If detected and controlled with medications, blood clots can be safely managed. However, if the clots become dislodged and travel to an artery, they can cause nearly instant death. For instance, more than 600,000 people have a pulmonary embolism each year and more than 10% of them die from the embolism, most of them within 30 to 60 minutes after symptoms start.
Source: The Gale Group. Gale Encyclopedia of Medicine, 3rd ed.";