Relationship between imaging features and clinical outcome following lung volume reduction surgery

Purpose: To study the relationship between preoperative imaging features and clinical outcome following lung volume reduction surgery. Materials and Methods: The preoperative inspiratory and expiratory chest radiographs (CXR), CT examinations (CT), and lung scans (VQ) in 50 sequential patients with six month clinical follow-up were reviewed and scored by a team of six radiologists and pulmonologists for features related to the severity and distribution of emphysema. Regression analysis was used to study the interaction of variables and the relationship with postoperative improvement in pulmonary function, arterial oxygenation, and exercise tolerance to identify features predictive of outcome. Results: There was clinical improvement in 85% of patients and a 5% mortality rate. There was greater improvement in patients with: 1) reduced diaphragm and chest wall excursion (r=.43, linear regression; p=.01, t-test), 2) increasing maximum chest width, diaphragm length, and ratio of lower to upper chest width (r=.28, p=.01), 3) crowded vessels or compressed lung (r=.52; p<.05; CXR > CT), 4) a larger percent of mildly diseased lung (r=.55; p<.01; CT > VQ), 5) greater heterogeneity in the regional distribution (r=.52; p<.01; CXR > CT > VQ), and 6) upper lobe predominant global distribution of emphysema (r=.58; p<.01; CT > CXR > VQ). A multiple regression model using compression, heterogeneity and upper lobe predominance was highly correlated with improvement in FEV₁ (r²=.50). Death was associated with a small percentage of mildly diseased lung and minimal heterogeneity (both p<.05). Conclusion: There is a highly significant association between thoracic structure, respiratory movement, emphysema severity and distribution demonstrated on imaging studies and clinical outcome following surgery. Clinical Implications: 1) Morphologic features demonstrated on radiographs alone can play an important role in guiding patient selection for lung volume reduction surgery. CT and lung scans provide useful supplemental information. 2) Chest shape, diaphragm excursion, regional heterogeneity, global distribution, lung compression, and quality of lung are important in predicting improvement. 3) The percentage of mild disease and degree of heterogeneity correlate with survival.