Serial imaging after pulmonary embolism and correlation with functional limitation at 12 months: Results of the ELOPE Study

Kim A Ma; Susan R Kahn; Arash Akaberi; Carole Dennie; Christopher Rush; John T Granton; David Anderson; Philip S Wells; Marc A Rodger; Susan Solymoss; Michael J Kovacs; Lawrence Rudski; Avi Shimony; Paul Hernandez; Shawn D Aaron; Elena Pena; Gad Abikhzer; Andrew M Hirsch; ELOPE Study group

doi:10.1002/rth2.12123

Serial imaging after pulmonary embolism and correlation with functional limitation at 12 months: Results of the ELOPE Study

Res Pract Thromb Haemost. 2018 Jun 17;2(4):670-677. doi: 10.1002/rth2.12123. eCollection 2018 Oct.

Authors

Kim A Ma¹, Susan R Kahn^{2

3}, Arash Akaberi³, Carole Dennie⁴, Christopher Rush⁵, John T Granton⁶, David Anderson⁷, Philip S Wells⁸, Marc A Rodger⁸, Susan Solymoss¹, Michael J Kovacs⁹, Lawrence Rudski², Avi Shimony¹⁰, Paul Hernandez⁷, Shawn D Aaron⁸, Elena Pena⁴, Gad Abikhzer⁵, Andrew M Hirsch²; ELOPE Study group

Affiliations

¹ Department of Medicine McGill University Montreal Canada.
² Department of Medicine Jewish General Hospital and McGill University Montreal QC Canada.
³ Center for Clinical Epidemiology Lady Davis Institute Montreal QC Canada.
⁴ Department of Diagnostic Imaging University of Ottawa Ottawa ON Canada.
⁵ Department of Nuclear Medicine Jewish General Hospital Montreal QC Canada.
⁶ Division of Respirology Department of Medicine University of Toronto Toronto ON Canada.
⁷ Department of Medicine Dalhousie University Halifax NS Canada.
⁸ Department of Medicine University of Ottawa and the Ottawa Hospital Research Institute Ottawa ON Canada.
⁹ Division of Hematology Department of Medicine University of Western Ontario London ON Canada.
¹⁰ Department of Cardiology Ben Gurion University Beer Sheva Israel.

Abstract

Introduction: Risk factors for exercise limitation after acute pulmonary embolism (PE) are unknown. As a planned sub-study of the prospective, multicenter ELOPE (Evaluation of Long-term Outcomes after PE) Study, we aimed to describe the results of serial imaging by computed tomography pulmonary angiography (CTPA) and perfusion scan during 1 year after a first episode of acute pulmonary embolism, and to assess the association between imaging parameters and exercise limitation at 1 year.

Methods: In a prospective cohort study, 100 patients were recruited between June 2010 and February 2013 at five Canadian university-affiliated hospitals. CT pulmonary angiography was performed at baseline and 12 months, perfusion scan at 6 and 12 months, and cardio-pulmonary exercise testing at 1 and 12 months. Imaging parameters included: on CT pulmonary angiography, CT obstruction index (CTO) (% clot burden in the pulmonary vasculature), and on perfusion scan, pulmonary vascular obstruction (PVO) (% perfusion defect). Abnormal cardio-pulmonary exercise test (primary outcome) was defined as percent of predicted peak oxygen uptake (VO2) <80%.

Results: Mean (median; SD) CT obstruction index was 28.1% (27.5%; 18.3%) at baseline, 1.2% (0%; 4.3%) at 12 months. Mean (median; SD) pulmonary vascular obstruction was 6.0% (0%; 9.6%) at 6 months, 5.6% (0%; 9.8%) at 12 months. Eighty-six patients had exercise testing at 12 months, and 46.5% had VO2 < 80% predicted. Mean (median; SD) CT obstruction index at 1 year was similar in patients with percent-predicted VO2 peak <80% vs >80% on 1-year cardio-pulmonary exercise testing (1.4% [0%; 5.7%] vs 1.0% [0%; 2.4%]; P = .70). Mean (SD) pulmonary vascular obstruction at 6 and at 12 months was similar in patients with percent-predicted VO2 peak <80% vs >80% (6 months: 5.9% [0%; 10.4%] vs 6.2% [4.5%; 9.0%]; P = .91; 12 months: 5.1% [0%; 10.2%] vs 6.0% [0%; 9.7%]; P = .71).

Conclusions: Imaging findings after pulmonary embolism did not predict exercise limitation. Residual thrombus does not appear to explain long-term functional limitation after pulmonary embolism.

Keywords: CT pulmonary angiography; dyspnea; exercise test; pulmonary embolism,; thrombosis; ventilation/perfusion lung scan.