation of local bleeding status and hematoma stabilization, thrombolytic therapy was given, and very satisfactory results were achieved.
2.Timing of thrombolytic therapy for acute pulmonary embolism
Domestic and international guidelines suggest that the time window for thrombolysis in acute pulmonary embolism is within 14 days, and thrombolysis within 48 hours has the best effect. However, many patients have been diagnosed with pulmonary embolism for more than 14 days, and our clinical observation and study found that most patients have thrombus in the pulmonary artery not formed at one time, but repeatedly dislodged thrombus in the limb vein and accumulated in the pulmonary artery layer by layer. For patients with acute massive or submassive pulmonary embolism, if there are patients with sudden aggravation of dyspnea within the last 1 month, thrombolysis must be considered in combination with the thrombus image characteristics of CT of pulmonary artery and ultrasound of limb veins.
3.The selection, dosage and usage of thrombolytic drugs for acute pulmonary embolism
At present, there are two types of thrombolytic agents for acute pulmonary embolism: non-thrombotic target-binding thrombolytic agents and thrombotic target-binding thrombolytic agents. The former are urokinase and streptokinase, and the latter are mainly recombinant tissue-type fibrinogen activator (rt-PA). rt-PA mainly acts on thrombus, and has high affinity and lysis effect on thrombus fibrin, i.e. rt-PA has selective thrombolytic effect without degradation effect on fibrinogen in blood paddle, so rt-PA has higher success rate of thrombolysis and lower risk of bleeding.
Foreign guidelines recommend a dose of 100 mg of rt-PA, and a study at Beijing Chaoyang Hospital in China found that the efficacy of 50 mg was comparable to that of 100 mg, but the risk of bleeding was lower, so the domestic recommendation is mostly 50 mg, which may be related to the average weight of the Chinese population. Our experience is that the selection of thrombolytic dose needs to be individualized. 50mg should be given for the first time to patients with weight <65kg, 100mg should be given intravenously for the first time to patients with weight ≥65kg, and 100mg rt-PA should be given to patients with large pulmonary artery thrombosis and combined lower limb venous thrombosis. If the thrombus load is still large, thrombolytic therapy can be given again.
4.Management after thrombolytic therapy for acute pulmonary embolism
After thrombolytic therapy for acute pulmonary embolism, continue to give Warfarin anticoagulation therapy and adjust INR (International Normalized Ratio) to 2.0~3.0 for 3~6 months. However, for patients with pulmonary embolism of unknown cause, especially those with recurrent deep vein thrombosis and pulmonary artery embolism, Warfarin should be given for a longer period of time or even for life, and the duration of Warfarin is still controversial.
5.Thinking about the implantation of lower limb filter
In case of repeated lower limb venous thrombosis or contraindication to thrombolysis or anticoagulation, thrombotic filter implantation is feasible. However, foreign body implantation itself is easy to form thrombosis, and the guidelines do not recommend active thrombosis filter implantation.