Introduction
Congenital heart disease (CHD) has an incidence of approximately 0.8% or approximately 8 out of every 1000 live births. These defects are derangements secondary to altered embryonic cardiovascular anatomy or the failure of a structure to progress beyond early stages of fetal development. Currently, nearly one million adults have CHD in the United States, and although many adults with CHD live with only a mild or repaired derangement, some have more severe conditions that if left untreated can be life threatening. In addition, many of these patients require multiple surgical and/or catheter-based interventions during childhood and potentially also in adulthood. Therefore, some of these important catheter-based interventions will be described in this chapter.
Catheterizations for patients with CHD are performed with either general anesthesia or moderate sedation with a combination of opiates and benzodiazepines. These procedures are performed using standard Seldinger technique in the femoral vein and femoral artery. Alternative venous access options include the internal jugular veins (high or low approach), subclavian veins, direct right atrial puncture, or a transhepatic vein approach. Arterial access may also be obtained from the arteries of the upper extremities (radial/axillary arteries) or the carotids. Anticoagulation is managed with heparin 100 units per kg body weight (maximum 5000-7000 units) for a goal activated clotting time (ACT) ≥200 to 250 seconds, depending on the procedure to be performed. Antibiotics are given to patients who receive an implanted device or who are deemed higher risk for bacterial endocarditis.
In general, baseline hemodynamic data are obtained in room air, precluding the need for a pulmonary vein PO 2 . Subsequently, the ratio of pulmonary blood flow (Q p ) to systemic blood flow (Q s ) is calculated according to the following formula: Q p /Q s = [(Ao 2 − MVo 2 )/(PVo 2 − Pao 2 )], where Ao 2 is the aortic oxygen saturation, MVo 2 is the mixed venous oxygen saturation, Pao 2 is the pulmonary arterial saturation, and PVo 2 is the pulmonary venous saturation. After hemodynamics, angiography is performed to further delineate the anatomy or lesion severity. For therapeutic procedures, a catheter is passed across the target area, such as stenosis, or abnormal shunt. A guidewire is then passed through the catheter to provide a track over which the delivery sheath and therapeutic devices are delivered. Balloon catheters are threaded directly, whereas stents and occlusion devices are protected or constrained within long delivery sheaths.
Catheter-Based Interventions for Congenital Heart Disease
Coarctation of the Aorta—Native or Restenosis for Intervention
Coarctation of the aorta occurs with a frequency of 8% of all congenital heart defects. Although usually diagnosed in early childhood, many patients are diagnosed and treated as adults. The natural history suggests that isolated coarctation may represent one aspect of more diffuse arteriopathy. Diffuse arterial wall stiffness and renal hypoperfusion lead to a resetting of the renin-angiotensin system and a hyper-renin state that, unfortunately, may not abate even after relief of the obstructed aorta. Also, although uncommon, cerebrovascular events from rupture of berry aneurysms may occur before or after relief of coarctation. An associated bicuspid aortic valve is present in 50% to 85% of patients with aortic coarctation, and a significant aortic gradient is particularly important to exclude when deciding on definitive therapy. Life expectancy beyond the sixth decade is unusual if the coarctation is not relieved, with a mean survival of approximately 35 years. The coarctation site is typically at the isthmus just beyond the origin of the left subclavian artery across from the ampulla of the ligamentum arteriosus. Collateral circulation often is present to bypass the obstructed aortic segment and provide blood flow to the lower body. The most common origins for these collateral are from the subclavian arteries through the internal thoracic arteries and the thyrocervical and costocervical branches. These vessels communicate with the intercostal arteries, which then perfuse the descending aorta distal to the obstructed aortic segment. This can produce diminished but palpable lower extremity pulses and also mask a severely obstructed aorta.
Prior to the catheterization and during follow-up, transthoracic echocardiography (TEE) can be used to interrogate the descending aorta, with a resting peak systolic velocity ≥3.2 m/s or a diastolic velocity of ≥1.0 m/s suggestive of significant aortic obstruction. Echocardiography also allows interrogation of the aortic valve and assessment of the ascending aortic root. More recently, magnetic resonance imaging (MRI) has become the imaging modality of choice ( Figure 36-1 ) both pre- and postcatheterization to assess the aorta and evaluate the coarctation segment anatomy. It also provides anatomical data regarding the aortic valve and ascending aorta. In the event of a contraindication to MRI (pacemaker or claustrophobia), or the lack of availability, computed tomography (CT) with contrast provides an acceptable alternative. In particular, multidimensional CT allows for 3D reconstruction similar to magnetic resonance angiographic methods.
Asymptomatic patients with a peak-to-peak gradient over 20 to 30 mm Hg across the coarctation site, by direct measurement in the catheterization laboratory, are considered for intervention. Also, symptomatic patients with a lesser gradient associated with a low cardiac output, or upper extremity hypertension and left ventricular (LV) hypertrophy, should be considered for intervention therapy. Other evolving indications for treatment include the presence of aortic aneurysms and symptomatic aneurysms of the circle of Willis. Young women who wish to bear children are also at risk, as there may be inadequate placental flow should they become pregnant.
Coarctation of the aorta after surgical repair of the aorta is referred to as “restenosis” as opposed to a native lesion. Often this occurs after an end-to-end surgical repair at the isthmus and can be due to aortic narrowing within the surgical site or potentially the transverse arch proximal to the surgical site. These later obstructive lesions are subcategorized as either proximal transverse arch (between the innominate artery and left carotid artery) or distal transverse arch (between the left carotid artery and left subclavian artery). Although few data exist regarding stent angioplasty within the transverse aortic arch, general experience has been that this is a safe and effective procedure. An arterial monitoring catheter is placed in the right upper extremity and a 4 Fr sheath is used to advance a 4 Fr pigtail to the aorta from the right radial artery. This catheter is used to monitor pressures during stent angioplasty of the distal transverse arch and to cineangiograms to determine appropriate stent placement distal to the origin of the left carotid artery. Transcatheter stent angioplasty for postoperative re-coarctation of the aorta at the isthmus has been demonstrated to be safe and effective. The technique usually involves a femoral arterial approach. The exchange length wire is placed in the ascending aorta or right subclavian artery. A high-pressure angioplasty balloon is used that is equal to or less than the diameter of the normal aortic segments around the stenosis (distal transverse arch or isthmus) and/or the diameter of the descending thoracic aorta near the diaphragm. The stent is mounted on an angioplasty balloon and delivered through a sheath at least 1 Fr to 2 Fr larger than is required by the angioplasty balloon. The stent length is dependent on the lesion length but is usually at least 35 mm to 40 mm in older patients. The stent can be fully dilated, but sometimes it is deemed safer to dilate the lesion over two procedures with 4 to 6 months between dilations.
Percutaneous angioplasty for coarctation has been performed since 1982, and the availability of stents has recently led to improved outcomes, to the extent that percutaneous intervention is now considered the procedure of choice in patients with re-coarctation following surgery. More recently aortic stents of adequate size have been available, and these are particularly effective in preventing complications from recoil of the aorta following angioplasty ( Figure 36-2 ). The size of the stent is never larger than the native aorta. Intravascular ultrasound has been useful in ensuring that there is adequate apposition of the stent against the aortic wall. A successful stent procedure is usually defined as a reduction in the peak gradient to near zero or less than 5 mm Hg.
Postcoarctation aneurysm formation was particularly a concern early in the experience of using angioplasty for native coarctation; resulting in the recommendation that native coarctation is better treated with surgical intervention. This concern has lessened more recently with the greater use of stenting, and many advocate a percutaneous approach in both native and postoperatively re-coarctation if the anatomy is suitable for stent placement. In general native coarctation should still be approached cautiously. For selected patients, stent placement may be considered as the primary intervention for native coarctation ( Figure 36-3 ) but should be considered in light of the need for growth of the aorta and risk for aneurysm formation. Also, the long-term outcome into late adulthood after stent placement has yet to be determined, and investigation continues.
Arteriovenous Fistulae or Malformations
Coronary Artery Fistulae
Coronary artery fistulae (CAF) are connections between the coronary arteries and a cardiac chamber or great vessel resulting in a “bypass” of the myocardial capillary bed. CAF occur in isolation (without other congenital heart defects), and the exact incidence is unknown. Most often they are discovered during routine coronary angiography, are clinically asymptomatic, and require no therapy. More than half of cases of CAF originate from the proximal right coronary artery, with the proximal left anterior descending coronary artery being the next most frequently involved (one third of cases), followed by the proximal circumflex coronary artery. Most of the CAF from either coronary artery terminate into the right side of the heart. The right ventricle (RV) is the most common site for drainage followed by the right atrium, coronary sinus, and pulmonary arteries ( ).
Since most of the patients with CAF are asymptomatic, the diagnosis is usually suspected when a continuous murmur is detected during routine visit or during examination for other reasons. On rare occasions the steal from the coronary bed will be of significance and result in angina symptoms. This poor distal coronary perfusion can usually be demonstrated during exercise testing with imaging methods. It is uncommon for coronary fistulae to be large enough that a substantial left-to-right shunt is present, and often no oximetric step-up can be demonstrated at catheterization even in angiographically appearing large fistulae. Reported symptoms due to a CAF include steal from the adjacent myocardium causing myocardial ischemia, thrombosis and embolism, cardiac failure, atrial fibrillation, rupture, endarteritis, and arrhythmias. Other reported rare complications include thrombosis within the fistula leading to acute myocardial infarction, atrioventricular arrhythmias, and spontaneous rupture of the aneurysmal fistula causing hemopericardium.
Access can be obtained in either the femoral or radial artery. A venous sheath is also placed in the event a rail technique or retrograde approach to deliver the occlusion device is deemed necessary. Selective coronary angiography is performed to confirm the diagnosis and delineate the anatomy of the CAF ( Figure 36-4 ). Detailed angiographic views in multiple projections are essential to the safe and effective treatment of a CAF.
Transcatheter intervention is indicated when there is evidence for coronary steal and clinical symptoms ( Table 36-1 ). CAF occlusion can be accomplished using various implantation techniques including various types of coils or vascular plugs ( Figure 36-5 ), depending on a favorable vessel size and shape in order to position without embolization. The main goal of treatment of CAF is complete occlusion with no residual fistulae. Catheter closure should be as distal to the end point of the fistula as possible to avoid possible occlusion of coronary branches to normal myocardium.
| INDICATION | METHODS | ACUTE SUCCESS | COMMENTS | |
|---|---|---|---|---|
| Coronary fistulae | Evidence of coronary steal | Coil occlusion | Technically high | Complications include unwanted branch occlusion or embolization |
| Pulmonary arteriovenous fistulae | Cyanosis Evidence of paradoxical emboli | Coil occlusion Occasionally Amplatzer or other occluder if fistula large | Technically high in selected lesions | Often multiple small fistulae present that are not amenable to coil occlusion Regrowth of collaterals high |
| Venovenous collaterals | Evidence of systemic hypoxemia or systemic embolic events | Coil occlusion if small or Amplatzer plug/PDA device if large collateral | Technically high in selected lesions | High long-term success rate Complications include residual leak, hemolysis, and embolization |
The recommended technique is a coaxial system using a coronary guide catheter of proper size and shape (usually 6 Fr to 8 Fr) is advanced to the ostium of the involved coronary artery, with a second catheter within this guide catheter (4 Fr or 5 Fr hemodynamic catheter), to advance a wire distally within the CAF. A rail technique from the venous access is often necessary to secure the wire position. Then an end-hole wedge balloon catheter is passed over this wire (retrograde or antegrade), leaving the guide catheter at the ostium of the coronary artery. The balloon is positioned distal to the last viable myocardial branch and is inflated with contrast to temporarily occlude the vessel for 5 to 10 minutes to assess the risk of ischemia with fistula occlusion. With large CAF this may not be possible to accomplish. If no detectable ischemic changes are noted, then the choice of occlusion technique is based on the size and shape of the CAF. Coils or devices can be used to close the CAF. If coils are chosen, they are usually deployed retrograde (going from the guide catheter inside the delivery catheter positioned distal), and if devices are chosen, usually the wire is snared and exteriorized from either the femoral or jugular vein and the proper size sheath is advanced into the fistula. Then the device is advanced from the vein to the fistula. The guide catheter is used for selective injections to guide the deployment site and to look for other feeding vessels.
Complete occlusion of the fistula may be achieved in more than 95% of the patients ( Figure 36-6 ). In the remaining patients, either further procedures may be required or managed conservatively if the residual fistulas are small. Procedurally related serious adverse events are uncommon but include embolization (within the coronary arteries), neurological events (systemic embolus), transient bundle branch block and myocardial infarction. Coil or thrombus migration remains the most common serious adverse event, and thus recent recommendations are to consider the use of detachable coils and use antiplatelet agents or anticoagulation post occlusion to prevent thrombosis and closure of the larger main coronary arteries. Currently, catheter closure of the CAF is considered to be a safe and effective alternative to surgery.
Pulmonary Arteriovenous Malformations
Pulmonary arteriovenous malformations (PAVM) are abnormal communications between pulmonary arteries and pulmonary veins. PAVM can either be congenital or acquired but this particular etiology is often difficult to differentiate. PAVM is especially common in patients with inadequate pulmonary blood flow containing systemic hepatic venous return. This occurs with various congenital heart defects but is common after a bidirectional Glenn (superior vena cava (SVA) anastomosed to the right pulmonary artery) for single ventricular physiology ( ). PAVM are also particularly common in patients with hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu syndrome) and are found in nearly 5% of patients with migraine headache with aura. Multiple small fistulae may also be seen in patients with hepato-pulmonary syndrome. The clinical presentation varies between no symptoms and severe illness. The most common clinical presentation includes epistaxis, dyspnea, and hemoptysis. Systemic hypoxemia may occur from the right-to-left shunt, and the resultant shunt may lead to paradoxical embolus resulting in stroke or transient ischemic attack (TIA).
When the PAVM are large enough (>2.5 to 3.0 mm) and/or create either systemic hypoxemia or evidence for systemic embolization, then transcatheter occlusion may be used ( Figure 36-7 ). Transcatheter occlusion of PAVM is considered the mainstay of treatment and the technique is similar to closure of the CAF. The most commonly used technique utilizes detachable coils or the vascular plug. Embolization of all entry vessels to the malformation is critical to prevent recanalization. The risk of migration through the malformation into systemic circulation has been decreased significantly with these more recent occlusion devices.
Anomalous Venovenous Connections Causing Systemic Hypoxemia
Anomalous venovenous connections may occur in patients with elevated systemic venous pressures, such as those who have had the Glenn or Fontan operation, or patients with stenoses or occlusions of the main systemic veins. Often these collaterals connect the left or right innominate vein or other systemic venous structures to the pulmonary veins or directly to the left atrium ( Figure 36-8 ). Similar to patients who have a persistent fenestration, the patient with venovenous collaterals will manifest clinically as systemic hypoxemia, with or without exercise, or a route for systemic embolic events. The standard angiograms to assess the systemic venous circuit for these malformations is a 10- to 25-cc biplane cineangiogram in the inferior vena cava (IVC) distal to the hepatic veins, a biplane cineangiogram at the proximal anastomosis of the Fontan or Glenn pathway, a biplane cineangiogram in the left innominate vein for the patient with a right-sided Glenn shunt, and angiograms in both SVA in those patients with bilateral Glenn shunts ( ). If these angiograms do not demonstrate the explanation for the patients’ systemic hypoxemia or embolic events we recommend agitated saline injections in the proximal right and left pulmonary arteries with simultaneous TEE, or chest wall echocardiography, to assess for tiny arteriovenous malformations in either lung. The lung with the least or no blood from the hepatic veins is most likely to have these later malformations. Transcatheter closure of the venovenous fistulae or larger arteriovenous malformations can be performed using Gianturco coils, vascular plugs, or vascular occlusion devices. Final angiography or agitated saline injections can be utilized to assess for immediate closure and systemic oxygen saturations at rest, or during follow-up exercise testing, can be checked to confirm improvement and future risk for embolic events. Transcatheter coil occlusion of these anomalous channels has been used successfully to reduce the right-to-left shunt.
