Further Discussion on Pulmonary Embolism—August 31, 2001

Further Discussion on Pulmonary Embolism—August 31, 2001

Pulmonary embolism (PE) is a relatively common condition, yet most cases are misdiagnosed. Deep vein thrombosis of the lower extremities is the most frequent cause of this disease, accounting for 80% of pulmonary embolisms. In the past, diagnosis relied solely on the textbook description of “wedge-shaped shadows pointing toward the pulmonary hilum.” In reality, however, this finding is clinically observed in less than 50% of cases, meaning that 50% of pulmonary embolisms are often misdiagnosed. When death occurs, it is often attributed to acute coronary spasm or occlusion. Deep venous thrombi in the lower extremities can originate from rheumatic heart valve damage or from the detachment of atherosclerotic plaques. Lung tissue has a dual blood supply and strong compensatory capacity; only when 50% of the pulmonary vasculature is obstructed do symptoms appear. Therefore, mild cases of PE may be asymptomatic, while severe cases can be life-threatening. Common symptoms include dyspnea in 85% of cases, chest pain in 80%, hemoptysis in 40–50%, syncope and shock in 20%, with those experiencing shock indicating major vascular occlusion and extreme danger.

Diagnosis: Blood gas analysis shows decreased partial pressure of oxygen and normal or decreased partial pressure of carbon dioxide, but this alone is not a definitive diagnostic criterion. Electrocardiogram reveals pulmonary P wave, right bundle branch block, nonspecific ST segment changes, and inverted T waves in leads V4 and V5. Chest X-ray findings depend on the location and size of the embolus; it may show bronchitis-like changes, reduced lung markings at the site of embolism, increased radiolucency, asymmetrical lung markings, small pleural effusion, and what is referred to as adhesion between the base of the lung and the thoracic cavity. The wedge-shaped shadow pointing toward the pulmonary hilum is actually rare. Right ventricular enlargement and pulmonary arterial cone enlargement may also be observed. Enhanced CT scan is a highly sensitive diagnostic method, while pulmonary angiography is the most accurate and reliable diagnostic method.

Treatment: In addition to standard treatments based on individual circumstances, anticoagulation and thrombolysis are key components of PE treatment. Anticoagulation involves intravenous infusion of 5,000–10,000 units of heparin, with a maintenance dose of 1,000 units per hour after the initial loading dose. Prothrombin time should be maintained at about twice the normal value. For thrombolytic therapy, domestic guidelines recommend using 20,000 units of urokinase per kilogram of body weight, with adults receiving 1 million units within two hours for optimal results.