Deliberate systemic hypotension to facilitate endovascular therapy of cerebral arteriovenous malformations: a computer modeling study

Abstract

With the aid of a computer model, this investigation describes the relationship between mean arterial pressure (MAP) reduction and its effect on total arteriovenous malformation (AVM) shunt flow, feeding artery velocities, and cerebral blood flow in hypotensive, structurally normal vascular beds adjacent to the AVM nidus. Simulations were performed for two feeding artery sizes (2 and 4 mm in diameter) and two AVM shunt flows (500 and 1000 ml/minute) with and without the presence of autoregulation in normal brain. Systemic arterial hypotension was simulated in a stepwise fashion by reducing aortic pressure from 100 to 10 mm Hg in 10-mm Hg steps. The percentage of MAP that resulted in a 50% reduction of shunt flow was calculated (%MAP reduction at half-maximal shunt flow). As the MAP decreased, the shunt flow decreased in a nearly linear fashion; the cerebral blood flow remained constant in neighboring brain until the MAP dropped below 60 and 80 mm Hg for the medium and large AVMs, respectively. The %MAP reductions at half-maximal shunt flow for the medium and large AVMs were not significantly different from 50%: 44% and 47%, respectively. Results for 2 and 4 mm AVM feeding artery sizes were similar. The decrease in both total shunt flow and flow velocity in feeding artery pedicles, potentially embolized by glue injection, were nearly linear with the institution of systemic hypotension. The presence or absence of autoregulation in normal brain, or different variations in the simulated angioarchitecture of the AVMs, did not affect this relationship in the model.