Incidence and clinical feature of pulmonary embolism in patients with deep vein thrombosis: a prospective study.

In 169 patients with suspected deep vein thrombosis (DVT), the incidence and clinical feature of pulmonary embolism (PE) was prospectively studied by means of noninvasive thrombosis tests (uptake tests, radionuclide venography) and combined ventilation (133Xe, 81mKr) and perfusion (99mTc microspheres) lung scanning. DVT was detected in 62% of patients (105/169). The incidence of PE in patients with confirmed DVT was 57% (60/105), a figure which is in excellent agreement with data from autopsy studies. Concerning the thrombotic source of emboli, the incidence of PE was 46% in patients with DVT confined to the calf but increased to 67% if the thigh, and to 77% if the pelvic veins were involved as well. Fifty-nine percent of PE were clinically silent, 19% had "minor signs", and 22% "major signs". The size of the perfusion defects correlated significantly with clinical symptoms. Only 23% of clinically symptomatic patients had a pathological chest X-ray. Incidence of both DVT and PE increased with advancing age, but in old patients the incidence of PE rose disproportionately.