Haemodynamic study of arteriovenous malformations using a hydraulic model

Despite the accumulation of intraoperative data on arteriovenous malformations (AVMs), details of the haemodynamics have not yet been elucidated. A hydraulic model was constructed from silicone and glass tubes to simulate a high-flow AVM. During stepwise obliteration of the nidus, haemodynamic changes were continuously measured in residual parts of the AVM and in the surrounding brain. The flow in the residual AVM decreased nonlinearly with the advance of obliteration. The feeder pressure increased markedly from 37 mmHg to 94 mmHg, while the drainer pressure decreased gradually. The flow volume in the surrounding brain increased markedly from 40 ml/min to 100 ml/min at an occlusion ratio of 60%, where the pressure gradient across the nidus reached 60 mmHg. In the presence of autoregulation, further obliteration showed no change in the flow volume with the increased pressure gradient to 93.7 mmHg. Under dysautoregulatory conditions the flow volume increased to 122 ml/min, although the pressure gradient was 8.3 mmHg lower than that under autoregulatory conditions. Simulation study is useful in understanding haemodynamic changes during the treatment of AVMs.