The scope of interventional catheterization in children and adults with congenital heart disease has grown tremendously over the past 40–50 years. Advancements since the mid-1980s have made it possible to delay or, in some cases, avoid open heart surgery for many defects such as pulmonary or aortic valve stenosis, patent ductus arteriosus, and atrial septal defects. With the advent of the 21st century, transcatheter valve replacement of failed surgical valves has introduced exciting new treatment options for patients with congenital heart disease. This rapid progression of catheter-based interventions highlights the need for imaging modalities that complement the interventionalists’ use of traditional x-ray fluoroscopy to safely and effectively perform both simple and complex interventions.
The purpose of this chapter is to discuss the role of echocardiography in facilitating transcatheter interventions in congenital heart disease. In addition, the use of echocardiography in preintervention planning and postintervention evaluation will be briefly reviewed.
Transthoracic (TTE), transesophageal (TEE), and intracardiac (ICE) echocardiography are each useful imaging options that have been well-described for use during cardiac catheterization. The details of image acquisition using these modalities are described elsewhere in this text and will not be repeated herein. However, the value of each modality will be discussed in the context of its advantages and limitations relative to other modalities in certain clinical situations. Table 36.1 provides a general summary of some of these advantages and disadvantages.
PRE- AND POSTPROCEDURE ECHOCARDIOGRAPHY
Because transthoracic echocardiography is the primary modality used to diagnose congenital heart defects, it is likewise the most commonly used modality for preintervention planning. In patients for whom TTE is inconclusive or incomplete in providing the necessary information to the interventionalist, TEE may provide better image quality and resolution, particularly of posterior structures and lesions. However, even with the best preprocedure imaging, some questions regarding the size, location, significance, or amenability of some lesions to intervention may only be answered at the time of catheterization.
Following transcatheter intervention, TTE is almost always the modality of choice for determining whether the lesion was appropriately treated. TTE is also used to assess for pericardial effusion that can result from vascular or myocardial perforation during the procedure.
COMMUNICATION BETWEEN IMAGER AND INTERVENTIONALIST
Except in situations using ICE where the interventionalist is also the echocardiographer, good communication between interventionalist and echocardiographer is vital. In such cases, the efficient and effective use of echocardiography for transcatheter interventions requires the participation of at least two individuals with different perspectives—one performing the procedure and another acquiring echo images. This arrangement works best when both parties have a consistent understanding of the patient’s anatomy and physiology. Furthermore, the information to be communicated between interventionalist and echocardiographer often changes over the course of the procedure, which can complicate the situation. Thus, it is important to use consistent, descriptive terminology that both individuals recognize. Generally this is best achieved by describing the specific lesions of interest both anatomically (e.g., anterior/posterior, superior/inferior, apical/basal) and relative to easily recognizable structures (e.g., atrioventricular valves, coronary sinus, aortic root, superior vena cava). Descriptors such as right, left, up, or down are confusing, as they can be understood in different ways depending upon one’s point of reference. If either person is unclear of what the other is describing, the procedure should be “paused” until they both have a clear understanding of the patient’s anatomy.
ATRIAL SEPTAL DEFECT AND PATENT FORAMEN OVALE (PFO) DEVICE CLOSURE
Device closure of ASD and PFO is one of the most common interventional procedures performed in the congenital catheterization lab. PFOs and most secundum ASDs can be closed safely from a transcatheter approach, obviating the need for surgical intervention. There are three currently available ASD closure devices: the AMPLATZER™ Septal Occluder (St. Jude Medical, St. Paul, MN, USA), the AMPLATZER™ “Cribriform” Multi-Fenestrated Septal Occluder (St. Jude Medical, St. Paul, MN, USA), and the GORE® HELEX® Septal Occluder (W.L. Gore and Associates, Newark, DE, USA).
Both the AMPLATZER™ Septal Occluder (ASO) and the Cribriform device (Fig. 36.1) consist of a semirigid nitinol wire outer frame with an inner Dacron® mesh layer. The outer frame has “memory,” meaning that it can be elongated and drawn into a delivery catheter and yet retain its configuration upon deployment. The configuration of the device is one of a “double-disk” design—a left atrial and a right atrial disk. While the Cribriform device has a narrow waist between the two disks, the ASO has a larger waist of variable diameter. The stated size of the Cribriform device (18, 25, and 35 mm) refers to the diameter of the right and left atrial disks. The size of the ASO (from 4 to 38 mm in varying increments) refers rather to the diameter of the central waist, which generally correlates with the measured size of the ASD being closed. Given the wide range of sizes available, the ASO can in principle be used to close very large defects. However, the presence of a very large ASD often reflects deficiencies in critical atrial septal rims needed to secure the device in place. AMPLATZER™ Septal Occluder devices are contraindicated if there is less than 5 mm of septal rim adjacent to certain anatomic structures: the right upper pulmonary vein, atrioventricular valves, coronary sinus, or inferior vena cava. While deficiency of the retroaortic rim is not an absolute contraindication to use of an AMPLATZER™ device, significant distortion of the aortic root by the device is discouraged.
Figure 36.1. AMPLATZER™ Septal Occluder devices. A: AMPLATZER™ Septal Occluder device on a deployment cable. B: AMPLATZER™ Multi-Fenestrated (“Cribriform”) Septal Occluder device. (Courtesy of St. Jude Medical, St. Paul, MN, USA.)
The HELEX® device also has a “double-disk” design, but different structural characteristics than the AMPLATZER™ device (Fig. 36.2). This device consists of a single nitinol wire frame that loops upon itself during device deployment to a specific diameter (15–35 mm in 5-mm increments). As with the Cribriform device, there is a narrow, negligible central waist between the proximal (right atrial) and distal (left atrial) helical disks. The wire frame is covered in expanded polytetrafluoroethylene (ePTFE), a thin synthetic membrane that serves to occlude the defect. The HELEX® is lighter and more compliant than the AMPLATZER™ Occluder device, but is limited in the size of defects for which it can be used. In general, HELEX® devices can close defects whose maximum diameter is 50% of the device size, rounded up to the nearest millimeter. For example, a 20-mm HELEX® device can close up to a 10-mm defect; a 35-mm device can close up to an 18-mm defect. Unlike the AMPLATZER™ devices, there are no stated contraindications related to the absence of critical septal rims. However, caution should be taken so that the device does not disrupt or distort surrounding structures, such as the atrioventricular valves or aortic root.
Preintervention Echocardiographic Assessment
The role of echocardiography in the assessment of patients undergoing transcatheter closure of ASDs begins in the preprocedure phase with careful patient selection. The primary question to be answered is whether the ASD should be closed. Indications for device closure include evidence of significant left-to-right shunt (manifested by right ventricular enlargement), ischemic stroke suggesting right-to-left thromboembolism, and, in some cases, hypoxia with exertion (orthodeoxia-platypnea).
Figure 36.2. GORE® HELEX® Septal Occluder Device. A: Photo of the GORE® HELEX® Septal Occluder device attached to the delivery system. B: Schematic drawing of the HELEX® device in vivo during deployment across a fenestrated atrial septum. (Courtesy of W.L. Gore and Associates, Newark, DE, USA.)
In most cases, TTE is adequate to diagnose and characterize defects that may be amenable to device closure. As part of the preprocedural assessment, it is important to define that the defect is morphologically an ostium secundum defect. Primum, sinus venosus, and unroofed coronary sinus-type ASDs are not recommended for device closure. Precath TTE is also useful for estimating the number, size, and locations of the defect, which can be useful for anticipating which device could be used for closure. These factors are also important for anticipating risk of complications, such as device embolization or erosion, as well as the possibility of unsuccessful closure. As discussed above, the absence of critical septal rims precludes device closure of certain ASDs (Fig. 36.3, Video 36.1). This information facilitates the discussion of these risks with the patient and family at the time informed consent is obtained.
ASDs can be single or multiple and may coexist with a PFO. The presence of multiple defects does not preclude transcatheter device closure, but recognition of atrial septal fenestration may help the interventionalist anticipate which device(s) may be best suited for use. A fenestrated atrial septum with multiple defects proximal to one another may be closed with a single device. Multiple devices can be used to close fenestrations that may not be close enough to be covered by a single device (Fig. 36.4).
Complete echocardiographic evaluation prior to device closure of ASDs should include an identification of any coexisting structural or physiologic defects that may warrant a surgical approach (e.g., severe tricuspid valve regurgitation) or that may preclude ASD closure altogether (e.g., right-to-left shunting due to Eisenmenger syndrome). Of particular importance is the assessment of pulmonary venous connections. While partial anomalous pulmonary venous connection is most commonly associated with a sinus venosus-type ASD, it can also be seen with secundum defects. The presence of anomalous venous connections is usually an indication for surgical repair, although some cardiologists still advocate for device closure in the presence of a single anomalous pulmonary vein, attesting that a single anomalous vein does not produce a significant left-to-right volume load.
Figure 36.3. Large Secundum Atrial Septal Defect. Short-axis, intracardiac echocardiographic image of a very large secundum atrial septal defect which is not suitable for device closure. There is almost complete absence of the posterior rim (asterisk) but a reasonable retroaortic rim (asterisks). RA, right atrium; LA, left atrium; AO, aorta.
Diagnosis of a PFO is often difficult with standard TTE. Saline contrast injection with Valsalva release can elicit right-to-left shunting of contrast across the PFO that can be appreciated by TTE. With Valsalva release, right atrial pressure exceeds that of left atrial pressure and bubbles from agitated saline pass across the PFO into the left atrium. If TTE is inconclusive, TEE may be necessary. When used, TEE can provide a better anatomic description of the PFO, including whether it has a “tunnel-like” configuration that may make device closure somewhat more difficult.
Indications for closure of a PFO are more controversial. A PFO rarely results in significant shunt volume and ventricular enlargement. Most cardiologists, however, would offer device closure of a PFO if there is evidence of paradoxical embolism with stroke or TIA, or in the context of orthodeoxia-platypnea.
Intraprocedure Echocardiographic Assessment
Echocardiography during device closure of ASDs is extremely useful to confirm the size and location of the defect(s) and feasibility for closure. Depending upon patient size, clinical scenario, and institutional preference, transthoracic, transesophageal, or intracardiac echocardiography can each be used to facilitate device closure. For small children with good acoustic windows and simple ASDs, TTE is often an adequate imaging modality. Which modality is used is typically determined by individual or institutional preference. While TEE and ICE provide excellent image quality for facilitating device closure of ASDs, they each have unique advantages and disadvantages as previously discussed. Our institutional practice has been to use ICE almost exclusively during device closure of ASDs and PFOs.
The first objective of intraprocedure echocardiography is to confirm or correct the findings from preprocedure imaging. Pulmonary venous connections should be assessed by ICE or TEE (described in Chapter 35). The atrial septum should be interrogated, both with two-dimensional echocardiography and color Doppler (Fig. 36.5, Video 36.2). The size of the defect should be defined. The presence of additional fenestrations that may not have been appreciated on TTE should be described. The position of the defect(s) relative to other cardiac structures, such as the IVC, SVC, right upper pulmonary vein, atrioventricular valves, and aortic root should also be detailed. Often “balloon sizing” is used as another method of measuring the size of the defect. With this technique, a soft sizing balloon is passed over a wire across the defect and inflated with dilute radiopaque contrast. As long as the diameter of the balloon at full inflation is larger than the defect size, there will be a distinct waist in the balloon. The balloon is deflated just until color Doppler demonstrates flow through the defect around the balloon. It is then inflated again slightly, just until the flow disappears. The waist of the balloon can be measured by fluoroscopically and by 2D echocardiography. The measurements obtained are then used for selecting the appropriate device type and size for defect closure.
Figure 36.4. Fenestrated Atrial Septum. A, Two-dimensional intracardiac echocardiographic image of multiple defects (asterisk) and a patent foramen ovale (arrow). B: Color flow Doppler showing multiple residual defects (asterisk) during initial attempted closure with a single GORE® HELEX® device (arrow). C: The fenestrations are ultimately closed using two HELEX® devices (arrows). RA, right atrium; LA, left atrium.
ICE or TEE can also provide useful insight into the morphology of PFOs. A PFO with a short segment of overlap between limbus and valve of the fossa ovalis can usually be closed quickly and easily. A longer “tunnel-like” overlap may require more careful device selection or alternative approaches for optimal closure (Fig. 36.6). Balloon sizing is usually not needed, but can be used if a better understanding of the length of the PFO tunnel is desired.
After anatomic evaluation of the defect, echocardiography is used to help with positioning and deployment of the device. Both TEE and ICE provide real-time imaging as the delivery system is advanced across the ASD or PFO. The distal disk of the device is advanced out of the deployment catheter. Echo imaging can be helpful to ensure that the distal disk is in the body of the left atrium, rather than abutting the free wall or in the pulmonary vein or appendage. The device-catheter system is withdrawn until the left atrial disk just abuts the atrial septum, at which time the right atrial disk is exposed. The device at this point is not yet released and can be withdrawn and repositioned or removed if necessary. Echocardiographic imaging confirms appropriate placement of the device and its relationship to surrounding structures. The presence of septal tissue between the two disks should be documented from multiple orthogonal views. In the setting of a deficient retroaortic rim, the disks should be shown to straddle the aortic root without significantly distorting it. Disruption of the integrity of the aortic root may manifest as increased aortic valve regurgitation. Further, the proximity of the device to the mitral and tricuspid valves and the inferior and superior venae cavae should be clearly defined.
Figure 36.5. Secundum Atrial Septal Defect. A: Two-dimensional intracardiac echocardiographic image of a single secundum atrial septal defect (asterisk) with adequate septal rims for device closure. B: Color flow Doppler demonstrating left-to-right shunting through the defect (asterisk). C: Imaging of an AMPLATZER™ Septal Occluder device (asterisk) before device release demonstrates appropriate device position. D: Following device release, color flow Doppler demonstrates small residual shunt through the device, which should close with time. RA, right atrium; LA, left atrium; AO, aorta.
Additionally, the device should be interrogated along its length to look for a residual shunt. Frequently, residual shunts around the device or through the device (in the case of AMPLATZER™ devices) can be appreciated immediately after device placement. Flow through AMPLATZER ™ devices is a normal phenomenon and does not indicate unsuccessful or incomplete closure (Video 36.3). Such residual shunts should resolve with endothelialization of the device. Shunts around the device often resolve over time, as well. However, some degree of shunting may persist, and is more commonly seen with HELEX® devices. This presents a challenging question of whether to reattempt closure with a different device or to allow the residual defect to close over time. In some cases, removal of the first device and closure with a larger device or placement of a second closure device may be warranted.
Upon release the orientation of the device may change, assuming a more “anatomic” position. At this point, it should be reassessed echocardiographically to confirm appropriate and secure position. Any residual shunt should also be documented.
Postprocedure Echocardiographic Assessment
Typically, a transthoracic echocardiogram is performed following device closure of an ASD or PFO prior to patient discharge from the hospital. The objectives of this study are to confirm appropriate device position, stability, and relationship of the device to the surrounding structures, and to document the presence of any residual shunt or thrombus related to the device. Significant residual shunt, device malposition, or device embolization may be addressed in the cardiac cath lab. In addition, the pericardial space must be assessed to look for an effusion that may suggest the presence of erosion or cardiac perforation. A new, significant pericardial effusion requires further assessment, which may include chest CT, TEE, or repeat catheterization to identify a cause. Device erosion warrants emergent surgical removal of the device, repair of the erosion, and closure of the ASD or PFO.
Following PFO device closure this echocardiographic assessment may include saline contrast injection through a peripheral IV with and without Valsalva maneuver to demonstrate the presence or absence of a residual right-to-left shunt. Given the high probability of a small residual shunt immediately following device closure, saline contrast injection is usually not done immediately after the procedure, but can be performed 3–6 months later.
Figure 36.6. Patent Foramen Ovale Closure. A: Intracardiac echocardiography shows a patent foramen ovale with a tunnel-like configuration (arrow). B: Color flow Doppler demonstrates spontaneous left-to-right flow through the foramen ovale (arrow). C: A guide wire (arrow) maintains position across the atrial septum following puncture of the valve of the fossa ovalis (septum primum). D: A GORE® HELEX® device is positioned across the site of puncture, closing the long tunnel foramen ovale. RA, right atrium; LA, left atrium.
VENTRICULAR SEPTAL DEFECT DEVICE CLOSURE
Device closure of ventricular septal defects (VSD) was first described in the late 1980s, but was not widely performed in the United States prior to FDA approval of the AMPLATZER™ muscular VSD (mVSD) occluder in the mid-2000s. Like other AMPLATZER™ devices, the mVSD occluder is a double-disk nitinol frame surrounding a core of Dacron® fabric (Fig. 36.7). The central waist is 7 mm long, accommodating the thickness of the muscular ventricular septum better than the ASO devices. The diameter of the waist represents the device size, which ranges from 4 to 18 mm in 2-mm increments.
Relative to ASD and PFO device closure, transcatheter device closure of muscular VSDs is an uncommon procedure. This is because most hemodynamically significant VSDs are in the membranous or inlet septum, in close proximity to heart valves and conduction tissue. While some membranous VSDs with ventricular septal aneurysm can be safely closed in the cardiac cath lab, device closure of most membranous and inlet VSDs is currently contraindicated. Furthermore, safety concerns prompt many cardiologists to recommend surgical closure of mVSDs in smaller infants.
Preintervention Echocardiographic Assessment
Echocardiographic evaluation of potential candidates for device closure of mVSDs is reasonably straightforward. Given the younger age at which congenital muscular VSDs manifest themselves, TTE is usually adequate for full preprocedure echocardiographic assessment. Recognition of the number, size, and location of the defects can be achieved from multiple echocardiographic imaging planes; parasternal long-axis, parasternal short-axis, and apical four-chamber views are particularly useful. Accurate measurement of defect size can be tricky, because a single defect often appears as multiple defects as it exits the left ventricle and passes through right ventricular muscular trabeculations. Location of the VSDs should be described both by anatomic position (anterior/posterior, basal/apical) as well as by their proximity to the atrioventricular and semilunar valves. Device closure is contraindicated if the defect is within 4 mm of any of the cardiac valves.
Figure 36.7. AMPLATZER™ Muscular Ventricular Septal Defect Occluder Device. (Courtesy of St. Jude Medical, St. Paul, MN, USA.)
Quantification of the hemodynamic effect of the mVSDs is also important for identifying defects that warrant device closure. Significant VSD shunting will manifest either as elevated right ventricular pressure or left heart enlargement. Small muscular VSDs with little shunt and no pressure or volume effect do not require surgical or device closure. Conversely, severely elevated RV systolic pressure in children over 1 year of age, particularly if there is right-to-left shunting across the VSD, should raise concern for irreversible pulmonary vascular disease (Eisenmenger syndrome). These patients also may not be candidates for VSD closure.
Intraprocedure Echocardiographic Assessment
Either TEE or ICE can be used during device closure of mVSDs, depending upon the clinical situation. Simple, mid-septal defects can be well-appreciated with ICE (Fig. 36.8), but apical defects may be better seen by TEE, given the better far-field resolution.
As it is with ASD device closure, the first goal of imaging at the time of mVSD device closure is to confirm the findings from the precath study—number, size, and location of the defects. Once that is achieved, the interventionalist can proceed with device selection and deployment. Typically, the size of the device chosen is determined by an angiographic measurement of the defect diameter. Depending upon image quality, this measurement can be corroborated by two-dimensional echocardiography. Rarely, balloon sizing can be used when angiography does not provide adequate opacification of the defect.
The AMPLATZER™ mVSD occluder is deployed in a similar fashion to the ASO device. The delivery system is advanced over a wire antegrade into the right ventricle and across the defect. The distal (left ventricular) disk is exposed within the left ventricular cavity and the system is withdrawn until the disk contacts the septum. The delivery sheath is then withdrawn over the device, exposing the proximal (right ventricular) disk.
Figure 36.8. Muscular Ventricular Septal Defect. A: Intracardiac “en face” echocardiographic view of a mid-muscular ventricular septal defect (between arrows). B: Color flow Doppler confirms the presence of a single defect.
At this point, with the device deployed but still attached to the delivery cable, reassessment of its position should be performed by echo (Fig. 36.9). Complete resolution of shunt may not be immediate, but significant flow around the device may mean that it is too small and should be replaced with a larger device. Disruption of the mitral valve is uncommon because of the lack of chordal attachments to the ventricular septum. The tricuspid valve, however, does have septal attachments and should be thoroughly evaluated. One should keep in mind that the delivery catheter and cable pass through the tricuspid valve, which may temporarily increase the degree of regurgitation. Therefore, identification of significantly increased tricuspid valve regurgitation should prompt closer investigation of the mechanism of regurgitation to determine whether it is related to the catheter/cable or to the device itself. If the device is the culprit, it should be removed and repositioned.
After the device is released, echocardiographic assessment should be repeated to ensure that the device remains stable with no significant shunt. With the delivery system and cable now removed, valve function should again be reevaluated to confirm that any previously noted increase in tricuspid regurgitation has improved.
Figure 36.9. Muscular Ventricular Septal Defect Device Closure. A: Transesophageal four-chamber echocardiographic view of a mid-muscular ventricular septal defect (asterisk). B: A similar image after placement of an AMPLATZER™ Muscular Ventricular Septal Defect Occluder device (asterisk). The right ventricular disk did not deploy correctly due to muscular trabeculations, but the device was stable and was left in place. RA, right atrium; LA, left atrium; RV, right ventricle; LV, left ventricle.
Figure 36.10. AMPLATZER™ Occluder Devices Used for Fistula Closure. A: AMPLATZER™ Vascular Plug-IV Occluder device. B: AMPLATZER™ Ductal Occluder device. (Courtesy of St. Jude Medical, St. Paul, MN, USA.)
Postprocedure Echocardiographic Assessment
Usually TTE is repeated after device closure prior to hospital discharge. The goals, as with ASD device closure, are to evaluate device position and function and to assess for any pericardial effusion that may have resulted from the catheterization. Device embolization has been reported, but not erosion. So, if present, a pericardial effusion likely represents catheter or wire-induced myocardial trauma rather than device erosion.
CLOSURE OF FISTULAE
Generally speaking, the term “fistula” refers to an abnormal, narrow connection between two anatomic chambers. Fistulous connections of the cardiovascular system may be between two vascular structures (e.g., arteriovenous fistula) or between two cardiac chambers (e.g., left ventricle–to–right atrial fistula), or between a vessel and cardiac chamber (e.g., coronary artery–to–right ventricle fistula, ruptured sinus of Valsalva aneurysm–to–right atrium). The direction of blood flow through the fistulous connection depends upon the relative pressure gradient between the connected chambers throughout the cardiac cycle and can be left-to-right, right-to-left, or bidirectional. The shunt volume is affected both by the resistance of the fistulous connection, which is a function of the diameter and length of the fistula, and by the pressure gradient across the connection. Indications for closure of fistulae are varied and depend upon the hemodynamic effect, as well as the type and location of the fistula. In general, fistulae which produce a significant shunt volume, resulting in distal chamber enlargement, warrant closure. Fistulae with right-to-left shunting, such as pulmonary arteriovenous (AV) fistulae, may be closed to treat systemic arterial desaturation or prevent paradoxical thromboembolism. Coronary artery fistulae often require closure to treat or prevent ischemia due to a coronary “steal” phenomenon as a result of inadequate coronary artery perfusion pressure.
Transcatheter closure of cardiovascular fistulae can be performed with a number of different closure devices, including coils, AMPLATZER™ vascular plugs, or AMPLATZER™ Ductal Occluder devices (Fig. 36.10). Because device selection and placement often involve a complex decision-making process, a detailed discussion is beyond the scope of this chapter.
Preintervention Echocardiographic Assessment
Thorough, preintervention evaluation often begins first with the recognition of a possible fistulous connection. Given the heterogeneity of the type, size, and location of cardiovascular fistulae, echocardiographic recognition can be very difficult. Unexplained enlargement of cardiac structures should raise concern for a significant fistulous connection. Fistulae involving the heart or proximal great vessels that result in a hemodynamically significant shunt, such as an aorta–to–right atrial fistula from a ruptured sinus of Valsalva, are usually easily recognizable by TTE. However, systemic or pulmonary arteriovenous fistulae may be more difficult to identify. In situations where the actual fistula is not seen echocardiographically, one must look for secondary signs of shunting. Dilatation of the superior vena cava with increased Doppler flow may suggest an intracranial AV malformation, just as increased inferior vena caval flow may represent a hepatic AV malformation. Connections resulting in right-to-left shunting can be better localized using saline contrast injection proximal to the presumed location of the fistula, while imaging the pulmonary veins and left atrium. Pulmonary AV fistulae result in the rapid appearance of bubbles in the left atrium shortly after they pass through the right ventricle. Bubbles appearing in the left atrium before they are seen in the right ventricle may represent a systemic-to-pulmonary venous connection. The location of the IV (right arm versus left arm) provides further insight into the location of the anomalous connection.
Coronary-cameral fistulae are often first suspected in the context of unexplained coronary artery dilatation. The high pressure (coronary artery) to low pressure (the distal chamber) connection leads to chronically increased blood flow into the affected coronary artery and, thus, dilatation of the artery. Often color flow Doppler can identify continuous flow through the fistula into the distal, low pressure chamber. The most common sites for coronary artery fistulae are right heart structures—coronary sinus, right atrium, and right ventricle.
While TTE is not always adequate to precisely describe the nature and location of a fistulous connection, it is useful in providing insight into the hemodynamic effect of the shunt. Cardiac chamber enlargement and any abnormal flow patterns should be thoroughly described. TEE may be beneficial when TTE suggests flow through a fistula but is unable to further characterize the connection. Necessary information before proceeding with device closure includes the accessibility of the fistula from a catheter-based approach and its relationship to surrounding structures—AV node, valve leaflets, etc. Additional imaging modalities, such as CT angiography, may be needed to confirm the diagnosis and facilitate care planning.
Intraprocedure Echocardiographic Assessment
As with the previously discussed device procedures, either TEE or ICE can be useful during device closure of intracardiac fistulae. Extracardiac fistulae and AV malformations are often not amenable to optimal TEE or ICE imaging. Traditional angiography is usually adequate to assess these lesions.
With the chosen modality, the echocardiographer first reevaluates the preintervention findings. TEE or ICE will provide more detailed information about the precise location of the fistula, its size, length, and proximity to vital cardiac structures. Though not always possible, the goal of device closure of clinically significant fistulae is to close the abnormal connection without disrupting “normal” surrounding structures. With coronary artery fistulae in particular, it is necessary to identify the “normal” coronary artery branches so that the closure device does not obstruct these smaller branches when placed. Angiography is usually the optimal imaging tool for identifying these smaller branches. It is also important to confirm the number of fistulous connections present. Particularly with coronary artery fistulae, there may be multiple very small connections that can complicate device closure, or make it altogether impractical.
Figures 36.11, 36.12, and 36.13 demonstrate some examples of device closures of various cardiovascular fistulae.
Postprocedure Echocardiographic Assessment
Postprocedure echocardiographic assessment should confirm the absence of significant effusion that may have resulted from trauma to the heart or blood vessels. When possible, the closure device should be evaluated for stability and effect (reduction or absence of shunt). Any evidence of thrombus on or near the device should be described and conveyed urgently to the interventionalist. Closure of coronary artery fistulae requires that particular attention be given to ventricular function, given the possibility of affecting coronary artery perfusion. A noticeable decrease in ventricular function or a change in regional wall motion should raise concern for ischemia, and should prompt reevaluation in the cath lab.
BALLOON ATRIAL SEPTOSTOMY
Balloon atrial septostomy was the first transcatheter intervention performed for congenital heart disease. It was first described by William Rashkind in 1966, and has since become commonly referred to as the “Rashkind septostomy,” or, simply “Rashkind.” Initially described for use in newborns with d-transposition of the great arteries with inadequate atrial-level mixing, the Rashkind septostomy can be used for many different types of congenital heart disease to increase atrial shunting or mixing.
Figure 36.11. Closure of Coronary Artery-to-Coronary Sinus Fistula. A: Two-dimensional intracardiac echocardiographic image of a coronary artery-to-coronary sinus fistula (arrow). B: Color flow Doppler showing shunt through the fistula (arrow). C: Device closure of the fistula using an AMPLATZER™ Vascular Plug-IV. D: Color flow Doppler demonstrates residual shunt through the device. RA, right atrium; RV, right ventricle; CS, coronary sinus; AO, aorta.
Figure 36.12. Closure of Ruptured Sinus of Valsalva Aneurysm. A: Two-dimensional intracardiac echocardiographic image of a sinus of Valsalva aneurysm that has ruptured into the right atrium (asterisk). B: Color flow Doppler demonstrates a significant aorta–to–right atrium shunt. C: Short-axis ICE imaging of the aortic valve shows a wire passing through the ruptured aneurysm (asterisk) into the right atrium in preparation for device placement. D: Color flow Doppler shows the aorta–to–right atrium shunt. E: ICE imaging shows appropriate placement of an AMPLATZER™ Ductal Occluder device (asterisk) within the aneurysm. RA, right atrium; RV, right ventricle; TV, tricuspid valve; SVC, superior vena cava; AO, aorta.
Remarkably, even after almost 50 years, the general technique for balloon atrial septostomy has remained the same. Specially designed septostomy balloons are advanced antegrade into the heart, typically via the femoral vein. The septostomy catheter has an angled tip, allowing the operator to direct it easily across the foramen ovale into the left atrium. With the tip of the catheter in the left atrium, the balloon is inflated with saline (or a saline/contrast mixture if fluoroscopy is used). It is withdrawn slightly until it abuts the atrial septum. A short, swift “jerk” on the catheter pulls the inflated balloon quickly across the septum, enlarging the PFO or ASD (Video 36.4). Occasionally, repeat septostomy with the same or a larger balloon is needed to create an adequate interatrial communication.
Figure 36.13. Closure of a Left Ventricle–to–Right Atrium Fistula. A: Two-dimensional transesophageal echocardiographic imaging from a four-chamber view of a fistulous communication between left ventricle and right atrium (arrow). B: Color flow Doppler demonstrates left ventricle–to–right atrium shunt (asterisk). C: A wire (arrow) is passed from the right atrium into the left ventricle. D: The fistula is closed with an AMPLATZER™ Ductal Occluder device (arrow). RA, right atrium; LA, left atrium; RV, right ventricle; LV, left ventricle.
Preintervention Echocardiographic Assessment
Preseptostomy echocardiography should focus on establishing the diagnosis of cyanotic congenital heart disease that requires either atrial-level shunting or mixing. Once the diagnosis is established, the atrial septum should be evaluated closely to determine whether there is an adequate atrial-level communication. This is easy to do in the presence of either hypoplastic right (e.g., tricuspid atresia, pulmonary atresia with intact ventricular septum) or left heart defects (e.g., hypoplastic left heart syndrome), where restriction at the atrial-level results in a significant pressure gradient between right atrium and left atrium. In situations such as these, color flow and spectral Doppler interrogation of the atrial shunt can be used to estimate this gradient. However, with d-transposition of the great arteries, right atrial and left atrial pressures may be similar, and flow across the atrial septum may be very low velocity and difficult to quantify. In such situations it is important to evaluate anatomic characteristics of the PFO or ASD and the baby’s clinical condition (pulse oximetry, acidosis, etc.). Any concern that the atrial-level mixing may be inadequate should prompt emergent septostomy, which can be life-saving.
Intraprocedure Echocardiographic Assessment
Many institutions perform emergent balloon atrial septostomy at the bedside using TTE guidance. Others perform the procedure in the more controlled environment of the cardiac cath lab. Regardless, TTE is a vital adjunct to performing the procedure safely and effectively. TEE does not provide any reasonable benefit over TTE and only adds time to an already time-sensitive procedure. Under echo guidance, the septostomy catheter is shown across the atrial septum. As the balloon is inflated, echo demonstrates that it is well positioned within the body of the left atrium and not within a pulmonary vein or across the mitral valve (Fig. 36.14). Echo further helps demonstrate adequate apposition of the balloon against the atrial septum prior to septostomy. Following septostomy, echo is used to reassess atrial-level mixing or shunting to determine whether further intervention is necessary. It is also important to assess the mitral valve to ensure that it was not damaged by the procedure. Overly vigorous septostomy, particularly if the atrial septum is thickened, can result in rupture of the pulmonary veins, so the absence of a pericardial effusion should also be demonstrated.
Figure 36.14. Balloon Atrial Septostomy. Subcostal coronal view using transthoracic echocardiography immediately prior to balloon atrial septostomy in a newborn with d-transposition of the great arteries. The balloon (asterisk) is inflated in the left atrium, abutting the atrial septum (arrow), and is shown to not be at risk of damaging the mitral valve or pulmonary veins. RA, right atrium; RV, right ventricle; LV, left ventricle.
Postprocedure Echocardiographic Assessment
Beyond immediate postseptostomy echocardiography, repeated postprocedure assessment by echo is rarely needed. If the clinical situation changes—decreasing oxygen saturation or worsening acidosis—the atrial septum should be reevaluated to ensure that there is still adequate flow across it.
Given the broad diversity of procedures performed in the congenital cardiac cath lab, there are numerous potential situations where echocardiography may be useful to the interventionalist. Beyond the discussion of the more common echo-facilitated interventions above, the following procedures that benefit from adjunctive echocardiography deserve a few brief comments.
Endomyocardial biopsy of the right ventricle is performed from an antegrade transvenous approach. A long sheath is passed across the tricuspid valve, and through it a bioptome is advanced towards the apical septum of the right ventricle. The bioptome has small “jaws” at the tip that grab the endomyocardium. The bioptome is then pulled back into the sheath, tearing off a small amount of tissue for sampling. This is repeated a number of times based upon the clinical indication.
Echocardiography during endomyocardial biopsy serves a few purposes. Biopsy carries a small risk of damage to the tricuspid valve, so valve function should be evaluated prior to biopsy as a baseline to which postbiopsy imaging can be compared. Some cardiologists prefer to use TTE at the time of biopsy to confirm position of the sheath and bioptome before obtaining the tissue sample. This helps to ensure that the sample is taken from the septum (rather than the free wall) below the moderator band, and away from tricuspid valve chordae. After biopsy, echocardiography demonstrates tricuspid valve function. Increased tricuspid regurgitation may represent damage from the bioptome. Severe tricuspid regurgitation often suggests avulsion of chordal structures (Fig. 36.15; Video 36.5). Also, the risk of myocardial perforation warrants evaluation of the pericardial space for the presence of an effusion.
Needle or radiofrequency atrial septal perforation is used for many purposes. It can be used to access the left atrium for hemodynamic measurements or structural interventions. On occasion, the creation of an interatrial communication through an intact septum is needed to relieve elevated left atrial pressure or to support cardiac output in the setting of severe pulmonary hypertension (Fig. 36.16). Echocardiography is not always necessary, but can be very useful to ensure a safe transseptal puncture. In smaller children, TTE usually provides adequate imaging of the atrial septum. ICE is a reasonable alternative in older children and adults.
Septal puncture is almost always performed from a femoral venous approach. Needle puncture is performed through a sheath and dilator together. With the needle withdrawn into the dilator, echocardiography helps to guide the position of the dilator tip to the fossa ovalis. A bicaval or short-axis view is usually optimal for demonstrating the position of the dilator. When the position of the sheath dilator against the fossa ovalis is confirmed, the needle is advanced out the tip of the sheath. Using short, quick jabs, the needle punctures the thin fossa ovalis. Real-time pressure tracings or injection of contrast through the hollow needle helps to confirm that the needle has passed into the left atrium rather than the aorta. The sheath and dilator are then advanced into the left atrium. Echocardiography is usually not needed after simple transseptal puncture has been performed.
Pericardiocentesis to drain a clinically significant pericardial effusion is not an “interventional cath” procedure, per se. However, because it is often performed with echocardiographic guidance, it bears some brief mention here.
Figure 36.15. Endomyocardial Biopsy. A: Transthoracic echocardiography following right ventricular endomyocardial biopsy demonstrates a flail septal leaflet of the tricuspid valve (arrow) damaged during the procedure. B: Color flow Doppler demonstrates severe tricuspid valve regurgitation (asterisk). RA, right atrium; LA, left atrium; RV, right ventricle; LV, left ventricle.
Pericardiocentesis can be performed for diagnostic or therapeutic purposes. Therapeutic pericardiocentesis is done to relieve the hemodynamics of tamponade—restriction to ventricular filling due to the effusion. The purpose of echocardiography is to identify the presence and severity of the effusion and to assess its hemodynamic effect. The ideal imaging plane for sizing the effusion is usually subcostal coronal (Fig. 36.17). This is also the typical approach for pericardiocentesis and placement of a mediastinal catheter. From this approach, the echocardiography can identify a reasonable “target” pocket of effusion towards which to direct the needle. Under sterile conditions and using echo guidance, a long needle punctures the skin below the xiphoid process and is advanced towards the pocket (usually directed towards the patient’s left shoulder) with gentle aspiration on an attached syringe. Puncture of the visceral pericardium should be met with immediate aspiration of fluid. If frank blood is aspirated and there is concern that the needle may have entered the heart, the needle can either be withdrawn slightly, pressure can be transduced through the needle, or a small volume of saline contrast can be injected. Contrast seen within the pericardial space and not in the heart confirms appropriate needle position. When the position of the needle in the pericardial space is confirmed, typically a long wire is advanced through the needle, and the needle is removed. A catheter is then advanced over the wire, usually a side-hole catheter such as a pigtail. Pericardial fluid can then be removed and sent for analysis. If there is concern for reaccumulation of fluid, the catheter can be secured in place for periodic aspiration of fluid. If a mediastinal catheter is not left in place, echocardiography can be performed following pericardiocentesis to ensure that there is no significant reaccumulation of fluid.
Figure 36.16. Transseptal Puncture. A: Transthoracic echocardiography from a subcostal view following transseptal puncture in a child with primary pulmonary hypertension. A wire (arrow) is across the atrial septum. Note the enlarged, hypertensive right atrium. B: Color flow Doppler following creation of an atrial septal defect demonstrates right-to-left shunting (arrow). RA, right atrium; LA, left atrium; RV, right ventricle.
Figure 36.17. Pericardiocentesis. Transthoracic echocardiographic imaging taken just below the xyphoid process shows a large circumferential pericardial effusion (asterisk) prior to pericardiocentesis. RV, right ventricle. LV, left ventricle.
Echocardiography is a vital resource for the interventional congenital cardiologist. Transthoracic, transesophageal, and intracardiac echocardiography can provide invaluable real-time anatomic and physiologic information that can facilitate efficient and safe intervention on children and adults with congenital heart disease.
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1.Following endomyocardial biopsy, which of the following is most important to evaluate echocardiographically?
A.Patency of the vena cavae
B.Right ventricular function
C.Left ventricular function
D.Tricuspid valve function
2.Which of the following echocardiographic modalities is most practical for facilitating balloon atrial septostomy in a child with transposition of the great arteries?
3.Which of the following is a potential advantage of intracardiac echo relative to transesophageal echo?
B.Does not require special training
C.Manipulation of the catheter does not require the operator to “scrub in”
D.Better far-field penetration
E.May not require a second operator other than the interventionalist
4.Which of the following is a disadvantage of intracardiac echocardiography relative to other modalities?
A.Does not have color-flow capabilities
B.Does not have spectral Doppler capabilities
C.Often requires additional vascular access
D.Poor resolution of posterior structures, such as the atrial septum
E.Interferes with fluoroscopic imaging
5.In the presence of which of the following findings would closure of an atrial septal defect using an AMPLATZER™ septal occluder device be contraindicated?
A.Multiple septal fenestrations
B.Retroaortic septal rim measuring 2 mm
C.Coronary sinus septal rim measuring 3 mm
D.Mild-moderate tricuspid valve regurgitation
E.Estimated right ventricular systolic pressure = 40 mmHg
6.Device closure of a ventricular septal defect may be considered in which of the following situations?
A.Inlet muscular VSD
B.Outlet muscular VSD
D.Tiny mid-muscular VSD
E.Muscular VSD below the moderator band
7.During an echocardiogram of an otherwise healthy seven-year-old referred for a murmur, you notice increased flow into the right coronary artery, which is 6 mm in diameter. Which of the following best explains this finding?
C.Giant cell arteritis
D.Traumatic coronary artery dissection
E.Ruptured sinus of Valsalva aneurysm
8.Which of the following imaging views is most useful during pericardiocentesis for a large pericardial effusion?
9.The following image demonstrates which of the following devices in vivo?
A.GORE® HELEX® septal occluder
B.AMPLATZER™ septal occluder
C.AMPLATZER™ muscular VSD occluder
D.AMPLAZTER™ vascular plug
E.AMPLATZER™ ductal occluder
10.A 50-year-old gentleman undergoes device closure of a patent foramen ovale with a GORE® HELEX® septal occluder device. Before discharge, transthoracic echocardiography demonstrates a moderate pericardial effusion that improves over the next week. Which of the following was the most likely cause of the effusion?
B.Excessive IV fluids
C.Renal failure due to contrast
D.Minor catheter or wire trauma
1.Answer: D. Of the choices listed, the greatest risk of endomyocardial biopsy is damage to the tricuspid valve.
2.Answer: A. Balloon atrial septostomy needs to be done quickly and efficiently; TTE is the quickest to set up and perform.
3.Answer: E. ICE can be performed by interventional cardiologists who have been appropriately trained. The remaining choices are not true of ICE.
4.Answer: C. ICE does require an addition intravascular sheath, which is a relative disadvantage.
5.Answer: C. AMPLATZER septal occluder devices are contraindicated in the presence of “deficient” septal rims (<5 mm) to the coronary sinus, atrioventricular valves, right upper pulmonary vein, and inferior vena cava. A deficient retroaortic rim is not a contraindication.
6.Answer: E. Device closure of muscular VSDs is contraindicated if the defect is near to any of the heart valves or if the defect is hemodynamically insignificant. A muscular VSD below the moderator band would be removed enough from the valves that device closure could be considered.
7.Answer: A. Coronary artery dilatation with increased coronary flow and without a significant history should raise concern for a coronary artery fistula.
8.Answer: D. The echo imaging plane for pericardiocentesis should parallel the procedural approach,. usually from a subcostal approach.
9.Answer: B. The parasternal short-axis image demonstrates an Amplatzer septal occluder device closing an atrial septal defect.
10.Answer: D. HELEX devices have not been associated with erosion, and erosion would likely not improve over the course of a week. Minor trauma from a catheter or wire can cause a small perforation in the atria that could heal over the matter of hours to days, resulting in a temporary effusion.