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.