Mid-Term Follow-up Of Left Atrial Appendage Occlusion During Off-Pump Coronary Artery Bypass Grafting And A Study Of A Novel Left Atrial Appendage Clip System

Part Ⅰ:Mid-Term Follow-up of Left Atrial Appendage Occlusion during Off-pump Coronary Artery Bypass Grafting in patients with Atrial FibrillationBackgroundAtrial Fibrillation(AF)is one of the most common arrhythmias in patients.The morbidity of atrial fibrillation increases with the age.Hemodynamic disturbances occur in patients with AF,and lead to atrial thrombosis,which significantly increases the risks of thromboembolic events.The most common source of thrombus in AF patients is Left Atrial Appendage(LAA).The LAA is an accessory structure of embryonic primitive left atrium.It’s a about 1.5～4cm long,with a smooth comb-like muscle in endocardial surface.It’s narrow,blind and tubular in shape.Meanwhile,the LAA also act as a volume regulator,hormones secretion and electrocardiographic conduction for left atrium.Closure of LAA may cause the changes in hemodynamic and electrolyte.In patients with AF during cardiac surgery,LAA closure is thought of as a mandatory procedure for prevention of cerebral embolism.Jeff S Healey started a study on Left Atrial Appendage Occlusion Study(LAAOS I)during Coronary Artery Bypass Grafting(CABG)in 2005,which is aborted due to the high rate of residual shunt.And then studies on LAAOS Ⅱ and LAAOS Ⅲ started on cardiac surgery.But these three LAAOS excluded the off-pump cardiac surgery.Coronary artery disease is one of the most common diseases,and about 6%～11.2%patients combine with AF.Until now,no studies on Off-Pump Coronary Artery Bypass Grafting(OPCABG)were reported now.Due to the lack of study in LAAO during OPCABG.Comparative studies between OPCABG with or without LAAO,the safety and effectiveness of LAAO in stroke prevention were evaluated,the different effects on hemodynamics and electrolyte were observed.The clinical experience will be summarized to provide guidance and reference for future clinical works.ObjectivesTo investigate the effect of LAAO during OPCABG on thromboembolic events;to understand the effect of LAAO on hemodynamics and electrolyte.Methods189 patients with a history of AF who underwent OPCABG were selected during March 2018 and March 2020,in whom 109 were males and 80 were females.The patients were 65.38±8.29 years old.According to the procedure of LAAO or not,the patients were divided into LAAO group(n=92 patients)and non-LAAO group(n=97 patients).And according to the different strategies of occlusion,the LAAO group were divided into clipping group and ligation group.The patients’ clinical data and followup results were collected.Patients were followed up by recording for stroke,changes in echocardiography,hemodynamic changes and electrolyte changes at 3 months,6 months,12 months and 24 months after discharge.The relevant data were statistically analyzed;the baseline characteristics,surgical outcomes and follow-up results were compared between different groups and subgroups.Results1.There were no difference in baseline data at sex,age,weigh,CHA2DS2VASc,medical history and so on(P>0.05)Compared with the non-LAAO group,the LAAO group significantly reduced the incidence of postoperative thromboembolic events.But no difference in operation time and perioperation complication.2.Compared with the ligation and suture group,the LAA clip has a higher rate of complete closure and reduces the risk of postoperative thromboembolic events.3.Compared with the non-LAAO group,the LAAO reduced postoperative systolic blood pressure and reduced the dosage and type of antihypertensive medication after one month and six months discharge,thus contributed to the management of blood pressure.It does not reduce the patient’s cardiac function and ejection function,and did not increase the patient’s dizziness and weakness and other symptoms of hypotension.Conclusions1.Compared with the non-LAAO group,the LAAO group significantly reduced the incidence of postoperative thromboembolic events.LAAO during OPCABG is safe,simple and effectively with low complication.3.Compared with the ligation group,the clipping group has a higher rate of complete closure.4.Compared with the non-LAAO group,the LAAO group reduced the type of antihypertensive medication,thus contributed to the management of blood pressure.Part Ⅱ:A Study of a Novel Left Atrial Appendage Clip SystemBackgroundThe LAA is the main site of thrombus formation in patients with atrial fibrillation.The LAAO technique is one of the common techniques for thromboembolic prevention.With the development of minimally invasive cardiac surgery and video-assisted thoracoscopic surgery.LAAO is becoming acceptable and popular.Due to the different locations,size and morphology of LAA,the current LAA clip(LAAC)system is not applicable and needs to be modified.In order to improve the flexibility and feasibility of LAAC implant to patients with isolated AF.A novel LAAC system was introduced.The preliminary animal trial was carried out to test the stability and safety in canine models,which would provide guidance for clinical use in future works.ObjectivesThe LAAC system was improved on the basis of previous products.The safety and effectiveness of the LAAC system will be tested in vitro and canine models.The data will be collected before and after the LAAO.The influence of hemodynamics and electrolytes after the LAAO will be analyzed.MethodsThe design and improvement of the novel LAAC system:Based on the different location,angle,size and morphology of LAA,the delivery system,release system,size and other structures of the LAAC system were modified.The physical,chemical and biological properties were tested.The test of LAAC system in vitro:the LAAC system was tested in a model with thoracic skeleton and porcine heart.The feasibility of LAAC system for different morphology of LAA were tested.And the steering and flexibility were tested,and the tightness of the endocardial surface was also tested.The test of LAAC system on animal:24 Labrador canines underwent LAAO with the new device.The LAAC were deployed via a minimal incision in the left 3rd or 4th intercostal space.The tightness of the LAAC was tested during the operation.The canines were euthanized at postoperative 7 days,60 days,90 days and 180 days.The LAA,heart,liver and kidney were observed by direct observation and histological examination.The progress of endothelialization was analyzed.The baseline,blood test,urine test and biochemistry were analyzed.ResultsA novel LAAC system was designed based on previous systems.The LAAC can be released from the different accesses and angles after the joint adjustment.The adjustment of LAAC can achieve a better alignment with LAA and a better LAAO.The physical,chemical and biological characteristics conform to the requirement of LAAO.The occlusion was achieved with a LAAC size 2-4mm larger than the root of LAA in vitro.All clips were tightly fixed in position.No displacement and residual shunt were found.The process is safe and no impingement on the surrounding structures was detected.LAAO were carried-out in 24 canines via a left minthoracotomy incision.The clips were applied successfully in all canines.The LAA necrosis at 7-day postoperatively.The endothelialization completed within the first 3 months.Atrophy of LAA occurred in the first 3 month.Fibrosis formed at the rest of LAA.ConclusionThe novel LAAC is well manipulated with a satisfied occlusion rate.It is beneficial for the video assisted thoracicscopic surgery and minimally invasive surgery.The LAAC is safe and effectively in animal trials.Part Ⅲ The Application Value of 3D Reconstruction of LAA in Left Atrial Appendage OcclusionBackgroundThe LAAO has been applied to clinic for preventing stroke due to AF.A specific assessment of LAA is needed before LAAO.The previous technique for LAA examination for LAA examination mainly depends on TEE.But it’s difficult for TEE to evaluate the morphology and location of LAA.With the application and development of CT scan and computer techniques,the 3D reconstruction technique was widely used in endovascular repair of aortic dissection and Transcatheter aortic valve replacement.With the aid of Materialise Mimics and 3D technology,we reconstructed the LAA and its surrounding structure.According to the segmentation analysis of heart chamber,the LAA structure and function can be measured,providing a more accurate evidence before operation.ObjectivesTo reconstruct a 3D-LAA image by Materialise Mimics software(Materialise HQ,Leuven,Belgium).The morphology and function of the left atrial appendage were analyzed by cavity separation technique.This provided an accurate clinical evidence for LAAO.Methods30 patients who underwent LAAO were selected from march 2021 to march 2022.The imaging data were collected during the CT examination.According to the 3D-reconstruction of heart chamber and LAA,the function and morphology of LAA were analyzed,so was the risk of thromboembolic event.ResultsThe 3D reconstruction technique gives a specific,directly,dynamically image for patients and doctors.The anatomy inside and outside of LAA were visualized before the operation.The 3D reconstruction helps to analyze the data of LAA precisely.The neck of LAA was measured 21.63±3.36mm in diameter,the depth of LAA was 24.93±3.85mm,the maximum volume of LAA is 8.19±1.14ml,the mean ejection fraction is 25%±12%.ConclusionWith the help of Materialise Mimics,it is easy to reconstruct the structure of LAA.The data from the 3D-module is useful in the procedure of LAAO.It helps the surgeon to select a proper sized LAAC and a proper located incision for the deployment of LAAC.