Experimental study of the influence of endoleak size on pressure in the aneurysm sac and the consequences of thrombosis

Background: This was an experimental study of endovascular aortic surgery, looking at the relationship between the size of an endoleak, pressure in th e aneurysm sac and the effect of thrombosis produced by coagulation. Methods: In three pigs, 16 saccular aneurysms were connected to the aorta b y various side branches with different diameters and lengths ('endoleaks'). Mean and pulse pressures were measured in the systemic circulation as well as in the aneurysm sac during the experiment. Duplex ultrasonography was u sed to determine whether the endoleak and the aneurysm were patent or throm bosed. Thrombosis was influenced by systemic tranexamic acid, fibrinogen in the aneurysm sac, Gelfoam in both endoleak and aneurysm sac, and by Histoa cryl glue in the endoleak. Results: With an open endoleak, the mean pressure in the aneurysm and the a orta was identical. Mean aneurysm pressure was lower with a thrombosed endo leak and was related to the diameter of the endoleak. Pulse pressure was re corded in the aneurysm sac when there was an open endoleak and a non-thromb osed aneurysm, and was related to the diameter of the open endoleak. Thromb osed endoleaks never produced pulse pressure in the aneurysm. If Histoacryl and Gelfoam induced thrombosis of the endoleak, the decrease in mean aneur ysm pressure was identical to that resulting from the spontaneous thrombosi s of endoleaks. Conclusion: An open endoleak results in systemic arterial pressure in the a neurysm sac. Pulse pressure is detected if the aneurysm is patent, but abse nt if there is complete or partial thrombosis of the aneurysm. Endoleak thr ombosis, either spontaneous or by embolization, is accompanied by a decreas e in mean pressure and the absence of pulse pressure in the aneurysm sac. T he extent to which these experimental findings are comparable to the clinic al situation represents a field of further research.