How can pulmonary embolism kill when active, no family traits, no drugs, smoking are young?

Clotting tendency: Clotting tendencies can occur in 8% of the population age 25 or older with increasing tendency with each decade. If a large enough clot forms in the veins of the legs and breaks off it can block the blood flow through the heart and pulmonary artery. Sudden death can be the consequence. It is all too frequently seen in clinical practice. Even minor trauma to the legs or immobility can cause this.

Trauma, immmobility: Risk factors for deep venous thrombosis, which is usually the cause of a pe, include trauma to the vessel (which promotes clotting) and immobility (often related to pain from the trauma).

OC: Oral contraceptives increase the risk of pulmonary embolism slightly. Also trauma and immobility (for example, being in bed for a prolonged period or a long airplane ride).

Extent of disease: Death from pulmonary embolism is related to the degree and extent of the clots in the lung . If greater than 50% of the pulmonary arteries are acutely occluded by blood clots the risk for death dramatically rises. Contributing factors also include delay in establishing the diagnosis.