Effect Of Ischemic Burden On The Opening Of Intrinsic Femoral Collateral Circulation In Rabbits

Objectives:To study the minimal ischemic burden for evoking maximal opening of native femoral collaterals and provide the basis for the clinical application of physiological ischemic training.Method:Twenty-six New Zealand adult rabbits (2.5±0.5kg) were subjected to complete occlusion of femoral artery with different ischemic burden (graded ischemic duration and frequency),randomly assigned to four groups. A: Optimal ischemic time preliminary screening, B: Optimal ischemic time intensive screening, C: Optimal ischemic interval, D: Optimal ischemic frequency. Femoral artery collateral blood flow (FCBF) was measured with microsphere technique.Results:1. FCBF increased at the onset of occlusion and reached the peak level at the 3rd min (P<0.01), then entered the plateau phase with the occlusion prolonging to 4min. 2. Compared to pre-occlusion, the regional blood flow increased significantly at the 2nd min after one episode of 3min ischemia (P<0.01). The maximal opening of native femoral collaterals maintained at least 5 minutes, but decreased gradually at the 8th min after reperfusion. 3. FCBF increased significantly after three repetitive 3min occlusions with 5min interval between each (P<0.01). A trend of decrease was shown with the ischemic stimulation reaching more than 3 times. Conclusion:The data suggests that the fully opening of native collateral circulation after artery occlusion requires 3min duration and maintains at least 5 minutes, which is augmented by three repetitive 3min occlusions with 5min interval. Increase of ischemic burden does not enhance FCBF further.