Postoconditioning accelerate myocardial inflammatory resolution demonstrated by C-14-methionine imaging and attenuates ventricular remodeling after severe ischemia and reperfusion

Objectives: We have revealed that methionine uptake can be a marker of macrophage infiltration after myocardial ischemia and reperfusion (JNM2013:54:431-6). We aimed to explore how postconditioning at reperfusion affects myocardial C-14-methionine uptake and ventricular remodeling using in a rat model of ischemia and reperfusion.

Methods: The left coronary artery was occluded for 30 min followed by reperfusion. At reperfusion, postconditioning was achieved by 6 repeated episodes of 10 sec reperfusion, each followed by 10 sec of occlusion. One, 3, 7, and 14 days after reperfusion, C-14- methionine (0.74MBq) was injected 20 min before sacrifice. One min before sacrifice, the left coronary artery was reoccluded and Tc-MIBI (150-180MBq) was injected to verify the area at risk. The methionine uptake ratio in an ischemic area was calculated by dividing the uptake value in an ischemic area by that of a normally perfused area. To examine the ventricular remodeling, cardiac echocardiography was performed 2 months after reperfusion.

Results: In control rats (n=22), methionine uptake ratios at day 1, 3, 7, 14 were 0.78±0.11, 1.85±0.16, 1.49±0.10, 1.25±0.04, respectively. With postconditioning (n=23), methionine uptake was similar at day 3 (1.90 ± 0.21), but, more reduced at day 7 (1.23±0.23, p<0.05) and day 14 (1.08±0.09, P<0.005). In postconditioning, uptake area of methionine to area at risk was similar to control at day 3 (0.69±0.09 vs 0.66±0.04) but decreased at day7 (0.65±0.06 vs 0.42±0.06, P<0.05) and day14 (0.54±0.07 vs 0.37±0.10, P<0.01). Echocardiography revealed that postconditioning reduced the ventricular end-diastolic (1.00 ± 0.06 cm to 0.83 ± 0.14 cm, P < 0.05) and systolic dimensions (0.90 ± 0.15 cm to 0.62 ± 0.19 cm, P < 0.05) and prevented a decline of ventricular percentage fractional shortening (10.5 ± 3.7 to 28.2 ± 10.7, P < 0.005).

Conclusion: Postconditioning did not affect peak methionine uptake, although postconditioning accelerated the reduction of methionine uptake at day 7-14, and attenuated ventricular remodeling. The results of the methionine imaging suggested that accelerated resolution of inflammatory process by postconditioning was related to the attenuation of ventricular remodeling after myocardial infarction. Research Support: None