Imaging of subendocardial adipose tissue and fiber orientation distributions in the human left atrium using optical coherence tomography.

Background: Optical coherence tomography (OCT) has the potential to provide real-time imaging guidance for atrial fibrillation ablation, with promising results for lesion monitoring. OCT can also offer high-resolution imaging of tissue composition, but there is insufficient cardiac OCT data to inform the use of OCT to reveal important tissue architecture of the human left atrium. Thus, the objective of this study was to define OCT imaging data throughout the human left atrium, focusing on the distribution of adipose tissue and fiber orientation as seen from the endocardium.

Methods And Results: Human hearts (n = 7) were acquired for imaging the left atrium with OCT. A spectral-domain OCT system with 1325 nm center wavelength, 6.5 μm axial resolution, 15 μm lateral resolution, and a maximum imaging depth of 2.51 mm in the air was used. Large-scale OCT image maps of human left atrial tissue were developed, with adipose thickness and fiber orientation extracted from the imaging data. OCT imaging showed scattered distributions of adipose tissue around the septal and pulmonary vein regions, up to a depth of about 0.43 mm from the endocardial surface. The total volume of adipose tissue detected by OCT over one left atrium ranged from 1.42 to 28.74 mm . Limited fiber orientation information primarily around the pulmonary veins and the septum could be identified.

Conclusion: OCT imaging could provide adjunctive information on the distribution of subendocardial adipose tissue, particularly around thin areas around the pulmonary veins and septal regions. Variations in OCT-detected tissue composition could potentially assist ablation guidance.