A COMPUTER-SIMULATION OF THE HEMODYNAMIC-EFFECTS OF INTRACRANIAL ARTERIOVENOUS MALFORMATION OCCLUSION

To study the effect of AVM occlusion on cerebrovascular haemodynamics, a simplified model was simulated consisting of a feeding artery suppl ying a capillary bed in parallel with a fistula-like malformation, bot h emptying into a draining vein. An electrical circuit analogue of the physiologic system was developed using lumped proximal and distal pre ssure dependent resistances, and capacitors representing vascular comp liance. Autoregulation was introduced as a pressure varying precapilla ry arteriolar resistance. Equations derived from the circuit model wer e simulated using a graphical modeling program. The model successfully simulates phenomena angiographically observed during embolization pro cedures. Fistula pressure is shown to rapidly fall following proximal AVM occlusion, in contrast to a marked rise seen with distal occlusion , which is associated with biphasic flow into and out of the fistula a nd the arterial feeder. The model predicts an increase in capillary pr essure and capillary flow which, depending on the magnitude of the flo w increase and the state of autoregulation, may result either in rever sal of ischaemia or hyperperfusion injury. Vascular overload is predic ted in the absence of autoregulation. There is, however, little potent ial for vascular overload when autoregulation is intact. The model rep resents a first step in the mathematical characterization of the pheno menon of hyperperfusion following