Volumetric and scintigraphic changes following endoscopic lung volume reduction
Introduction: Endoscopic lung volume reduction (ELVR) is an emerging therapy for emphysematous COPD. While volumetric adaptations following ELVR have reiteratedly been focused on, the interaction of volume and perfusional-ventilatory changes remains undetermined. We therefore took aim at defining the extent of interdependency of ELVR-mediated volumetric and scintigraphic adaptations.
Methods: We enrolled 24 patients (64.3 ± 8.8yrs, 58.3% male) with COPD heterogeneous emphysema undergoing ELVR with endobronchial valves (EBV, Zephyr®, Pulmonx, Inc.). Mean baseline FEV1 and RV were 32.9% and 256.0% predicted, respectively. The day prior to ELVR and eight weeks thenceforth, ventilation/perfusion scintigraphy was conducted and complemented by single photon emission computed tomography (SPECT).
Results: After ELVR, target lobe volume decreased by 444.6 ml in absolute and 36.8% in relative terms (p = 0.004) and correlated with target lobe perfusional changes (p = 0.04) that in turn were linked to target lobe ventilatory adaptations (p = 0.03). Both volume and perfusion/ventilation were primarily redistributed to the contralateral, non-concordant and ipsilateral, non-treated lobes. Clinical responsiveness to ELVR assessed by 6MWT and defined by a post-procedural improvement in 6MWT-distance ≥25 meters was exhibited by 17 patients (70.8%), correlated with a decrease in NT-proBNP (Spearman's rho: -0.96; p < 0.001), but was uninfluenced by the extent of volumetric and scintigraphic adaptations. This finding may be ascribed to the quality in terms of pulmonary capacity of the lobes to which ventilation and perfusion is directed, rather than to the mere quantity of shifted air and blood flows.
Discussion: ELVR is accompanied by volumetric and scintigraphic adaptations with consistent redistributive pattern. Pre-procedural evaluation of contralateral lung's emphysematous destruction and functional capability may be a valuable tool to predict ELVR efficacy.