Pulmonary embolism can be distinguished between acute and chronic based on the duration of the patient's illness, symptoms, and supplemental examinations. Typically, patients with acute pulmonary embolism have no prior similar symptoms and suddenly experience severe symptoms such as chest pain, difficulty breathing, and coughing up blood. Additionally, through supplemental examinations like blood tests, abdominal ultrasound, and pulmonary artery CT angiography, it is possible to determine whether the thrombus is fresh or old. In contrast, chronic pulmonary embolism often presents with prolonged symptoms. Patients usually do not experience chest pain or cough, and the main issue is chronic breathing difficulty. In severe cases, pulmonary heart disease may occur, and patients may have swelling in the face and limbs. Ultrasound and pulmonary artery CT angiography can reveal the characteristics of the thrombus, which differ from those seen in acute pulmonary embolism. Thus, these examinations can help determine whether the condition is acute or chronic.