The majority of lethal pulmonary emboli originate in the deep pelvic veins and the veins of the lower extremities, although a significant percentage embolize from the cavernous sinus, internal jugular vein, right heart, and deep venous system of the arm (5-15 per cent). Predisposing conditions include carcinomatosis, prostatic and pancreatic cancer, congestive heart failure, sepsis, obstructive pulmonary disease, and stroke.

Massive embolization to the main pulmonary arteries can lead to immediate cardiovascular collapse and death related to vasovagal shock, right heart failure, or acute pulmonary insufficiency. Multiple small emboli, more often than larger emboli, can cause diffuse bronchospasm and vasoconstriction through the release of systemic and locally active substances such as serotonin, bradykinin, and prostaglandins, although their role in death from pulmonary embolus has not been clearly shown. The occlusion of pulmonary artery branches leads to unperfused alveoli, resulting in a ventilation-perfusion mismatch. Ultimately, surfactant production is impaired, with edema and atelectasis leading to a congestive state that grossly resembles pulmonary infarction, although, because of the dual blood supply of the lung, true infarction occurs in less than 10 per cent of cases.

The clinical sequelae of pulmonary emboli as a consequence of this cascade include the following: hyperventilation, as evidenced by an increased minute ventilation, pulmonary restriction, indicated by a decreased vital capacity, bronchoconstriction, with its attendant decrease in forced expiratory volume per unit time (FEV 1), hypoxemia, and pulmonary hypertension.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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