Quantification of fiber orientation in the canine atrial pacemaker complex using optical coherence tomography

Abstract

The atrial pacemaker complex is responsible for the initiation and early propagation of cardiac impulses. Optical coherence tomography (OCT), a nondestructive imaging modality with spatial resolutions of ∼1 to 15 μm, can be used to identify unique fiber orientation patterns in this region of the heart. Functionally characterized canine sinoatrial nodes (SAN) (n ¼ 7) were imaged using OCT up to ∼1 mm below the endocardial tissue surface. OCT images were directly compared to their corresponding histological sections. Fiber orientation patterns unique to the crista terminalis (CT), SAN, and surrounding atrial myocardium were identified with dominant average fiber angles of 89 AE 12 deg, 110 AE 16 deg, and 95 AE 35 deg, respectively. Both the CT and surrounding atrial myocardium displayed predominantly unidirectionally based fiber orientation patterns within each specimen, whereas the SAN displayed an increased amount of fiber disarray manifested quantitatively as a significantly greater standard deviation in fiber angle distribution within specimens [33 AE 7 deg versus 23 AE 5 deg, atrium (p ¼ 0.02); 18 AE 3 deg, CT (p ¼ 0.0003)]. We also identified unique, local patterns of fiber orientation specific to the functionally characterized block zone. We demonstrate the ability of OCT in detecting components of the atrial pacemaker complex which are intimately involved in both normal and abnormal cardiac conduction.

Imaging myocardial fiber orientation using polarization sensitive optical coherence tomography

“…Ultrasound elastic tensor imaging [6] has also been explored due to its faster acquisition speed. In addition, optical coherence tomography (OCT) has been explored to quantify fiber orientation in heart muscles [7,8]. Although OCT has a smaller field of view and penetration depth than MRI and ultrasound imaging, its superior spatial resolution makes it possible to reveal fiber organization at the microscopic level.…”

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

“…While this study focused on adipose tissue and fiber orientation, it is also possible for OCT to provide features corresponding to fibrosis, as has been described in prior OCT studies. 8,11 Previously, OCT has also been used to describe myofiber orientation within animal models, ex vivo, [28][29][30][31][32][33][34][35][36][37] with some studies incorporating optical clearing 30,34 or serial sectioning 37 methods to improve imaging depth. Polarization-sensitive OCT, which provides additional contrast by measuring changes in the polarization state of light as it passes through a medium, 38 has also been used to provide additional sensitivity to fiber organization.…”

Depth-resolved mapping of muscular bundles in myocardium pulmonary junction using optical coherence tomography

“…[4][5][6][7][8][9] Since the orientation of myofiber tracts plays a central role in the function of the heart, a number of approaches have been reported to quantify the average fiber direction, such as ones based on the fast Fourier transform (FFT) 5 and edge detection. 4,[6][7][8][9] Recently, a weight orientation vector summation algorithm was presented for estimating fiber orientation at each pixel within a grayscale image to improve the accuracy of fiber orientation, assuming myofiber fills the entire image. [10][11][12] Since muscular bundles are covered by fibrous tissues in myocardium pulmonary junction, in this study, we pay more attention to the extension of muscular bundles rather than the myofiber orientation.…”