Stent jail of the renal arteries in stent graft exclusion of AAA. An in vitro study of 3 different stent types.

Background: The success of endoluminal stent grafts (ELG) is critically dependent on secure proximal fixation of the graft. Different types of stent grafts with uncovered proximal portions for transrenal fixation are obtainable. The present in vitro study was designed to elucidate how the flow parameters were altered by stent jail of the renal arteries with respect to different stent design.
Methods: The experiments were performed in an in vitro pulsatile circulation model. An aortic segment with bilateral side branches (like renal arteries) constructed of an ePTFE graft was perfused in the circulation model. The flow measurements were based on the ultrasound transit-time method. By varying the frequency from 30 to 100 bpm the flow parameters were altered and recorded continuously. Renal stent jailing was carried out using different stent types: Gianturco-Z-Stent, Palmaz-Stent, Powerlink Endologix.
Results: The flow in the aortic model increased from 1100 ml per minute to 3330 ml per minute depending on the pump frequency. In the control group without stent jail the renal flow was measured between 240 ml per minute up to 810 ml per minute. The ratio of renal flow was between 0.22 and 0.24 of the aortic flow. In the Palmaz group the ratio was between 0.21 and 0.24, in the Gianturco group between 0.23 and 0.25, and in the Powerlink group between 0.24 and 0.25 (unpaired-"t"-test: n.s.).
Conclusions: The covering of the renal arteries and/ or superior mesenteric artery in case of long bared proximal stent raises the question whether the stent jail may result in flow reduction in the arteries covered or not. The present in vitro study demonstrated that the flow in the renal arteries is not decreased by these stent jails.