Polarimetric Signatures of Coronary Thrombus in Patients With Acute Coronary Syndrome

Background: Intravascular polarization-sensitive optical frequency domain imaging (PS-OFDI) offers a novel approach to measure tissue birefringence, which is elevated in collagen and smooth muscle cells, that in turn plays a critical role in healing coronary thrombus (HCT). This study aimed to quantitatively assess polarization properties of coronary fresh and organizing thrombus with PS-OFDI in patients with acute coronary syndrome (ACS). Methods and Results:The POLARIS-I prospective registry enrolled 32 patients with ACS. Pre-procedural PS-OFDI pullbacks using conventional imaging catheters revealed 26 thrombus-regions in 21 patients. Thrombus was manually delineated in conventional OFDI cross-sections separated by 0.5 mm and categorized into fresh thrombus caused by plaque rupture, stent thrombosis, or erosion in 18 thrombus-regions (182 frames) or into HCT for 8 thrombus-regions (141 frames). Birefringence of coronary thrombus was compared between the 2 categories. Birefringence in HCTs was significantly higher than in fresh thrombus (Delta n=0.47 (0.37-0.72) vs. Delta n=0.25 (0.17-0.29), P=0.007). In a subgroup analysis, when only using thrombus-regions from culprit lesions, ischemic time was a significant predictor for birefringence (ss (Delta n)=0.001 per hour, 95% CI [0.0002-0.002], P=0.023). Conclusions: Intravascular PS-OFDI offers the opportunity to quantitatively assess the polarimetric properties of fresh and organizing coronary thrombus, providing new insights into vascular healing and plaque stability.

Automated summary

In this study, PS-OFDI was used to quantitatively assess the polarization properties of coronary thrombus in ACS patients, revealing significantly higher birefringence in organizing thrombus compared to fresh thrombus. Additionally, ischemic time was identified as a significant predictor for birefringence in thrombus regions from culprit lesions.