A Review Of Computed Tomography Pulmonary Angiograms In Three Teaching Hospitals: The Rise Of Sub-Segmental Pulmonary Emboli and Their Management

The availability of Computed Tomography Pulmonary Angiography (CTPA) has led to an increase in the number of investigations for Pulmonary Embolism (PE). With more widespread use of these high resolution scans, the frequency of identification of isolated Small Sub-segmental Emboli (SSPE) is also expected to increase. Current clinical practice guidelines do not make any treatment distinctions for SSPE, though the benefits of anticoagulation for SSPE have not been established.

To review the frequency of Pulmonary Embolism and Sub-segmental Pulmonary Embolism identified through CTPA as well as their management

Retrospective review of 2213 patient charts who underwent CTPA in three Hamilton teaching hospitals from 2009-2011. In depth chart review of patients with SSPE was undertaken to determine the frequency with which patients who received anticoagulation therapy for SSPE. The frequency of bleeding complications and recurrent thrombosis were also investigated in this detailed SSPE chart review.

Our patient population (mean age 65) consisted of 1099 medical inpatients (50%), 702 surgical inpatients (32%) and 412 (18%) emergency department patients.

PE was identified in 26 % of scans (n=576). Of these, SSPEs were the only identified thrombus in 82 patients (4% of total scans and 14% of identified PEs). In 55 of these 82 SSPEs, in addition to the SSPE, an alternative diagnosis that might explain the PE symptoms was found.

Fifty-two percent (n=43) of the patients with an SSPE received therapeutic anticoagulation. In these life threatening bleeding occurred in 2 patients. There was no documented recurrent thrombosis or thrombosis-related deaths in three month follow-up among the 39 patients who did not receive anti-coagulation for SSPE.

Of the 1,608 CTPAs that did not identify PE, an alternative diagnosis to account for the patient’s symptoms was identified on CT in 1078 (67%) and no alternative cause was found in 531 (33%).

Our study demonstrated a much lower frequency of pulmonary embolism in comparison to approximate 50 % pre-test probability of a positive scan seen in studies which validated CTPA for the diagnosis of PE. Isolated SSPEs accounted for 14% of all PEs found in our study population – and were present in 4% of all patients undergoing CTPA. A substantial proportion of patients were anti-coagulated SSPE (52%) and two developed life-threatening bleeding complications. No recurrent VTE was documented in patients who were not anticoagulated for PE, though follow-up was limited to hospital records. Randomized controlled trial data is needed to further investigate the risks and benefits of anticoagulation in patients with SSPE.

No relevant conflicts of interest to declare.