Acute Airway Effects of Bronchial Thermoplasty Assessed by Optical Coherence Tomography (OCT)

Background: Bronchial Thermoplasty (BT) is an endoscopic treatment for severe asthma targeting airway smooth muscle (ASM) with thermal energy. The extent of treatment effect is largely unknown. Optical coherence tomography (OCT) is a high resolution imaging technique, using near-infrared light, that generates near-histology cross sectional images of the airway wall. Aim: Assess the extent of acute airway wall effects of BT with OCT and compare these to the untreated right middle lobe (RML). Methods: 15 severe asthma patients were treated with BT. During the third procedure, OCT imaging was performed in BT treated (sub)segmental airways in the upper lobes, 6 weeks earlier treated right lower lobe and untreated RML. Results: OCT was feasible and safe. 57 airways were imaged. 3 distinct OCT patterns were identified: low intensity scattering of (1) bronchial and (2) peribronchial edema and (3) high-intensity scattering of epithelial sloughing (Fig 1). Edema was observed in all BT-treated airways and 1/3 of the untreated RML. Furthermore, these patterns extended more distal than the BT catheter treatment area and beyond the ASM layer and diminished after 6 weeks. Epithelial sloughing occurred in 11/14 of treated airways and was absent in the RML. Conclusions: Acute Bronchial Thermoplasty effects can be safely assessed by OCT. These OCT-identified effects extended distal to the BT treated area and beyond the targeted ASM layer.