Aortic valve stenosis (AS) and pulmonary valve stenosis (PS) are common forms of congenital heart disease, with aortic stenosis comprising 3% to 8% and PS comprising 8% to 10% of all congenital heart disease. Balloon valvuloplasty, first performed in the early 1980s, represents first-line therapy in the adolescent and young adult population, especially in AS patients who wish to avoid replacement with a mechanical valve. Following balloon valvuloplasty, AS recurrence and Aortic insufficiency (AI) progression with freedom from aortic valve replacement at 10 years is 76% and freedom from reintervention at 10 years is 46%, prompting discussions regarding surgical versus transcatheter approach as a primary intervention for AS.¹,² In contrast, there is a low rate of reintervention for PS following balloon valvuloplasty despite a significant risk for developing at least moderate pulmonary regurgitation over time (ie, occurs in up to 60% of patients in long-term follow-up of greater than 10 years).³

Treatment with balloon valvuloplasty is an American Heart Association (AHA) Class I recommendation for isolated valvar AS with resting peak systolic transvalvular gradient via catheter measurement of greater than or equal to 50 mm Hg (Level of Evidence B) or greater than or equal to 40 mm Hg if there are symptoms of angina or ST-T wave changes on an electrocardiogram (EKG) at rest or with exercise (Level of Evidence C). Valvuloplasty may be considered (Class IIb recommendations) in AS patients with resting peak systolic valve gradient of greater than or equal to 40 mm Hg but without symptoms or ST-T wave changes if the patient desires to become pregnant or participate in competitive sports (Level of Evidence C) or if peak systolic valve gradient in the catheterization lab is less than 50 mm Hg in a heavily sedated or anesthetized patient if a nonsedated Doppler study finds a mean valve gradient to be greater than or equal to 50 mm Hg (Level of Evidence C)⁴ (Figure 45.1).

Current AHA guidelines recommend pulmonary valvuloplasty for patients who have “valvar PS with peak-to-peak catheter transvalvular gradient or peak instantaneous gradient of greater than or equal to 40 mm Hg or clinically significant pulmonary valvar obstruction in the presence of right ventricular dysfunction” as Class I recommendation (Level of Evidence A).⁴

Aortic valve morphology is intrinsic to outcomes of balloon aortic valvuloplasty with regard to postprocedural gradient, degree of aortic insufficiency, and freedom from reintervention over time.⁵,⁶ However, single-center and multicenter studies fail to show consensus. The presence of more than mild insufficiency, small aortic valve annulus, or presence of other cardiac lesions (such as subaortic membranes) would warrant surgical intervention rather than a transcatheter-based approach. Most pulmonary valves are amenable to valvuloplasty. Exceptions to this are severely dysplastic pulmonary valves, especially those associated with Noonan syndrome, and patients with significant subvalvular or supravalvular obstruction; patients with these conditions are better suited for surgical correction when indicated.

Balloon valvuloplasty is considered a nonsurgical first step to relieve significant AS or PS. The appropriate balloon(s) size(s) are important in the final result.

For AS, diagnostic catheterization, with the patient heparinized, is performed to document the gradient across the aortic valve, degree of aortic insufficiency, aortic valve annulus dimensions, and left ventricular function. Left ventricular and ascending aortic angiograms are performed to evaluate aortic valve annulus, left ventricular function, and baseline aortic insufficiency (Figure 45.1). A retrograde arterial or antegrade venous approach via atrial transseptal catheterization can be utilized for intervention. Single-balloon or double-balloon techniques can be utilized; double-balloon technique requires two access sites but offers smaller arterial sheath sizes than a single balloon technique. A balloon diameter is chosen that is 0.8 to 1.0 the diameter of the aortic valve annulus. Rapid right ventricular pacing can be performed to aid in the stability of the balloon during inflation (Figure 45.2). After each inflation, repeat pressure measurement across the valve and angiography in the ascending aorta should be performed to evaluate
the degree of residual stenosis and presence of aortic insufficiency (Figure 45.2 and e-Figure 45.1). Although most centers use angiography as the gold standard to assess aortic insufficiency during the procedure, echocardiography is used to assess change over time in most centers. A technically adequate dilation will often yield a residual peak-to-peak valvular systolic gradient of less than or equal to 20 to 35 mm Hg with 0 to 1 grade increase in aortic insufficiency.

For PS, a diagnostic right heart catheterization is performed to evaluate right ventricular pressure and pressure gradient across the pulmonary valve. A right ventriculogram is performed to evaluate right ventricular size and function and measure the pulmonary valve annulus, typically in cranial and straight lateral projections (Figure 45.3). After pulmonary valve annulus diameter is confirmed, a balloon whose diameter is 120% to 140% of the pulmonary valve annulus is chosen. A balloon size larger than 140% could lead to annulus rupture. We typically start with 120% of annulus diameter because more aggressive valvuloplasty is associated with post-valvuloplasty pulmonary regurgitation. Sufficient relief of stenosis is often achieved with one inflation of the balloon. After each inflation, repeat pressure measurements across the pulmonary valve are obtained, with a goal of postprocedure transvalvular gradient of less than 30 mm Hg ( e-Figure 45.2). A repeat right ventriculogram is performed to evaluate for any injury to the right ventricular outflow tract. Post-valvuloplasty pulmonary insufficiency should be assessed by transthoracic echocardiography as the degree of pulmonary insufficiency is often exaggerated on angiography.

Balloon aortic valvuloplasty is considered a palliative procedure because the morphology of the valve remains abnormal and the rate of reintervention is high with both surgical valvulotomy and a transcatheter approach, with balloon aortic valvuloplasty having 10-year freedom from reintervention of 46% and surgical aortic valvuloplasty a 10-year freedom from intervention of 73%.¹,⁷ Technical success of the procedure is limited by valve annulus, as increasing balloon to annulus ratio increases the risk of aortic insufficiency. Balloon pulmonary valvuloplasty is limited by the size of the pulmonary valve annulus owing to the risk of annulus rupture with the use of a large balloon to annulus ratios.

Routine cardiology follow-up with echocardiography at 1 month, 6 months, and then yearly is typical and is imperative owing to the risk of recurrent valve stenosis and progressive valve insufficiency. Routine EKGs should be performed to evaluate for ST-T wave changes. Exercise stress testing can be considered in patients with exertional symptoms.

Native pulmonary artery stenosis can occur in isolation, association with genetic syndromes (ie, Alagille syndrome), or combination with other forms of congenital heart disease. In adolescents and adults, postoperative pulmonary artery stenosis is more commonly seen and is caused by scar tissue, vascular distortion, folding or extrinsic compression from surrounding structures. Long-standing branch pulmonary artery stenosis can lead to right ventricular pressure overload, pulmonary insufficiency, and eventually right ventricular failure if left untreated.

Management of pulmonary artery stenosis is dependent upon multiple factors: the size of the patient, number of affected vessels, and concomitant lesions. In the adolescent and young adult population, most cases of pulmonary artery stenosis can be treated in the cardiac catheterization lab, either with balloon angioplasty and/or stent placement.

Precatheterization planning is important, particularly in postoperative patients. Attention should be paid to the original anatomy, operative procedures including patch material used on the pulmonary arteries, and any prior cardiac catheterizations and interventions that were previously performed, including prior stents utilized. For example, patients with transposition of the great arteries who have undergone a Le-Compte maneuver (draping their pulmonary arteries across the aortic root) require careful assessment of the aortic position, coronaries location, and bronchus location, particularly before pulmonary artery stent placement.

Transthoracic echocardiography should be performed prior to catheterization to evaluate right ventricular size and function, right ventricular pressure, and proximal branch pulmonary arteries. Right ventricular pressure more than half to two-third systemic pressure or a gradient greater than 20 to 30 mm Hg across the branch pulmonary artery often requires intervention.⁴ Perfusion scans help evaluate the flow discrepancy between lungs in patients with unilateral branch pulmonary stenosis; flow discrepancy of 70/30% or worse is an indication of evaluation/intervention. In patients with complex disease, noninvasive imaging with computerized tomography (CT) or magnetic resonance angiograms and three-dimensional (3D) printing is particularly helpful in complex bilateral proximal stenoses ( e-Figure 45.3).

Diagnostic right heart catheterization is performed to document hemodynamics and degree of stenosis across the branch pulmonary arteries. Main pulmonary artery angiograms are performed to delineate the areas and degree of stenosis. Choosing the appropriate camera angles is of utmost importance, as
foreshortening of the vessel could lead to inappropriate measurements and stent choice. 3D rotational angiography can assist with ideal angles for intervention. When multiple lesions are present, such as in patients with repaired tetralogy of Fallot with major aortopulmonary collaterals or patients with peripheral pulmonary stenosis, interventions should be performed distal to proximal so that there are no multiple catheter and wire exchanges across freshly dilated or stented vessels. Balloon angioplasty is often performed prior to stenting, as this alone may lead to a satisfactory result and alleviate the need for stent placement. Angioplasty also gives information on the compliance of a vessel.

Although initial balloon selection for angioplasty varies by operator, a starting diameter of approximately two times the narrowest diameter of the vessel is often chosen. If there is no resolution of a waist on the balloon at full inflation, then the vessel is considered noncompliant. Cutting balloons have been shown to be effective in treating resistant lesions.⁸ Despite aggressive balloon angioplasty, there remains a high rate of stenosis or restenosis. Stent placement offers better short- and long-term results.⁹,¹⁰ In some patients, a prior stent that was placed when the patient was much smaller may need further dilation. If the stent cannot be enlarged to an adequate diameter, intentional fracturing of these stents has been shown to be safe and effective, allowing for the placement of a larger stent.¹¹,¹²

Complications related to balloon pulmonary angioplasty and stent placement are not insignificant, with a serious adverse event rate of 10% noted in a multi-institutional registry. Adverse events include vascular or cardiac trauma, arrhythmia, hemodynamic compromise, pulmonary edema, and/or bleeding from reperfusion injury.¹³ These procedures should be performed by operators who are well-versed in the management of these complications.

Vessels that are too compliant yield unsatisfactory results related to vessel recoil after balloon dilation. Noncompliant vessels can be resistant to angioplasty, even with the use of high- or ultra-high-pressure balloons and cutting balloons. Stent placement in these situations may not immediately improve the vessel stenosis, but these lesions can often be successfully re-dilated at a later date. To date, there is not a stent commercially available that will expand with somatic growth; therefore, recurrent interventions even into adulthood are often necessary to re-dilate a previously placed stent in childhood.

Balloon pulmonary angioplasty has a high incidence of restenosis, and thus, these patients should be followed longitudinally. Patients with stents also require routine follow-up, as in-stent restenosis can develop, and the stent often needs to be re-dilated over time to account for patient growth.

Current research includes the development of biodegradable stents, a temporary scaffold that allows for remodeling of the vessel and then disappears, thereby eliminating the need for re-dilation of a permanent stent.

Conduits from the right ventricle to pulmonary artery are commonly used for the repair of patients with truncus arteriosus, tetralogy of Fallot with pulmonary artery atresia, pulmonary valve atresia without ventricular septal defect (VSD), Ross procedures, and various other forms of complex biventricular anatomy where there is a need to establish continuity between the right ventricle and branch pulmonary arteries. Unfortunately, bioprosthetic conduits do not grow with the patient and degenerate over time.¹⁴ This results in conduit stenosis, insufficiency, or most commonly, both. Transcatheter intervention has become the mainstay of therapy for diseased conduits in which the conduit remains appropriately sized for the patient, and transcatheter valve technology for congenital heart disease has evolved significantly over the past decade.¹⁵

Valve therapy in congenital heart patients is predominantly for use in the pulmonary position. The first Food and Drug Administration (FDA)-approved transcatheter valve for use in patients in the pulmonic position was the Melody valve (Medtronic, Minneapolis, MN, USA) but was only approved for use within right ventricle to pulmonary artery conduits.¹⁶ With the use and approval of bioprosthetic valves in adult patients with aortic valve disease, more valves have become available for use in larger diameter outflow tracts (ie, Sapien S3 and XT [Edwards Lifesciences, Irvine, CA, USA]). Although
conduit therapy was a significant step in preventing congenital patients from undergoing multiple operations for conduit revisions, it did not address the large population of patients with large diameter outflow tracts whose diameter far exceeded the upper limits of the Melody valve and, in many cases, the Edwards family of valves. To meet this demand, several valves have now been developed and are undergoing trial to treat the larger outflow tracts, thus providing the interventionalist the tools to treat all dysfunctional outflow tracts whether native or conduit.

Conduit intervention is necessary when there is evidence of hemodynamically significant stenosis and/or insufficiency, in the presence of right ventricular dysfunction, right ventricular pressure overload, and/or progressive symptoms of exercise intolerance. The goal of conduit intervention is to relieve obstruction and, if possible, restore valve function if the conduit is of adequate size and the anatomy amenable. Transcatheter pulmonary valve implantation is indicated in patients with evidence of right ventricular volume overload; when right ventricular end-systolic volume greater than 140 mL/m², it does not return to normal size and volume with valve replacement. Thus, earlier intervention is warranted to optimize right ventricular remodeling.¹⁷ Right ventricular dysfunction and even left ventricular dysfunction related to this are also indications for proceeding with transcatheter pulmonary valve replacement.

Primary anatomic considerations include conduit size, patient size, vascular access, location of the coronary arteries, and presence of any other significant lesions that may complicate the procedure such as acute angle of the branch pulmonary arteries or significant proximal branch pulmonary artery stenosis. For transcatheter valves, candidacy is related to the dimension of the outflow tract to be implanted, specifically, the size and length of the landing zone. This can be determined by 3D preprocedure imaging (CT or cardiac magnetic resonance imaging [CMRI]) but must be confirmed with balloon sizing prior to valve implantation¹⁸ (Figure 45.4). The Melody valve, which is a bovine jugular vein sewn to the Cheatham-platinum stent, is suitable for conduit diameters up to 22 mm. When dilated beyond this, there is an increased risk of creating valvular insufficiency. For larger diameter outflows (ie, up to 29 mm), the Sapien family of transcatheter heart valves can be utilized. Beyond this diameter, transcatheter treatment at the time of this writing is limited to research studies. In patients who have undergone a Ross operation with dilated neoaortic roots in close proximity to the conduit, creation of aortic valve insufficiency should be assessed during compliance testing (see below) to evaluate for distortion of the neo-ascending aorta.

Prior to catheterization, a 3D imaging study (CT or CMRI) is performed to assess the right ventricular outflow tract and conduit anatomy, the branch pulmonary artery anatomy, and the relationship of the coronary arteries to the conduit or valve landing zone, so that the operator may anticipate any potential problems¹⁸ (Figure 45.4). Obstruction below the conduit should be excluded. If any concern arises regarding possible coronary artery compression, selective angiography may need to be performed during compliance testing¹⁹ ( e-Figure 45.4).

Right and left heart catheterization is performed to evaluate the right ventricular pressure, the gradient across the dysfunctional right ventricular outflow tract or conduit, the assessment of any hemodynamically significant branch pulmonary artery stenosis, and assessment of coronary artery position. Assessing ventricular compliance using diastolic pressure measurements is helpful in understanding the impact of right ventricular volume overload. Conduit interventions are limited currently by conduit size. Resolving early stenosis with a combination of angioplasty and or stent placement can help prolong the time to conduit revision.¹⁵ However, in adolescents and adults, surgical conduit or valve replacement is indicated in patients with conduits too small for their size. In addition, transcatheter valve therapy is not indicated in conduits less than 16 mm in diameter, as the Melody valve is approved for implant conduit sizes of 16 to 22 mm. The Sapien XT is only approved for conduits greater than 20 mm in size. In patients whose conduit size is 16 mm or larger, however, restoring pulmonary valve function with a transcatheter valve is feasible. This typically requires some type of “preparation” of the conduit with bare-metal or covered stents to optimize the conduit diameter and prevent recoil and later fracture of the Melody valve stent. For heavily calcified conduits, primary covered stent placement might be indicated to prevent complications from conduit injury or rupture. Because conduit rupture may occur even in noncalcified conduits, covered stents are being considered in these conduits as well.²⁰ Intervention depends highly on anatomic characteristics including proximity of the coronary arteries to the conduit, other associated lesions which may or may not be amenable to transcatheter intervention, and compliance of the conduit itself. When undertaking these procedures, one must be prepared for the two most significant and potentially catastrophic complications: conduit rupture and/or coronary compression/distortion.¹⁹,²⁰,²¹