Discussion
Patients with atrial fibrillation (AF), which is the most common arrhythmia, have an increased risk for stroke (9) ranging from 2% to >10% per year, depending on additional risk factors (10). As a result, AF is responsible for 15% to 20% of all ischemic strokes (11).
The mortality and disability rates of atrial fibrillation are high, which seriously threatens the life and quality of life of patients. Anticoagulation or NOACs is the choice of therapy, but due to the existence of anticoagulant contraindications and other factors, some patients refuse or are not allowed drug treatment.
The Cox maze procedure is now a routine surgical procedure for AF, whether combined with other surgical procedures or lone AF. For nonvalvular atrial fibrillation, thoracoscopic PVI with bipolar radiofrequency prevents recurrence of paroxysmal AF (69%-91% freedom from arrhythmias at 1 year) (12-14). Sinus rhythm without severely symptomatic recurrences of AF is found in up to 70% of patients with paroxysmal AF, and around 50% in persistent AF (15). Therefore, neither surgery nor catheter ablation can completely cure atrial fibrillation, and patients are still at risk of embolization complications. Long-term oral anticoagulants can also lead to uncontrolled bleeding complications.
According to the statistics, more than 90% of thrombi of patients with non-valvular atrial fibrillation originate in the left atrial appendage. In recent years, many clinical studies home and abroad have shown that LAAO can reduce the risk of stroke in patients with atrial fibrillation. A multicenter clinical study of 110 patients showed that treatment with LAAO can reduce the risk of stroke, major bleeding, and death compared with other therapeutic strategies (16).
The regular 2D transesophageal echocardiogram can show each side of the LAA, enabling observation of the presence of a thrombus and measurement of its largest and least diameters and the depth of the LAA. However, there is no imaging advantage for an LAA with a complex structure or different opening forms.
Three-dimensional TEE can be used to quickly obtain a perpendicular LAA section, and the multi-section surface can display the diameter of the LAA opening in real time, reduce the steps required during surgery, and shorten the measurement time. It can directly image the complex anatomical structure of the LAA and display its shape, internal structure, and thrombus (17) in 3D images. Therefore, it plays an important role in screening patients, selecting a suitable plugging device, and ensuring the sealing effect.
After the successful release of the plugging device, TEE can evaluate its position and residual shunt at multiple angles and on multiple planes. More importantly, TEE can dynamically display the changes in the above observation indexes during the pushing and pulling experiment in real time.
In order to make full use of the advantages of TEE, we have been able to complete percutaneous endocardial LAA occlusion under the guidance of TEE alone, avoiding the radiation of doctors and patients (18). In the cases of thoracoscopic radiofrequency ablation, we also performed percutaneous LAA occlusion guided by TEE. However, there was still a risk of cardiac injury or even pericardial tamponade due to the long operation path of atrial septal puncturing and occluder releasing. Therefore, we improved the method of the LAA occlusion. The left pulmonary vein ablation incision was used to implant the device of LAA occlusion through the epicardial membrane under the guidance of thoracoscopy and TEE. The improvement is more intuitive, of which the path is shorter, and the risk of bleeding is significantly reduced.
Although the left atrial appendage can be treated through ligation, resection and suture, and even auricular clamp, the left atrial appendage has various structural variations and is not completely isolated from the type of broad substrates, which makes the surgical approach unable to completely isolate the left atrial appendage. Moreover there was evidence to suggest that residual LAA flow or incomplete LAA exclusion could increase stroke risk (19).
With the maturity of radiofrequency ablations of atrial fibrillation assisted by thoracoscopy, the success rate is also increasing. At present, Wolf surgery is performed in our center on the front line of the 4th intercostal axillary line on the right and the 3rd intercostal axillary line on the left. For patients with the need for closure of the LAA, ligation or clamping of the LAA performed through the epicardial membrane can be directly assisted by thoracoscopy. The advantage of this method is that it reduces the operating path and takes less time than the femoral vein route. Since the direction of the implanted closure is in the body to the opening of the left atrium appendage, the direction of releasing the occluder must also be in the reverse direction of the femoral vein pathway, and only the Amplatzer device currently has such characteristics. During the operation, special attention should be paid to placing the purse-string sutures as far as possible away from the base part to allow maximum space for the release of the two sealing plates. Otherwise, it will lead to the release of the fixed disc of the sealing device, part of which is outside the epicardial membrane, causing bleeding. A Prolene line can be put in place before the sealing device is implanted. The purpose of this line is to fix the sealing device to the outer cardiac membrane after its release, so as to prevent its displacement. A pericardial pad or felt pad can be added to the epicardial surface to prevent rupture of the heart due to tension of the occluder.
For this modified LAA occlusion, we encountered some initial difficulties. For example, the conveying and releasing system of the Amplatzer device were prepared for percutaneous LAA occlusion, but this method did not need too long conveying and releasing system, so we shortened the conveying sheath and releasing cable, so that it could adapt to this improved method. In addition, the choice of the sealing devices should not be too large, which can just block the opening of the left atrial appendage. Otherwise, bleeding may occur because the left atrial appendage is not deep enough to expose the oversized fixed disc to the outside of the purse.