In the intervention of atrial septal defect, it is often encountered that when the blocker is released, the blocker cannot be clamped on both sides of the atrial septal defect, and part of the blocker enters the right atrium and gets stuck in the middle of the atrial septal defect hole, which is called “unbuttoning” of the blocker. This phenomenon is called “unbuttoning” of the blocker. It is mainly seen in large septal defects, septal defects with short margins, and septal defects with thin margins. Because the blocker does not reach the desired site accurately, repeated adjustments of the blocker position are required, and the number of intra-atrial manipulations of the catheter, sheath, and blocker is high and the operation time is long, increasing the risk of thromboembolism and atrial wall perforation. The recognition of this phenomenon and the understanding of its management play an important role in improving the success rate of interventional treatment of atrial septal defects and reducing the incidence of complications, which are sometimes related to the success or failure of treatment. This article briefly introduces the phenomenon of unbuttoning and the treatment methods.
I. Awareness of the unbuttoning phenomenon
1, the mechanism of the phenomenon of unbuttoning
The main reason for the unbuttoning phenomenon is the relationship between the size of the atrial septal defect and the diameter of the blocker, which is easy to occur if the blocker is small. In addition, short margins on one side of the septum or soft margins, especially thin margins of the septal defect, are also common reasons for the unbuttoning phenomenon. When the blocker is retracted intraoperatively, a part of the left atrial disk of the blocker is dislodged into the right atrium, so that the blocker is not placed on either side of the atrial septal defect, but stuck in the middle of the defect.
2. Imaging characteristics
Under ortho-fluoroscopy, the blocker is I-shaped and there is resistance to retraction. In the left anterior 45 degree plus head-to-angle 25 degree projection position, the blocker failed to present an I-beam shape parallel to the atrial septum.
3.Ultrasound characteristics
Ultrasound was performed on the apical four-chamber cardiac view and on the subxiphoid two-atrial heart with the blocker stuck in the atrial septal defect. The blocker failed to hold on the aorta in the short-axis aortic view.
II. Treatment
1.Left atrial intracardiac shaping technique
The operation steps are to place the delivery sheath in the left atrium, release the left atrial disc, gently push the blocker and hold it against the atrial wall, fix the sheath and continue to push out the blocker until the posterior part of the blocker is about 1-2cm inside the delivery sheath, then quickly pull back the delivery sheath and blocker toward the right atrium, and the blocker quickly springs back and is added to both sides of the atrial septal defect. This method is often effective when repeated pushing of the blocker cannot reach the desired position.
2. Application of a delivery sheath.
A specially designed long sheath, available in 10F and 12F, has a double bend at its distal end and two posterior bends that help to angle the left atrial disc to the atrial septum. Under ultrasound and X-ray guidance, if the left atrial disc starts to be placed in an unsatisfactory position, the blocker is included in the sheath, the sheath is turned against the clock to point the distal end downward in a posterior direction, and the left atrial disc is released again to ensure that it is parallel to the atrial septum.
3.Left upper pulmonary vein method
It can be applied to most patients with large atrial septal defects. The delivery sheath is placed in the left superior pulmonary vein, the blocker is delivered to the distal end of the sheath tube without exiting the sheath tube, and then the left atrial disc of the blocker is released in the right superior pulmonary vein by withdrawing the sheath tube, the blocker is in a long gourd shape, continue to withdraw the delivery sheath tube, the waist of the blocker and the right atrial disc are released at the right atrium, and the left atrial disc is rebounded by gently pulling back and pushing forward the delivery rod, and the two discs are clamped on both sides of the septal defect. When applying, care should be taken not to insert the sheath too deep and too shallow; if it is deep, when releasing the blocker, the left atrial disk piece of the blocker is too much in the pulmonary vein and not easily rebounded; if it is shallow, the left atrial disk of the blocker slips into the left atrium when releasing. Therefore, the appropriate depth should be grasped. Generally to enter into the pulmonary vein about 1.5cm.
4.Right upper pulmonary vein method
When the left upper pulmonary vein method cannot successfully place the blocker, the left upper pulmonary vein method can be chosen. The method to enter the right upper pulmonary vein is to deliver the sheath and place it in the left atrium, and turn the sheath against the clock. Alternatively, it is safer to enter the right superior pulmonary vein through the catheter and guidewire before feeding the delivery sheath along the guidewire. After the delivery sheath is placed in the right superior pulmonary vein, the procedure is the same as that for the left superior vein. The left atrial disc and waist of the blocker form a sphere in the pulmonary vein. When the sheath reaches the right atrium, the right atrial disc is quickly released and the blocker is gently pulled and pushed forward, which is seen to bounce rapidly and the blocker is rapidly deformed and clamped on both sides of the septal defect.
5 .Catheter-assisted method
After releasing the left atrial disc, a dilating tube is fed through the atrial septal defect orifice to reach the left atrium, and the anterior upper part of the blocker is held against the blocker when releasing it to prevent it from dislodging into the right atrium. Once the right atrial disc is released, withdraw the auxiliary sheath tube.
6. Balloon-assisted technique
It can be applied to the interventional treatment of large atrial septal defects. The balloon is filled at the septal defect during blocker release to make the large septal defect relatively smaller and to provide support to prevent the blocker from dislodging into the right atrium.
7. Right coronary guiding catheter-assisted technique
It is generally used for blockers smaller than 16 mm. The blocker is preloaded into the 8F right coronary guiding catheter, and then the blocker and guiding catheter are fed through the delivery sheath placed in the left atrium to the front end of the delivery sheath, which is retracted into the inferior vena cava to ensure that the guiding catheter is in the left atrium. This technique is only used in pediatric patients.
The application of the above techniques has improved the success rate of interventional treatment of atrial septal defects, and complications arising from the application of these techniques have not yet occurred, suggesting that the correct application of these techniques is safe. It is worth trying in clinical practice.