Systematic study of occult pulmonary thromboembolism in patients with deep venous thrombosis

This study was carried out to evaluate the prevalence and extension of pulmonary thromboembolism (PTE) in symptom-free patients with symptomatic deep venous thrombosis (DVT) of lower limbs and to evaluate their possible implication in the adequate treatment of thromboembolic disease.

We prospectively studied, using noninvasive examination (pulmonary spiral computed tomography [CT] angiography), 159 consecutive patients with acute DVT confirmed by duplex scanning without symptoms of PTE. CT was repeated at 30 days to study evolution of these clinically occult PTE.

We observed silent PTE in 65 patients (41%) in all levels of lower limb venous thrombosis. Prevalence of PTE showed significant association with male sex (P =.001) and previously diagnosed heart disease (P =.023). There was no significant association between the level of DVT and the presence of PTE nor the DVT side and thromboembolic pulmonary localization. Of the 65 patients with positive CT exploration results for PTE, 52 had characteristics of acute PTE, 10 had chronic PTE, and 3 patients had both. Chronic PTE was found more frequently in patients with previous episodes of DVT (P =.024). A total of 165 pulmonary artery-affected segments were found at several locations: 5 main, 35 lobar, 58 interlobar, and 67 segmental. Multiple segments were affected in 59% of patients. Repeat CT examinations were performed at 30 days in 53 of 65 patients with positive CT scanning results. In 48 cases (90.6%) PTE had completely disappeared.

Silent PTE occurred frequently in association with clots of lower limbs. The CT scan had a good availability and cost-effectiveness to detect clinically underestimated PTE. The incorporation of this exploration in the systematic diagnostic strategy of most patients with DVT to establish the extension of thromboembolic disease at diagnosis may be useful in the evaluation of added pulmonary artery symptoms and treatment strategies.