[Experimental simulation study on EC-IC bypass--Part 1: Optimum conditions for bypass on the basis of hydraulic and theoretical models with autoregulation mechanism].

There have been several reports about unexpected occlusive change of stenotic lesion in the internal carotid artery (ICA) or middle cerebral artery (MCA) following bypass surgery, rupture or formation of an aneurysm after carotid ligation and ICA EC-IC bypass for the treatment of inaccessible ICA aneurysm. These suggest that operation for one vessel causes hemodynamic changes in others, not only near the operation site but in remote sites. Although complete hemodynamic analysis in the brain and quantitative speculation of the possible effect of a cerebrovascular operation are essential to prevent these complications, these measures are usually very difficult to carry out because multiple factors are related mutually in complex fashion in a living body. One effective means to simulate these changes would be the use of a vascular model. A hydraulic model of unilateral ICA stenosis (resistance of stenosis: R) with EC-IC bypass (resistance of bypass: Rby) has been manufactured with silicone and glass tubes. Peripheral vascular resistance (Rp) is adjusted to obtain an arterial flow of 180 ml/min at poststenotic pressures of 60, 70, 80, 90, and 100 mmHg. To simulate the autoregulation mechanism, appropriate Rp is selected for each combination of R and Rby so as to make, as far as possible, a hemispheric flow (sum of stenosis flow and bypass flow) of 180 ml/min. The Rp with the lowest value (60/180 mmHg/ml/min) is to be chosen in flow conditions of lower than 180 ml/min, where autoregulation is no longer functioning. Twelve kinds of stenosis segments with an inner diameter from 0.37 to 2.59 mm are prepared and used in the models.(ABSTRACT TRUNCATED AT 250 WORDS)