Currently, there are 3 levels of pulmonary tethering, low risk, intermediate risk, and high risk, based on the severity of the occurrence of pulmonary tethering, and the risk profile. Usually, the mortality rate of high-risk is about 30%, while the mortality rate of low-risk and intermediate-risk is not available, so the overall mortality rate of pulmonary embolism is about 3%. Note that as long as the patient is at high risk of pulmonary embolism, he must be admitted to the intensive care unit because the mortality rate is very high. As for the patients at low and medium risk, there is usually no risk in most cases through anticoagulation therapy. Therefore there is no absolute mortality rate for pulmonary embolism, but rather the outcome varies depending on the severity.