Autograft or Allograft Aortic Root Replacement in Children and Young Adults With Aortic Valve Disease: A Single-Center Comparison

Biomechanics of Pulmonary Autograft as Living Tissue: A Systematic Review

Introduction: The choice of valve substitute for aortic valve surgery is tailored to the patient with specific indications and contraindications to consider. The use of an autologous pulmonary artery (PA) with a simultaneous homograft in the pulmonary position is called a Ross procedure. It permits somatic growth and the avoidance of lifelong anticoagulation. Concerns remain on the functionality of a pulmonary autograft in the aortic position when exposed to systemic pressure. Methods: A literature review was performed incorporating the following databases: Pub Med (1996 to present), Ovid Medline (1958 to present), and Ovid Embase (1982 to present), which was run on 1 January 2022 with the following targeted words: biomechanics of pulmonary autograft, biomechanics of Ross operation, aortic valve replacement and pulmonary autograph, aortic valve replacement and Ross procedure. To address the issues with heterogeneity, studies involving the pediatric cohort were also analyzed separately. The outcomes measured were early- and late-graft failure alongside mortality. Results: a total of 8468 patients were included based on 40 studies (7796 in pediatric cohort and young adult series and 672 in pediatric series). There was considerable experience accumulated by various institutions around the world. Late rates of biomechanical failure and mortality were low and comparable to the general population. The biomechanical properties of the PA were superior to other valve substitutes. Mathematical and finite element analysis studies have shown the potential stress-shielding effects of the PA root. Conclusion: The Ross procedure has excellent durability and longevity in clinical and biomechanical studies. The use of external reinforcements such as semi-resorbable scaffolds may further extend their longevity.

The effectiveness and safety of pulmonary autograft as living tissue in Ross procedure: a systematic review

BACKGROUND

Reports on effectiveness and safety after the implant of pulmonary autograft (PA) living tissue in Ross procedure, to treat both congenital and acquired disease of the aortic valve and left ventricular outflow tract (LVOT), show variable durability results. We undertake a quantitative systematic review of evidence on outcome after the Ross procedure with the aim to improve insight into outcome and potential determinants.

METHODS

A systematic search of reports published from October 1979 to January 2021 was conducted (PubMed, Ovid Medline, Ovid Embase and Cochrane library) reporting outcomes after the Ross procedure in patients with diseased aortic valve with or without LVOT. Inclusion criteria were observational studies reporting on mortality and/or morbidity after autograft aortic valve or root replacement, completeness of follow-up >90%, and study size n≥30. Forty articles meeting the inclusion criteria were allocated to two categories: pediatric patient series and young adult patient series. Results were tabulated for a clearer presentation.

RESULTS

A total of 342 studies were evaluated of which forty studies were included in the final analysis as per the eligibility criteria. A total of 8,468 patients were included (7,796 in pediatric cohort and young adult series and 672 in pediatric series). Late mortality rates were remarkably low alongside similar age-matched mortality with the general population in young adults. There were differences in implantation techniques as regard the variability in stress and the somatic growth that recorded conflicting outcomes regarding the miniroot vs the subcoronary approach.

DISCUSSION

The adaptability of lung autograft to allow for both stress variability and somatic growth make it an ideal conduit for Ross's operation. The use of the miniroot technique over subcoronary implantation for better adaptability to withstand varying degrees of stress is perhaps more applicable to different patient subgroups.

Mid-term Outcome of 100 Consecutive Ross Procedures: Excellent Survival, But Yet to Be a Cure

The Ross procedure offers excellent short-term outcome but the long-term durability is under debate. Reinterventions and follow-up of 100 consecutive patients undergoing Ross Procedure at our centre (1993-2011) were analysed. Follow-up was available for 96 patients (97%) with a median duration of 5.3 (0.1-17.1) years. Median age of the patient cohort was 15.2 (0.04-58.4) years with 76 males. 93% had underlying congenital aortic stenosis. Root replacement technique was applied in all. The most common valved conduits used for reconstruction of the right ventricular outflow tract were homografts (66 patients) and bovine jugular vein (Contegra^R) graft (31 patients). Additional procedures included Ross-Konno procedure (14%), resection of subaortic stenosis/myectomy (11%) and reduction plasty of the ascending aorta (25%). One patient died within the first 30 days (1%). Late deaths occurred in 4 patients (4%) 0.5-4.5 years postoperatively: causes included pulmonary hypertension due to endocardial fibroelastosis (2), subarachnoid haemorrhage (1) and sudden cardiac death (1). Five-year survival was 93.6 (95% CI 88.1-99.1)%. Moderate or severe aortic (autograft) regurgitation needing reoperation occurred in 8 patients with a 5-year freedom from autograft reoperation of 98.5 (95.6-100)%. Five-year freedom from reintervention (surgery or catheter based) on the right ventricular outflow tract conduit was 91.5 (85.5-96.5)%. Univariate predictors of this reinterventions were smaller graft size (p = 0.03) and use of a Contegra^R graft (p = 0.04). Ross procedure can be performed with low mortality and good survival in the long term. Most of the reinterventions are related to the neo-right ventricular outflow tract and may be partly attributed to the lack of growth. While the Ross Procedure remains an invaluable option for aortic valve disease in children, new solutions for the neo-pulmonary valve as well as for the less often occurring problems on the autograft are needed.

Tissue-Engineered Heart Valves: A Call for Mechanistic Studies

Heart valve disease carries a substantial risk of morbidity and mortality. Outcomes are significantly improved by valve replacement, but currently available mechanical and biological replacement valves are associated with complications of their own. Mechanical valves have a high rate of thromboembolism and require lifelong anticoagulation. Biological prosthetic valves have a much shorter lifespan, and they are prone to tearing and degradation. Both types of valves lack the capacity for growth, making them particularly problematic in pediatric patients. Tissue engineering has the potential to overcome these challenges by creating a neovalve composed of native tissue that is capable of growth and remodeling. The first tissue-engineered heart valve (TEHV) was created more than 20 years ago in an ovine model, and the technology has been advanced to clinical trials in the intervening decades. Some TEHVs have had clinical success, whereas others have failed, with structural degeneration resulting in patient deaths. The etiologies of these complications are poorly understood because much of the research in this field has been performed in large animals and humans, and, therefore, there are few studies of the mechanisms of neotissue formation. This review examines the need for a TEHV to treat pediatric patients with valve disease, the history of TEHVs, and a future that would benefit from extension of the reverse translational trend in this field to include small animal studies.

Aortic Valve Replacement and the Ross Operation in Children and Young Adults

BACKGROUND

There are several options available for aortic valve replacement (AVR), with few comparative reports in the literature. The optimal choice for AVR in each age group is not clear.

OBJECTIVES

The study sought to report and compare outcomes after AVR in the young using data from a national database.

METHODS

AVR procedures were compared after advanced matching, both in pairs and in a 3-way manner, using a Bayesian dynamic survival model.

RESULTS

A total of 1,501 patients who underwent AVR in the United Kingdom between 2000 and 2012 were included. Of these, 47.8% had a Ross procedure, 37.8% a mechanical AVR, 10.9% a bioprosthesis AVR, and 3.5% a homograft AVR, with Ross patients being significantly younger when compared to the other groups. Overall survival at 12 years was 94.6%. In children, the Ross procedure had a 12.7% higher event-free probability (death or any reintervention) at 10 years when compared to mechanical AVR (p = 0.05). We also compared all procedures except the homograft in a matched population of young adults, where the bioprosthesis had the lowest event-free probability of 78.8%, followed by comparable results in mechanical AVR and Ross, with 86.3% and 89.6%, respectively. Younger age was associated with mortality and pulmonary reintervention in the Ross group and with aortic reintervention in the mechanical AVR. Of all 3 options, only the patients undergoing the Ross procedure approached the survival of the general population.

CONCLUSIONS

AVR in the young achieves good results, with the Ross being overall better suited for this age group, especially in children. Although freedom from aortic valve reintervention is superior after the Ross procedure, the need for homograft reinterventions is an issue to take into account. All methods have advantages and limitations, with reinterventions being an issue in the long term for all, more crucially in smaller children.

Contemporary outcomes after surgical aortic valve replacement with bioprostheses and allografts: a systematic review and meta-analysis

Many observational studies have reported outcomes after surgical aortic valve replacement (AVR), but there are no recent systematic reviews and meta-analyses including all available bioprostheses and allografts. The objective of this study is to provide a comprehensive and up-to-date overview of the outcomes after AVR with bioprostheses and allografts reported in the last 15 years. We conducted a systematic literature review (PROSPERO register: CRD42015017041) of studies published between 2000–15. Inclusion criteria were observational studies or randomized controlled trials reporting on outcomes of AVR with bioprostheses (stented or stentless) or allografts, with or without coronary artery bypass grafting (CABG) or valve repair procedure, with study population size n ≥ 30 and mean follow-up length ≥5 years. Fifty-four bioprosthesis studies and 14 allograft studies were included, encompassing 55 712 and 3872 patients and 349 840 and 32 419 patient-years, respectively. We pooled early mortality risk and linearized occurrence rates of valve-related events, reintervention and late mortality in a random-effects model. Sensitivity, meta-regression and subgroup analyses were performed to investigate the influence of outliers on the pooled estimates and to explore sources of heterogeneity. Funnel plots were used to investigate publication bias. Pooled early mortality risks for bioprostheses and allografts were 4.99% (95% confidence interval [CI], 4.44–5.62) and 5.03% (95% CI, 3.61–7.01), respectively. The late mortality rate was 5.70%/patient-year (95% CI, 4.99–5.62) for bioprostheses and 1.68%/patient-year (95% CI, 1.23–2.28) for allografts. Pooled reintervention rates for bioprostheses and allografts were 0.75%/patient-year (95% CI, 0.61–0.91) and 1.87%/patient-year (95% CI, 1.52–2.31), respectively. There was substantial heterogeneity in most outcomes. Meta-regression analyses identified covariates that could explain the heterogeneity: implantation period, valve type, patient age, gender, pre-intervention New York Heart Association class III/IV, concomitant CABG, study design and follow-up length. There is possible publication bias in all outcomes. This comprehensive systematic review and meta-analysis provides an overview of the outcomes after AVR with bioprostheses and allografts reported during the last 15 years. The results of this study can support patients and doctors in the prosthetic valve choice and can be used in microsimulation models to predict patient outcomes and estimate the cost-effectiveness of AVR with bioprostheses or allografts compared with current and future heart valve prostheses.

Regression of left ventricular hypertrophy in children following the Ross procedure

OBJECTIVES

Left ventricular hypertrophy (LVH) frequently accompanies the progression of aortic valve disease in children. The extent of LVH regression following surgical relief of aortic valve disease in children has not been clearly elucidated. We hypothesized that significant regression of LVH will occur in children following the Ross procedure.

METHODS

We examined LVH over time in children <18 years of age who underwent the Ross procedure. Left ventricular mass index (LVMI) and corresponding z scores were calculated based on height, age and gender. Left ventricular hypertrophy was defined as an LVMI of > 39 g/m(2.7) and a z score of >1.6.

RESULTS

Twenty-five children underwent the Ross procedure. The left ventricular mass increased proportionally with the growth of the child from baseline to the latest follow-up at 7.3 ± 2.9 years (121.1 ± 81.5 vs 133.1 ± 79.8 g, P = 0.4). However, 96% (24/25) of children demonstrated LVMI regression from baseline. Mean LVMI decreased from 70.8 ± 31.2 to 41.8 ± 16.6 g/m(2.7) (P < 0.001). Similarly, LVMI z scores decreased from 2.2 ± 1.2 to 0.2 ± 1.9 (P < 0.001). Freedom from LVH was 83% at 10 years. Examination of LVMI and z scores over time demonstrated that the largest decrease occurred after the first year, with continued gradual decline over 10 years of follow-up.

CONCLUSIONS

The Ross procedure is effective in reversing LVH in children with aortic valve disease.