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Disease or dysfunction of the aortic valve in pediatric patients presents a substantial challenge. Valve preservation, even if not the definitive solution, is always optimal. Successful repair will enable somatic growth and avoid repeated valve replacement and the need for systemic anticoagulation. When repair of the aortic valve is not possible in pediatric patients, replacement of the valve requires the most suitable (or, often, the least unsuitable) choice for each patient. The limitations of the typical replacement options (pulmonary autografts, mechanical valves, stented bioprostheses, and homografts) have led us to explore the use of stentless xenografts.
Herein, we present a case of aortic valve replacement with a stentless porcine xenograft in one of the youngest and smallest patients reported to date. Use of the xenograft enabled a proper fit with a small aortic annulus, precluded the need for subsequent systemic anticoagulation, and averted a transvalvular gradient and the creation of 2-valve disease. We believe that the stentless porcine xenograft is feasible for use in pediatric patients who require aortic valve replacement.
Disease or dysfunction of the aortic valve in pediatric patients presents a substantial challenge. Valve preservation is always the optimal solution, if not definitive. Successful repair enables somatic growth and avoids the need for repeated valve replacement and systemic anticoagulation. In patients who are not amenable to primary repair, options include implantable pulmonary autografts (by means of the Ross operation), mechanical valves, stented bioprostheses, and homografts. Each option has considerable drawbacks, which led us to explore the application of stentless xenografts in the pediatric population. Here, we report the case of one of the youngest and smallest patients to have received a stentless porcine xenograft (Freestyle®, Medtronic, Inc.; Minneapolis, Minn) in the aortic position.1
In February 2008, a previously asymptomatic 7-year-old girl (weight, 19.5 kg; body surface area, 0.85 m2) with a history of bicuspid aortic valve and mild aortic stenosis presented at another hospital after a 2nd syncopal episode that was associated with exercise. Her cardiac enzyme levels were substantially elevated, and electrocardiography showed inferolateral ST changes. Transesophageal echocardiography (TEE) showed normal biventricular function, moderate aortic insufficiency, and flow reversal in the left main coronary artery (LMCA).
Because of the patient's hemodynamic instability, deteriorating function, and progressive ischemia, she was transferred to our institution, where TEE revealed a trileaflet aortic valve and a diminutive, hypoplastic left coronary cusp that was partly fused to the aortic wall (Fig. 1). Severe aortic insufficiency and prolapse of the cusp into the orifice of the LMCA were seen (Fig. 2). The aortic annulus was estimated to be 14 mm in diameter (Z score, 0.14).
The patient underwent urgent surgical exploration. The free edge of the left coronary cusp was found to be fused to the aortic wall superior to the left coronary ostium, and only a small opening communicated with the ostium. This configuration caused the left coronary cusp to prolapse intermittently into the corresponding sinus and obstruct the LMCA. The right and noncoronary cusps were elongated and redundant.
A complex repair was attempted; however, persistent aortic insufficiency necessitated valve replacement. After the cusps were resected and the coronary buttons were fashioned, a 19-mm probe was inserted into the aortic root. A 19-mm Freestyle full-root stentless porcine xenograft was implanted with the use of interrupted pledgeted sutures and after the usual 180° rotation of the graft. The coronary arteries were reimplanted into the graft as buttons.2 Postoperative TEE revealed no aortic stenosis, no aortic insufficiency, and left ventricular systolic function that was within lower normal limits (Fig. 3).
On postoperative day 5, the child was discharged from the hospital in good condition. She was prescribed furosemide twice daily, and an 81-mg aspirin, a low-dose angiotensin-converting enzyme inhibitor, and a β-blocker once daily. At hospital discharge and at 1 year of follow-up, transthoracic echocardiography revealed normal left ventricular function and end-diastolic dimension without aortic stenosis or insufficiency.
Our patient is one of the youngest and smallest children to have undergone aortic root replacement with a stentless xenograft.1 Given the complexities of aortic valve repair in pediatric patients, the chief goal of surgical intervention—a durable repair—is not always possible. Options for replacement include pulmonary autografts, mechanical valves, stented bioprostheses, homografts, and now stentless xenografts. Valve selection must be suited to the patient.
Although the Ross operation is a rather challenging surgical procedure, its advantage is that the implanted autograft is capable of growth. Furthermore, the autograft and the right ventricle-to-pulmonary artery valved conduit typically do not require systemic anticoagulation. A distinct disadvantage of the Ross operation is the creation of double-valve disease from single-valve disease. In addition, long-term outcomes are often negatively affected by the development of neoaortic and pulmonary insufficiency and by the need for surgical reintervention.3,4 Many parents decide against this surgical option for their children, as did the parents of our patient.
Mechanical valves are typically very durable and are subject to low failure rates; however, they inhibit annular growth and have a built-in transvalvular gradient, particularly in the smaller sizes that are used in pediatric patients. The need for systemic anticoagulation presents challenges for active children and young adults. Furthermore, there is a 1% annual risk of thromboembolic complications.5 Pannus ingrowth can also lead to mechanical failure of the valve leaflets, which requires eventual reoperation.
Stented bioprosthetic valves typically require only aspirin therapy, but their effective valve area is usually even smaller than that of corresponding mechanical valves. Furthermore, stented bioprosthetic valves will not usually fit within a small root. For these reasons, they are not used frequently in pediatric patients.
Homografts tend to provide excellent hemodynamic results and are commonly used in pediatric aortic valve replacement. However, these conduits have limited durability secondary to graft stenosis and degeneration, and some last only a few months before substantial regurgitation develops.6 This outcome is widely seen in North America, where regulations governing preservation techniques may play a role in limiting durability in comparison with results achieved abroad.
In adults, the Freestyle stentless porcine xenograft has excellent long-term durability and hemodynamic function, with minimal transvalvular gradients in the aortic position.7 This graft has been particularly useful in adults with small aortic annuli who have needed aortic valve replacement. In children, this valve has been used successfully as a right ventricle-to-pulmonary artery conduit in the Ross operation and in pulmonary valve replacement, with encouraging outcomes.8,9 However, the xenograft's durability in terms of accelerated conduit calcification and failure in pediatric patients is a concern, and few long-term data are available. These prostheses undergo anticalcification treatment during processing,10 and preliminary data suggest that this contributes to positive short- and intermediate-term outcomes.1,11,12
We believe that use of the Freestyle stentless porcine xenograft is a reasonable option in pediatric patients who require aortic valve replacement. In our patient, we avoided a mechanical aortic valve that would have required systemic anticoagulation. Instead, we implanted an adult-sized, full-root bioprosthesis that avoided a transvalvular gradient and the creation of double-valve disease. More formal evaluation of this application of stentless xenografts, with long-term follow-up, is warranted.
Address for reprints: Jorge Salazar, MD, Department of Surgery, University of Mississippi Medical Center, 2500 N. State St., Jackson, MS 39216