Since percutaneous balloon pulmonary valvuloplasty (BPV) for pulmonary valve stenosis (PS) was first successfully performed by Rubio-Alverez and Limon-Lason¹ using a ureteral catheter in 1950s, it has become the standard of care for treatment of isolated PS over surgical valvotomy.^2,3 In 2000, based on these experiences, the percutaneous pulmonary valve implantation (PPVI) was first performed by Bonhoeffer et al⁴ in a patient with a dysfunctional of right ventricle–to–pulmonary artery conduit. In 2010, the Melody valve (Medtronic, Minneapolis, MN) became commercially available in the United States under a humanitarian device exemption protocol and, more recently, was awarded postmarket approval by the US Food and Drug Administration. Since then, PPVI has been performed in over 4500 patients in more than 30 countries worldwide. In this chapter, we will review BPV and PPVI with particular focus on the indication, technical aspect, clinical outcomes, and potential complications.

Patient Selection and Clinical Indication

Isolated PS is a relatively common disorder, accounting for approximately 10% of all congenital heart defects,^3,5 and it varies in regard to severity of obstruction to the pulmonary orifice size, leaflet morphology (eg, dome-shaped, unicommissural, bicuspid, or dysplastic tricuspid valve), and annulus (eg, hypoplastic or enlarged annulus).⁶ Other congenital cardiac defects that may be associated with PS include atrial septal defect, ventricular septal defect, tetralogy of Fallot, transposition of the great arteries, double-outlet right ventricle, and ventricular inversion.⁷ Significant obstruction may lead to an inability to augment pulmonary blood flow during exertion, resulting in exercise-induced fatigue, syncope, or chest pain. Physical examination reveals a systolic ejection murmur with maximal intensity at the left upper sternal border, and transthoracic echocardiography is key to determining the severity and morphologic diagnosis. Once a severe PS is diagnosed, cardiac catheterization is performed in order to provide appropriate therapy.

Given the relative low risk and high likelihood of a long-standing good result, the generally accepted indication of BPV is more than moderate degree of PS (echocardiographic peak instantaneous pressure gradients ≥50 mm Hg or mean Doppler pressure gradients ≥30 mm Hg for symptomatic patients and peak Doppler pressure gradients ≥60 mm Hg or mean pressure gradients ≥40 mm Hg for asymptomatic patients) with less than moderate pulmonary valve regurgitation.⁸ BPV provides an immediate reduction of pulmonary valvular gradients and modest increase of pulmonary pressure and cardiac index. Improvement in right ventricular dysfunction frequently results in reduction of tricuspid regurgitation and right-to-left shunt if it exists.⁹ Patients with mild (gradient <30 mm Hg) stenosis are contraindicated for intervention, as natural history studies have demonstrated the benign natural history of mild PS at follow-up.¹⁰ Even in the asymptomatic patient, severe PS should be treated to prevent myocardial damage associated with long-term right ventricular pressure overload.^11,12 Exercise testing may induce abnormal hemodynamic response due to low cardiac output in these patients.

Technique

BPV is performed most commonly under local anesthesia with procedural sedation, with continuous noninvasive heart rate, pressure, and oxygen saturation monitoring. Although transfemoral venous access is commonly preferred, transaxillary, transjugular, or transhepatic venous access can be successfully performed as well.^13-15

A balloon wedge catheter (Arrow International Inc., Reading, PA) is usually used for right-sided pressure measurements, obtaining right ventricular and then pulmonary artery pressures. If a simultaneous gradient is required, a dual lumen catheter can demonstrate simultaneous gradient across the pulmonary valve. Simultaneous recording of the right ventricular pressure and femoral arterial pressure also helps in assessing the severity of the pulmonary valve; right ventricular peak systolic pressure ≥75% of peak systolic systemic pressure is considered significant as well, particularly in younger patients. After gradient evaluation, right ventriculogram is performed in the right ventricle with left lateral projection (Fig. 45-1A). A straight anteroposterior view helps to assess the right ventricular size and ejection fraction, whereas the left lateral view, which is perpendicular to the pulmonary valve annulus, helps to determine the single plane assessment of valvular annular dimension. Left-sided catheterization and angiography are usually not warranted. After crossing the catheter through the pulmonary valve, 0.035-inch exchange length wire is passed to the pulmonary artery (left pulmonary artery is preferable) through the catheter already in place, and then the catheter is removed. If the size of the femoral venous sheath does not accommodate the selected balloon catheter, the sheath may be upsized to an appropriate size at this point. The selected balloon angioplasty catheter is advanced and positioned at the pulmonary valve. Tyshak II balloons (NuMed, Inc., Hopkinton, NY) are usually preferred due to their low-profile cross-sectional area for introduction. Landmarks from the previous ventriculogram or balloon indentation on fluoroscopy may help in positioning the balloon during inflation. The balloon is inflated with diluted contrast material (~15%) using a syringe and hand inflation. The balloon is rapidly inflated until the disappearance of the sharp part of the balloon waist and no greater than the burst pressure of the balloon (Fig. 45-1B-C). Conservative balloon sizing is important to avoid the creation of significant pulmonary regurgitation and rupture of pulmonary annulus. The current recommendation is to use a balloon diameter 1.2 to 1.3 times the pulmonary annulus based on follow-up data,^16,17 except for pediatric patients with a dysplastic pulmonary valve, in whom it is recommended to use a diameter 1.4 to 1.5 times the pulmonary annulus.¹⁸ Use of balloon diameters more than 1.5 times the pulmonary annulus may result in annular injury.

For larger annuli, the double-balloon technique may be considered if the largest single balloon is inadequate. The following formula is used to calculate the effective balloon size¹⁷: [D₁ + D₂ + Π (D₁/2 + D₂/2)]/Π. D₁ and D₂ are the diameters of each balloon used. This formula has been further simplified,¹⁹ as follows: effective balloon diameter = 0.82 (D₁ + D₂). The double-balloon technique produces less hypotension during the procedure because it allows right ventricular output in between the balloons during inflation. However, single-balloon valvuloplasty is currently preferred due to its ease and simplicity, with usually excellent outcomes compared to the double-balloon technique.²⁰

Following balloon valvuloplasty, repeat hemodynamic measurements are undertaken to assess the results of the valvuloplasty. If the result is not satisfactory (gradient in excess of 30 mm Hg), a repeat dilatation with a larger balloon is considered. Once the catheter and guide wire are removed, a right ventriculogram is performed to evaluate for any complication, such as tricuspid regurgitation or pulmonary annular injury.

The patient is observed overnight with heart rate, blood pressure, and pulse oximetry monitoring for any late complications. Clinical reevaluation at least once using echocardiography is generally recommended for follow-up.

Clinical Outcomes and Potential Complications

The Valvuloplasty and Angioplasty of Congenital Anomalies Registry reported mortality of 0.24% (mostly neonate and young infant) and major complication of 0.35% from 822 BPV procedures from 26 sites.²¹ Major acute complications were inversely related to age and mostly associated with cardiac catheterization as follows.

Injury of the right ventricular outflow tract occurs in 0.1% of patients undergoing BPV.²² Because the right ventricular infundibulum is lacking in elastic fibers as compared with the pulmonary trunk, it is susceptible to tearing and dissection. An oversized balloon, especially in neonatal patients with a narrowed infundibulum, may result in myocardial injury and thereby increase the risk of right ventricular perforation.²³ The uncommon but feared complication of “suicidal right ventricle” may result after BPV in which muscular spasm after relief of valvar PS occurs. Patients with significant infundibular gradients that develop after valvuloplasty may benefit by acute administration of fluids to expand the right ventricle or administration of β-blocker medications to slow the heart rate.²⁴

Pulmonary regurgitation is less common and less severe following balloon valvuloplasty than following open surgical valvotomy. However, if one includes milder degrees of pulmonary regurgitation, it has been reported in approximately 60% to 90% of cases,^25,26 and the degree of pulmonary regurgitation may increase with time. Although most patients do not require surgical intervention for increased pulmonary regurgitation, clinical follow-up is recommended in patients with more than mild pulmonary regurgitation to identify the small number of patient with late development of severe pulmonary regurgitation and right ventricular dysfunction in whom pulmonary valve replacement would be warranted.²⁷ This cohort may now be considered for PPVI as well, and this will be discussed later in this chapter. See also the section titled “Percutaneous pulmonary valve implantation.”

The complication of severe tricuspid regurgitation has been demonstrated to occur in 0.2% of patients, although it is primarily confined to neonatal patients due to the tricuspid papillary muscle rupture being caused by the proximal part of the inflated balloon.²²

Other potential complications are arrhythmia (eg, complete heart block, right bundle branch block, ventricular tachycardia), pulmonary thromboembolic events, and acute pulmonary edema. In the younger patient with severe PS, the pulmonary vascular bed may have been exposed to long-standing hypoperfusion and remodeling. As such, it may not be able to adapt to acute increases in pulmonary blood flow after resolution of the valvar stenosis, which can result in acute pulmonary edema. Fortunately, such acute pulmonary edema is frequently transient in nature.

Late complications at follow-up include femoral vein stenosis or occlusion, which occurs in approximately 7% to 19% of patients (more likely in infants) but is mainly asymptomatic. Restenosis of the pulmonary valve is uncommon but can be detected by follow-up echocardiography in about 8% to 10% of patients.^21,28 Repeat BPV is first considered; however, subsequent surgical intervention is reported in 10% to 16% of cases at 10 years.^28,29 The risk factors of recurrence identified in previous studies are primarily a balloon–to–pulmonary valve annulus ratio <1.2 and immediate postvalvuloplasty gradient >30 mm Hg.^26,30 A small annulus due to dysplasia and postsurgical or complex PS were also found to be a predictive factors for restenosis,²⁸ and surgery may be generally recommended in these patients.

Comparison With Surgery

In surgical series for open approaches to PS, mortality rates vary from 3% to 14%, and recurrence rate range from 0% to 8%.²⁸ Due to baseline differences between patient populations, it is difficult to compare directly the effectiveness of BPV and surgical valvotomy. However, in the present era, BPV has become the initial standard of care due to the far less invasive nature with less mortality and comparable relief of obstruction with less regurgitation compared to open surgery.³¹

Aneurysmal Poststenotic Dilation

Poststenotic dilation of the pulmonary artery is relatively common in congenital PS, but the natural history remains unclear, although it is likely benign in most cases.³² Typical poststenotic dilation diameter involves the main and left pulmonary arteries. BPV serves to relieve the stenosis and may prevent further poststenotic dilation. Rarely, the left pulmonary artery dilatation after BPV may be due to traumatic injury from a long and large balloon. Recommended modifications include using a smaller initial balloon ratio and using shorter balloons to minimize risk of injury to the left pulmonary artery.

Clinical Indications and Patient Selection

Dysfunction of a surgically placed pulmonary valve, manifesting as some combination of stenosis or regurgitation, is a common problem after surgical repair of right-sided congenital heart disease. Surgical pulmonary valve replacement using a valved conduit or tissue valve has been a long-standing therapy that has been performed with low mortality.³³ However, dysfunction of the bioprosthetic valve occurs in more than half of the patients by 10 years postoperatively.³⁴ As a result, the majority of such patients have been faced with the prospect of multiple repeat open-heart surgeries during their life. Therefore, patient management strategy has been based on delaying surgical intervention for as long as possible, so that the number of open-heart surgeries performed on any individual patient is kept to a minimum. However, this approach bears the risk of delaying surgery beyond a theoretical point of limited return when right ventricular dysfunction and impaired exercise capacity might be irreversible.