Pulmonary Vein Sign on Unenhanced-MRI as a Sign of Severe Pulmonary Embolism

Background: Increased right ventricle-to-left ventricle (RV/LV) ratio on computed tomography pulmonary angiography (CTPA) has been reported as a poor prognostic indicator in patients with acute pulmonary embolism (PE). It has also been reported that pulmonary vein sign (PVS) on CTPA is a rare finding of PE. Objectives: To evaluate PVS on CTPA and unenhanced magnetic resonance imaging (MRI) in patients with PE suspicion. We also aimed to investigate the relationship between the severity of PE and presence of PVS, RV/LV ratio and combination of these two on unenhanced MRI. Patients and Methods: One-hundred-twelve patients with PE suspicion who underwent CTPA and unenhanced-MRI [steady state free precession (SSFP)] within the first 48-hours constituted the study group. All CTPA images were evaluated for the presence, location and severity of PE by observer-1. Two observers (observer-2 and 3), independently evaluated unenhanced-MR images for the presence of PVS without knowing the results of CTPA. Then, these 2 observers reviewed the CTPA and MRI images together with observer-4 to reach the final consensus for the presence of PVS and measurement of RV/LV ratio. Cohen’s Kappa analysis was used to assess the agreement between observers. Relationship between the mean PE index and imaging findings (PVS, RV/LV) were calculated. Results: Presence of PVS on CT or MRI is significantly correlated with PE index and patients with PVS had more severe PE than those without. Presence of both PVS and RV/LV ratio > 1 on MRI indicates more severe pulmonary embolism than absence of PVS or RV/LV ratio > 1. There was a very good agreement for the detection of PVS between two observers on unenhanced MRI. Conclusion: PVS on CTPA or unenhanced MRI can be used as a sign of severe PE and it may also be an indicator of right heart dysfunction.