Valve repair is the gold standard in aortic valve disease, particularly in pediatrics, as it allows for somatic tissue growth and avoids lifelong anticoagulation. However, there are instances where a valve can no longer be repaired, leaving replacement as the only option. Selecting the optimal substitute for the aortic valve in children is a complex issue that requires evaluating short- and long-term risk-benefit ratios, with scientific evidence on this subject being notably scarce. Presently, it is extremely challenging to inform parents about their child’s life expectancy following valve replacement, the number of reinterventions required, anticoagulation needs, thrombotic or bleeding risks, or how these risks may evolve over time.
The therapeutic arsenal includes several options for aortic valve replacement: mechanical or biological prostheses, homografts, the Ross procedure (pulmonary autograft), and since 2007, the Ozaki technique, which replaces aortic leaflets with autologous or heterologous pericardium, allowing annular growth.
This article aims to review the literature on aortic valve replacement in children and perform a microsimulation to estimate mid- and long-term outcomes of different substitutes. A systematic review of literature on aortic valve replacement in patients under 18 years of age from 1990 to 2021 was conducted. Studies on pediatric Ross procedure, mechanical valve replacement, biological valve replacement, and homografts were included. Early events were defined as those occurring within 30 days, and late events as those occurring beyond 30 days. Time-to-event data were collected, and a microsimulation model was applied.
A total of 68 studies were evaluated, of which only one was prospective and another exclusively evaluated the outcomes of bioprostheses. A total of 5259 patients were studied, with an average follow-up of 5.9 years and 37,435 patient-years. The mean age of patients undergoing the Ross procedure, mechanical valve replacement, and homograft was 9.2 years, 13 years, and 8.4 years, respectively. Early mortality for the Ross procedure, mechanical valve replacement, and homograft was 3.7%, 7%, and 10.6%, respectively, while late mortality was .5%/year, 1%/year, and 1.4%/year, respectively. Microsimulation at 20 years estimated a survival of 18.9 years for the Ross procedure and 17 years for mechanical valve replacement. The estimated reintervention rate on the aortic valve at 20 years was 42% for the Ross procedure and 17.8% for mechanical valves.
The authors concluded that the outcomes of aortic valve replacement in the pediatric population are suboptimal, with high mortality, particularly in younger patients, and a significant reintervention rate. In this context, they advocate for the Ross procedure, as it appears to offer a survival advantage over mechanical valve replacement.
COMMENTARY
There is no perfect substitute for the aortic valve, as this study’s results clearly illustrate. The Ross procedure, described by Donald Ross in 1967, replaces the aortic valve with living tissue that can accommodate somatic growth. However, it is a technically complex procedure that “burdens” the right side of the heart to replace the left side. In other words, it transforms a single-valve disease into a two-valve disease. The procedure involves implanting a pulmonary autograft in the aortic position, a tissue designed to withstand relatively low pressures, as its medial layer is structurally thinner than aortic tissue. Over time, patients have shown a risk of annular dilation requiring reintervention, either with prosthetic replacement or, in some cases, a David procedure if the leaflets are unaffected. Not mentioning the multiple right-sided reinterventions that the patients will require.
Replacement with a prosthesis condemns the annular growth. Biological prostheses are rarely used due to their poor durability; the only published study on this included 24 patients for whom a Ross procedure was not feasible, with a follow-up period of just 46 months. Homografts do not last much longer and exhibited the highest rates of mortality and reintervention in this study. The drawbacks of homografts include their limited availability, erratic deterioration depending on the patient’s age and growth rate, immune response, and blood group incompatibilities. For most surgeons, this substitute is considered a last resort. Mechanical prostheses, while the most common alternative, are not without risks, with a thromboembolic event and stroke rate of .4%/year each. Ensuring effective anticoagulation management in children is challenging, causing significant concerns for patients, families, and healthcare providers.
Based on the presented data, extrapolating adult outcomes to pediatric substitutes would be a mistake. Even within the pediatric population, we cannot generalize outcomes, as a Ross procedure in an infant with mortality rates around 16.3% is not comparable to the 3.7% in older children. Similarly, a Ross-Konno procedure, necessary in cases of severe left ventricular outflow tract obstruction, differs from a standard Ross procedure. A mechanical valve implanted at 7 years of age carries a higher risk of reintervention and prosthesis-related adverse events than one implanted at 17 years. This explains the high annular enlargement rate recorded in the study. Substitutes should not be evaluated in isolation but tailored to patient profiles. Mortality, reintervention, and thromboembolic events should not be the sole considerations. Quality of life offered to patients must also be considered, including the lifelong need for anticoagulation with mechanical prostheses and the estimated 42% reintervention rate on the aortic valve at 20 years with the Ross procedure, alongside multiple right ventricular outflow tract reinterventions.
As for the study’s limitations, it should be noted that this is a meta-analysis of highly heterogeneous retrospective studies, lacking a control group. Studies with fewer than 20 patients were excluded. The microsimulation was based on linear event rates, so caution is required when interpreting these values. Lastly, the Ozaki technique was not mentioned as a potential comparator. This technique replaces the aortic leaflets while preserving the annulus, thus allowing annular growth similar to the Ross procedure. It does not involve manipulation of the right heart. Although it is not a definitive solution for aortic valve disease, it serves as a bridge to complete the patient’s somatic development before implanting a larger prosthesis.
What is the best substitute for the aortic valve? Perhaps no technique is inherently superior. The choice of surgical technique should depend on the patient’s profile. As surgeons, we must not focus solely on the short term but reflect on the quality of life we can offer our patients in the long term.
REFERENCE:
Notenboom ML, Schuermans A, Etnel JRG, Veen KM, van de Woestijne PC, Rega FR, et al. Paediatric aortic valve replacement: a meta-analysis and microsimulation study. Eur Heart J. 2023 Jun 27:ehad370. doi: 10.1093/eurheartj/ehad370. Epub ahead of print.
