By Chandra Dass, MBBS, DMRD, Director, Cardiothoracic Imaging, Temple University Hospital
Figure 1. Frontal chest radiographs. a) Pre-procedural radiograph with severe emphysematous upper lobes. b) Complete collapse of the left upper lobe (white arrow) at two weeks after EBV placement. Elevated left dome of diaphragm secondary to volume loss (black arrow).
Chronic obstructive pulmonary disease (COPD) is one of the leading causes of mortality and morbidity worldwide. The National Emphysema Treatment Trial (NETT) demonstrated that lung volume reduction surgery can improve pulmonary function, exercise capacity, and quality of life in selected subgroups of COPD patients, yet not all patients are good candidates for surgery. Clinical trials of bronchoscopic lung volume reduction (BLVR) procedures have sought to establish an effective and safe alternative approach for those patients. Of these, endobronchial deployment of one-way valves (EBV) currently has the largest pool of supporting scientific data available.1,2,3
An expert panel, including Temple’s Dr. Gerard Criner, updated the recommendations for patient selection and best practices for endoscopic lungvolume reduction with EBV in 2019. Based on the results of multiple randomized clinical trials (RCTs),3 the panel found that certain image-based COPD patient phenotypes show better outcomes from EBV therapy. High-resolution CT imaging plays a major role in patient selection, target lobe identification, and the management of post-procedural adverse events.
With the recent FDA approval of the Pulmonx Zephyr® and Olympus Spiration® Valve systems, bronchoscopic lung volume reduction using one-way EBVs is increasingly used in patients with advanced emphysema who remain symptomatic despite optimal medical management and are poor surgical candidates. To avoid misinterpretation of imaging studies, it is important for pulmonologists to understand the types of EBV used, and the expected normal imaging findings following placement of EBV. See Figures 1 and 2 for examples.
Given the higher incidence of pneumothorax after EBV placement, chest radiographs are required within 4 and 24 hours of EBV valve placement and daily thereafter until discharge. Significant volume reduction or atelectasis of the treated lobe may be observed within the first few days, although in some patients it may take up to a month. Criteria for premature reevaluation of these patients have been established and imaging plays an important role in their evaluation and management. Expert panels recommend a low-dose CT scan at around 30–45 days post-procedure to assess valve placement, particularly if there is breathing deterioration or no perceived improvement.4 Evaluation of MDCT scans focuses on the valve count, valve location (migration/malpositioning), and target lobe(s) volume change (TLV).
Figure 2. Axial HRCT images at the level of upper lobes. a) Pre-procedural CT showing severe emphysema in both upper lobes. b) Partial collapse of the left upper lobe at 24 hours after EBV placement. c) Complete collapse of the left upper lobe at 30 days with EBVs in situ. Mediastinal shift towards left due to volume loss.
In conclusion, CT and chest radiography are valuable tools for planning and follow-up evaluation of bronchoscopic lung volume reduction treatment for COPD patients. The outcome of EBV therapy is maximized in certain image-based COPD phenotypes. HRCT imaging plays a major role in patient selection, target lobe identification, and in the management of post-procedural adverse events.
1 Criner, G.J., et al. 2018. A Multicenter Randomized Controlled Trial of Zephyr® Endobronchial Valve Treatment in Heterogeneous Emphysema (LIBERATE). Am J Respir Crit Care Med. 198(9): 1151–1164. doi: 10.1164/ rccm.201803-0590OC.
2 Criner, G.J., et al. 2019. Improving Lung Function in Severe Heterogenous Emphysema with the Spiration® Valve System (EMPROVE). A Multicenter, Open-Label, Randomized, Controlled Trial. Am J Respir Crit Care Med. 200 (11): 1354–1362. doi: 10.1164/rccm.201902-0383OC.
3 Low, S.W., et al. Endobronchial Valves Therapy for Advanced Emphysema: A meta-analysis of randomized trials. J Bronchology Interv Pulmonol.26: 81–9. doi: 10.1097/LBR.0000000000000527.
4 Herth, F.J.F., et al. 2017. Endoscopic Lung Volume Reduction: An Expert Panel Recommendation – Update 2017. Respiration 94(4): 380–388. doi: 10.1159/000479379.