Changes in Lung Perfusion in Patients Treated with Percutaneous Mechanical Thrombectomy for Intermediate-Risk Pulmonary Embolism

Background: Current pulmonary embolism treatment options rely heavily on anatomical clot location. However, anatomical location does not necessarily determine adverse outcomes; rather, clinical severity is secondary to the degree of perfusion impairment. Dual-energy computed tomography pulmonary angiogram (DE-CTPA) can map perfusion at the time of pulmonary embolism diagnosis. Single-photon emission computed tomography ventilation-perfusion scans allow for perfusion tracking similar to DE-CTPA. Methods: We present 3 patients with intermediate-risk pulmonary embolism treated with mechanical thrombectomy using the Inari FlowTriever System (Inari Medical, Irvine, Calif). Lung perfusion scoring was applied to pre-procedure and post-procedure imaging. We graded perfusion of each lobe in 3 planes. If the entire lobe was perfused, a score of 3 was assigned. If lung perfusion is normal, total perfusion score is 15. All patients had pre-procedure and follow-up transthoracic echocardiograms. Results: All 3 patients were diagnosed with pulmonary embolism via DE-CTPA that showed right ventricle strain and had deep venous thrombosis. Following mechanical thrombectomy, patients immediately experienced improvement in perfusion score; scores continued to improve at follow-up. All patients also had improvement in right ventricle size or function on follow-up echocardiogram. Discussion: Intermediate-risk pulmonary embolism often has large initial clot burden that predicts residual pulmonary vascular obstruction. Residual pulmonary vascular obstruction is associated with increased risk of death, recurrent thrombus, and chronic thromboembolic pulmonary hypertension. Clot removal via thrombectomy may decrease the prevalence of residual pulmonary vascular obstruction by improving lung perfusion. We found that mechanical thrombectomy increased lung perfusion immediately and at follow-up assessments.