Background and Purpose-To test the hypothesis that neither "steal" as cortical ischemia caused by reduced perfusion pressure nor "breakthrough" on the grounds of loss of pressure autoregulation exist in brain tissue surrounding arteriovenous malformations (AVMs), we established patterns of cortical oxygen saturation (SO 2 ) adjacent to AVMs and its behavior after alterations of mean arterial blood pressure. Methods-With a microspectrophotometer, SO 2 was scanned in the cortex around AVMs of 44 patients before and after resection and in that of a non-AVM group (nϭ42) before transsylvian dissection. Autoregulation was evaluated by linear regression analysis after elevation of mean arterial blood pressure (5 g/min IV noradrenaline

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The rhythmogenic properties of vascular smooth muscle are closely coupled to a functioning circulation. The electrical and mechanical oscillations in cells of spontaneously rhythmic organs of the cardiovascular system could originate in the allosteric qualities of the enzyme phosphofructokinase.

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