Electron beam tomography of interpulmonary saddle embolism: Extent and vascular distribution

Purpose: The purpose of this work was to assess morphology and secondary signs of interpulmonary emboli extending across the bifurcation of the main pulmonary artery (PA). Method: Retrospective evaluation of 780 electron beam tomographic studies of the chest yielded 17 cases of interpulmonary saddle embolism. Length, diameter, vascular distribution of the emboli, and secondary findings were prospectively assessed by two blinded reviewers. Follow-up studies were carried out in 12 of 17 patients (71%). Result: Mean total length of the emboli was 46.6 cm (range 20.9-81.5 cm). The mean diameter of the saddle embolus was significantly smaller at the level of the bifurcation than in the left or right PA (4.5, 7.7, and 7.4 mm, respectively p < 0.01). Dilatation of the right heart was found in 10 of 17 cases (59%). At follow-up, the saddle state was no longer present in 8 of 12 patients (67%). Conclusion: Interpulmonary saddle emboli appear to be a transient form of acute pulmonary embolism, the site of predilection for rupture of the embolus being the level of the bifurcation. Their frequency may therefore be underestimated.