A review of pulmonary autograft external support in the Ross procedure

External Scaffold for Strengthening the Pulmonary Autograft in the Ross Procedure

Despite offering several potential benefits over standard prosthetic aortic valve replacement, the use of the pulmonary autograft has been limited to date due to concerns over the risk of pulmonary autograft expansion and the need for reintervention. Several techniques using materials with biomimetic potential have been developed to reduce this complication. The incidence, risk factors, and pathophysiology of pulmonary autograft dilatation are discussed in this article. This seminar will provide an overview of the techniques of external pulmonary autograft support and their advantages and limitations. It also considers future directions for further investigation and future clinical applications of external pulmonary autograft support. Dilatation of the autograft is more likely to occur in patients with aortic regurgitation and a dilated aortic annulus. External scaffolding may prevent autograft stretching and expansion in these specific cases. However, from a biomimetic point of view, any permanent scaffold potentially restricts the movement of the autograft root. This reduces some of the benefits associated with the use of autologous tissue, which is the priority of the Ross procedure. To address this issue, several bioresorbable matrices could be used to support the root during its initial adaptive phase. Control of blood pressure with aggressive therapy is the first line to avoid this problem in the first year after pulmonary autograft implantation, together with support of the annular and sinotubular junction in some selected cases. This is the best way to maintain stable autograft root dimensions while preserving root dynamics. However, to determine the efficacy of this combined external support and best medical management, it is important to perform regular imaging and clinical follow-up.

Bicuspid Aortic Valve in Children and Young Adults for Cardiologists and Cardiac Surgeons: State-of-the-Art of Literature Review

Bicuspid aortic valve disease is the most prevalent congenital heart disease, affecting up to 2% of the general population. The presentation of symptoms may vary based on the patient's anatomy of fusion, with transthoracic echocardiography being the primary diagnostic tool. Bicuspid aortic valves may also appear with concomitant aortopathy, featuring fundamental structural changes which can lead to valve dysfunction and/or aortic dilatation over time. This article seeks to give a comprehensive overview of the presentation, treatment possibilities and long-term effects of this condition. The databases MEDLINE, Embase, and the Cochrane Library were searched using the terms "endocarditis" or "bicuspid aortic valve" in combination with "epidemiology", "pathogenesis", "manifestations", "imaging", "treatment", or "surgery" to retrieve relevant articles. We have identified two types of bicuspid aortic valve disease: aortic stenosis and aortic regurgitation. Valve replacement or repair is often necessary. Patients need to be informed about the benefits and drawbacks of different valve substitutes, particularly with regard to life-long anticoagulation and female patients of childbearing age. Depending on the expertise of the surgeon and institution, the Ross procedure may be a viable alternative. Management of these patients should take into account the likelihood of somatic growth, risk of re-intervention, and anticoagulation risks that are specific to the patient, alongside the expertise of the surgeon or centre. Further research is required on the secondary prevention of patients with bicuspid aortic valve (BAV), such as lifestyle advice and antibiotics to prevent infections, as the guidelines are unclear and lack strong evidence.

Our 7-year experience supporting the Ross autograft with the novel technique of Personalized External Aortic Root Support

Objective

The Ross operation is a widely accepted option for aortic valve replacement in children, and evidence shows its excellent results in terms of hemodynamics and durability. However, indications are still limited due to the fact that it is a technically demanding procedure, only performed by specialized surgeons. On top of that, and despite numerous techniques being applied, autograft dilatation remains a key disadvantage, which can lead to graft failure. In recent years, the ExoVasc Personalized External Aortic Root Support (PEARS) has proven to be a safe and effective option to prevent aortic root dilatation in various aortopathies and is a technique that lends itself to support the pulmonary autograft in the Ross operation.

Methods

During the past 7 years, we have used the ExoVasc PEARS graft, manufactured from the patients' pulmonary artery measurements from computed tomography scan data, to support the pulmonary autograft in the Ross operation. This graft (manufactured by Exstent Ltd, UK) is implanted at the same time as the autograft. We have reviewed all the patients who underwent this surgery, including demographic data, aorta measurements, operative data, and follow-up assessment consisting of periodic echocardiograms and magnetic resonance imaging scans.

Results

Fifty patients were included in the study. Mean age at the time of the operation was 29.84 years, the youngest patient was 9 years-old. Nineteen patients (38%) had previous sternotomies; 11 of them having had a previous aortic valve replacement. Seventy-two percent of patients had initially a bicuspid aortic valve. Mean diameter of the ascending aorta was 3.83 cm. Forty-four percent of patients required a concomitant reduction aortoplasty due to mismatch sizes between the ascending aorta and the autograft. Mean bypass and crossclamp times were 200.66 and 151.14 minutes, respectively. Median length of stay was 6 days. Mean follow-up was 16.88 months. Two patients required subsequent aortic valve replacement (1 had rheumatic valve disease and the other had iatrogenic damage in his autograft valve leaflet). Ascending aorta dimensions remain stable when compared with immediate postoperative studies. There were no deaths.

Conclusions

The ExoVasc PEARS graft has proven to be an excellent support in the Ross operation to prevent the autograft failure related to autograft dilatation that can offer several advantages compared with other existing techniques. With this type of support, we believe the Ross indications can be expanded to multiple clinical scenarios, given the good long-term results this operation offers in terms of durability, life expectancy, and hemodynamics.

Drivers of vascular growth and remodeling: A computational framework to promote benign adaptation in the Ross procedure

In the sixties, Dr Donald Ross designed a surgical solution for young patients with aortic valve disease by using the patients' own pulmonary valve. The Ross procedure is the only aortic valve replacement technique that can restore long-term survival and preserve quality of life. The main failure mode of the Ross procedure is wall dilatation, potentially leading to valve regurgitation and leakage. Dilatation occurs due to the inability of the pulmonary autograft to adapt to the sudden increase in loading when exposing to aortic pressures. Previous experimental data has shown that a permanent external support wrapped around the artery can prevent the acute dilatation of the arterial wall. However, the textile support leads to stress-shielding phenomena due to the loss of mechanical wall compliance. We present a pragmatic and modular computational framework of arterial growth and remodeling predicting the long-term outcomes of cardiovascular tissue adaptation, with and without textile wrapping. The model integrates mean, systolic and diastolic pressures and assumes the resulting wall stresses to drive the biological remodeling rules. Rather than a single mean pressure or stress deviation from the homeostatic state, we demonstrate that only pulsatile stresses can predict available experimental results. Therefore, we suggest that a biodegradable external support could induce benign remodeling in the Ross procedure. Indeed, a biodegradable textile wrapped around the autograft fulfills the trade-off between prevention of acute dilatation on the one hand and recovery of arterial wall compliance on the other hand. After further validation, the computational framework can set the basis for the development of an actual biodegradable external support for the Ross procedure with optimized polymer mechanical properties and degradation behavior.

Personalized external aortic root support in aneurysm disease

PURPOSE OF REVIEW

To bring together and annotate publications about personalised external aortic root support reported in the 18 months preceding submission.

RECENT FINDINGS

The total number of personalised external aortic root support (PEARS) operations is now approaching 700 in 30 centres in Australia, Belgium, Brazil, Czech Republic, Great Britain, Greece, Ireland, Malaysia, Netherlands, New Zealand, Poland and Slovakia. There are continued reports of stability of aortic dimensions and aortic valve function with the only exceptions known being where the surgeon has deviated from the instructions for use of the device. The median root diameter of Marfan patients having PEARS was 47 mm suggesting that the existing criterion of 50 mm is due for reconsideration. The peri-operative mortality currently estimated to be less than 0.3%. The first recipient remains alive and well after 18 years. The use of PEARS as an adjunct to the Ross operation to support the pulmonary autograft is being explored in several centres.

SUMMARY

The operation requires proctoring and adherence to a strict operative protocol and with those precautions excellent results are attained. The evidence and opinions provided in the cited publications indicate that PEARS is a proven and successful prophylactic operation for aortic root aneurysm.

Survival and freedom from reoperation after the Ross procedure in a Russian adult population: A single-center experience

Objectives

To evaluate our 12-year experience with the Ross procedure in adults.

Methods

A retrospective analysis of 215 cases of the Ross procedure was performed. The mean age of the patients was 36 ± 11.1 years, and the male to female ratio was 75% to 25%, respectively. The pulmonary autograft was placed into the aortic position using the full-root replacement technique and its modified versions. The right ventricular outflow tract was reconstructed using a pulmonary homograft in all cases.

Results

The 30-day mortality after the operation was 0.9% (2 patients). The median duration of follow-up was 6.1 years (interquartile range, 6.5 years) and was complete in 86% of cases. The survival at 12 years was 94.7% and was comparable with the survival rate of the general population matched for age and sex. At the end of the follow-up, freedom from reoperation due to pulmonary autograft and homograft dysfunction was 89.1% and 99%, respectively.

Conclusions

In our series, the Ross procedure resulted in low early mortality and excellent survival in adults. The long-term survival was not statistically different from the survival of the general population. The pulmonary homograft offered an excellent durability and freedom from reoperation.

Supporting the Ross procedure: preserving root physiology while mitigating autograft dilatation

PURPOSE OF REVIEW

The purpose of this article is to describe the optimized approach to nonrepairable aortic valve disease in young adults with a Ross procedure, while preserving the dynamic physiology of the aortic root.

RECENT FINDINGS

As the techniques for supporting pulmonary autografts continue to be refined, and the applicability of the Ross procedure continues to expand, an assessment of the various techniques based on aortic root physiology is warranted. Semi-resorbable scaffolds show promise in ovine models for improving the Ross procedure. Recent long-term outcomes for the Dacron inclusion technique in comparison to more physiologic methods of support emphasize the importance of balancing the prevention of early dilatation with the preservation of root haemodynamics. As this review will synthesize, the dynamic physiology of the root may be preserved even in patients at a higher risk of autograft dilatation.

SUMMARY

The favourable long-term outcomes of the Ross procedure can be partly attributed to the ability of the autograft to restore dynamism to the neoaortic root. Patient-specific modifications that respect root physiology can tailor the Ross procedure to address each patient's risk factors for early dilatation and late failure. As such, the Ross procedure should be recognized as an increasingly favourable solution for a wide spectrum of nonpreservable aortic valve disease in young adults.

Understanding Pulmonary Autograft Remodeling After the Ross Procedure: Stick to the Facts

The Ross, or pulmonary autograft, procedure presents a fascinating mechanobiological scenario. Due to the common embryological origin of the aortic and pulmonary root, the conotruncus, several authors have hypothesized that a pulmonary autograft has the innate potential to remodel into an aortic phenotype once exposed to systemic conditions. Most of our understanding of pulmonary autograft mechanobiology stems from the remodeling observed in the arterial wall, rather than the valve, simply because there have been many opportunities to study the walls of dilated autografts explanted at reoperation. While previous histological studies provided important clues on autograft adaptation, a comprehensive understanding of its determinants and underlying mechanisms is needed so that the Ross procedure can become a widely accepted aortic valve substitute in select patients. It is clear that protecting the autograft during the early adaptation phase is crucial to avoid initiating a sequence of pathological remodeling. External support in the freestanding Ross procedure should aim to prevent dilatation while simultaneously promoting remodeling, rather than preventing dilatation at the cost of vascular atrophy. To define the optimal mechanical properties and geometry for external support, the ideal conditions for autograft remodeling and the timeline of mechanical adaptation must be determined. We aimed to rigorously review pulmonary autograft remodeling after the Ross procedure. Starting from the developmental, microstructural and biomechanical differences between the pulmonary artery and aorta, we review autograft mechanobiology in relation to distinct clinical failure mechanisms while aiming to identify unmet clinical needs, gaps in current knowledge and areas for further research. By correlating clinical and experimental observations of autograft remodeling with established principles in cardiovascular mechanobiology, we aim to present an up-to-date overview of all factors involved in extracellular matrix remodeling, their interactions and potential underlying molecular mechanisms.

Current Therapeutic Options in Aortic Stenosis

Aortic stenosis is the most common valvular disease requiring valve replacement. Valve replacement therapies have undergone progressive evolution since the 1960s. Over the last 20 years, transcatheter aortic valve replacement has radically transformed the care of aortic stenosis, such that it is now the treatment of choice for many, particularly elderly, patients. This review provides an overview of the pathophysiology, presentation, diagnosis, indications for intervention, and current therapeutic options for aortic stenosis.

The Choice of Pulmonary Autograft in Aortic Valve Surgery: A State-of-the-Art Primer

The Ross procedure has long been seen as an optimal operation for a select few. The detractors of it highlight the issue of an additional harvesting of the pulmonary artery, subjecting the native PA to systemic pressures and the need for reintervention as reasons to avoid it. However, the PA is a living tissue and capable of adapting and remodeling to growth. We therefore review the current evidence available to discuss the indications, contraindications, harvesting techniques, and modifications in a state-of-the-art narrative review of the PA as an aortic conduit. Due to the lack of substantial well-designed randomized controlled trials (RCTs), we also highlight the areas of need to reiterate the importance of the Ross procedure as part of the surgical armamentarium.

Personalized external aortic root support

OBJECTIVES

Implantation of a personalized external aortic root support (PEARS) can prevent dilatation of the aortic root and ascending aorta in patients with aortopathy of various aetiologies. Because PEARS is an emerging technology, all aspects concerning indications, surgical technique and safety should be elucidated. Our goal was to summarize all of these aspects so that physicians and patients would have sufficient information to evaluate this alternative approach.

METHODS

Between April 2004 and March 2020, 317 patients underwent PEARS operations at 25 surgical centres in 9 countries.

RESULTS

The most common indication was Marfan syndrome (57%). The single perioperative death represented a mortality of 0.3%. The long-term experience comprises 871 patient/years with 1 patient living for 15 years and 19 patients living for more than 10 years.

CONCLUSIONS

PEARS seems to be a promising method of treatment of dilatation of the aortic root and/or ascending aorta. Multicentre observational studies are needed to gain more experience because this operation is still uncommon and the number of operations per surgeon/centre is low.

Lights and Shadows on the Ross Procedure: Biological Solutions for Biological Problems

The Ross procedure represents a valid option for aortic valve replacement in young adults and was repeatedly shown to restore survival to that of the age- and sex-matched general population. However, its major drawback relies in the risk of pulmonary autograft (PA) dilation, negative histological remodeling and need for reoperation. Several techniques and materials to reinforce the PA have been proposed. They mainly include Dacron, personalized external aortic root support with a polyethylene terephthalate mesh system, autologous aortic tissue and bioresorbable materials. Synthetic materials, despite widely used in cardiac surgery, have significant biocompatibility issues with the PA and their interaction with this living structure translates into negative remodeling phenomena and disadvantageous biomechanical behaviors. Conversely, biomaterials with tailored degradable profiles might be able to reinforce while integrating with the PA and enhance its remodeling capabilities. The recent advancement in this field are here discussed.