An embolism is a lodging blood clot that developed and originated in the vein system (commonly in the legs) or in the artery system (usually in the heart). On the one hand a pulmonary embolism for example a blood clot travelling in the vein system, blocking a pulmonary vessel (characterized by shortness of breath and coughing up blood). A stroke on the other hand arises in the arterial system blocking an artery supplying the brain (sudden paraesthesia, paralysis, impaired vision) or for example occluding an artery in the leg (sudden pain in the leg or in the calf when walking).