Abstract 186: Use of Optical Coherence Tomography to Study Arteriogenesis After Hind-Limb Ischemia

Abstract

Introduction: Because of their small size, direct measurement of collateral artery flow and diameter is difficult, so laser Doppler perfusion is used as a surrogate with micro-computerized tomography (microCT) performed to assess collateral networks and diameters after sacrifice. We applied optical coherence tomography (OCT) to measure artery diameter, flow, and velocity serially after hindlimb ischemia. Hypothesis: OCT is superior to microCT for measuring arteriogenesis. Methods: OCT was performed on the hindlimb musculature of male C57BL/6 mice, ages 3-5 months (n=5) bilaterally prior to unilateral femoral artery ligation, immediately after, and weekly for four weeks. Femoral artery and collateral artery diameter, flow, and axial velocity were measured. On postoperative day 28, mice were sacrificed by pressure perfusion fixation with formalin and injected with contrast. MicroCT was then performed at 18 micron resolution. Collateral artery diameter and vessel density from 3-d reconstructed datasets were analyzed using Matlab. Results: Figure 1 shows representative OCT (1A) and microCT (1B) images. Femoral artery flow and axial velocity decreased significantly after ligation (0.046 ± 0.040 from 2.1 ± 0.5 mm 3 /sec, p =0.006 and 1.1 ± 1.0 from 16.0 ± 1.1 mm/sec, p <0.001). The velocity of the ligated femoral was still significantly slower at 28 days (5.0 ± 1.9 vs 11.9 ± 1.0 mm/sec). Collateral artery flow reversed direction after ligation. At 28 days, the velocity in the collateral artery had increased significantly (12.4 ± 2.1 from 1.7 ± 1.0 mm/sec at baseline). MicroCT tended to overestimate the unligated collateral diameter (95 ± 9 vs 63 ± 8 microns by OCT, p =0.0537), but was accurate for the ligated side collaterals. Conclusions: Optical coherence tomography provides important physiologic and structural data regarding arteriogenesis following hindlimb ischemia and is superior to microCT for assessment of arteriogenesis.