Morphological Observation Of Aortic Remodeling After TEVAR Of Type B Aortic Dissection And Its Impact On Long-Term Survival

BackgroundComplicated type B aortic dissection(TBAD)is a common critical aortic disease which often leads to catastrophic consequences.Thoracic endovascular aortic repair(TEVAR)is recommended by Guideline of the European Association of Cardiovascular Diseases for TBAD.In TEVAR,primary intimal tear is covered by aortic endograft which is placed in the aortic true lumen(TL),and blood flow into the false lumen(FL)is reduced.Aortic remodeling(AR)is initiated by TEVAR.Aortic remodeling refers to the process of aortic morphological changes after TEVAR.Its contents include:changes in diameter,area and volume of TL and FL,changes in thrombosis and patency of FL,and changes in sources of blood supply of abdominal artery branches.The mortality rate of AD patients is reduced by TEVAR,but the risk of second operation and complication rates which has been confirmed and paid more and more attention are higher.Common complications include aneurysmal dilatation of abdominal aorta and leakage after TEVAR.Some complications are the result of poor aortic remodeling,while others are the cause of poor aortic remodeling.The occurrence of complications can be detected by aortic remodeling in advance or in time,therefore,secondary surgery can be avoided or done earlier.At the same time,more and more literatures show that good AR can prolong the survival time of patients.However,AD often involves the whole long thoracoabdominal aorta,in which there are multiple intimal tears and hemodynamic disorders.Therefore,the AR after TEVAR,especially in the area without stent coverage,remains unclear.Therefore,aortic remodeling after TEVAR deserves attention and research.There are different problems in the literature on AR.The traditional two-dimensional measurement methods were used by many literatures to measure the diameter of true and false lumen which were three-dimensional to reflect the situation of aortic remodeling.This method was not entirely reliable,especially in the tortuous aorta or the true and false lumen were teared spirally.The diameter or area of the aorta at a single level often fails to reflect the changes of the whole vascular lumen.The change of vascular lumen volume can reflect the real situation of AR better than the diameter and area,but which is refer to in only a few literatures.Some details of AR,including changes in the source of blood supply to the branch arteries,are not yet available.The AR of TBAD was described by the morphological changes of true and false lumen diameter,area,volume,FL thrombosis,the patency of FL and branch artery blood supply after TEVAR.The regularity of AR was analyzed by the data collected before operation,3 months,6 months and 12 months after operation,and the survival risk factors of dissection patients after TEVAR were analyzed.MethodsThe clinical data of patients with AD and CT DICOM were collected prospectively.Aortic dissection was treated with TEVAR.Regular enhanced CT scan was performed after TEVAR during follow-up.CT DICOM data were collected before operation,3 months,6 months and 12 months after operation,and then introduced into image post-processing workstation for 3D reconstruction.The diameters and areas of the seven planes of the left subclavian artery(P1),2cm(P2)far from the left subclavian artery,the middle of the descending aorta(P3),the diaphragm(P4),the opening of the abdominal trunk(P5),the opening of the upper renal artery(P6),and the bifurcation of the abdominal aorta(P7)were further measured.The true and false lumen volumes of thoracic aorta and abdominal aorta were measured,and the thrombosis and patency of the false lumen of thoracic aorta and abdominal aorta were observed.The blood supply of celiac artery,superior mesenteric artery,bilateral renal artery and bilateral iliac artery branches coming from TL or FL were observed.The data pre-and after TEVAR were compared to display the effect of TEVAR on AR and the regularity of AR.ResultsA total of 56 patients were enrolled in this study.There were 2 type IIIA AD(2/56,3.6%)and 54 type ?B AD(54/56,96.4%).There were 44 males(44/56,78%)and 12 females(12/56,22%)with an average age of 54± 13.8 years.The diameter of the four planes of thoracic aorta(P1-P4)TL increased gradually at 3 months and 6 months post-operation,and stabilized gradually at 12 months post-operation.The diameter of the thoracic FL(P2-P4)decreased post-operation,especially at 3 months post-operation.The diameter of abdominal aorta true lumen(P5,P6 and P7)also increased significantly at 3 months after TEVAR.However,the diameter of P5 and P6 true lumen decreased slightly after 6 months.The diameter of P5 FL did not change significantly after operation,but the diameter of P6 and P7 FL even increased gradually after operation.The area of thoracic aorta true lumen(P1,P2,P3 and P4)gradually increased after operation,especially at 3 months after TEVAR.The area of the FL after operation was gradually reduced compared with which pre-operation.The TL area of P5,P6 and P7 was larger than that pre-operation,while the FL area of P6 and P7 was larger than that pre-operation.The total area of P5,P6 and P7 was larger than that pre-operation.The volume of the true thoracic aorta gradually increased after the operation,while the volume of the false thoracic aorta gradually decreased,but the total volume of the thoracic aorta remained basically unchanged.The volume of abdominal aorta after 3 months was larger than that before operation.There was no significant difference between the volume of abdominal aorta after 6 months and that before operation.The volume of abdominal FL decreased 3 months after operation,but the volume of abdominal aortic FL increased 6 months and 12 months after operation.The total volume of abdominal aorta gradually increased,especially at 12 months after operation.The modified aortic remodeling index(MARI)of thoracoabdominal aorta and thoracic aorta increased significantly at 3 months and 6 months after operation,but tended to be stable at 12 months after operation.The MARI of abdominal aorta increased significantly at 3 months after operation,and decreased slightly at 6 months and 12 months after operation,but remained stable.MARI of thoracoabdominal aorta,thoracic aorta and abdominal aorta were negatively correlated with complications and mortality.Aortic FL thrombosis gradually after TEVAR.At 12 mons post-operation,total thrombosis of thoracic FL was 67.3%,while partial thrombosis of abdominal FL was 80%.The degree of aortic thrombosis was negatively correlated with complications and deaths.The patency of FL decreased gradually after operation.80%of the abdominal FL remained partially patent.The blood supply of branch arteries gradually changed to TL,and the proportion of TL blood supply gradually increased.The risk of death with complications was 5.565 times higher than that without complications.ConclusionsTEVAR is an effective and safe treatment for complicated acute TBAD.TEVAR promotes aortic remodeling in TBAD.The rermodeling of thoracic aorta was better than that of abdominal aorta.The abdominal false lumen is partly thrombosis and partly patent for a long time after TEVAR,which is a risk for aortic dilatation.Complications after TEVAR which is poor aortic remodeling closely related to are the most important risk factor of death.