Recurrent pulmonary embolism in patients treated because of acute venous thromboembolism: a prospective study.

OBJECTIVE: To evaluate the risk of pulmonary embolism (PE) despite adequate heparin therapy in a large series of patients with acute deep venous thrombosis and/or pulmonary embolism. DESIGN: Prospective study. SETTING: University Hospital Germans Trias i Pujol, Badalona, Spain. MATERIALS: 348 patients admitted because of deep venous thrombosis in the lower limbs and/or pulmonary embolism. A baseline lung scan was obtained initially in every patient, whether the original diagnosis was PE or deep vein thrombosis (DVT). Repeat chest X-ray and lung scans were obtained routinely at 8 days of heparin onset. OUTCOME MEASURES: The primary trial endpoint was a finding of confirmed, clinically apparent recurrent PE; in addition, laboratory evidence of subclinical PE at the repeat scan was also considered. RESULTS: PE recurrences were found in 23/348 patients (7%). No significant differences were found in age and sex distribution, or in the degree of DVT proximity between patients who developed and those who did not develop recurrences. Recurrent PE was more commonly found in patients with scintigraphic evidence of PE on admission, irrespectively of the original diagnosis being DVT or PE (18/151 vs. 3/155; p = 0.0005, Fisher's exact test). Recurrences were also more common in patients in whom thrombosis developed in the absence of any known risk factor (10/70 vs. 13/278; p = 0.007). The logistic regression analysis confirmed the statistical significance of these two clinical variables. CONCLUSIONS: Pulmonary embolism despite adequate heparin therapy is not an uncommon event. It appears possible to identify a subgroup of patients at a higher risk, and, modify treatment accordingly.