Prognostic Significance of Asymptomatic Pulmonary Embolism on Routine Ventilation-Perfusion Scans after Lung Transplantation

Abstract

<h3>Purpose</h3> Asymptomatic pulmonary embolism (PE) is a challenging clinical entity with unclear treatment implications. This is also true of PE detected on routine studies after lung transplant were clot may be donor derived. Our program performs routine ventilation-perfusion (VQ) scans at 3-months post-transplant to establish baseline airway and vascular function but in some cases, these are positive for PE. We hypothesized that asymptomatic PE in this context would carry a benign prognosis irrespective of therapy. <h3>Methods</h3> We studied VQ scans obtained routinely at 3-months post-transplant from double lung transplant recipients in our program between 2004-2016. The risk group was patients whose studies were interpreted as high probability for PE. We used chi square testing for the relationship between PE with 1-year survival. We also used Kaplan Meier analysis with log rank testing and t-tests for the association with overall survival and peak forced expiratory volume in 1 second (FEV1) percent predicted. <h3>Results</h3> 373 patients met inclusion criteria, of whom 35 (9%) had VQ scans interpreted as high probability for PE. The PE group were less likely to have had severe primary graft dysfunction (3% vs. 19%; p=0.03) but were otherwise similar to patients without PE. 7 patients in the PE group (20%) were treated with therapeutic anticoagulation and the remainder treated expectantly. Patients with PE had similar 1-year survival (100% vs. 98%, p=1.00), overall survival (log rank p=0.90) and peak FEV1% predicted (94% [SD 20%] vs. 92% [SD 21%]; p=0.58). We observed no differences between treated and untreated PE. <h3>Conclusion</h3> Asymptomatic PE diagnosed on routine post-transplant VQ scan was not associated with a difference in survival or lung function, irrespective of therapy. This may suggest these changes are donor derived and not reflective of recipient hypercoagulability.