Abstract 153: The Role of Contralateral Cerebrovascular Myogenic Dysfunction in Hyperglycemic Stroke
Admission hyperglycemia worsens clinical outcomes in acute ischemic stroke (AIS) but the mechanism remains controversial. Our previous studies showing that even a modest acute elevation in blood glucose amplifies vascular injury and neurological deficit emphasize the importance of an intact cerebrovasculature in functional outcomes. Given that stroke lowers perfusion even in the nonischemic hemisphere, the impact of hyperglycemic AIS on cerebrovascular reactivity in the contralateral hemispheres needs to be determined.
Hypothesis: Acute hyperglycemia exacerbates cerebrovascular myogenic dysfunction in the contralateral hemisphere causing cerebral blood flow (CBF) impairment and worsening stroke outcomes.
Methods: Weight-matched male Wistar rats (n=6-8) were subjected to 30 min middle cerebral artery occlusion (MCAO)/45 min reperfusion after administration of saline or 40 % glucose solution 10 min before procedure. Myogenic tone of isolated MCAs was determined across the pressure range. In another set of animals (n=5), infarct size, edema and neurologic deficit were measured in rats exposed to 30 min hyperglycemic MCAO/24 h reperfusion. Cerebral perfusion was evaluated with laser Doppler flowmetry.
Results: The myogenic tone was decreased in both ischemic and nonischemic sides albeit to a different degree (at 80mmHg 5±0.85† and 7.8±0.7*, respectively vs sham 9.4±0.9). Interestingly acute hyperglycemia exacerbated myogenic dysfunction (at 80mmHg 4.8±0.3***) and amplified CBF reduction in the nonischemic hemisphere (MCAO 4.5±3.1% vs hyperglycemic MCAO 22.3±7.1% *p<0.05). When ischemic injury was superimposed with acute hyperglycemia, this led to infarct size expansion (35.6±6.1% vs 15.7±1.6 % *p<0.05), increased edema (15±2.7% vs 7.2±1% *p<0.05) and more pronounced neurological deficit (#p<0.001).
Conclusion: Our results provide evidence that there is early loss of tone in the contralateral hemisphere, augmented myogenic dysfunction in hyperglycemia is associated with poor stroke outcomes, and that the nonischemic hemisphere may be a novel target for the management of AIS. (†P<0.001, *P<0.05 vs sham, ***p<0.001 vs nonischemic hemisphere)
- © 2012 by American Heart Association, Inc.