Residual pulmonary thromboemboli after acute pulmonary embolism

Abstract Background After an acute pulmonary embolism (PE), the complete resolution of thromboemboli may not be routinely achieved. The rate of persistence may depend on the time and the diagnostic technique used for evaluation. Patients and methods Patients were diagnosed with acute PE by means of computed tomography angiography (CTA). While they were receiving anticoagulant therapy, a second CTA was used to explore the rate of persistence of residual thromboemboli. During the initial episode, the plasma levels of Troponin I and natriuretic peptide, patient demographics, and hemodynamic and gas exchange data were evaluated as risk factors for persistence of pulmonary thromboemboli. Results In this study 166 patients were diagnosed. A second CTA was not made in 46 (28%) patients for different reasons. In 120 (72%) patients a second CTA was made 4.5 [SD2.34] months after the initial episode (range 2–12 months). Complete clearance of thrombi occurred in 89 (74%, 95% CI 65–81) patients. Residual thrombi remained in 31 (26%, 95% CI 18–34) patients. In 6%, 13% and 81% of the patients the size of the residual thrombi was greater, similar to and smaller than initially diagnosed, respectively. The risk factors for residual thrombi included the thrombotic burden (OR 1.95), the alveolar to arterial difference of oxygen (OR 1.64), and the clinical antecedents of venous thromboembolic disease (OR 0.65). Conclusions After 4.5 months of anticoagulant therapy, residual pulmonary thromboemboli persisted in 26% of the patients. The risk factors for residual thromboemboli include a greater initial thrombotic burden, a deeper gas exchange disturbation and a history of previous venous thromboembolism.