Incomplete Recovery of Lung Perfusion After 3 Months in Patients with Acute Pulmonary Embolism Treated with Antithrombotic Agents

We assessed the time course of lung perfusion after 3 mo of anticoagulant therapy for acute pulmonary embolism (APE) on the basis of perfusion lung scan (PLS) findings for 157 patients included in the Tinzaparin ou Heparin Standard: Evaluation dans l'Embolie Pulmonaire Study (THESEE), a multicenter, randomized, nonmasked trial comparing standard, continuous, adjusted-dose intravenous heparin with once-daily, subcutaneous, low-molecular-weight heparin in patients with APE. We calculated the percentage-of-vascular-obstruction score (PVOs) on PLSs on the day of diagnosis of APE (PVOsD1), on day 8 (PVOsD8), and after 3 mo (PVOsM3) and the mean relative changes in PVOs on day 8 versus the day of diagnosis and after 3 mo versus the day of diagnosis. Mean PVOsD1 +/- SD was 49% +/- 20%, PVOsD8 was 29% +/- 18%, and PVOsM3 was 19% +/- 18%. PVOsD1 was at least 50% in 49% of patients. Reperfusion did not correlate with age, importance of initial obstruction, or clinical severity of disease at inclusion in THESEE. Relative change after 3 mo versus at diagnosis was lower in the 87 patients with associated prior cardiopulmonary disease than in those without. In the 43 patients with a history of thromboembolic disease, neither mean PVOsD1 nor the time course of PVOs was different from those in patients without a history of thromboembolic disease. Residual defects after 3 mo were observed in 104 patients (66%), including 13 with a PVOs of at least 50%. These results emphasize the need for a control PLS at completion of anticoagulant therapy for APE, even in patients with full resolution of symptoms.