Atrial septal defect
Indications
Device closure of an atrial septal defect (ASD) is indicated for patients with secundum defects less than 38 mm in diameter, who have evidence of right ventricular volume overload, and do not have associated cardiac abnormalities that would otherwise be better suited to a surgical approach ( Fig. 19.1 ). Coexistent conditions that might prompt consideration of surgical repair include severe atrioventricular valve insufficiency or anomalous pulmonary venous drainage. Patients with severe pulmonary hypertension (pulmonary artery [PA] systolic pressure more than two-thirds systemic) or patients with significant left ventricular diastolic dysfunction may need special investigations before closure is performed. Meticulous hemodynamic catheterization with determination of Qp:Qs ratio and pulmonary arteriolar resistance is necessary in the patient with significant pulmonary hypertension. In patients with suspected severe left ventricular diastolic dysfunction, it may be prudent to measure the left atrial or pulmonary capillary wedge pressure with temporary balloon occlusion of the ASD, avoiding closure in those with a substantial rise in left heart filling pressures. The advice of a congenital heart disease specialist or pulmonary hypertension specialist may be desirable.
AHA guidelines
| ASD should be diagnosed by imaging techniques, with demonstration of shunting across the defect and evidence of right ventricular volume overload and any associated anomalies | I | C |
| Closure of an ASD either percutaneously or surgically is indicated for right atrial and right ventricular enlargement with or without symptoms. ( Level of Evidence: B ) | I | B |
| Closure of an ASD, either percutaneously or surgically, is reasonable in the presence of 1) paradoxical embolism (Level of Evidence: C) or 2) documented orthodeoxia-platypnea (Level of Evidence: B) | IIa | B/C |
| Closure of an ASD, either percutaneously or surgically, may be considered in the presence of net left-to-right shunting, PA pressure less than two-thirds systemic levels, pulmonary vascular resistance (PVR) less than two-thirds systemic vascular resistance, or when responsive to either pulmonary vasodilator therapy or test occlusion of the defect (patients should be treated in conjunction with providers who have expertise in the management of pulmonary hypertensive syndromes) ( Level of Evidence: C ) | IIb | C |
| Patients with severe irreversible pulmonary arterial hypertension (PAH) and no evidence of a left-to-right shunt should not undergo ASD closure ( Level of Evidence: B ) | III | B |
Devices
Currently approved devices include the Amplatzer Septal Occluder (ASO), the Amplatzer Cribriform Occluder (Abbott Laboratories, Abbott Park, IL), and the Gore Cardioform devices (W. L. Gore and Associates, Flagstaff, AZ) ( Fig. 19.2 , Table 19.1 ). The ASO is a self-centering device and sized by the waist between the right and left atrial discs. It is suitable for defects up to 38 mm in diameter. The Amplatzer Cribriform device is designed for covering multiple or fenestrated defects in the atrial septum. It is not a self-centering device and is sized by the external diameter of the equal-sized left and right atrial discs. The Gore Cardioform device is also noncentering and sized by the external diameter. Because of a lack of a self-centering mechanism, the Cardioform device, available up to 30 mm in diameter, can only be used for closing ASDs up to about half this size, or 17 to 18 mm. Recently, the Gore Cardioform ASD Occluder has been approved by the Food and Drug Administration (FDA) for ASDs sized 8 to 35 mm in diameter. This device is self-centering and similar in construction to the Gore Septal Occluder.
| Device Sizes | Defect Sizes | |
|---|---|---|
| Amplatzer ASD | 4-38 mm | Up to 38 mm |
| Amplatzer Cribriform | 18, 25, 35 mm | Fenestrations <35 mm |
| Gore Cardioform Septal Occluder | 15, 20, 25, 30 mm | Up to 15-17 mm |
| Gore Cardioform ASD Occluder | 27, 32, 37, 44, 48 mm | 8-35 mm |
Preprocedural imaging
Transesophageal echocardiography (TEE) is most commonly employed to define the size, shape, and tissue rims of the ASD in the adult patient. A rim dimension of 5 mm or greater is ideal. A search for multiple or fenestrated defects is important. Examination of the pulmonary veins and determination of right ventricular systolic pressure, atrioventricular valve regurgitation, and left ventricular (LV) diastolic function are also important, the latter especially in adult patients with heart failure. Right ventricular enlargement is a hallmark of right ventricular volume overload and should be present if the ASD is hemodynamically significant. Catheterization and hemodynamic measurements are usually not required, unless there is significant pulmonary hypertension or evidence of LV diastolic dysfunction.
Procedural imaging
Intraprocedural echo guidance can be performed with TEE or with intracardiac echo (ICE). The latter obviates the need for general anesthesia but does require additional venous access. Confirmation of the defect size and rims is most important, and balloon sizing with a compliant sizing balloon may provide additional information on defect size if echo imaging is not adequate. During and after device deployment, careful examination of the device discs for proper positioning, lack of prolapse from the left atrium to right atrium, and evaluation of a residual shunt are mandatory.
Procedural aspects
Femoral venous access is achieved; rarely does one need arterial access. An 8F or 10F ICE catheter is positioned in the mid-right atrium. The ASD is usually crossed with a balloon catheter and guidewire or occasionally a multipurpose catheter and guidewire. After heparinization to an activated clotting time (ACT) of 200 seconds or greater, an extra-stiff Amplatzer exchange wire is positioned in the left or right superior pulmonary vein, and a delivery sheath—and subsequently a closure device—is advanced across the atrial septum into the left atrium. The left atrial disc is deployed, the entire apparatus is pulled back against the atrial septum, and the right atrial disc is deployed. After echocardiographic imaging demonstrates suitable device position (i.e., no significant residual edge shunting and no interference with adjacent cardiac structures), the device can be deployed.
Device sizing may be performed in several ways. Most defects are elliptical in shape. For defects of moderate size and well-established rims, dimensions may be measured echocardiographically in two planes, usually long and short axis. Alternatively, a “stop-flow” technique may be used with a contrast-filled balloon inflated just enough to stop shunt flow on the echocardiogram. The orthogonal dimensions of this balloon can be then measured fluoroscopically and echocardiographically. It may be difficult to measure the exact dimensions in larger defects or those with deficient rims using the stop-flow technique. Three-dimensional echocardiographic imaging performed preprocedurally may be useful in these patients. An ASO of 2 to 6 mm larger than the defect diameter is selected, usually reserving the larger size for defects with floppier or thinner rims. The Amplatzer Cribriform Occluder has no centering component and must be placed in a fenestration, which allows coverage of other nearby defects; therefore the echo should be used to measure the maximum distance between fenestrations, and a device larger than this dimension should be chosen (with the largest device being 35 mm). The Gore Cardioform Septal Occluder device is similar in function and could be placed in a fenestration or in a defect just over half of its diameter (i.e., 30-mm device for 17- to 18-mm defect). The Gore Cardioform ASD Occluder is placed similarly to the ASO.
Difficult deployment may occur in patients with deficient rims, especially the anterior or retroaortic rim. Alterations in angulation of the device using a modified delivery catheter or placement of the guidewire in the right upper pulmonary vein may be required. There are other various techniques, including pulmonary vein deployment of the left atrial (LA) disc, and balloon-assisted technique. The assistance of an experienced pediatric interventional cardiologist may be useful with larger defects. Proctoring will be necessary for the initial use of these devices.
Complications
Deairing a long sheath placed in the left atrium can be problematic, but this long sheath is required for the Amplatzer devices. Air embolism usually manifests as chest pain and ST-segment deviation from air entering the right coronary artery or, less commonly, as neurologic symptoms. An air embolus can be avoided by careful catheter flushing and avoidance of developing an air–fluid level in the catheter hub. This is best achieved by keeping the hub of the catheter low on the table. A thrombus developing on the guidewire or device during implantation can be avoided by adequate anticoagulation. Atrial fibrillation can occur during device implantation or shortly thereafter and is usually self-limited. If spontaneous resolution does not occur, cardioversion should be done.
Device embolization can occur with larger defects, particularly when the rims are small, absent, or floppy. Embolization can occur either into the left atrium and arterial system or into the pulmonary artery. It is best avoided by proper device sizing and careful inspection of the device seating before full release after deployment. Embolized devices can be retrieved with a snare and large-bore sheath in most cases. Typically, a sheath at least 2F larger than the original delivery system will be needed, and a bevel cut into the tip may facilitate bringing the snared device into the retrieval sheath. Device erosion is a rare complication of the Amplatzer device. It occurs in 0.1% to 0.2% of cases, and is likely related to apposition of the LA disc against the LA wall or aorta. There is some relation to device oversizing and deficiency of the retroaortic rim, and careful imaging before and after deployment is warranted. Figs. 19.3 to 19.5 and Video 19.3 demonstrate ASD closure.
Follow-up
Our current practice is an outpatient or one-night hospitalization with rhythm monitoring and transthoracic echocardiographic imaging after device placement to evaluate device position and to rule out pericardial effusion. Aspirin therapy and endocarditis prophylaxis are recommended for 6 months. Patients then are typically followed up at 6 months with another limited echocardiographic examination and then annually.
Procedural steps for ASD closure
