The clear images of TEE[9、10] and the ability of displaying the intracardiac structures in real time cause TEE to act as the eyes of the surgeon. Preoperative TEE can be performed to accurately evaluate VSDs and related conditions, and the TEE doctor and surgeon discuss the selection of an appropriate surgical plan and an occluder. Intraoperative TEE can performed precise position and effectively guide device to close the VSDs and can reduce the operative time, increase the success rate of surgery, and reduce the risks. Postoperative TEE can immediately be performed to carefully and comprehensively evaluate and ensure the success and safety of the procedure.
The process of the guide wire advancing into the left ventricle from the right ventricle through the defect is key to the success and the determinant of the procedure duration. If the puncture site in the right ventricular surface is positioned incorrectly, the guide wire is difficult to enter the left ventricle. The puncture site must be relocalized. If the localization is accurate, and the shape of the PmVSD is appropriate, the process of the guide wire advancing into the left ventricle ventricle can be completed within a few seconds. However, the puncture site must be avoid being located near the coronary artery to prevent damaging the coronary artery. The surgeon can see the coronary artery through the ultraminimal incision. Such result cause a certain angle between the puncture site and the VSD inevitably, and can increase the difficulty of the procedure. If the angle is too wide, the intercostal incision can be appropriately extended.
PmVSDs have a variety of shapes due to hyperplasia of the right ventricular fibrous tissue and the adhesion of tricuspid valve. The defects can have an irregular tunnel-like shape, multiple shunts orifices in the right ventricular side, and various directions of blood flow. In this situation, it is more difficult to perform the PmVSD closure via the LPUMI incision under the guidance of TEE. When selecting a puncture site, it is necessary to consider that the site can facilitate the guide wire to entering the left ventricle through the defect. Completion of the closure is fully dependent on the monitoring and guidance of TEE and the experience of the TEE doctor and surgeon. Skillful cooperation is critical to the success. Sometimes, the two orifices in the AMS are far apart and even form a flat angle. In this condition, both the orifices and the VSD presented at a 90° angle. If the guide wire is completely aligned with a orifice, it is not difficult to insert the guide wire into AMS, but it is very difficult to enter the left ventricle by 90° rotation. Under the guidance of TEE, a puncture site and direction is selected with a certain angle with both the VSD and the shunt orifice to make easier of inserting the guide wire into the left ventricle (Fig. 2A). In “S-shaped” or “semiannular” tunnel-like membrane defects, it is necessary to frequently adjust the direction of the guide wire tip to pass the defect. During the procedure, the TEE doctor guides the surgeon according to the TEE images to change the directions of the guide wire in real time and to advance the guide wire smoothly to pass these unusual defects. With patience and tacit collaboration, experienced TEE doctor and surgeon can complete some challenging PmVSD’s device closure.
When the delivery sheath was advanced into the left ventricle, TEE was used to guide the sheath to reach the left ventricular outflow tract but not to contact the aortic valve or the anterior mitral leaflet during the cardiac cycle to prevent valve damage. It must be noted that the device can only be released if the delivery sheath is located in the left ventricular outflow tract. If the device is released in the left atrium, mitral orifice, or aorta, it is likely to cause damage to the valves and/or the chordae tendineaes, resulting in mitral or aortic regurgitation. one child undergoing the procedure in the early stage of this study had a small amount of mitral regurgitation after surgery, beceace the delivery sheath was inserted too deeply and deployment of the left disk of the device caused the rupture of chordae tendineae.
According to the TEE results, the appropriate occluder is selected to avoid device displacement or residual shunts caused by an undersized device and to avoid aortic regurgitation and TR caused by an oversized device. If the upper edge of the PmVSD is less than 2 mm from the aortic valve, it is recommended to use an eccentric device to close the VSD. However, it is difficult for TEE to assess defects and measure distances occasionally due to irregular shapes caused by adhesion of the right ventricular fibrous tissue and tricuspid valve. And it may lead to unsuccessful closure. In our study, a patient with a PmVSD size of 6 mm by TTE measurement underwent finally VSD repair under CPB because mild to moderate AR was present after the VSD was closed with a #7 concentric occluder or a #7 eccentric occlude in turn. Another patient with a PmVSD size of 5.5 mm by TTE measurement underwent finally VSD repair under CPB because the #6 or #8 concentric occluder was detached or migrated respectively, during the push-pull maneuver, and an obvious residual shunt was present.
During device closure of a tunnel-like defect, TEE showed that the occluder resembles a “mushroom pedicle”, indicating that the right disk was still located in the tunnel and has not been fully deployed. The surgeon necessarily retracted the right disk and pulled tensely the sheath to fully deploy the right disk. After the deployment of the device disks was completed, the device was tested by the push-pull maneuver under TEE guidance to ensure successful closure of the VSD.
When the interventricular septum at the edge of the VSD is thin, a residual shunt can be present within the device. When the device disks can not cover all of the shunt holes in the right ventricular septum, a residual shunt can be present at the its edge. At this moment, the residual shunt condition should be carefully evaluated, and the appropriate treatment method should be selected according to the size and the flow rate of the residual shunt. If the residual shunt at the edge of the device is > 2 mm with high-speed flow, a larger device should be selected, or repair surgery should be performed under CPB. A small residual shunt (≤ 2 mm [16] with a flow rate < 2.5 m/s) can all be cured spontaneously. In this study, it is found that in children with multiple shunts orifices in AMS, even a small residual shunt with flow velocity > 2.5 m/s exists after occluder, the device can be released if the device is stable. And the residual shunt tends to heal gradually. The right ventricular outflow tract obstruction significantly decrease during the 4th month’s follow-up. It may be related to the shape of the device getting better with heart beats and right ventricular outflow tract widening with growing .
Limitations
This study was limited by being a single-center study. Our hospital is a children’s hospital and the age of the research subjects was between 10 months and 127 months old. This study is not a prospective randomized study, we just reviewed the previous results and draw the conclusion about the important value of TEE.