The patient, a 60-year-old female, was diagnosed with pulmonary embolism by CT pulmonary arteriography (CTPA) after 2 months of recurrent chest tightness and shortness of breath with activity. She was discharged from the hospital after 15 days of improvement with warfarin and low molecular heparin. After discharge from the hospital, he kept taking warfarin and monitored the blood international normalized ratio (INR) to meet the standard. The symptoms disappeared after 6 months of medication. The patient continued to take the drug until 1 year, and stopped it on his own because he had no obvious conscious symptoms. Six months after discontinuation, the patient’s symptoms worsened again with lower limb edema. The CTPA examination again suggested bilateral pulmonary artery embolism. He was hospitalized, and took warfarin again and reached the standard. After discharge from hospital, he has been taking the medication for 2 years and his symptoms have not recurred. 1.Why did the symptoms of the patient with pulmonary embolism recur? The recurrence of this patient’s disease is related to the reoccurrence of pulmonary embolism. There are two prognosis of pulmonary embolism: one is to stop taking warfarin after 6 months, and the symptoms have not recurred, so no further treatment is needed; the other is to take warfarin for at least 6 months, and then the symptoms recur within a year after stopping, and the symptoms worsen. The latter case is more common in clinical work. The causes of symptom recurrence include primary and secondary risk factors. Primary risk factors: related to abnormal gene expression, gene mutations, gene polymorphisms, and differences in gene expression are responsible for the occurrence of primary venous system thrombosis (VTE). In Western countries, activated protein C resistance (APC I R) caused by factor V Leiden mutations and mutations in the prothrombin gene are the most common causes of VTE in Caucasians. In our country, protein S deficiency is the most common primary risk factor for the development of VTE. Patients with the above conditions can present with easy embolism. Secondary risk factors: include surgery and trauma, lower extremity deep vein thrombosis, malignancy, pregnancy and oral contraceptives, obesity, bed rest, varicose veins, etc. It should be emphasized that secondary risk factors also act mostly through primary risk factors, i.e. abnormal gene expression may play a key role in the recurrence of symptoms. 2.How to adjust the oral warfarin dose in patients with pulmonary embolism? Oral warfarin must be at the standard, i.e., INR maintained between 2 and 3. The initial dose is 2.5 to 5mg/day. Since warfarin takes several days to reach its full effect, it should be applied overlapping with heparin for at least 4 to 5 days. Warfarin should be monitored daily until the INR is reached, then two to three times a week for the next two weeks, and then once a week or less depending on the stability of the INR. If long-term treatment is required, monitor approximately once every 1 to 3 months and adjust the warfarin dose. When a dose increase is needed, it can be done in increments of 0.5 to 1 mg at a time until the target is reached. When dose reduction is needed, it can also be reduced in 0.5 to 1mg increments each time, and severe overdose can be stopped. In patients with pulmonary embolism (or atrial fibrillation) combined with stable coronary artery disease, aspirin can no longer be added to avoid the occurrence of bleeding, and warfarin alone can be used. 3.High INR treatment strategy Common bleeding sites of warfarin are oral (gum) bleeding, nasal bleeding, subcutaneous petechiae or hematomas, subconjunctival bleeding, microscopic or naked eye hematuria, respiratory bleeding, increased menstruation or black stool. It has been observed that a moderately elevated INR (4.0-10.0) and a dose of VitK1 1.0-2.5 mg can cause a rapid decrease in the INR of patients within 24 h. If the INR is greater than the target value but less than 5.0, there is no bleeding, and there is no need for rapid recovery of INR (e.g., surgery), then reduce the dose or discontinue the drug only once and reduce the application after the INR has recovered the target value; if the INR is between 5.0 and 9.0 and there is no significant bleeding, the oral VitK1 can be repeated while stopping warfarin once and taking VitK1 1.0 to 2.5 mg in a single dose and monitoring the INR daily; if the If INR exceeds 9.0 and there is no clinical bleeding, a high dose of VitK1 3-5 mg should be administered to reduce INR significantly within 24-48 h. Oral VitK1 can be repeated if needed; if INR needs to be reversed rapidly or if there is severe bleeding or INR exceeds 20.0, then VitK1 10 mg should be administered intravenously and can be repeated every 12 h with appropriate supplementation. fresh plasma or plasminogen concentrate. 4.How long should warfarin be taken for patients with pulmonary embolism? There is no unified international standard on how long warfarin should be taken for patients with pulmonary embolism. The author suggests that warfarin should be taken for at least 6 months; for patients who stop using warfarin and relapse, it is recommended that warfarin should be taken for life.