An embolus (that is, an abnormal particle circulating in the blood) located in the pulmonary artery and thereby blocking blood circulation to the lung. Usually the embolus is a blood clot that has developed in an extremity (for instance, a deep venous thrombosis), detached, and traveled through the circulation before becoming trapped in the pulmonary artery.

Narrowing of peripheral arteries with reduction of blood flow to the limbs. This feature may be quantified as an ankle-brachial index of less than 0.9, and may be manifested clinically as claudication.

Repeated episodes of inflammation of a vein associated with venous thrombosis (blood clot formation within the vein).

Increased activity of coagulation factor V, Factor V, which is activated to factor Va by means of minute amounts of thrombin (and inactivated by larger amounts of thrombin). Activated factor V (fVa) is a cofactor in the formation of the prothrombinase complex.