“…4.5.6 Syncope is infrequent, but may occur regardless of the presence of haemodynamic instability.7 In more severe cases, cyanosis, syncope and circulatory instability occur, and sometimes peripheral edema may be present. 8 Syncope in the setting of pulmonary embolism can be the result of three possible mechanisms. First, greater than 50% occlusion of the pulmonary vascular tree causes right ventricular failure and impaired left ventricular filling, leading to a reduction in cardiac output, arterial hypotension, reduced cerebral blood flow, and ultimately syncope.…”