Pulmonary embolism is a general term for a group of diseases caused by emboli blocking the pulmonary arterial system, including pulmonary thromboembolism, fat embolism syndrome, amniotic fluid embolism, air embolism, etc., of which pulmonary thromboembolism is the most common type, and pulmonary embolism usually means pulmonary thromboembolism. The thrombus that causes pulmonary thromboembolism mainly comes from deep vein thrombosis, most commonly in the veins of the lower limbs and pelvic veins. Acute pulmonary thromboembolism is one of the medical emergencies, and the condition is dangerous. Chronic pulmonary thromboembolism is mainly caused by recurrent small-scale pulmonary embolism, which has no clinical manifestation in the early stage but can cause severe pulmonary hypertension in the long term.
Risk factors.
Venous blood stasis, endothelial damage of the venous system, and hypercoagulable state of blood are the 3 main factors of venous thrombosis.
Common high incidence conditions.
Pregnancy/puerperium, prolonged air or car travel, oral contraceptive use, obesity, smoking, advanced age.
Trauma/fractures (mostly hip and spinal cord injuries), post-surgical procedures (mostly after total hip replacement or knee replacement), implantation of artificial prostheses, braking/prolonged bed rest for various reasons, central venous cannulation.
Stroke, nephrotic syndrome, congestive heart failure, acute myocardial infarction, malignancy, Crohn`s disease (Crohn`sdisease), chronic venous disease.
Increased blood viscosity, platelet abnormalities, intravenous chemotherapy for tumors, true erythrocytosis, macroglobulinemia.
Pathophysiological features.
The pathophysiological changes and severity of pulmonary thromboembolism are influenced by a variety of factors: size and number of emboli; interval of embolism, whether other cardiopulmonary diseases are combined, and the rate of thrombus dissolution and metabolism.
In mild cases, there can be no conscious symptoms; in severe cases, the resistance of pulmonary circulation suddenly increases, resulting in a sharp decrease in cardiac blood displacement, and patients may experience shock, cerebrovascular and cardiovascular blood supply deficiency, leading to syncope or even sudden death.
Symptoms.
Dyspnea is the most common symptom, which appears or worsens after activity and is often confused with exertional angina.
Chest pain: seen in most people with pulmonary embolism, characterized by significantly increased pain with deep breathing or coughing, angina-like chest pain is less common and is an important symptom easily confused with angina.
Coughing up blood: The sudden appearance of coughing up blood without previous lung disease should alert the possibility of pulmonary embolism, mostly in small amounts, but occasionally in large amounts, which may lead to death by asphyxiation.
Cough: mostly dry, without sputum or a small amount of white sputum
Syncope: It may be the only or the first symptom, suggesting a large embolism area and a poor prognosis
Restlessness, panic or even near-death feeling: seen in most patients, considered to be related to pain or hypoxemia
abdominal pain: may be related to diaphragmatic irritation or intestinal bleeding
One or several of these symptoms may be present in each case, resulting in a lack of distinctive features and often misdiagnosis or underdiagnosis. The so-called “pulmonary infarction triad”, i.e., dyspnea, chest pain, and coughing up blood, is only seen in a small number of patients and also suggests a poor prognosis.
Ancillary tests.
Plasma D-dimer: D-dimer is a soluble degradation product of cross-linked fibrin produced under the action of fibrinolytic system. After the onset of thrombotic disease due to physiological lysis of thrombus to increase the concentration of hematoma, the sensitivity of thrombotic disease is high, but the specificity is low, mostly used to exclude pulmonary embolism, myocardial infarction and other critical thromboembolic diseases.
CT pulmonary angiography: It is the first choice for clinical diagnosis of pulmonary embolism. At present, high-row CT can determine the location and scope of thromboembolism, and can also show other chest diseases outside the lung and lung at the same time, which helps to differentiate from other diseases. Iodine contrast agent should be applied during the examination, and those who are allergic to iodine agent should not be examined.
Magnetic resonance imaging: It has the same significance as CT angiography and is suitable for patients with iodine contrast allergy.
Echocardiography: Some indirect signs can be detected. In a few patients, proximal pulmonary artery thrombosis or right heart thrombosis can be detected.
Arterial blood gas analysis: hypoxemia can occur in more than 15% of pulmonary vascular obstruction, and most acute patients present with PaO2 <80 mmHg and a decrease in PaCO2 in those with hyperventilation
Electrocardiogram: most of them have no specific degeneration, but it can help in differential diagnosis. Some cases may show SⅠQⅢTⅢ sign (deepening of S wave in lead I, Q/q wave and T wave inversion in lead III); other changes include complete or incomplete conduction block, pulmonary P wave, etc.
Differential diagnosis.
Because the severity of pulmonary embolism varies greatly with the symptoms, it should be differentiated from coronary heart disease, acute heart failure, aortic coarctation, pneumothorax, severe asthma, severe pneumonia, pleurisy;, chronic pulmonary heart disease, etc.
Main treatment modalities.
1. anticoagulation therapy: it is the basic treatment, which can improve the survival rate and reduce the recurrence rate, and should be applied to patients without contraindications. Commonly used drugs: warfarin
2. Thrombolytic therapy: for large pulmonary thromboembolism (presence of hypotension, cardiogenic shock) it is recommended to apply thrombolytic therapy within 14 days. There is a risk of complicated bleeding. Commonly used drugs are: urokinase, streptokinase, recombinant tissue-type fibrinogen activator (rt-PA)
3. Surgical and interventional treatment: including surgical pulmonary artery thrombectomy, interventional pulmonary artery dissection and aspiration of thrombus, placement of venous filter, etc., generally used for those who have poor results of medical drug treatment. Endarterectomy of pulmonary artery thrombosis is feasible in some chronic patients.
Prevention.
Prevention is carried out for risk factors of thromboembolism, such as active treatment of lower limb infection and varicose veins, careful assessment of the risk of thrombosis in hospitalized and long-term bedridden patients, encouraging patients to get out of bed as early as possible after surgery, and giving prophylactic anticoagulation to those who are confirmed to be at higher risk of thrombosis.