How do you prevent a pulmonary embolism from causing a pulmonary infarction and/or pneumonia?

Once an embolus has reached the lung, it is a little too late to act other than by performing thrombectomy. It is more important to prevent blood clot formation in the veins, by judicious use of anticoagulants.

I would try and prevent the pulmonary embolism from occurring in the first place. Afterward, it is often too late to definitively prevent further complications such as lung infarction or pneumonia. However, the treatment for preventing pulmonary embolism and treatment of a pulmonary embolus is often similar, and is usually centered around anticoagulation or lytic therapy to prevent/dissolve clot