Discussion

In the pediatric patient population, management of aortic valve disease presents a significant challenge with the overall goal of preserving the left ventricular function while also minimizing the number of reoperations required over a lifetime. Challenges involving younger patients necessitate a more complex approach due to variable anatomy, ongoing somatic growth, and available prosthesis size.5 Historically, balloon or open surgical valvotomy were used as the initial strategies to treat aortic valve disease in children and young adults, however, these techniques are associated with poor long-term outcomes and the need for additional surgical interventions within 10 years.1-3 Aortic cusp extension valvuloplasty is an alternative that allows for better management of younger patients, with recent literature reporting favorable outcomes associated with more long-term durability.2-4 Younger patients with particular challenges involving underlying cardiac anatomy can benefit from aortic valvuloplasty, and advocates cite superior freedom from re-operations and acceptable preservation of the left ventricle function.1-5 This surgical strategy allows for annular growth until the use of a more permanent prosthesis placement is feasible. 
While aortic valvuloplasty is a refined surgical method that demonstrates improvements compared to traditional balloon or open surgical valvotomy, the durability of the technique is still limited by the type of patch replacement material for cusp tissue.5 Traditional materials commonly used for valve repair include autologous pericardium, preserved homograft, bovine pericardium, and polytetrafluorethylene (PTFE).2-4 However, in both short and long-term studies, several reports cite major concerns related to lack of growth potential, calcification, thickening, and eventual degradation.1-5  Consequently, the type of material remains a major weakness in leaflet replacement surgeries, and the search for the optimal material continues to evolve as many new biological and synthetic options become available.4 Extracellular matrix (ECM), such as CorMatrix (CorMatrix Cardiovascular, Inc, Atlanta, GA), is one such material that was developed as a promising alternative because of its ability to resist calcification and serve as an interim biological scaffold that enables the propagation and regeneration of a patient’s own cells to ultimately repair tissues.1 Many centers have used it for valve repair in the tricuspid, mitral, aortic, and pulmonary valve, yet the reported outcomes vary (Table 3). 
Czub and associates reported using CorMatrix for tricuspid valve repair in the treatment of a patient with infective endocarditis. No tricuspid regurgitation or reinfection at 6-month follow-up was reported.10 Other case studies also found favorable short-term outcomes in tricuspid and mitral valve repairs with CorMatrix, reporting successful repairs, excellent valve function, and good hemodynamic results at 3-month follow-up.11,12 Luk and associates, however, reported more long-term results with 10 and 12-month follow-up outcomes and found delayed post-operative infection and perforation of the MV leaflet after histological examination of explanted CorMatrix in 2 adults.13
Outcomes using CorMatrix in mitral valve repair also varied in reports studying larger patient populations, even in those with similar follow-up times. Gerdish and associates reported using CorMatrix for mitral valve repair to treat mitral regurgitation in 19 patients. Only 3 MV reoperations were required, and the repaired valves showed good function and no evidence of calcification at median 10.9-month follow-up.14 In contrast, Kelley and associates reported the use of CorMatrix for mitral valve repair in 44 patients, with 8 patients (32%) suffering recurrence of severe MR and 7 patients (28%) requiring re-operation for patch failure at 12-month follow-up.15 In this case, differences in valve technique possibly contributed to the discrepancy in outcomes. In both studies, repair was used to treat mitral valve regurgitation with comparable follow-up times, but Gerdish and associates performed a partial or subtotal leaflet extension, while Kelley and associates performed an anterior leaflet augmentation.14,15 
Interestingly, the literature describing aortic valve repairs using CorMatrix do not indicate good outcomes, irrespective of follow-up time. Hoffman and associates reported significant valve insufficiency in 5 (83%) pediatric patients at 4 months to a 1-year follow-up, Mosala and associates demonstrated similar bad outcomes at 4-year follow-up for a pediatric patient requiring a re-operation for valve failure, severe calcification, fibrosis, and retraction.16,17 Furthermore, the studies comparing CorMatrix and autologous pericardium also reported no significant advantages for CorMatrix from histological, echocardiogram, and clinical data. Zaidi and associates reported the median length of time in situ for CorMatrix was approximately 2 months, significantly less than the reported time for leaflet extension for autologous pericardium.18 Nathan and associates also found that aortic valve repair with CorMatrix is associated with earlier time to reintervention compared to autologous pericardium at 5-year follow-up.19 
Due to the variability of outcomes reported in the literature, the utility and advantages of CorMatrix in valve repairs remains uncertain. Nevertheless, our findings are congruent with the previous reports for the use of CorMatrix in aortic valve repair, and specifically demonstrates these outcomes in the pediatric patient population receiving repair using the cusp extension technique. Additionally, a recent study suggest that biomaterial patches are not optimal for leaflet extensions or reconstructions where the patch has a free edge.9 The retraction of the edges where the collagen reabsorbs without tissue contact can cause insufficiency, which is a possible explanation for the mechanism of failure seen in the CorMatrix extracellular membrane patch recipients.