Background: Pulmonary embolism (PE) remains poorly understood. Rates of clinical outcomes such as death and recurrence vary widely among trials. We therefore established the International Cooperative Pulmonary Embolism Registry (ICOPER), with the aim of identifying factors associated with death.

Methods: 2454 consecutive eligible patients with acute PE were registered from 52 hospitals in seven countries in Europe and North America. The primary outcome measure was all-cause mortality at 3 months. The prognostic effect of baseline factors on survival was assessed with multivariate analyses.

Findings: 2110 (86.0%) patients had PE proven by necropsy, high-probability lung scan, pulmonary angiography, or venous ultrasonography plus high clinical suspicion; ICOPER accepted without independent review diagnoses and interpretation of imaging provided by participating centres; 3-month follow-up was completed in 98.0% of patients. The overall crude mortality rate at 3 months was 17.4% (426 of 2454 deaths, including 52 patients lost to follow-up): 179 of 397 (45.1%) deaths were ascribed to PE and 70 of 397 (17.6%) to cancer, and no information on the cause of death was available for 29 patients. After exclusion of 61 patients in whom PE was first discovered at necropsy, the mortality rate at 3 months was 15.3% (365 of 2393 deaths). On multiple-regression modelling, age over 70 years (hazard ratio 1.6 [95% CI 1.1-2.3]), cancer (2.3 [1.5-3.5]), congestive heart failure (2.4 [1.5-3.7]), chronic obstructive pulmonary disease (1.8 [1.2-2.7]), systolic arterial hypotension (2.9 [1.7-5.0]), tachypnoea (2.0 [1.2-3.2]), and right-ventricular hypokinesis on echocardiography (2.0 [1.3-2.9]) were identified as significant prognostic factors.

Interpretation: PE remains an important clinical problem with a high mortality rate. Data from ICOPER provide rates and highlight adverse prognostic categories that will help in planning of future trials of high-risk PE patients.