1. Cardiovascular obstructions in adult congenital heart disease (CHD) often involve branch pulmonary artery stenosis and postsurgical baffles, homografts, and conduits.

2. Stenting various cardiovascular obstructions in adult CHD requires a good understanding of available stents and balloons of all sizes and all of their unique characteristics.

3. Intravascular stenting should accommodate for adult growth potential of the patient.

4. Accurate measurements and basic techniques of angioplasty and stenting of large pulmonary and systemic vessels are essential in the management of adult CHD.

Balloon Angioplasty

Much procedural knowledge, technique development, and refinement in the use of static balloon angioplasty can be traced to the results of the Valvuloplasty and Angioplasty of Congenital Heart Disease Registry (VACA).² Although there are many manufacturers of balloons who use different materials, sizes, and lengths, all balloons impart a certain advantage or disadvantage for specific lesions. It is imperative for an active catheterization lab to carry and become familiar with a wide array of inventoried balloons. An ideal balloon has a low profile and folds tightly over a catheter shaft with short shoulders.³ It should dilate to a predetermined diameter at maximal pressure without overexpanding and then deflate rapidly so as to assume its original native configuration for retrieval. The effectiveness of angioplasty is caused by appropriately tearing tunica intima and distention of the medial vascular layer,⁴ which at times requires high-pressure balloons usually made of thicker material and having larger profiles.

The suspect vessel is visualized on angiogram using contrast injection with biplane imaging profiling the lesion to allow for accurate calibrated measurements of length and diameter, as well as any important side branches. Occasionally, multiple angles are needed to best profile a vascular stenosis, especially if it is located adjacent to a superimposed larger structure (Figure 23–1). The standard practice of using the French size of a catheter as a measurement reference should be avoided. Whereas this technique is acceptable for comparable coronary diameters, the larger sizes of major vessels involved in CHD render this technique too inaccurate. A 10% error in the reference measure could result in a miscalculation of several millimeters. Choosing the proper frame for measurement is also important. Although it is natural to select the frame with the best contrast outlining the target vessel, it is actually more important to select the frame with the largest diameter. Because of the pulsatility of some vessels, there may be a significant difference between the largest and smallest diameters during systole and diastole of a cardiac cycle (Figure 23–2). This is especially true for systemic arteries such as the aorta. Introduction of dynamic angiography and three-dimensional (3D) rendering adds another important modality for better understanding the anatomy before an intervention.

Once measurements are made, the lesion is crossed with an end-hole catheter and placed as far distal as possible. In adults with branch pulmonary artery stenosis and a dilated right atrium and ventricle, passage of any catheter across the right heart may be challenging and require all kinds of techniques to avoid catheter and wire buckling within the atrium or ventricle. A very useful technique is to shape a “left pulmonary artery (LPA)” or “right pulmonary artery (RPA)” curve with the stiff end of a guidewire to help guide the catheter into position. Once this is achieved, a stiff wire is introduced in a manner maximally accommodated by the lumen of the balloon catheter so as to allow for appropriate support and maintain balloon position for dilation. A commonly used wire is an Amplatz Super Stiff “short tip” (Boston Scientific, Natick, Mass.). These have only a 2-cm floppy tip at the end to maximize the length of stiff wire crossing the right ventricular outflow tract. The chosen length and diameter of a balloon that will not impinge on smaller caliber vessels undergoes a “negative prep” to remove all air while not altering the tight factory folding with a large syringe of 1:3 to 1:5 dilute contrast/saline, a three way stopcock, and a pressure monitor inflation device. The larger the balloon, the less concentration of contrast to saline is needed to visualize the inflation, and the quicker the inflation and deflation.

Once the balloon is prepared, it is advanced over the stiff wire to the target lesion. A second sheath on the contralateral femoral vein is often placed to advance a catheter to the site of interest for angiography to determine exact positioning. Keep in mind that it is not uncommon for the native geometry to be altered by the combination of a balloon catheter and stiff wire. Whereas incorrect positioning from altered geometry only results in a repeat dilation, an incorrectly positioned stent after implantation can lead to disastrous results. When the desired position is achieved, an inflation device with a pressure gauge is used until the waist is relieved or maximal inflation pressure is achieved. Depending on the vessel, cardiac output may be completely obscured, and inflation and deflation should be carried out quickly. In the presence of calcium, care should be taken to avoid vessel dissection. In general, the target diameter should be the diameter of the normal adjacent vessel, or no more than 3 to 4 times the minimal diameter, whichever is less.

Stenting

Clinical use of intravascular stents has grown since its early use in peripheral and branch pulmonary arteries in humans.5,6 Stents are indicated when vascular elastic recoil or external compression results in restenosis in spite of adequate angioplasty. Since the early days of stenting using the Palmaz stents (Johnson and Johnson, Bridgewater, N.J.), stents are now available in a wide variety of materials, tensile strength, or cell design; self-expanding or balloon-expandable; and in various diameters and lengths. Unlike coronary artery disease, in which most vessels are similar in size, vascular obstructions in CHD can vary widely in location and size and present in all ages from infancy to adulthood. Hence it is prudent to use a stent that can be serially dilated to the normal adult size of the vessel in which it is implanted.

Even in adult patients, it may be necessary to stage a serial dilation in severely stenotic vessels, especially those that are calcified and in the systemic circulation.

As with balloons, a functional catheterization lab should stock a full assortment of stent types for specific lesions. In general, stents used for CHD are broken into four broad categories based on maximal diameters. “Small” stents are coronary stents that can be dilated to 4 or 5 mm and used to maintain shunt or ductal patency in lesions with ductal dependency for systemic or pulmonary flow. “Medium” stents can be expanded to 12 mm and should be used in small lobar and segmental pulmonary arteries or to maintain Fontan fenestration patency. “Large” stents can be expanded to a diameter of 18 mm and should be used in proximal branch and large lobar pulmonary arteries. “Extra-large” stents are expandable to 24 mm and should be used in coarctation of the aorta and right ventricular outflow tract conduits. Although most small and medium sized stents are available premounted, most large and extra-large stents are hand-mounted and balloon-expanded. Specific features of various commercially available stents are beyond the scope of this chapter.

Class I: 1. Pulmonary angioplasty is indicated for the treatment of significant peripheral branch pulmonary artery stenosis (see text for definition of “significant” stenosis) or for pulmonary artery stenosis in very small patients in whom primary stent implantation is not an option (Level of Evidence: B).

Class IIa: 1. Pulmonary angioplasty is reasonable to consider for treatment of significant distal arterial stenosis (as defined in the introduction to Pulmonary Artery Angioplasty and Stent Placement) or for stenosis in larger, more proximal branch pulmonary arteries that do not appear to be amenable to primary stent implantation (Level of Evidence: B).

Class IIb: 1. Pulmonary angioplasty may be considered for treatment of significant main pulmonary artery stenosis that results in an elevation of pressure to more than two thirds of systemic pressure in the proximal pulmonary artery segment or in the right ventricle (in the absence of pulmonary valve stenosis). This stenosis is usually a form of supravalvar pulmonic stenosis, which is not particularly responsive to balloon dilation alone (Level of Evidence: C).

Class I: 1. Primary intravascular stent implantation is indicated for the treatment of significant proximal or distal branch pulmonary artery stenosis when the vessel/patient is large enough to accommodate a stent that is capable of being dilated to the adult diameter of that vessel (Level of Evidence: B).

Class IIa: 1. It is reasonable to consider pulmonary artery stent implantation in critically ill postoperative cardiac patients when it has been determined that significant branch pulmonary artery stenosis is resulting in a definite hemodynamic compromise in a patient/vessel of any size, particularly if balloon dilation is unsuccessful (Level of Evidence: B). 2. Primary intravascular stent implantation is reasonable in the treatment of significant stenosis of the main pulmonary artery segment that results in elevation of the right ventricular pressure, provided that the stent definitely will not compromise a functioning pulmonary valve and will not impinge on the pulmonary artery bifurcation (Level of Evidence: B).

Class IIb: 1. It may be reasonable to implant small pulmonary artery stents that lack the potential to achieve adult size in small children as part of a cooperative surgical strategy to palliate severe branch pulmonary artery stenosis. These stents may need to be enlarged surgically or removed during a future planned operation (e.g., conduit replacement, Fontan completion) (Level of Evidence: C).