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 Mills² 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.

Description and Special Anatomic Considerations

Device closure of patent foramen ovale (PFO) was first described in 1987⁷ 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.

Imaging Findings

Preoperative Planning

Because most patients undergo PFO device closure for prevention of stroke recurrence, it is essential to evaluate the patient’s prior neurologic events and to ensure that they were cryptogenic and likely related to the PFO. Stroke associated with paradoxical embolism is a diagnosis of exclusion, so it is imperative to rule out other potential causes of stroke including cerebral aneurysm, carotid or vertebral vessel abnormalities, atrial arrhythmias, left atrial appendage thrombus, cardiomyopathy, and a hypercoagulable state. Standard pre–device closure evaluation includes head and neck MRI or MRA; carotid ultrasonography; saline contrast transesophageal echocardiography with Valsalva maneuver (Fig. 27-12); and hypercoagulable screen, including proteins C and S, antithrombin III, factor V Leiden, prothrombin 20210, methylenetetrahydrofolate reductase (MTHFR), anticardiolipin antibody, and homocysteine. This work-up is essential to help guide decisions about the appropriateness of implanting a device and the optimal medical strategy during the endocardialization process. If there is controversy about the presence or size of the PFO, a saline contrast transcranial Doppler study of the middle cerebral artery with Valsalva maneuver is sensitive,¹⁵ allowing quantification of the amount of right-to-left shunting. The test is not specific to a PFO; pulmonary arteriovenous malformations will also result in a positive test result. Because of a small incidence of atrial arrhythmias after device placement, a baseline electrocardiogram should also be obtained.

FIGURE 27-12 Four-chamber transthoracic echocardiogram with saline contrast injection. Left, No right-to-left shunting at rest. Right, Repeated saline injection with Valsalva maneuver demonstrates large right-to-left shunt through the PFO. LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle.

Procedural imaging includes fluoroscopy with or without echocardiography, most commonly intracardiac imaging. Unlike for an ASD, the angiogram must be performed in the right atrium to demonstrate the right-to-left shunting, best shown on profile in the lateral plane (75 degrees left anterior oblique and 5 degrees caudal; see Fig. 27-11).

Description and Special Anatomic Considerations

Patent ductus arteriosus (PDA) is the persistence of a normal fetal connection between the proximal descending aorta and the proximal left pulmonary artery that allows the right ventricle to bypass the lungs and pump deoxygenated blood through the descending aorta to the placenta for oxygenation. Normal ductal closure occurs within the first 12 hours after birth by contraction and cellular migration of the medial smooth muscle in the wall of the ductus, resulting in protrusion of the thickened intima into the lumen, causing functional closure. Final closure with creation of the ligamentum arteriosum is completed by 3 weeks of age; permanent sealing of the duct by infolding of the endothelium, disruption of the internal elastic lamina, and hemorrhage and necrosis in the subintimal region lead to replacement of muscle fibers with fibrosis. This process of closure is incomplete in 1 in 2000 live births and accounts for up to 10% of all congenital heart disease.¹⁶

PDA was one of the first congenital heart lesions treated by interventional techniques, first reported by Porstmann in 1967.¹⁷ There have been substantial refinements in devices and techniques during the last 35 years, but for the last 15 years, interventional catheter treatment has been the preferred therapy in most large centers worldwide. It is a particularly attractive technique in adults, in whom surgical ligation and division can be a problem because of calcified ductal tissue and increased surgical risks. The technique is simple, consisting of placement of a device or vascular occlusion coil in the PDA either antegrade from the femoral vein or retrograde from the femoral artery. Once it is implanted, the device physically occludes ductal flow, and during the first 6 to 8 weeks after implantation, endothelial overgrowth covers the device or coil from both the pulmonary artery and aorta, sealing the PDA permanently closed.

Several different closure devices are currently used because of the significant variability of ductal anatomy. The most common anatomic shape is conical with a large aortic ampulla that narrows at the pulmonary artery end; however, other distinct anatomic forms exist, including “tubular” without a narrowing at the pulmonary artery end, “complex” with narrowing at both the aortic and pulmonary ends, and a short “window” that is an anatomy commonly found in adults.¹⁸ Different closure tools and techniques may be needed to effectively address these less common PDA anatomic subtypes. The most commonly used technique for closure of PDAs less than 2.5 mm is retrograde placement of embolization coils. For large ducts, antegrade placement of an Amplatzer duct occluder device is the preferred method.

Indications

PDA closure is indicated in all patients with left atrial or left ventricular enlargement due to left-to-right shunting or pulmonary artery pressure elevation. Small PDAs that do not result in hemodynamic effects are still at risk for the development of endocarditis. Controlled trials comparing antibiotic prophylaxis with device closure for the prevention of endocarditis have not and will not be performed because of the limited number of patients and the low incidence of endocarditis. There have been no late reports of endocarditis after interventional closure of the ductus, although procedural infections have occurred rarely. Current clinical recommendations are for device or coil closure in small PDAs if they are audible on physical examination.

Contraindications

Patients with systemic pulmonary hypertension and right-to-left ductal shunting should not have the PDA closed. If pulmonary hypertension is noted during catheterization, an accurate assessment of the degree of hypertension and the reactivity of the pulmonary bed must be made during temporary occlusion of the ductus. A second venous sheath should be placed so that simultaneous pulmonary artery pressure measurement and pulmonary vascular resistance calculations can be made while balloon occlusion of the PDA is performed. If there is a baseline left-to-right shunt and a decrease in pulmonary artery pressures with balloon occlusion, ductal closure is indicated.

Outcomes and Complications

Transcatheter ductal closure procedural success has been extremely high, with rates of complete closure above 96%.^19,20 The procedure takes approximately 2 hours, with discharge within 6 hours. Full activity may resume within 48 hours of the procedure. No anticoagulation or antiplatelet therapy is recommended after the coil closure procedure, although most centers recommend daily aspirin for 4 to 6 months after Amplatzer duct occluder or device closure. Procedural complications are uncommon, occurring in fewer than 5%.^19,20 Hemolysis causing anemia may occur if a residual shunt is present after closure with either coils or a device and requires repeated catheterization with placement of additional embolization coils. The major complication associated with coil closure of the PDA is coil embolization to the lungs; however, this is a technical issue that occurs at or immediately after implantation, and the incidence significantly decreases with the operator’s experience. It is related to either undersizing of the coil or malposition on placement. In all but a very few patients, the coils can be snared from their embolized position in the pulmonary artery and removed from the body without sequela. Device embolization, thrombus, and ductal aneurysm have been reported in fewer than 1%.

Imaging Findings

Preoperative Planning

A complete physical examination and thoracic echocardiography are necessary to make the diagnosis before intervention. Transthoracic echocardiography will show an abnormal systolic left-to-right color flow jet into the main pulmonary artery or proximal left pulmonary artery directed inferiorly and anteriorly. The central pulmonary arteries will be dilated, as will the left atrium and left ventricle if the shunt is significant. The ductus itself can be imaged from the left parasternal area. Pulmonary artery pressure estimate can be obtained with the PDA Doppler flow velocity. The hemodynamic significance of the PDA can be assessed by measurement of retrograde flow in the descending aorta (Fig. 27-13). In the adult, in whom echocardiography imaging may be poor, MRI should be performed to demonstrate the PDA anatomy clearly. Unusual variations of the ductus arteriosus include origin from the inferior aspect of the transverse arch and from the proximal innominate or subclavian artery (Fig. 27-14). These are usually associated with more complex forms of congenital heart disease. The anatomy of the ductus can vary significantly; the most common is conical, with the narrowing at the pulmonary artery end (Fig. 27-15). The ductus in the adult tends to be short or window-like (Fig. 27-16) and may have significant calcification. These various ductal anatomies can all be closed interventionally but require a variety of closure devices (Fig. 27-17).

FIGURE 27-13 Left, Parasternal echocardiographic image of a PDA with Doppler assessment of diastolic left-to-right flow into the main pulmonary artery (MPA). Right, Doppler assessment of the descending aorta (DAO) with significant retrograde flow.

FIGURE 27-14 Descending aortic (DAO) angiogram in an infant with right aortic arch and PDA arising from the left innominate artery supplying the left pulmonary artery (LPA). LCA, left carotid artery; LSCA, left subclavian artery; RCA, right carotid artery; RSCA, right subclavian artery.

FIGURE 27-15 A series of lateral descending aortograms showing a variety of ductal anatomies, all amenable to interventional closure.

FIGURE 27-16 Lateral angiogram in a 65-year-old patient showing a short window-like ductus arteriosus, commonly seen in adults. DAO, descending aorta; MPA, main pulmonary artery.

FIGURE 27-17 Series of lateral descending aortograms after interventional closure of various ductal anatomies. Upper left, Coil closure. Upper right, Amplatzer duct occluder I. Lower left, Amplatzer duct occluder II. Lower right, STARFlex device.

Postoperative Surveillance

The majority of patients can be discharged on the same day or the next morning after the procedure. Predischarge evaluation should include a physical examination to assess for recurrence of ductal murmur (it will have disappeared with successful closure) and sheath insertion site. If a murmur is present or there is concern of device or coil positioning at the time of closure, imaging of the ductal device is necessary, either chest radiography or echocardiography. Uncommon but significant complications associated with ductal closure include proximal left pulmonary artery stenosis and mild coarctation related to device protrusion, both of which can and should be evaluated by echocardiography. If left pulmonary artery stenosis is confirmed on echocardiography, a nuclear medicine pulmonary flow scan should be obtained to evaluate the physiologic significance of the obstruction. After device placement, endothelialization occurs during the first 6 to 12 weeks. Although it is uncommon, development of a small leak next to the coil (Fig. 27-18) or device can occur (<1%), so follow-up echocardiography at 4 to 6 months after closure is critical to ensure complete closure.

FIGURE 27-18 Lateral angiogram of a 2-year-old child after single coil closure of a moderately sized PDA. Left, Residual leak through the ductus over the superior edge of existing coil. Right, Complete closure after placement of a second coil. DAO, descending thoracic aorta.

Description and Special Anatomic Considerations

Balloon dilation and more recently stent repair are becoming the treatments of choice for coarctation of the aorta in many centers in older children and adults. Coarctation is most often a discrete narrowing of the proximal descending thoracic aorta just distal to the origin of the left subclavian artery at the site of the ductus ligamentum. It represents 7% of all patients with congenital heart disease and results in upper extremity hypertension, left ventricular hypertrophy, and eventually ventricular failure if it is left untreated. Hypoplasia of the distal transverse arch occurs in up to 10% of patients. Although it is much less common, coarctation of the distal thoracic aorta or abdominal aorta does occur, often in association with vasculitis or genetic syndromes such as Williams syndrome. It should be considered during the initial evaluation of systemic hypertension and can easily be diagnosed on physical examination by decreased femoral pulses with a delay compared with radial pulses and blood pressure differential between the arms and legs. A 2/6 systolic ejection murmur can often be heard at the left upper sternal border and over the left side of the back. The narrowing is due to thick intimal and medial ridges that protrude posteriorly and laterally into the aortic lumen.²¹ Intimal proliferation and elastic lamina disruption occur distal to the ridges because of the high-velocity jet impact on the distal aortic wall. Cystic medial necrosis with disarray and loss of medial elastic tissue occurs commonly in the adjacent aorta and may extend to the ascending aorta as well. It is this abnormality that may lead to late aneurysm formation. The body’s compensatory response to coarctation is the development of vessels that bypass the obstruction, collateral vessels from the innominate, carotid, and subclavian arteries that connect to the thoracic aorta below the level of the coarctation, often connecting through the intercostal arteries. Enlargement of the intercostal arteries due to this collateral flow is the mechanism for rib notching seen on chest radiography in older patients with severe native coarctation.

Indications

Any coarctation with a gradient of more than 10 mm Hg and significant upper body hypertension or left ventricular hypertrophy without additional cause should be treated. For mild coarctation, it is imperative to use stent implantation to ensure complete resolution of the mild obstruction. Mild coarctations with a gradient of less than 20 mm Hg without hypertension or left ventricular hypertrophy should be considered for stent repair if collaterals are present or the patient has an abnormal blood pressure response to exercise. Patients with coarctation gradients of more than 20 mm Hg at rest even without upper body hypertension should be repaired. Patients with mild coarctation (<20 mm Hg) without upper body hypertension should have blood pressure checks every 6 to 12 months with ongoing surveillance for the development of left ventricular hypertrophy.

Contraindications

Patients with coarctation gradients of less than 20 mm Hg with no evidence of collateral flow, hypertension, left ventricular hypertrophy, or abnormal blood pressure response to exercise do not need treatment. Patients with significant hypoplasia and obstruction of the transverse aortic arch in the area of the origin of the carotids should be excluded. Stent repair with jailing of the carotids may be appropriate in the rare patient at extremely high surgical risk; however, for the majority of patients with this lesion, surgical repair should be performed. Any patient with an existing aneurysm should also be cautiously considered. Covered thoracic stents may have a role in this setting, although there are limited data at present. Aortic wall dissection, aneurysm, and rupture associated with stent implantation are uncommon but increase in frequency with the age of the patient and the degree of aortic calcification associated with the coarctation.²² These patients must be considered carefully, and covered stent implantation versus surgery should be considered.

Outcomes and Complications

Balloon dilation for treatment of coarctation was first performed in the early 1980s in children with good success in both native and postoperative recoarctation.²³ Its efficacy in adults was found to be similar to that in children²⁴; however, there remained a small but significant failure rate with residual gradient of more than 20 mm Hg in approximately 15% of patients treated. Stent implantation for repair of coarctation was performed sporadically in the early 1990s in children; it was first reported in adults in 1995 with very promising results.²⁵ Since that time, stent repair has become the treatment of choice for coarctation in many centers because of the improved success rate and low restenosis rate, although controlled trials are not available. Procedural success has been reported in more than 95% of patients, with residual obstruction of less than 20 mm Hg. Recurrent stenosis has been extremely rare, occurring in fewer than 5%, usually in younger patients, and is generally mild. Complications have been reported in up to 20% and include aneurysm, perforation, stroke, and death in fewer than 3%.²⁶ In addition, femoral artery complications including arteriovenous fistula and pseudoaneurysm have been reported in association with the larger arterial sheaths required for the procedure.

Imaging Findings

Preoperative Planning

Echocardiography is useful to confirm the diagnosis and to evaluate location and severity of the obstruction. However, spatial resolution is limited, particularly in older adolescents and adults, so to determine exact anatomic dimensions, either thoracic CT or MRI (Fig. 27-19) is needed. MRI gives the added benefit of assessment of the severity of obstruction as well as the significance of collateral flow (Fig. 27-20). Special attention should be paid to the surrounding aortic diameter, including the distal transverse arch, the coarctation diameter, and the location relative to the carotid and left subclavian arteries, as well as to the presence of existing aneurysm, poststenotic dilation, and calcification. Final assessment of the coarctation is performed during the procedure with biplane angiography, including during and after balloon dilation or stent implantation (Fig. 27-21).

FIGURE 27-19 Three-dimensional reconstruction of MR angiogram in a patient with severe discrete native coarctation of the aorta.

FIGURE 27-20 A, MRI series in a teenager with coarctation assessing proximal and distal vessel magnitude and phase to calculate flow. B, Flow data from images in A indicate significant collateral flow bypassing the area of coarctation, with greater flow seen in the distal thoracic aorta than immediately after the site of coarctation.

FIGURE 27-21 Serial lateral ascending aortic angiograms in a 16-year-old with coarctation: left, discrete coarctation; middle, platinum bare-metal stent implant; and right, resolution of obstruction after implantation.

Postoperative Surveillance

Most patients are discharged on the day after the implantation or dilation, and chest radiography should be performed before discharge to ensure stable stent placement. Because late aneurysms may occur in up to 7% as late as 10 years, ongoing imaging surveillance is required. Current recommendations are for CT or MRI scan 6 to 12 months after implantation (Fig. 27-22). If an aneurysm is detected, annual evaluations are required. If no aneurysm is detected, repeated imaging every 4 to 5 years is recommended.

FIGURE 27-22 Cardiac CT in 16-year-old girl several years after stent repair of native coarctation.

Description and Special Anatomic Considerations

Balloon dilation of segmental pulmonary artery stenosis with stent repair of more proximal lesions has become the standard of care because of limited and challenging surgical success. Branch pulmonary artery stenosis is a rare congenital lesion in isolation but is often associated with complex congenital heart lesions after surgical repair, especially tetralogy of Fallot. Other associated lesions include truncus arteriosus or pulmonary atresia with ventricular septal defect after right ventricle–to–pulmonary artery conduit placement, transposition of the great arteries after arterial switch repair, and pulmonary artery sling after reimplantation. Branch pulmonary artery stenosis decreases perfusion to the affected lung and, if severe, causes hypertension in the nonaffected lung and right ventricle. Distal pulmonary artery stenosis promotes pulmonary insufficiency, which compounds the decrease in cardiac output and increased workload on the right ventricle seen in these patients. Patients can be asymptomatic with right ventricular hypertension but often present with exercise intolerance.

Indications

The systolic gradient across branch pulmonary artery stenosis is, in isolation, a poor determinant of the need for treatment and can be interpreted only by also considering quantitative pulmonary flow data. Normal distribution of pulmonary flow is 55% to the right lung and 45% to the left lung. Patients with a reduction of more than 15% of flow or an absolute flow of less than 1 L/min/m² in the affected lung should be considered for stent repair. Patients with any degree of contralateral pulmonary artery hypertension, right ventricular hypertension, or right ventricular hypertrophy should be aggressively treated to prevent progression, as should patients with significant pulmonary insufficiency associated with the branch pulmonary artery stenosis.

Contraindications

Adult patients after repair of complex congenital heart disease such as tetralogy of Fallot or truncus arteriosus are complex, often with multiple anatomic, hemodynamic, and arrhythmia issues in addition to their branch pulmonary artery stenosis. It is critical that these patients are evaluated completely and that a comprehensive plan is made in coordination with a cardiologist familiar with congenital heart disease and involving an electrophysiologist, cardiothoracic surgeon, and interventionalist. If surgical revision of the underlying repair is required, a surgical approach to the branch pulmonary artery stenosis may be preferable.

Outcomes and Complications

Balloon dilation of branch pulmonary artery stenosis was initially described in 1983 by Lock and colleagues²⁷; however, only 50% of lesions responded, with a significant restenosis rate. With the availability of larger peripheral stents in the early 1990s and their application to pulmonary artery branch stenosis,²⁸ stent placement has rapidly become the treatment of choice in school-age children and adults because of improved success and low restenosis rates. Shaffer and coworkers²⁹ reported results in more than 130 children and adults with postoperative branch pulmonary artery stenosis; in more than 65%, stent implantation increased lesion diameter by more than 100%, with a median gradient reduction from 46 to 10 mm Hg and right ventricle–to–systemic pressure ratio reduction from 60% to 40%. Long-term results have been excellent, with restenosis rates below 5%. Complications are rare, occurring in fewer than 4% of cases overall, and include hemoptysis, aneurysm, perforation, refractory ventilation-perfusion mismatch, and death. Technical issues, such as device malposition and embolization, have been reported in less than 2% and are quite rare with recent improvements in balloon and stent technology. Recent use of cutting balloons has further improved results to more than 90% success for segmental pulmonary artery stenosis resistant to standard dilation and stenting techniques.³⁰

Imaging Findings

Preoperative Planning

Echocardiography allows accurate assessment of tricuspid regurgitation, right ventricular hypertrophy and dilation, and pulmonary insufficiency before the procedure. It is limited in the evaluation of proximal pulmonary artery stenosis and poor in the evaluation of segmental branch stenosis. MRI, CT, and angiography (Fig. 27-23) remain the best imaging for anatomic stenosis information in the pulmonary arteries. In addition to anatomic information, physiologic information of relative flow to pulmonary segments is crucial before the procedure for interventional decision-making. This should be assessed with either nuclear medicine pulmonary flow scan (Fig. 27-24) or MRA. These flow data are critical and must be coupled with anatomic and pressure data at the procedure to optimize clinical decision-making.

FIGURE 27-23 Anteroposterior angiogram in the left pulmonary artery of an 8-year-old girl with severe subpulmonary artery segmental stenosis due to a chronic thrombotic disorder.

FIGURE 27-24 Nuclear pulmonary flow scan in a child with severe proximal right pulmonary artery stenosis before and after stent repair showing a marked increase in flow to the right lung.

Postoperative Surveillance

Postoperative type and frequency depend on the type and location of treatment (angioplasty alone versus stent implantation) as well as on the presence of vessel injury or aneurysm after treatment. For proximal pulmonary artery lesions treated with balloon angioplasty alone, echocardiography coupled with pulmonary flow scan evaluation at 4 months, then yearly thereafter, is adequate. For more distal stenosis with stent implantation, CT angiography is optimal for imaging, although cardiac MRI (Fig. 27-25) can be used (artifact will depend on stent type—currently both stainless steel and nitinol stents are commonly being used). Nuclear medicine pulmonary flow scan evaluation yearly is needed if flow data cannot be accurately obtained by MRI. If an acute aneurysm develops with the procedure early (Fig. 27-26), more frequent CT or MRI is required during the first year to ensure no progression.

FIGURE 27-25 Left, Axial black blood MRI images of a 5-year-old child 1 year after right pulmonary artery (RPA) stainless steel stent repair. Right, MRA reconstruction. Note the stent artifact in the proximal right pulmonary artery.

FIGURE 27-26 Lateral angiograms in the main pulmonary artery (MPA) of a 3-year-old child with proximal left pulmonary artery stenosis: left, angiogram before dilation; middle, balloon dilation; and right, after dilation, showing a significant aneurysm extending to the origin of the left upper lobe segment (LUPA). LLPA, left lower lobe segmental branch.

Description and Special Anatomic Considerations

Pulmonary valve implantation for pulmonary insufficiency is an active area of development in percutaneous treatment of congenital heart disease. Pulmonary insufficiency with associated right-sided heart dilation and dysfunction is a common occurrence late after repair of tetralogy of Fallot and truncus arteriosus. Although it is tolerated well in childhood, recent information shows that chronic pulmonary insufficiency limits right ventricular function and shortens life span. Surgical repair requires tissue valve implantation, either a homograft or stented autograft. Although quite effective, these valves last only 15 to 20 years, necessitating multiple repeated operations over a lifetime. In 2000, Bonhoeffer and colleagues³¹ reported the first percutaneous pulmonary valve implantation using a bovine jugular valve sewn inside a balloon-expandable platinum stent. Since that time, more than 450 patients have been treated. Commercial valves are now available in Europe and are currently under investigation in the United States.

Anatomic considerations before percutaneous pulmonary valve implantation include degree of pulmonary insufficiency and stenosis, degree of right ventricular dilation and dysfunction, size and anatomy of the right ventricular outflow tract (RVOT) and main pulmonary artery, and presence of branch pulmonary artery stenosis.

Indications

Indications for treatment of pulmonary insufficiency include right ventricular dilation (>140 mL/m²), regurgitant fraction above 20%, worsening tricuspid regurgitation, and symptoms of exercise intolerance. Pulmonary stenosis with insufficiency should be treated if there is significant right ventricular hypertrophy, right ventricular pressures above 3/4 systemic, worsening tricuspid regurgitation, or symptoms of exercise intolerance (peak predicted).

Contraindications

Current limitations to percutaneous pulmonary valve implantation are due to both the large sheath size required for the implant and the stented valve maximum diameter (Fig. 27-27). The procedure currently requires a sheath larger than 20F; therefore, most operators restrict use to patients weighing 25 kg or more. Commercially available implants are limited to a maximum diameter of 24 mm, limiting their use in the RVOT or main pulmonary artery to lesions no larger than 22 mm in diameter. This limitation will be relaxed as newer devices are developed to expand to larger diameters. The RVOT must be more than 14 mm in diameter to ensure proper functioning of the valve with expansion. In addition, the location of the coronary arteries relative to the RVOT and main pulmonary artery area is crucial for determination of eligibility. Although uncommon, there are patients after surgical repair of tetralogy of Fallot or truncus arteriosus whose left or right coronary artery courses directly behind the obstructive RVOT. Placement of a stent in these patients will result in coronary compromise and myocardial infarction and can cause death.

FIGURE 27-27 Bovine jugular venous valve sewn onto a stainless steel stent mounted on an 18-mm balloon. Note compressed size relative to the 22F sheath.

Outcomes and Complications

The procedure is successful in 95% of implantations, with significant reduction in right ventricular systolic pressures (63 mm Hg to 45 mm Hg) and of RVOT gradients (37 mm Hg to 17 mm Hg).³² Pulmonary insufficiency, severe in all patients before implantation, was absent in more than 60% and trivial or mild in 38% after 18 months of follow-up. Procedural complications included acute surgery for RVOT and existing homograft dissection in 5%, with no associated mortality. Late complications included endocarditis and reobstruction due to sternal compression or stent fracture. Repeated stent dilation or stent implantation inside the existing stent is needed in up to 12% because of late stenosis or fracture. Freedom from reoperation is 84% at 5 years. Percutaneous valve implantation results in resolution of right ventricular dilation (142 to 91 mL/m²) and improved submaximal exercise tolerance at 1 year.³³

Imaging Findings

Preoperative Planning

Preoperative imaging is crucial to determination of eligibility for this procedure as well as for planning. CT or MRI is required to adequately assess the right ventricle, RVOT, main pulmonary artery, and branch pulmonary artery anatomy to determine dimensions. MRI gives the added benefit of pulmonary regurgitant fraction assessment (Fig. 27-28) as well as relative branch pulmonary flows. Specific attention to coronary artery anatomy in the area of the RVOT to assess for large coronary branches immediately posterior to the RVOT is crucial. If coronary artery anatomy is not clear from CT or MRI or there are significant concerns, selective coronary angiography with simultaneous test RVOT balloon expansion is required during the procedure (Fig. 27-29). Angiography in the main pulmonary artery is performed after implantation to assess valve positioning and function (Fig. 27-30). Procedural echocardiography, either transesophageal echocardiography or intracardiac, is useful as well for assessing residual stenosis and insufficiency immediately after implantation to determine the need for additional dilation or stenting.

FIGURE 27-28 Left, Black blood cardiac MRI of 14-year-old patient after repair of tetralogy of Fallot with right ventricular dilation due to pulmonary regurgitation. Middle and right, The velocity-encoded cine MRI for magnitude and phase in the main pulmonary artery (PA). Lower image, The data graphed, demonstrating pulmonary flow with a 42% regurgitant fraction.

FIGURE 27-29 Left, Anteroposterior selective right coronary artery (RCA) angiogram during balloon dilation of stenotic right ventricle–to–pulmonary artery homograft. Notice the large conal branch of the right coronary artery crossing just posterior to the homograft with significant compression from the inflated balloon. Right, The corresponding lateral image.

FIGURE 27-30 Lateral angiogram in the main pulmonary artery (MPA) of a 6-year-old child after valved stent implantation. Notice the trivial degrees of regurgitation into the right ventricle (RV).

Postoperative Surveillance

Before discharge, echocardiography and chest radiography are repeated to assess residual stenosis, insufficiency, and stent integrity. Repeated echocardiographic evaluation (Fig. 27-31) is appropriate every 6 months with CT or MRI evaluation annually to assess right ventricle size, in-stent restenosis, stent integrity, and pulmonary regurgitant fraction. If the patient is stable with a competent valve, these assessments can be lengthened to every 2 to 3 years.

FIGURE 27-31 Echocardiogram 6 months after stent pulmonary valve implantation in a 6-year-old. Left, Systolic frame showing mild blood flow acceleration across the stent valve, indicating mild residual stenosis. Middle, Diastolic frame showing trivial regurgitant flow. Right, Doppler image quantifying mild stenosis with no significant regurgitation, indicating that the implanted valve is functioning well. MPA, main pulmonary artery; PI, pulmonary insufficiency; PS, pulmonary stenosis; RV, right ventricle.

KEY POINTS

A majority of common congenital heart defects are now repaired in the catheterization laboratory with transcatheter techniques.

Device closure is now the treatment of choice for secundum atrial septal defect and patent foramen ovale.

Coil or device closure is currently the treatment of choice for patent ductus arteriosus.

Stent repair is an effective option for treatment of both native and recurrent coarctation for school-age children, adolescents, and adults.

Pulmonary insufficiency can now be treated with transcatheter stented valve implantation in adolescents and adults.

Imaging modalities including echocardiography, angiography, CT, and MRI are crucial for pretreatment evaluation, implantation guidance, and surveillance after repair in patients with congenital heart disease treated with interventional catheterization.