Accelerated heart rate in advanced stage of lung adenocarcinoma may be caused by decreased lung ventilation, enlarged tumor compressing blood vessels, heart, etc. It may also be caused by thoracic and abdominal fluid and increased pressure in thoracic and abdominal cavities. 1. Decrease in lung ventilation: further enlargement of tumor in late stage of lung adenocarcinoma may lead to decrease in lung ventilation, which may result in hypoxia and lead to compensatory increase in heart rate. 2. Pressure on blood vessels and heart: if the tumor volume increases and presses the heart and blood vessels, there may be hypoxia, which requires faster heart rate to provide nutrients; in addition, if the content of hemoglobin decreases, it will also make the heart rate accelerate. 3. Thoracic and abdominal fluid: if patients with advanced lung adenocarcinoma have thoracic fluid and ascites, the pressure of thoracic cavity and abdominal cavity will be increased, which will also cause the heart rate to increase. If patients with advanced stage of lung adenocarcinoma have rapid heart rate, they should consult doctor in time to find out the cause of the disease and have specific treatment according to the cause of the disease.