Direct continuous measurement of draining vein pressure during Onyx embolization in a swine arteriovenous malformation model

Objective Periprocedural intracranial hemorrhage secondary to intranidal flow redirection may develop after arteriovenous malformation (AVM) embolization. We hypothesized that continuous draining vein pressure monitoring may identify clinically relevant hemodynamic changes during devascularization. Our goal was to characterize the draining vein pressures in a swine rete mirabile AVM model during embolization with Onyx. Methods An acute swine AVM model was constructed in six animals. Baseline, transoperative and final AVM area measurements were used to determine the degree of AVM embolization. Continuous video recordings were captured at 10 s intervals of active embolization. Draining vein pressure, arterial feeder pressure and heart rate were continuously monitored. Results The baseline and post-embolization mean draining vein pressures were 49.8 +/- 17.2 and 33.0 +/- 11.7 mm Hg (p=0.01), mean arterial pressures were 79.8 +/- 19.4 and 79.6 +/- 25.2 mm Hg (p=0.94), mean transnidal pressures were 35.8 +/- 19.7 and 45.4 +/- 33.7 mm Hg (p=0.37) and mean heart rates were 81.1 +/- 11.9 and 83.1 +/- 12.8 bpm (p=0.38), respectively. The draining vein pressure was averaged according to the degree of AVM embolization and represented as a relative change compared with the baseline draining vein pressure, and the slopes were found to decrease in all cases (p=0.02). In half of the animals the draining vein pressure decreased progressively as the AVM was embolized. In the remaining animals the venous pressure only started to decline after the AVM had been devascularized by > 50%. Conclusions The draining vein pressure response during Onyx embolization in the swine AVM model is heterogeneous. Continuous draining vein pressure monitoring is feasible and may potentially identify clinically relevant hemodynamic changes during AVM embolization.