CEREBRAL ARTERIOVENOUS MALFORMATION FEEDING ARTERY ANEURYSMS - A THEORETICAL-MODEL OF INTRAVASCULAR PRESSURE CHANGES AFTER TREATMENT

OBJECTIVE: A quantitative model may be used to estimate the magnitude of expected pressure changes along the vascular tree with shunt ablati on and may provide information to assess the hemodynamic risk of arter iovenous malformation (AVM) treatment. METHODS: A computer model of th e cerebral circulation was applied to estimate the changes in intravas cular pressure, velocity, biomechanical stress, and shear stress that might be expected from either endovascular or surgical ablation of AVM s. Two AVM sizes and two feeding artery constellations were simulated. The effect of different shunt flows on vascular pressure was modeled. In each simulation, AVMs were occluded in a stepwise fashion. The eff ects of systemic hypertension and hypotension in various vascular zone s were also simulated. RESULTS: As large (1000 ml/min) AVMs were occlu ded, the mean feeding arterial pressure increased from 18 to 68 mm Hg; the percent-occlusion at half-maximal pressure increase was 92%. For medium (500 ml/min) AVMs, feeding arterial pressure increased from 37 to 66 mm Hg; the percent-occlusion at half-maximal pressure increase w as 71%. During manipulation of systemic pressure, hemodynamic changes in the circulation close to the nidus were proportionally less than ch anges in systemic pressure; the degree of proportionality depended on the magnitude of AVM shunt flow. CONCLUSION: In this simulation, shunt obliteration increased pressure in the nidus and feeding arteries wit h little effect on the proximal circulation. The shunt provided a ''bu ffering'' effect, i.e., higher flow fistulas were exposed to smaller v ariations in intravascular pressure in feeding artery and nidal pressu res during manipulation of systemic pressure.