Is it safe to withhold long-term anticoagulation therapy in patients with small pulmonary emboli diagnosed by SPECT scintigraphy?

Background: The need for anticoagulation therapy (AC) in patients with subsegmental pulmonary embolism (SSPE) diagnosed by computed tomography of the pulmonary arteries (CTPA) has been questioned, as these patients run low risk for recurrent venous thromboembolism (VTE) during 3 months of follow-up. Whether this applies also to patients with small PE diagnosed with pulmonary scintigraphy has not yet been evaluated, however. Methods: We therefore retrospectively evaluated 54 patients (mean age 62 ± 19 years, 36 [67 %] women) with small PE diagnosed by ventilation/perfusion singe photon emission computed tomography (V/P SPECT) who did not receive conventional long-term AC. Results: More than half of our patients (36[67 %]) received less than 48 h of AC, 11 (20 %) patients were treated for 2-14 days, and 7 (13 %) for 15-30 days. The majority (28 [52 %]) of our patients had a non-low simplified pulmonary emboli severity index (S-PESI), and 7 (13 %) had malignancy. D-dimer was negative in 18 (33 %), positive in 10 (19 %), and not analyzed in 28 (52 %) patients. Phlebography of the lower extremities had been performed with negative result in one patient. During 90 days of follow up no deaths or PE occurred. Seven patients were readmitted to hospital, whereof two (2/54 [4 %]) were diagnosed with deep venous thrombosis (DVT) necessitating AC therapy. Conclusion: In conclusion, withholding longterm AC therapy in patients with SSPE diagnosed by V/P SPECT resulted in 4 % risk for recurrence of VTE during 90 days of follow up, and can therefore currently not be recommended.