Incidence and distribution pattern of pulmonary saddle emboli: Diagnosis by electron beam tomography (EBT)

Purpose: To determine the incidence of acute pulmonary emboli extending across the bifurcation of the main pulmonary artery, lobar arteries or segmental arteries (interpulmonary, interlobar or intersegmental saddle emboli, respectively). Methods: 128 patients with clinically suspected acute pulmonary embolism underwent electron beam tomography (EBT). 140 scans were acquired in the continuous volume scanning mode (3 mm slice thickness). 100 ml of contrast material were intravenously administered. Studies were reviewed for the presence of acute pulmonary embolism and the number and location of interpulmonary, interlobar or intersegmental saddle emboli. Saddle emboli were defined as emboli extending across the bifurcation of a vessel into both branches by at least 5 mm each. Results: 30 of 128 (23.4%) patients (15 men; mean age 59 +/- 17 years) had acute pulmonary embolism. One or more saddle emboli were present in 20 of 30 patients (66.7%), a total of 77 saddle emboli were detected ranging from 1 to 10 per patient. Distribution of the saddle emboli in the 20 patients was as follows: 5 interpulmonary, 28 interlobar and 44 intersegmental. Conclusions: Pulmonary saddle emboli are present in the majority of patients with acute pulmonary embolism. They are often multiple and may be found at different levels of the pulmonary arterial vasculature.