Abstract 14957: Investigation of Myocardial Birefringence using Polarization-Sensitive Optical Coherence Tomography in a Mouse Model of Myocardial Infarction

Abstract

Introduction: Although several imaging modalities have been utilized to characterize myocardium, the birefringence of myocardium has not been spotlighted. The polarization-sensitive optical coherence tomography (PS-OCT) is a novel imaging method for the characterization of tissue birefringence. Hypothesis: The birefringence of infarcted myocardium would be different from non-infarcted myocardium. We examined the myocardial birefringence in a mouse coronary artery ligation model using PS-OCT. Methods: Male C57B/6 mice (20-30g) underwent thoracotomy and the ligation of left anterior descending artery. At post-myocardial infarction (post-MI) 3 hours or on post-MI day 28, the left anterior wall of the mice was imaged with PS-OCT in vivo and ex vivo. The local phase retardation for tissue birefringence, the local principal axis directional uniformity for tissue orientation, and the degree of polarization uniformity were demonstrated and compared with collagen fiber staining (picrosirius red). For PS-OCT system, wavelength-swept laser with 140 nm bandwidth (center wavelength = 1,280 nm) and 120 kHz A-line rate was used. Results: The endocardial border could be detected by high birefringence of myocardium. There was no difference in the birefringence between systole and diastole. The infarcted anterior wall showed dyskinesia or hypokinesia. The systolic wall thickening was lower in the infarcted wall compared to the normal anterior wall. At post-MI 3 hours, there was no significant change in myocardial birefringence. On day 28, the infarcted myocardium with scar tissue showed low level of local birefringence with irregular tissue orientation compared to the normal myocardium. The 3D reconstructed images were used to differentiate transmural or subendocardial MI. Conclusions: Our study demonstrated that the PS-OCT would be helpful for the evaluation of myocardial function and tissue characterization in myocardial infarction.