PURPOSE: The National Emphysema Treatment Trial (NETT) demonstrated that lung volume reduction surgery (LVRS) resulted in greater improvements in FEV1 and quality of life (i.e., SGRQ) for patients with upper lobe predominate as compared to non-upper lobe predominate emphysema. A radiologist determined if the disease was upper lobe predominate emphysema by qualitative assessment of a computed tomography (CT) scan. Recently, a quantitative measure of emphysema distribution, the heterogeneity index (HI), has been developed. This study examined the effect of baseline emphysema heterogeneity, as quantified by HI, on changes in FEV1 and SGRQ following LVRS as well as the percent of patients achieving a clinically meaningful improvement in these measures at different post-LVRS time-points.
METHODS: The NETT dataset was acquired from the NHLBI Data Repository and analyzed retrospectively. All LVRS subjects with CT, FEV1, and SGRQ data were included in this analysis (n=361). To quantify the distribution of emphysema, HI was determined from CT data by calculating the tissue-to-air volume ratio (TAR) for all lobes. Then the ratio of lower lobe TAR to upper lobe TAR for both lungs was calculated and summed to quantify HI. HI=2.00 indicated homogeneous disease and HI>2.0 represented upper lobe predominant emphysema. Changes in FEV1 (%) and SGRQ (absolute) were calculated between baseline, 6 months, and each yearly time-point out to five years, and were plotted against HI intervals. Average changes of the population and percent of subjects with a clinical meaningful improvement (CMI; FEV1=12% and SGRQ=-4) were calculated.
RESULTS: The mean HI=3.08 indicated predominately upper lobe disease for the analyzed population. Increases in baseline HI, indicating increases in emphysema severity in the upper lobes, corresponded to larger increases in average FEV1 and SGRQ. The percentage of patients with CMI in FEV1 and SGRQ increased with HI.
CONCLUSION: Baseline HI appears to be an important predictor of CMI in FEV1 and SGRQ for LVRS.
CLINICAL IMPLICATIONS: Quantitative measures of emphysema heterogeneity, such as HI, may be useful in selecting patients for LVRS.
DISCLOSURE: Joseph Anderson, No Financial Disclosure Information; Product/procedure/technique that is considered research and is NOT yet approved for any purpose. National Emphysema Treatment Trial (NETT) is conducted and supported by the NHLBI in collaboration with the NETT Study Investigators. This Abstract was prepared using a limited access dataset obtained from the NHLBI and does not necessarily reflect the opinions or views of the NETT or the NHLBI.