Silent pulmonary embolism in patients with deep venous thrombosis: a systematic review

Purpose: To determine, by systematic review of the literature, the prevalence of silent pulmonary embolism in patients with deep venous thrombosis.

Methods: Twenty-eight included published investigations were identified through PubMed. Studies were selected if methods of diagnosis of pulmonary embolism were described; if pulmonary embolism was stated to be asymptomatic; and if raw data were presented. Studies were stratified according to whether silent pulmonary embolism was diagnosed by a high-probability ventilation-perfusion lung scan using criteria from the Prospective Investigation of Pulmonary Embolism Diagnosis, computed tomography pulmonary angiography, or conventional pulmonary angiography (Tier 1), or by lung scans based on non-Prospective Investigation of Pulmonary Embolism Diagnosis criteria (Tier 2).

Results: Silent pulmonary embolism was diagnosed in 1665 of 5233 patients (32%) with deep venous thrombosis. This is a conservative estimate because many of the investigations used stringent criteria for the diagnosis of pulmonary embolism. The incidence of silent pulmonary embolism was higher with proximal deep venous thrombosis than with distal deep venous thrombosis. Silent pulmonary embolism seemed to increase the risk of recurrent pulmonary embolism: 25 of 488 (5.1%) with silent pulmonary embolism versus 7 of 1093 (0.6%) without silent pulmonary embolism.

Conclusion: Silent pulmonary embolism sometimes involved central pulmonary arteries. Because approximately one third of patients with deep venous thrombosis have silent pulmonary embolism, routine screening for pulmonary embolism may be advantageous.