Feasibility Study Of Left Ventricular Outflow Tract As Anchoring Zone Of Jing's Valved-Fenestrated Endograft System

Background:Aortic dissection is the most serious disease involving the aorta.Stanford classification defines aortic dissection based on the location of the proximal tear: Stanford type A aortic dissection with the proximal tear in the ascending aorta account for 65% of all aortic dissection,and Stanford Type B aortic dissection with the proximal tear located in aortic arch or decending aorta account for 35%.The tear located in the approximately 1/3of the ascending aorta is the most common type of aortic dissection which account for about 30%.In the acute phase,its mortality rate rises by 1% per hour which can cause acute left ventricular dysfunction,followed by multiple organ dysfunction / failure such as lungs and kidneys which greatly increases the risk of open surgery.Once the lesion involing the root of aorta occurs,the prognosis is very poor.The current clinical treatment plan is to receive open surgery as soon as possible and reconstruct the aortic arch,ascending aortic dissection,aortic valve and coronary artery.Due to the long operation time and huge trauma,the patients experienced the double injuries of multiple organ damage and the trauma of open surgery.After surgery,the incidence of multiple organ failure such as heart,lung,kidney,and brain is high.About 28% of patients with ascending aortic dissection involing the aortic root are difficult to tolerate open surgery and have to be treated conservatively with drugs.This group of patients has the highest mortality rate(>90%)and the worst prognosis.Endovascular treatment is gradually becoming the first-line method for the treatment of vascular diseases due to its advantages such as less surgical trauma,fewer complications during hospitalization and fewer days of hospitalization.It has been widely used to treat abdominal aortic aneurysm,aortic arche and descending aortic dissection.However,due to the lack of sufficient proximal anchoring zone and complex anatomy surrounding the root of the ascending aorta(the lesion often involves important structures such as the left and right coronary arteries,coronary sinus and aortic valve),there is currently no internationally-available endovascular treatment for ascending aortic dissection involving aortic root.Our center has proposed for the first time in the world: Jing's valved-fenestrated endograft system,which can reconstruct the the root of ascending aorta of pigs,the surgical success rate is greater than 95%,and the animal can survive for a long time.However,the anatomical structure of the ascending aortic root of pigs is quitedifferent from that of the human body.The ascending aorta of the pig is short which is about 2 cm.Its shape is relatively straight and the arch is narrow.While,the ascending aorta of the human is relatively long which is about 8 cm.Its shape is relatively curved and the arch is relatively flat.Therefore,a more adequate proximal anchoring zone is needed to stabilize the position of the Jing's valved-fenestrated endograft,otherwise the endograft may be displaced under the impact of high-speed blood flow in the ascending aorta.This will cause misalignment of the coronary fenestrations and cause disastrous consequences.Current clinical experience suggests that the appropriate proximal endograft anchoring zone should be around 10mm-15 mm,and the proximal of the ascending aortic dissection involving the aortic root is the left ventricular outflow tract.At present,TAVI surgery using laser-engraved stent-grafts believes that the distance in the left ventricular outflow tract as the graft's proximal anchoring zone cannot exceed 5mm.Excessive implantation of the endograft may cause anterior mitral dysfunction and myocardial electrical conduction disturbances.However,it is currently believed that the laser-engraved stent is harder and more compressive around the myocardium,while the woven stent-graft is softer.Therefore,a woven stent-graft that extends into the left ventricular outflow tract at an appropriate distance may avoid the above complications.This project will improve the configuration of the Jing's valved-fenestrated endograft by the woven stent-graft and focus on the impact of different lengths and oversizing on the anterior mitral valve and myocardial electrophysiological conduction.To find the most appropriate proximal anchoring zone scheme and make it more suitable for clinical cases.Objective:(1)To study the anatomical structure and imaging characteristics of the left ventricular outflow tract of the human heart,and to provide evidence for improving the configuration of Jing's valved-fenestrated endograft and making it more suitable for clinical cases;(2)Improving the configuration of Jing's valved-fenestrated endograft system and completing vitro simulation experiments with human hearts,preliminary verification of the safety and effectiveness of the improved Jing's valved-fenestrated endograft system and exploring the proper expansive length of Jing's valved-fenestrated endograft into the left ventricular outflow tract;(3)Complete the healthy animals' experiments by Jing's valved-fenestrated endograft system,and verify the effects of different oversizing of Jing's valved-fenestratedendografts on the myocardial electrical conduction,and preliminary verification the feasibility and safety of Jing's valved-fenestrated endografts in treating aortic dissection involving the ascending aortic root.Methods:(1)5 cases of human heart specimens were dissected,and the anatomy of the root of ascending aorta and the left ventricular outflow tract were mainly studied.The perimeter,area,longest diameter and shortest diameter of the aortic valve annulus and extending into the left ventricular outflow tract at 5mm,10 mm,and 15 mm were measured by ECG-gating CTA respectively in systolic and diastolic phases.(2)According to the first part of human heart anatomy and imaging data,improve the Jing's valved-fenestrated endograft system and performing human heart in vitro experiment to explore the relationship between the length of the Jing's valved-fenestrated endograft extending into the left ventricular outflow tract and the anterior mitral valve.(3)Based on the second part of the study,exploring the effects of the Jing's valved-fenestrated endograft extending into the left ventricular outflow tract with different oversizing on myocardial electrical conduction by healthy animal experiments.The most appropriate oversizing of the Jing's valved-fenestrated endograft was selected by the ECG at pre-operation and 1 week,1 month after operation.Results:(1)Preliminary understanding of the anatomical structure of the ascending aortic root and left ventricular outflow tract on human heart and the morphological characteristics of left ventricular outflow tract of the patient by imaging data;(2)Initially verify the safety and effectiveness of the improved the Jing's valved-fenestrated endograft system in vitro human heart experiment.At the same time,15 mm is considered that the appropriate proximal extension of the Jing's valved-fenestrated endograft into the left ventricular outflow tract which will not affect the function of anterior mitral valve.(3)Initially verify the safety and effectiveness of the improved the Jing's valved-fenestrated endograft system in healthy animal experiments,and conclude that the10% oversizing of woven stent-graft may not cause severe myocardial electrical conduction disturbances.Conclusion:Preliminary verification of the safety and effectiveness of the improved Jing's valved-fenestrated endograft system by in vitro human heart and healthy animal experiments.It was initially concluded that the 10% oversizing of the woven stent-graft extending into the left ventricular outflow tract to 15 mm will not severely affect the function of anterior mitral valve or myocardial electrical conduction.The improved Jing's valved-fenestrated endograft system will provide new ideas for the treatment of aortic dissection involving the ascending aortic root.