The Research Of Split-type Branched Stent-grafts For Thoracic Aortic Disease

Objective:To invent a new branched stent-graft technique for ascending aortic and aortic arch lesions, which is regardless of specific anatomic couditions in aortic arch.methods:The concept of split-type branched stent-grafts, which includes several umbrella branched stent-grafts and an aortic stent-graft with a sunk part and prefabricated side holes, was researched. According to the thoracic aortic anatomic situations in experimental ceaines and human bodies, three kinds of split-type branched stent-grafts with different sizes (large-sized, medium-sized, small-sized) were designed and manufactured with NiTi stents, prosthesis and radiopaque markers.With appropriate duct models to mimic corresponding thoracic aorta, the three sets of split-type branched stent-grafts were deployed experimentally in vitro. Experiment in vivo was performed with the medium-sized split-type branched stent-grafts and a crossbred canine.Results:Diameter and length of the three manufactured aortic stent-grafts were34mm X210mm,26mm X80mm and16mm X40mm respectively. Diameter of branched stent-grafts were14mm,12mm and8mm respectively.The aortic stent-graft included a middle section with a sunk part and cylindrical front and rear sections. The depth and length of the sunk parts were9mmX103mm,14mm×40mm and10mm×20mm respectively. All the branched arterial orifices were covered by the sunk part where side holes were prefabricated. The diameter of side holes were12mm,10mm and6mm respectively. After the aortic stent-graft deployed, there will be an interval between aortic wall and prosthesis because of the sunk design. The interval connected with all branched arteries and aorta that preserved all branched arteries patent.The main part of branched stent-graft was cylindrical, tapered or trumpet shaped. The umbrella bottom was used to connected with the side hole on aortic stent-graft.In the in vitro deployment experiment of the small-sized split-type branched stent-grafts, the aortic stent-graft deployed well with unconspicuous interval between aortic well and prosthesis. All branched stent-grafts were advanced smoothly from distal branched duct, and were deploy as planned.The aortic stent-graft of the medium-sized split-type branched stent-grafts was deployed as planned. The front and rear prosthesis were adjacent to internal surface of the duct, and the sunk part of the middle section formed an obvious interval that covered the orifices of all branched ducts. However, when the delivery system of the branched stent-graft advanced, the aortic stent-graft was pushed forward and upward, which caused migration of the aortic stent-graft. The interval between the duct and prosthesis was compressed, and the delivery system was folded. The branched stent-graft couldn't be deployed as planned. The morphology and character of duct that was different from thoracic aorta was the main reason. Besides, the delivery system that was not flexible enough was another problem.All stent-grafts of the large-sized split-type branched stent-grafts were deployed as planned. The aortic stent-graft covered partial ascending aorta, aortic arch and the proximal descending aorta. The sunk part in the middle section formed an obvious interval between the internal surface of the duct and prosthesis at the region where branched ducts originated. All branched stent-graft positioned accurately and deployed well, complied with the shape of branched ducts and connected firmly with the aortic stent-graft. Because of the adequate front and rear section of the aortic stent-graft, the deployment process of the branched stent-grafts didn't cause any migration of the aortic stent-graft.In vivo experiment was performed using a crossbred canine with appropriate sized thoracic aorta that was fit to the medium-sized split-type branched stent-grafts. The proximal NiTi stent was deployed incompletely after the deployment of the aortic stent-graft, which formed a70°angle between the proximal stent-graft and aorta wall. The stent expanded finally after CODA balloon catheter to dilate the position. The branched stent-grafts were deployed and reconstructed branched arteries well. However, both of the positions of the two branched stent-grafts were not accurate, part of two branched stent-graft deployed in the lumen of the aortic stent-graft, which caused stenosis of the aortic stent-graft. The profile of the proximal aortic stent-graft changed when the branched stent-grafts deployed. The was not surgical related complication happened. The specimen of thoracic aorta and the deployed stent-graft were checked, the split-type branched stent-grafts were deployed as planned, the connections between stent-grafts were firm. The proximal aortic stent-graft twisted, and the last two stents overlapped partially. Both of the two branched stent-grafts were not deployed in the branched arteries, but the two branched arteries were reconstructed well.Conclusion:The feasibility of the split-type branched stent-grafts was confirmed by the research. The stent-grafts can be used in ascending aorta and aortic arch and reconstruct all branched arteries reliable simultaneously. With advanced stent-grafts design and delivery system, the efficiency of the split-type branched stent-grafts will be better.