The clinical course of pulmonary embolism patients anticoagulated for 1 year: results of a prospective, observational, cohort study

Background: Few studies have examined the clinical course of pulmonary embolism (PE) in patients anticoagulated continuously for 1 year. Objective: We sought to determine the incidence of death, recurrent PE and bleeding during anticoagulation in the first year after acute PE, and to assess associated risk factors. Methods: All consecutive PE patients who were referred to our center in Pisa, Italy between 2001 and 2005 received a conventional initial treatment, followed by vitamin K antagonists [international normalized ratio (INR), 2.0-3.0] for 1 year. They were followed-up at scheduled times at the study center. The development of recurrent PE was objectively documented and recorded. Results: Out of 497 patients, 48 (9.6%) developed recurrent PE, which was fatal in 36. Of these 48 events, 39 occurred within 10 days of diagnosis and only two patients had a non-fatal recurrent PE between 6 and 12 months. Risk factors associated with the risk for overall recurrent PE were persistent severe dyspnoea (P = 0.007), a high perfusion defect score index (PDI) (P = 0.003) and cardiopulmonary co-morbidities (P = 0.005). Unprovoked presentation (P = 0.030), persistent severe dyspnoea (P = 0.011) and a high PDI (P = 0.001) predicted the risk for fatal PE. Overall bleeding incidence was 3.4%, no cases of bleeding occurred between 180 and 360 days post-diagnosis. Conclusions: In spite of conventional anticoagulation, a proportion of patients with PE experience both a fatal and non-fatal recurrent embolism within the first year. The large majority of these occur within the days proceeding diagnosis, with only a small minority occurring in the last 6 months. No bleeding was observed after 6 months. Therefore, prolonging anticoagulation for 1 year represents both a safe and effective treatment.