Interventional Techniques

Preprocedural Nursing Considerations

A thorough chart review should be conducted within 30 days of the procedure. The patient's current health condition should be assessed for infectious processes that could postpone an elective procedure. Consideration should be given to mitigating existing comorbidities prior to the procedure, to decrease risk. For example, patients with chronic renal insufficiency may receive prophylactic renal protection with hydration and N-acetylcysteine prior to contrast administration, in an effort to preserve kidney function. Patients with diabetes may need to adjust insulin dosing to avoid hypoglycemia, or hold oral hypoglycemic agents to prevent lactic acidosis. Discussion of specific care concerns with the patient's existing specialists should take place well in advance of the procedure, to customize a periprocedural care plan. In addition, medication review is necessary to modify key therapeutics such as chronic anticoagulants or antiplatelet agents, which may need to be held or reduced in dose several days prior to procedure. Consideration of bridge anticoagulation therapy (e.g., low-molecular-weight heparin) may be necessary for patients with a high risk for thrombus, such as those with prosthetic heart valves. Use of an anticoagulant agent with a short half-life maintains anticoagulation for days prior to the procedure but decreases the risk of periprocedure bleeding with discontinuation hours prior to the procedure. Finally, inquire about any allergies that may require either treatment prior to the procedure (e.g., contrast allergy) or development of an alternate periprocedural medication plan (e.g., penicillin allergy).

Before the procedure, a provider must complete a history and physical. The exam could take place the day prior to, or day of, the scheduled procedure. Discuss changes or increases in symptoms since referral with the interventional cardiologist. Red flags such as decrease in feeding, desaturations, or increased work of breathing could warrant expediting the procedure or, occasionally, delaying the procedure.

Providers must be familiar with procedures to serve as a resource to patients and families. The provider sets expectations for care immediately after a procedure (e.g., supine positioning to prevent bleeding, monitoring equipment, and possibly a urinary catheter), which can facilitate a smooth postprocedure experience for patients and families. The developmental level of the patient is necessary to keep in mind during this counseling encounter. It is necessary to provide guidance in terms that both patients and families can understand. Use of a child life specialist should be considered when both appropriate and available.

Preprocedural Planning

Consent should ideally be obtained either during outpatient consultation or in a dedicated preprocedural clinic that provides parents the opportunity to discuss relevant issues, prior to the “stress” of the procedure.

The consent should be obtained by a person suitably qualified, with sufficient knowledge to explain the procedural details and its risks or, ideally, by the interventional cardiologist. It is unreasonable to expect to receive a blanket consent, covering all procedures, although detailed consent for specific anticipated events might be obtained. The patient and the family should have sufficient time and information to make a fully informed decision. Because it is difficult to approach parents during catheterization for consent to additional procedures, treatment of life-threatening complications or events that may lead to significant deterioration in the health of the patient must be performed as deemed necessary.

The planning of an interventional catheterization procedure cannot be overemphasized. Procedural planning aids in giving sufficient time to order necessary laboratory equipment and devices not stocked on a regular basis. Admission of the patient should include a meeting with the patient and family, explaining details and risks associated with the procedure, so that any doubts and fears specifically pertaining to the procedure are reclarified. All investigations should be reviewed on the day of the procedure. A repeated clinical examination of the patient helps determine the need for any additional investigations. Imaging should be reviewed to reconfirm the diagnosis and the indication for the procedure and to reverify planned approaches to the intervention. Ideally, the symptoms, findings on clinical examination, and investigations should be reviewed by a team of doctors, including the primary cardiologist, the interventional cardiologist, the imaging cardiologist, the anesthetist, and, if applicable, the cardiac surgeon, to maximize the information leading to the procedure. An approach based on consensus also adds to the safety and efficacy of the decision-making process because individuals with different areas of expertise contribute in a complementary manner, maximizing the benefit to every patient of this team-based philosophy. Use of additional cross-sectional imaging, such as three-dimensional echocardiography, magnetic resonance imaging, or computerized tomography, can add significantly to the clinical information by providing details of complex cardiac anatomy that could suggest the need for a modified approach or even contraindicate catheterization. Decisions regarding access, via the femoral, jugular, or hepatic approach, for example, choice of sheaths, catheters, wires, dosage of contrast agents, and projections to be used, can be made with reasonable certainty before starting the procedure. It is always helpful to discuss the whole strategy in a stepwise manner with cardiology fellows in training, catheterization laboratory staff (including nurses and technologists), anesthetist, and any other staff involved with the procedure. Steps that can be performed quickly and safely should be identified and delegated to assistants in the interest of time, particularly for long procedures.

Vascular Access

The conventional approach, namely to have both an arterial and a venous access, works in almost all situations where interventional catheterization is performed. Femoral, internal jugular, subclavian, axillary, carotid, and hepatic vascular approaches have all been used for various interventions. The possible need for reintervention should be borne in mind, thus avoiding unnecessary access, especially in smaller patients. Repeated catheterization, prolonged periods in intensive care, and multiple operations for complex staged palliative procedures can make access difficult due to repeated use of the vessels. Ultrasound-guided access allows for visualization of vessels, detects unusual arrangements and thrombosed veins and arteries, and also reduces the risk of inadvertent vascular puncture. Stenosis or atresia with luminal continuity of systemic veins may have to be dealt with by crossing the site with a floppy-tipped guidewire and use of long sheaths, which track across the stenosis and provide access to the central circulation. On the arterial side, in small neonates or infants, vascular cut-down has been used to access the carotid or axillary arteries for interventions on the aortic valve or arch. More recently, percutaneous access to the carotid and axillary arteries have been used to facilitate PDA stent implantation in neonates. In neonates and small infants, the availability of small catheters and sheaths, of 3-Fr and 4-Fr sizes, has facilitated procedures and reduced the risk of vascular injury, although this remains the highest risk group for arterial thrombosis.

Catheters and Guidewires

In infants and children, angled and curved-tipped catheters are most commonly used in situations where catheters need to be maneuvered through tight bends and small chambers and vessels. The operator needs to have sufficient knowledge of the differences in the types of catheter when performing cardiac and peripheral interventions in order to modify the approach to access difficult sites. Hydrophilic catheters, such as the Glide catheter (Terumo), Medi-tech, or Boston Scientific products, track well over guidewires into difficult sites. Balloon-tipped catheters, such as the Berman angiographic catheter or the balloon wedge catheter, are useful for wedge injections or to cross atrioventricular valves without entrapment in the intercordal spaces. Catheters of short length help to make manipulation easy in small babies. Long catheters in older patients help to form loops in dilated proximal chambers, such as the right atrium, to provide stability, and allow tracking into distal vessels such as the pulmonary trunk. Increasingly, complex lesions require use of a coaxial system, which may involve passage of a microcatheter through a directional catheter, which itself may be passed through a long sheath.

Guidewires are used to access vessels, stabilize catheters, and provide easy access for multiple crossings of stenotic lesions. A soft hydrophilic wire, such as the Terumo, with an angled tip, can be used to enter small tortuous vessels. A stiff exchange length wire, such as the 0.035-inch, 260-cm product from Cook Medical, is usually required to obtain multiple hemodynamic measurements, to provide stability across a lesion, for multiple crossings after interventions, to perform angiography, and to mount balloon catheters, stents, or large sheaths. Ultrastiff wires, such as the Lunderquist wire (Cook Medical), have increasingly important roles with delivery of large-profile stiff interventional equipment, such as transcatheter valves, but these require both knowledge and caution because they may be associated with considerable risk of distal vascular injury (guidewire perforation).

Anticoagulation

Heparin is most commonly used as an anticoagulant during cardiac catheterization to prevent thrombosis during and after the procedure. Some operators monitor heparin's effect by measuring the activated clotting time or the partial thromboplastin time, albeit that most use a standard dose based on the weight of the patient.

For short procedures, a single dose of 50 to 100 units per kilogram body weight of heparin is typically administered after vascular access is obtained. For long procedures, between 100 and 200 u/kg body weight is administered and may be repeated either after 2 to 3 hours or by monitoring either the activated clotting or the partial thromboplastin times. The direct thrombin inhibitor bivalirudin is an alternative to heparin, which has some pediatric dosing data to support its use. Protamine may be used to reverse the effect of heparin should there be persistent bleeding from the site of access.

Balloon Dilation

Balloon dilation is performed to relieve stenosis of valves, vessel walls, surgically created pathways, or intracardiac structures such as a fenestration in the atrial septum. There have been significant advances in the size, profile, design, and materials used in balloon catheters, facilitating their use in various applications. Design of coaxial balloons has reduced the time required for inflation and deflation, with only transient hemodynamic compromise. The size of the balloon used for a particular procedure not only depends on the diameter of the lesion to be dilated, but also on the diameter of the contiguous and noncontiguous normal anatomic structures. The use of an oversized balloon increases the chance of a successful dilation of the lesion but also increases the risk of trauma to the target lesion and to contiguous anatomic structures. Balloons have been used to treat valvar stenosis when fusion of the leaflets along their zones of apposition is responsible for reduction in the area of the effective valvar orifice. The principle of creating a controlled tear or split in the commissure, but not in the leaflet, thus improving excursion of the leaflets, provides a larger area of effective orifice and thus relieves the stenosis. Because the valve is abnormal, competence may be affected to various degrees after balloon dilation. Pulmonary, aortic, mitral, and tricuspid valves have all been treated by balloon valvuloplasty for different diseases. However, the technique is not useful in treating valves associated with significant hypoplasia at the basal hinge point of the leaflets. Dilation of semilunar valves is performed commonly for congenital lesions, and dilation of atrioventricular valves is performed almost exclusively for acquired lesions. The technique used in performing balloon valvuloplasty also forms the basis for angioplasty and implantation of stents. High-pressure balloons have been more recently used in dilating highly resistant lesions, such as calcified conduits, postoperative anastomotic stenosis, or native pulmonary arterial stenosis. Cutting balloons have been used in substrates that do not respond to standard balloon angioplasty, such as severe pulmonary arterial stenosis or recurrent pulmonary venous stenosis, with encouraging results. Balloon-in-balloon catheters, known as BIB catheters (NuMed), have been very useful in implanting stents in the aorta, pulmonary arteries, and conduits. The inner balloon is an additional tool to help confirm the position before deployment of the stent, and the serial dilation helps to reduce stent malposition and foreshortening. The use of two balloons simultaneously for valvuloplasty was first introduced for dilation of the mitral valve. It provides a large effective diameter of the combined balloons and has been used in pulmonary valvuloplasty in adults who have a large diameter of the pulmonary outflow tracts. Stability of the balloon during inflation depends on choice of a balloon of correct length and diameter, appropriate selection of a stiff guidewire, obtaining appropriately distal position for the guidewire, and achieving a rapid sequence of inflation and deflation. Stability could be further aided by using techniques to reduce stroke volume, such as rapid ventricular pacing, mainly but not exclusively for lesions in the systemic circulation. In balloon valvuloplasty, the size of the balloon is chosen based on the size of the target valve annulus measured. In pulmonary valvoplasty, the balloon size is usually 120% to 140% of the measured diameter of the valve at the basal hinge points of the leaflets. In aortic valvoplasty, the size is usually 80% to 100% of the diameter at the hinges of the leaflets. A serial approach to aortic valvuloplasty with interval reassessment of residual gradient and degree of valvar incompetence can prevent the development of an adverse outcome. Size for dilating coarctation of the aorta equals the diameter of the distal transverse arch, prior to the development of hypoplasia or stenosis, or a size is chosen not greater than four times the diameter of the lesion but less than the diameter of the descending aorta at its position close to the diaphragm. The length of the balloon should not be so short as to produce instability during inflation or make capture of the lesion difficult and not too long to cause trauma to the proximal or distal structures (including the adjacent tricuspid valve, as is the case with pulmonic valvuloplasty). The size of the patient should be taken into consideration in choosing the correct balloon. Balloons are filled with dilutions of contrast medium 1:3 and 1:5 with saline, chosen based on balloon size and location, as well as patient thickness, and should be de-aired thoroughly to reduce the risk of air embolism, should the balloon rupture. If the margins of the balloon, at its ends, are parallel, it suggests that inflation is at nominal pressure, and any further inflation can increase the risk of rupture. After successful dilation, hemodynamics and angiography should be repeated to evaluate results and assess complications. Further evaluation by echocardiography, cross-sectional imaging, or lung perfusion scan is imperative to decide long-term management.

Stent Angioplasty

Stents are capable of maintaining patency of vessels and prevent elastic recoil after balloon dilation. There have been major advances in stent technology, and their impact can be easily observed in congenital cardiology. Typically, stents are cut from stainless steel tubes with a laser or made from platinum alloy wires welded together. Stents can be expanded on balloons or be self-expanding when made of shape-memory alloy (nitinol) and delivered from a constraining sheath. Self-expanding stents are used in patients who, or structures which, have already achieved their potential for growth and typically offer benefit in regions of dynamic stress (e.g., femoral artery). Balloon-expandable stents can be redilated within limits, each distinct to the specific model of stent chosen, and may be used in children and adults. The design of the cells may be open, such as the ev3 LD series (Medtronic, Inc.), avoiding jailing or covering of neighboring arterial branches, closed, such as the Palmaz Genesis or XL series (Cordis), or a hybrid of these two designs, such as the Formula series (Cook Medical). The properties of materials considered favorable for use in congenital cardiology are those with a low profile, good radial strength and flexibility, and ability to withstand cyclic compressive stresses of the cardiovascular system. The diameter of the stent should also have the potential to reach maximal dimensions of the vessel wall, as seen in a typical adult. However, in small infants, a premounted biliary stent or coronary arterial stent may be used in circumstances of severe hemodynamic compromise, despite their limited final maximal diameter. This is especially true in patients in whom subsequent surgical revision (e.g., conduit replacement) is inevitable; moreover, intentional transcatheter stent fracture is an increasingly viable potential. Stents are implanted using balloons of appropriate size through long, large-bored, sheaths to reach the lesion. Stents may be premounted on the balloons or may need to be crimped on to the balloon manually or by using a crimping device. The length of the balloon should always be equal to or longer than the length of the stent but ideally not by much, to avoid “dog boning,” which can shorten a desired stent's length. The diameter of the balloon determines the final diameter of the stent. Stability of the stent during deployment can be improved by using the BIB catheters, extra-stiff wires, long sheaths, and rapid right ventricular pacing to reduce stroke volume. The luminal surface of the stent endothelializes in 8 to 10 weeks, and patients may need to take antiplatelet agents or, in some situations, anticoagulants during this period to prevent in-stent thrombosis and restenosis.

Risks associated with stent angioplasty include dis­lodgement and embolization, trauma to the vessel walls, fracture of the stent, and restenosis. Covered stents made by fashioning expanded polytetrafluorethylene to balloon-expandable or self-expanding stents have been used in situations where the risk of vascular injury and aneurysm is considered to be high or to exclude existing vascular pathology, such as a pseudoaneurysm or dissection. The use of covered stents in younger patients is limited by their size and the caliber of the delivery systems currently available. Covered stents approved by regulatory agencies throughout the world are now readily available. Newer bioabsorbable stent platforms are currently being investigated to reduce restenosis and improve vasomotion in coronary arterial lesions. Such stents could prove useful in treating stenoses of small vessels in infants and children, albeit temporarily, thus allowing for normal growth without the need for later surgical stent transection or intentional stent fracture to facilitate further interventional therapy.

Closure of Septal Defects and Vascular Occlusion

The advent of shape-memory alloy has revolutionized transcatheter interventions for intracardiac and extracardiac shunts. Nitinol is the most common alloy used. Several devices for closing septal defects and vascular occlusion are currently available. The most commonly used occluder, the Amplatzer Septal Occluder (now manufactured by Abbott Medical), has a central occluding component, with left- and right-sided discs. A Dacron polyester patch sewn into the device is responsible for thrombogenicity and acute occlusion. A large number of devices are available around the world that largely mimic the design of the ASO device, including the Occlutech ASD occluder, which is very popular in Europe. The second most commonly used occluder in the United States is the Cardioform Septal Occluder (W.L. Gore & Associates), which consists of a nitinol coil frame with Gore-Tex covering on the left- and right-sided discs. This device covers the defect but does not contain a central occluding component and thus is not self-centering like the Amplatz device. The Gore Cardioform ASD Occluder, currently in clinical trial, offers a hybrid approach to ASD closure with a nitinol coil frame and Gore-Tex covering but also containing an anatomically adaptable central component that fills the defect itself. Sizing of a septal defect is performed by transesophageal or intracardiac echocardiography, with or without inflating a balloon across the defect during the procedure. Reported complications of such closure devices eroding through the atrial or aortic walls, and devices designed to occlude ventricular septal defects (VSDs) causing complete heart block, emphasize the importance of choosing a device of appropriate size and the ongoing need for further device development. Various practice strategies, from oversizing to reduce the risk of device embolization, to appropriate sizing to reduce the risk of trauma to contiguous structures, have been used.

Valvar Heart Disease

Pulmonary Valve

Pulmonary Valvar Stenosis

As already discussed, the initial description of balloon dilation of pulmonary valve stenosis was made by Kan and colleagues in 1982. Since then, the technique has been accepted as a first-line treatment for congenital valvar pulmonary stenosis. Balloon dilation is usually indicated in the presence of related cardiac symptoms (such as poor feeding in an infant or exertional intolerance in an older child), when the gradient across the stenotic valve is 40 mm Hg or more, or when there is an increase in right ventricular systolic pressure by more than half of the systemic pressure. However, the indications for the procedure are different in neonates with a ductal-dependent pulmonary circulation, when gradients are unreliable. The presence of a dysplastic valve with ductal-dependent pulmonary blood flow (critical pulmonary stenosis) is an accepted indication for treatment.

The right ventricular pressure is measured, after which right ventricular angiography is performed in the lateral projection to measure the diameter of the ventriculoarterial junction at the basal attachment of the valvar leaflets. The stenotic pulmonary valve is crossed using an end-hole catheter, such as a balloon-tipped catheter or a directional catheter (e.g., Judkins right coronary). A guidewire, from 0.014 to 0.035 inch in diameter, is passed through the catheter into a branch of the pulmonary artery (PA) supplying the lower lobe of either lung. In neonates, the guidewire may be placed across the patent arterial duct into the descending aorta, for maximal wire “purchase.” A balloon that is between 110% and 140% of the diameter of the measured valve is passed through the sheath in the femoral vein over the wire and advanced across the pulmonary valve. The balloon is rapidly inflated and deflated with dilute contrast across the stenotic valve. A significant waist is typically visualized on the balloon, which resolves with further dilation, until only a mild persistent annular waist remains, consistent with the use of a balloon that is slightly larger than the valve. The balloon is then withdrawn, with the guidewire still in place, and a catheter is passed into the pulmonary arteries to reassess the hemodynamics with a pressure pullback. The Multitrack catheter can be useful in this scenario because it allows measurement of both right ventricular pressure and the gradient across the pulmonary valve, coupled with the ability to perform angiography before and after dilation of the balloon without loss of position of the guidewire. That stated, most operators do not feel that routine right ventriculography is strictly necessary following routine and uncomplicated balloon pulmonary valvuloplasty. In patients with a very dysplastic pulmonary valve, and a poor response to routine pulmonary valvuloplasty, high pressure angioplasty balloons can be used, with acceptable relief of the stenosis. The technique of balloon valvuloplasty is more demanding in neonates, especially in those without critical pulmonary stenosis, whereby transductal wire position cannot be established and there is no secondary source of pulmonary blood flow to be relied upon periprocedurally. Although balloon dilation of pulmonary valvar stenosis carries low risks when performed in infants and children older than 1 year, there is significant morbidity and mortality in the early neonatal period. In neonates, it is the size and function of the right ventricle that determines outcome. High right ventricular pressure, an irritable myocardium with a risk of arrhythmia, and equipment-related splinting of the tricuspid valve can all lead to hemodynamic instability. This necessitates rapidity of the procedure, use of a relatively soft guidewire, and very short periods of balloon inflation, which may be helped by using balloons with low profile. The presence of an atrial level shunt generates cyanosis but not severe hypotension during balloon inflation.

Adequate relief of the stenosis, with a reduction in the transvalvar gradient and in right ventricular systolic pressure, is achieved in the majority of patients. However, occasionally, there may be very little immediate reduction in gradient across the pulmonary valve. This is because of associated dynamic infundibular muscular stenosis, which disappears over a period in a similar fashion to that observed after surgical pulmonary valvotomy. Repeat balloon valvoplasty, after a few months, in those patients where the initial result was suboptimal, can produce a further reduction in gradient. Occasionally, the severely dysplastic pulmonary valve may not respond adequately to one or more attempts at balloon dilation, and surgical volvotomy, valvectomy, or transannular patch are considered. Serious complications of balloon dilation include a tear of the pulmonary trunk or perforation of the heart. In general, the complication rate, at 0.4%, is low, and reported mortality is no more than 0.2%. The consequences of chronic pulmonary regurgitation, nonetheless, has historically been underestimated, and more conservative dilation is now recommended in an effort to reduce the degree of chronic pulmonic regurgitation.

Balloon dilation of the pulmonary valve can also be carried out as a palliative procedure in patients with tetralogy of Fallot and other complex two-ventricle congenital cardiac malformations, typically in a subset with isolated valvar pulmonary stenosis. It can also be performed in patients with a functionally univentricular circulation to augment pulmonary blood flow and improve the size of the pulmonary arteries prior to staged palliations or repair. The basic principles of the procedure in these situations are the same as for isolated congenital valvar pulmonary stenosis, although crossing the stenotic subpulmonary outflow tract can be challenging. Problems with atrioventricular conduction (e.g., heart block) can occur if the position of the atrioventricular bundle is abnormal. A more conservative approach is followed to avoid excessive flow of blood to the lungs or excessive pressure in the pulmonary arteries and to reduce the risk of pulmonary regurgitation.

Valvar Pulmonary Atresia With Intact Ventricular Septum

The transcatheter interventions available to alter the course of this lesion (see also Chapter 43 ) include relief of right ventricular outflow obstruction with perforation of the atretic pulmonary valve followed by balloon pulmonary valvuloplasty ( Fig. 18.1A–B and Fig. 18.2A, C ). In some cases, stenting of the arterial duct may be necessary to augment pulmonary blood flow, especially in the setting of right ventricular diastolic dysfunction and/or borderline hypoplasia. Furthermore, enlargement of the atrial communication by balloon atrial septostomy may be necessary in a select subgroup to reduce right atrial hypertension and improve systemic cardiac output. Occasionally, stenting of the subvalvar muscular RVOT is necessary in the setting of residual subvalvar obstruction. A more detailed consideration of patient selection, procedural approach, and outcomes is discussed in Chapter 30 .

Implantation of Pulmonary Valves

Bonhoeffer and colleagues described the first transcatheter implantation of a valve in the pulmonary position, placing the device in a dysfunctional prosthetic right ventricular to PA conduit to relieve stenosis and regurgitation. In fact, this initial transcatheter pulmonary valve (TPV) implant preceded the first transcatheter aortic valve implant by 18 months! The Medtronic Melody TPV is made of a modified bovine jugular vein segment sutured inside a balloon-expandable platinum-iridium stent and is deployed using a custom-made long-sheathed delivery catheter, known as Ensemble (Medtronic). The Melody TPV was the first commercially available TPV. The system contains a BIB catheter inside a long sheath with a “carrot” dilator at the tip, facilitating direct entry into the skin without the need for an independent sheath. Current systems have outer balloons of 18-, 20-, and 22-mm diameter. The outer balloon determines the final diameter of the implanted valve, which should approximately equal the nominal diameter of the conduit (up to 110% of the nominal diameter) when inserted surgically in the RVOT. More recent experience suggests important conduit dilation beyond the 110% of the nominal diameter may be accomplished, although the risk of conduit injury is increased. The valve is suitable for insertion in RVOT conduits (including surgically implant bioprosthetic pulmonary valves) in patients with circumferential-valved conduits implanted surgically during their definitive repair or at subsequent surgical revision. Clinical experience does suggest good valve function is maintained outside of this working range (both in smaller and slightly larger diameter substrates). Magnetic resonance imaging helps to define the morphology of the outflow tract and the bifurcation of the pulmonary trunk, determine right ventricular volume and ejection fraction, and quantify the pulmonary regurgitant fraction. Echocardiography is used for postprocedural surveillance and hemodynamic monitoring.

The Edwards Sapien XT Transcatheter Heart Valve (Edwards Lifesciences), developed as a balloon-expandable transcatheter aortic valve, has more recently been approved in the United States for use in the pulmonic position. The Sapien XT valve is made of bovine pericardial tissue leaflets sewn into a cobalt chromium stent frame and is deployed using the NovaFlex+ delivery catheter. To reduce the required sheath profile (as the system was designed for aortic valve delivery), the valve is mounted onto the shaft of the catheter and then balloon-mounted within the inferior vena cava after introduction through the femoral sheath. The XT valve is marketed in 23-, 26-, and 29-mm diameters and is thus capable of treating larger-diameter RVOT conduits than is Melody TPV. Robust clinical data are lacking. The third-generation Sapien valve—S3 or Sapien 3—is currently in trial for pulmonic implantation and is expected to offer several benefits over the XT system, including an outer skirt (to minimize the risk of paravalvar leak) and a more flexible delivery system (to facilitate delivery to the RVOT).

TPV replacement is typically performed under general anesthesia. Although multiple approaches may be used, the following description is typical and well regarded. A balloon-tipped or curved-tip catheter is inserted through the femoral (routinely) or jugular vein (less commonly) to access the distal lower lobe of the left or right PA, often with the aid of a floppy-tipped or angled Glidewire. A super-stiff or ultra-stiff guidewire, of 0.035-inch diameter and exchange length, with a preformed curve, is then positioned in the distal PA. A Multitrack catheter is passed over this stiff wire to assess hemodynamics and to perform RVOT and PA angiography ( Fig. 18.3A ). Some operators do choose to perform angiography prior to establishing distal PA interventional wire position. Different projections are used to define the morphology of the outflow tract, the bifurcation of the pulmonary arteries, and to assess the pulmonary regurgitation, with extreme cranial angulation on the “A” plane and straight lateral on the “B” plane typical. In cases of conduit stenosis, serial conduit angioplasty with high-pressure and Kevlar-wrapped ultrahigh-pressure angioplasty balloons (Bard Vascular) is the next step. The initial angioplasty balloon is chosen to be approximately 2 to 4 mm larger than the minimal conduit diameter, based on preprocedural imaging and baseline angiographic assessment. Subsequent angioplasty balloons are chosen in increasing 2-mm increments. It is extremely important that the operator perform repeat conduit angiography after each dilation, to be sure conduit injury is identified when it is still mild. This process is complete when the conduit has been serially dilated to the intended TPV implant diameter. Nonselective aortography performed through a pigtail catheter inserted into the aortic root, during conduit balloon angioplasty at the intended TPV implant diameter, is performed to define the coronary arterial anatomy and rule out the presence of extrinsic coronary artery compression. This step is key to reduce the incidence of coronary artery compression, which can be catastrophic. Coronary compression occurs in 5% to 6% of planned TPV cases and is more likely in the setting of an anomalous coronary artery course. Selective coronary angiography may be performed with or without conduit angioplasty if coronary compression is suspected. Once the outflow tract is deemed suitable for implantation, consideration is given to the placement of covered or bare-metal stents, prior to actual valve implantation. A covered stent may be used in the setting of existing or acquire conduit injury. One or more bare-metal stents may be used to bear the compressive forces typically present in the setting of a retrosternal RVOT conduit, to avoid transferring these forces to the valve-stent itself. In the case of Melody TPV, the platinum-iridium stent is rather soft and pliable, and stent fracture has been well established as a mode of early valve failure (recurrent pulmonic stenosis). The use of prestent placement has effectively reduced, if not eliminated, the incidence of Melody stent fracture. It has become common practice to use prestents in the RVOT conduit until the conduit gradient is eliminated (or reduced substantially) and minimal stent recoil is present following deflation of the angioplasty balloon.

Following complete preparation of the RVOT, the valve-stent is prepared according to the manufacturers’ directions, which typically begins with serial washings to dilute the glutaraldehyde preservative. In the case of Melody, the valve is then hand-crimped, first onto a 3-mL syringe, and then onto the prepared BIB catheters of the Ensemble delivery system, with care taken to elongate the stent frame, while it is crimped onto the balloon. The integrated long sheath is then advanced carefully to fully cover the Melody valve during delivery. In the case of Sapien, the valve is mounted onto the shaft of the delivery balloon, using an included crimper device. This valve will be delivered to the RVOT through a short venous sheath in an uncovered fashion. The femoral venipuncture is dilated in a graded fashion, if necessary, and the delivery system is advanced either through the skin directly (Melody) or through the included eSheath (Sapien). At this point, the Melody TPV may be advanced directly to the RVOT landing zone. The Sapien THV must first be “mounted” onto the balloon portion of the delivery catheter, which is accomplished in straightforward fashion using the integrated delivery system in the inferior vena cava, prior to advancement through the right heart. Each delivery system can be looped in the right atrium to facilitate delivery of the valve-stent into an appropriate position, although the Ensemble system is typically a bit more forgiving in this regard. The NovaFlex+ system includes dual articulation adjustment capability (flexion), thereby facilitating delivery (although this system was designed to facilitate retroaortic delivery to the aortic valve). Standard principles of manipulation ensure delivery of the device in the RVOT without losing position of the wire. Once within the conduit, the Melody TPV is uncovered by pulling back on the outer sheath; the pusher catheter is withdrawn in the case of Sapien XT delivery. Calcification of the conduit, or the bare-metal stent(s) itself, usually provides good landmarks for optimal positioning. The valve is deployed by inflating the delivery balloon(s). Hemodynamic assessment and angiography are then performed after implantation (see Fig. 18.3B ). In patients with a significant residual gradient, post dilation with a high-pressure balloon may be considered.

TPV replacement has now been carried out for dysfunction of the RVOT in patients with repaired tetralogy of Fallot and variants, transposed arterial trunks with VSD and pulmonary stenosis, the Ross operation for left ventricular outflow disease, and repaired common arterial trunk, and others. The majority of the patients had a homograft in the RVOT but valve-in-valve implantation within an existing surgical bioprosthetic pulmonary valve is also common. There was a significant reduction in right ventricular systolic pressure, the gradient across the outflow tract, and improvement in pulmonary competence after valvar implantation, with no procedural mortality. Survival was 95.9% at 72 months. The incidence of complications decreased with subsequent implantations as a result of improvements in selection of patients and design of the device. Fractures remain an important cause of restenosis, being seen after one-fifth of insertions, and can be managed with a second implantation within the initial one. Early detection and anticipatory management of the fractured stent can be aided by chest radiography and echocardiography at regular intervals. Five-year freedom from reintervention and valve explantation was 76% and 92%, respectively. Endocarditis of a TPV is an important clinical problem to recognize because the diagnosis is associated with a substantial risk of morbidity and even mortality. Although data on the risk following Sapien implantation remain sparse, Melody TPV–related infective endocarditis carries an annual hazard of approximately 2.3% to 2.5%, which is similar to the Medtronic Contegra bovine jugular vein conduit risk.

Adolescents and adults who have undergone repair of the RVOT without use of a conduit (typically in tetralogy of Fallot), but have suffered aneurysmal dilation, will generally require pulmonary valve replacement to preserve right ventricular function and avoid right heart failure. The Melody TPV has been used in this setting, typically when residual pulmonary valve stenosis persists, but the maximal implantation inner diameter of 22 to 24 mm limits greater use in this dilated RVOT substrate. The Sapien XT and S3 valves have been increasingly used in this setting, whereby their larger maximal implantation diameter (outer diameter approaches 30 to 31 mm for the S3 valve) facilitates stability in the relatively dilated RVOT (see Fig. 18.3C–D ). Despite reasonable success in this “native” or patched RVOT substrate using balloon-expandable technology, the large diameter and compliant nature of the RVOT in this population begs for a purpose-built nitinol-frame self-expanding device. Although no such device has yet been approved as of the writing of this chapter, both Medtronic and Edwards have self-expanding native RVOT pulmonary valve replacement technology in clinical trial. The Medtronic Harmony TPV (Medtronic) is a porcine pericardial tissue valve mounted on a self-expanding nitinol frame with polyester covering. The valve is delivered via a custom-made delivery system with retractable sheath. A series of lengths and sizes are in development; the first design performed well in early feasibility testing. The Edwards Alterra Adaptive Prestent (Edwards Lifesciences) is a self-expanding nitinol frame covered stent with a central rigid landing zone intended to accommodate a commercial 29-mm Sapien 3 valve. The Adaptive Prestent is preloaded in a custom-designed delivery system with tapered tip. Following Prestent implantation, either at the same procedure or staged to a second procedure, a 29-mm Sapien 3 valve would be delivered to the rigid landing zone within the Prestent, completing the transcatheter PVR procedure. The Venous P-valve (MedTech) is another self-expanding TPV replacement option—with encouraging early results—that is currently used throughout Asia. These self-expanding devices are likely to be most suited to treat isolated pulmonary regurgitation in dilated native or patch-augmented RV outflow tracts.