The effect of ischemia-reperfusion injury on measures of vascular function

BACKGROUND: Ischemia-reperfusion injury results in conduit vessel endothelial dysfunction as assessed by flow-mediated dilatation (FMD). The effect on the potentially more important microvascular circulation has not been well studied. The objective of our study was to assess the effect of ischemia-reperfusion injury on microvascular function including peripheral arterial tonometry (PAT) hyperemic index. METHODS: 45 healthy volunteers free of cardiovascular disease were recruited (mean age 35 +/- 14 yrs, 29 men). Using ultrasound, the flow-mediated dilation (FMD) and hyperemic velocity (VTI) of the brachial artery were measured following a 5-minute forearm cuff occlusion. Simultaneously, the PAT hyperemic index was measured. Ischemia was then induced by a 15-minute upper arm occlusion and within 15 minutes of recovery the vascular measures were repeated. RESULTS: Ischemia caused a significant reduction in FMD (7.9 +/- 4.0 to 4.7 +/- 3.5, p=0.0001). The hyperemic VTI, a measure of microvascular function, was unaffected following ischemia-reperfusion (92 +/- 30 vs. 97 +/- 37 cm, p=0.236). Finally, PAT index was also unchanged by the intervention (2.07 +/- 0.8 vs. 2.04 +/- 0.7, p=0.742). CONCLUSIONS AND DISCUSSIONS: Ischemia-reperfusion caused conduit and not resistance vessel endothelial dysfunction. The PAT-index was unchanged suggesting that this measure is more closely aligned with resistance than conduit vessel function. This has implications for its use as a measure of vascular function in clinical research.