CHAPTER 27 Congenital Percutaneous Interventions

Imaging has always played a key diagnostic role in the management of children with congenital heart disease. During the last 20 years, two major developments in the field have transformed the use of imaging in clinical management: (1) with the development of interventional catheter-based treatment strategies, the majority of common congenital heart diseases are now treated in the catheterization laboratory instead of in the operating suite; and (2) because of the successful treatment of children with congenital heart disease, there are now as many adults living with congenital heart disease as there are children. These changes have led to the evolution and use of imaging techniques to guide procedural treatments applicable to infants, children, and adults. This chapter reviews the common percutaneous interventional procedures for the treatment of congenital heart disease and illustrates the key role that imaging plays in their success.

ATRIAL SEPTAL DEFECT

Description and Special Anatomic Considerations

Secundum atrial septal defect (ASD), one of the more common congenital heart defects, represents 6% to 10% of all congenital anomalies, occurring in 1 in 1500 live births.¹ Secundum ASDs are due to absence, perforation, or deficiency of the septum primum. This defect typically occurs sporadically but has been linked to genetic abnormalities such as Holt-Oram syndrome and mutations on chromosome 5p.

Device closure of an ASD was first performed in 1974 by King and Mills ² with a 24-gauge surgically placed femoral sheath and a double-sided disk device. Technology and technique have been modified and refined over the years; however, the procedure remains conceptually identical. A collapsible double-sided disk device with a metal frame and fabric patches is positioned antegrade through a long femoral sheath (6F to 10F) across the secundum ASD. On extrusion from the sheath, the device expands, creating a patch on both sides of the septum, clamping the rim of tissue surrounding the ASD. The endocardium grows in to cover the device to create a permanent seal. Because of the need for surrounding rim tissue, device closure is limited to secundum-type defects and is not applicable to either primum (no inferior posterior rim) or venosus (no superior rim) ASDs. With recent technologic advances, device closure has rapidly become the treatment of choice for secundum ASDs.

Indications

Device closure is indicated for any size secundum ASD with evidence on echocardiography of right ventricular volume overload. ASD should also be closed in patients with symptoms of exercise intolerance or history of cryptogenic stroke. There is mounting evidence that ASD closure, even in the elderly, can improve maximal oxygen consumption.³ ASDs have been closed by device in small children, including infants; however, the most common timing for elective closure appears to be between 2 and 4 years of age.

Contraindications

There are no absolute contraindications to device ASD closure except for patients with active thrombus in the left atrium and those with a known allergy to the device implant materials, particularly the nickel in the device frames, although this is an extremely rare condition. Patients who are hypercoagulable, particularly those with disorders that predispose to arterial clots, should be considered very carefully as the post-placement risk of clot formation during the endocardialization process may be significantly increased. Patients with significant left ventricular dysfunction also must be monitored closely after the procedure because of the potential for the development of acute left atrial hypertension and resultant pulmonary edema. Diuretics immediately after closure may be helpful in this subgroup of patients. Patients with pulmonary hypertension must be considered carefully but may benefit as long as there is a left-to-right shunt at rest.

Outcomes and Complications

Concurrent controlled trials comparing surgical closure with device closure have shown efficacy rates of more than 96% with significantly lower complication rates and hospital stay.⁴ Most patients can be discharged on the day of the procedure, with return to full activity within 48 to 72 hours, significantly reducing costs and medical resources.⁵ Early complications have been minor and occur in fewer than 9% of patients; they consist primarily of transient arrhythmias, vascular injury, and asymptomatic device embolization. Serious complications have been rare but include thrombus formation on the device, heart block requiring pacing, and cardiac perforation.⁶

Imaging Findings

Preoperative Planning

When an ASD has been diagnosed, complete transthoracic echocardiography should be performed to evaluate the suitability for device closure. This includes specific attention to the pulmonary vein drainage as well as to the size and location of the defect, including tissue rims to the atrioventricular valves, inferior vena cava, right pulmonary veins, aortic valve, and roof of the atrium. If the transthoracic study is inadequate to delineate these structures, OmniPlane transesophageal echocardiography should be performed. Documentation of an adequate atrial septal rim circumferentially (>3 mm, especially at the posterior inferior inlet portion; Fig. 27-1) and evaluation for additional defects, tissue strands, or septal aneurysms with perforations are essential (Fig. 27-2). Identification of all pulmonary veins, particularly the right upper, is essential because of the association of partial anomalous pulmonary venous return with sinus venosus ASD.

FIGURE 27-1 Transthoracic echocardiograms in various planes evaluating size of ASD and presence of surrounding rim tissue. AO, aortic valve; L, liver; LA, left atrium; RA, right atrium; RV, right ventricle.

FIGURE 27-2 Schematic and intravascular echocardiographic images of a patient with multiple ASDs. LA, left atrium; RA, right atrium.

There is current interest in the use of three-dimensional echocardiography as well as MRI for the preprocedure evaluation of ASD. Certainly, these modalities improve detection of an anomalous pulmonary vein and give a more complete understanding of the shape of the defect. This may permit more accurate measurement of the long-axis dimension of the defect, which is helpful for choosing the appropriate type and size of device. Although these modalities give additional information, their clinical advantage in typical ASDs is not proved, and they do add to cost and medical service use. In patients with unusual anatomy, they are invaluable (Fig. 27-3).

FIGURE 27-3 MRI series in a 50-year-old person with dextrocardia, polysplenia, interrupted inferior vena cava with azygos continuation, and large ASD. AoV, aortic valve; LA, left atrium; LPV, left pulmonary vein; LV, left ventricle; MV, mitral valve; RA, right atrium; RPV, right pulmonary vein; RV, right ventricle.

Procedural imaging for device implantation is a combination of echocardiography and biplane fluoroscopy. In my practice, I use surface echocardiography for implantation in children younger than 6 years (Fig. 27-4) and intracardiac echocardiography for older patients (Fig. 27-5). Transesophageal echocardiography is used in older patients in some institutions; however, it necessitates general anesthesia for the procedure. Balloon sizing of the defect is often done and can be useful to detect multiple defects (Fig. 27-6). There has been experimental animal work with active MRI for device implantation (Fig. 27-7), although there has been no human clinical application to date.

FIGURE 27-4 Parasternal short-axis surface echocardiogram guiding delivery of a HELEX device for ASD closure in a 3-year-old child. AO, aorta; LA, left atrium; RA, right atrium.

FIGURE 27-5 Intracardiac echocardiogram guiding delivery of an Amplatzer device for ASD closure in a 16-year-old. LA, left atrium; RA, right atrium.

FIGURE 27-6 Intracardiac echocardiogram assessing test balloon occlusion diameter showing a second ASD. LA, left atrium; RA, right atrium.

FIGURE 27-7 MRI-guided Amplatzer ASD closure in a swine model. AO, aorta; IVC, inferior vena cava; LA, left atrium; MPA, main pulmonary artery; RV, right ventricle; RA, right atrium.

Postoperative Surveillance

The cornerstone of surveillance after implantation remains transthoracic echocardiography. Patients are seen 1, 6, and 12 months after implantation to ensure appropriate device position, to rule out thrombus formation, and to assess right ventricular size and function. In most patients with right ventricular dilation, ventricular size returns to normal by 12 months after implantation. Commonly used devices have different imaging properties by echocardiography and radiography (Fig. 27-8). There have been frame fractures after implantation in certain devices (STARFlex and HELEX); therefore, chest radiography or, if necessary, fluoroscopy is needed at 6 to 12 months of follow-up (Fig. 27-9). MRI (Fig. 27-10) and CT can be used to image septal devices after implantation but have not shown additional clinical utility to date.

FIGURE 27-8 Series of images showing a photograph (top row), lateral radiograph (middle row), and four-chamber echocardiographic image (bottom row) of the three most common devices currently available for ASD closure: HELEX (left column), Amplatzer ASO (middle column), and STARFlex (right column).

FIGURE 27-9 Lateral chest radiograph showing fracture of the two superior arms of the right atrial disk in a STARFlex device 6 months after implantation.

FIGURE 27-10 MRI of a 5-year-old child showing complete closure of a large ASD with an Amplatzer septal occluder device. LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle.

PATENT FORAMEN OVALE

Description and Special Anatomic Considerations

Device closure of patent foramen ovale (PFO) was first described in 1987 ⁷ for the prevention of recurrent stroke associated with paradoxical embolus.⁸ It has also been used to prevent right-to-left shunting causing desaturation in patients with orthodeoxia-platypnea syndrome.⁹ The foramen ovale is a flap valve in the atrial septum created by overlap of the superior anterior septum secundum on the inferior posterior septum primum (Fig. 27-11). It is present in all fetuses during development to direct oxygenated venous return from the placenta through the inferior vena cava across the atrial septum, bypassing the right ventricle and unexpanded lungs, to fill the left ventricle, allowing optimal cerebral perfusion. After birth, with redistribution of flow due to lung expansion resulting in an increased left atrial pressure, the PFO closes and seals permanently in 65% to 80% of people, age dependent.¹⁰ However, in 20% to 35% of the normal population, the foramen ovale does not fibrose closed and remains patent, allowing unidirectional flow from right to left if right atrial pressure exceeds left atrial pressure. This is physiologically insignificant for most people unless the amount of right-to-left shunting is significant, causing orthodeoxia-platypnea syndrome, or an embolus crosses right to left, resulting in a cryptogenic transient ischemic attack or stroke. Approximately 55% of patients who have had a stroke have a PFO,¹¹ suggesting that it plays an important role in some of these patients.

FIGURE 27-11 Right atrial left anterior oblique and caudal angiogram showing the most common PFO anatomy. LA, left atrium; RA, right atrium; SVC, superior vena cava.

During the last 14 years, interventional device closure of PFO has become an attractive alternative therapeutic strategy to surgical PFO closure or lifelong anticoagulation for stroke prevention. No controlled comparative studies with these other treatment strategies exist for PFO closure, although several active multicenter protocols in stroke patients are currently comparing device closure with medical therapy for prevention of recurrent stroke. Good comparative data from the ASD literature suggest that the efficacy of device closure of ASD is similar to that of surgical closure, with a significant reduction in complications, hospital stay, recovery time, and medical resource use.⁴

Indications

Potential indications for PFO device closure include any patient who has had or has substantial risk for a cryptogenic stroke in the setting of a PFO. Absolute indications for PFO device closure remain controversial because there are limited controlled data comparing different treatment strategies and evaluating long-term follow-up. However, several clinical situations clearly warrant device closure, including patients with active venous thrombosis in the setting of a cryptogenic stroke, patients with recurrent cryptogenic stroke while they are receiving anticoagulation, patients with recurrent cryptogenic stroke and contraindications to anticoagulation, and scuba divers who have had significant decompression sickness but insist on continuing to dive. On the basis of current data, PFO device closure may be a reasonable therapeutic alternative for patients with an initial cryptogenic stroke and no additional risk factors.

Contraindications

There are no absolute contraindications to device PFO closure except for patients with active thrombus in the left atrium and those with a known allergy to the device implant materials, particularly the nickel in the frame, although this is extremely rare. Patients who are hypercoagulable, particularly those with disorders that predispose to arterial clots, should be considered very carefully as the post-placement risk of clot formation on the device during the endocardialization process may be significantly increased. However, those patients who are predisposed to venous clots may be the very patients who benefit the most in the long term, albeit with a potentially increased thrombus risk during the first 6 months after implantation. Patients who require anticoagulation long term for other issues may obtain limited benefit from device closure.

Outcomes and Complications

Procedural success with PFO device closure is 98% to 100%, with complete closure rates of 51% to 96% at 6 months on evaluation by saline contrast transesophageal echocardiography.¹²^,¹³ Recurrent neurologic event risk after PFO device closure is 1% to 2% annually, with a 96% 1-year and a 90% to 94% 5-year event-free rate.¹²^,¹³ These results are significantly influenced by selection of patients because some patients who undergo device closure may have recurrent strokes unrelated to either the PFO or the device. More definitive information about recurrent stroke risk will be available from controlled randomized trials now under way comparing device closure with medical therapy. Procedural complications are uncommon, occurring in fewer than 2% of patients; they include stroke, transient ischemic attack, transient myocardial ischemia (these three due to air or clot embolism with the large delivery sheaths in the left atrium), device malposition or embolization, cardiac perforation with tamponade, and local femoral vein injury.¹² Late complications include atrial arrhythmias in 4% of patients, although most are mild and require no treatment,¹⁴ and thrombus formation on the device.