Aortic Valve Reconstruction With Autologous Pericardium Versus a Bioprosthesis: The Ozaki Procedure in Perspective

Machine Learning and Statistical Shape Modelling Methodologies to Assess Vascular Morphology before and after Aortic Valve Replacement

Introduction: Statistical shape modelling (SSM) is used to analyse morphology, discover qualitatively and quantitatively unique shape features within a population, and generate mean shapes and shape modes that show morphological variability. Hierarchical agglomerative clustering is a machine learning analysis used to identify subgroups within a given population in relation to shape features. We tested the application of both methods in the clinically relevant scenario of patients undergoing aortic valve repair (AVR). Every year, around 5000 patients undergo surgical AVR in the UK. Aims: Evaluate aortic morphology and identify subgroups amongst patients who had undergone AVR, including Ozaki, Ross, and valve-sparing procedures using SSM and unsupervised hierarchical clustering analysis. This methodological framework can evaluate both pre- and post-surgical variability across subgroups undergoing different surgeries. Methods: Pre- (n = 47) and post- (n = 35) operative three-dimensional (3D) aortic models were reconstructed from computed tomography (CT) and cardiac magnetic resonance (CMR) images. Computational analyses for SSM and hierarchical clustering were run separately for the two subgroups, assessing (a) ascending aorta only and (b) the whole aorta. This allows for exploring possible variations in morphological classification related to the input shape. Results: Most patients in the Ross procedure subgroup exhibited differences in aortic morphology from other subgroups, including an elongated ascending and wide aortic arch pre-operatively, and an elongated ascending aorta with a slightly enlarged sinus post-operatively. In hierarchical clustering, the Ross aortas also appeared to cluster together compared to the other surgical procedures, both pre-operatively and post-operatively. There were significant differences between clusters in terms of clustering distance in the pre-operative analyses (p = 0.003 for ascending aortas, p = 0.016 for whole aortas). There were no significant differences between the clusters in post-operative analyses (p = 0.47 for ascending, p = 0.19 for whole aorta). Conclusions: We demonstrated the feasibility of evaluating aortic morphology before and after different aortic valve surgeries using SSM and hierarchical clustering. This framework could be used to further explore shape features associated with surgical decision-making pre-operatively and, importantly, to identify subgroups whose morphology is associated with poorer clinical outcomes post-operatively. Statistical shape modelling (SSM) and unsupervised hierarchical clustering are two statistical methods that can be used to assess morphology, show morphological variations, with the latter being able to identify subgroups within a population. These methods have been applied to the population of aortic valve replacement (AVR) patients since there are different surgical procedures (traditional AVR, Ozaki, Ross, and valve-sparing). The aim is to evaluate aortic morphology and identify subgroups within this population before and after surgery. Computed tomography and cardiac magnetic resonance images were reconstructed into 3D models of the ascending aorta and whole aorta, which were then input into SSM and hierarchical clustering. The results show that the Ross aortic morphology is quite different from the other aortas. The clustering did not classify the aortas based on the surgical procedures; however, most of the Ross group did cluster together, indicating low variability within this surgical group.

Midterm results after aortic valve neocuspidization

Objectives

Aortic valve neocuspidization with autologous pericardium is gaining increasing attention as a surgical treatment option for aortic valve disease. However, little is known about midterm durability and valve-related events.

Methods

Patients undergoing aortic valve neocuspidization between 2016 and 2021 were included. Transthoracic echocardiography was performed before the operation, at discharge, and annually thereafter. Data were analyzed for incidences of structural valve deterioration, bioprosthetic valve failure, survival, freedom from reoperation, and hemodynamic performance.

Results

A total of 162 patients underwent aortic valve neocuspidization (mean age, 52.6 ± 16.6 years; range, 13-78 years); 114 (70.4%) were male. A total of 132 patients presented with a bicuspid aortic valve (81.5%) and 126 patients presented with aortic valve stenosis (77.8%). Concomitant procedures were performed in 63 patients (38.9%). Mean follow-up was 3.5 ± 1.2 years. At discharge, peak and mean pressure gradients were 15.6 ± 7.2 mm Hg and 8.4 ± 3.7 mm Hg, respectively, with a mean effective orifice area of 2.4 ± 0.8 cm2. After 5 years, peak and mean pressure gradients were 14.5 ± 4.6 mm Hg and 7.5 ± 2.2 mm Hg, respectively, with a mean effective orifice area of 2.3 ± 0.8 cm2. At 5 years, cumulative incidences of moderate and severe structural valve deterioration and bioprosthetic valve failure were 9.82% ± 3.87%, 6.96% ± 3.71%, and 12.1% ± 4.12%, respectively. Survival was 97.3% ± 1.4%, and freedom from reoperation was 91.3% ± 2.4%.

Conclusions

Aortic valve neocuspidization accomplishes low pressure gradients early after initial surgery and during follow-up. Survival in this young patient population is excellent. The main reason for reoperation is endocarditis, and rates for structural valve degeneration are low.

Mid-Term Outcomes of Aortic Valve Repair Without Aortic Root Replacement: A Single-Center Experience

Background Aortic valve (AV) repair is a challenging procedure due to its complexity, lower reproducibility, and steep learning curve. To examine its durability and validity, we investigated mid-term outcomes following AV repair without aortic root replacement. Methods Between March 2007 and May 2018, we retrospectively identified 14 patients who underwent AV repair without aortic root replacement at our institution. We investigated their baseline characteristics and postoperative outcomes, including the reoperation rate due to aortic regurgitation (AR) recurrence. Furthermore, we divided them into two groups: those who required reoperation due to AR recurrence (Group R) and those who did not require reoperation (Group F), and statistically compared them. Results The median age was 52.5 years (IQR: 42.0-60.8), with 11 male patients (78.6%). Eight patients (57.1%) had a bicuspid AV. Five cases (35.7%) underwent reoperation due to AR recurrence during a median follow-up period of 5.5 years. There were no significant differences in baseline characteristics between Group R (n=5, 35.7%) and Group F (n=9, 64.3%), including AR etiology, AV repair procedure, and intraoperative AR grade after the final declamp. All cases in Group R had at least mild to moderate AR on the echocardiogram before discharge. Regarding the AR grade before discharge, Group R had a significantly higher grade than Group F (p = 0.013). Conclusions The indication for AV repair for AR might need to be reassessed due to the considerable mid-term reoperation rate. Cases of AV repair with more than mild AR at discharge should be carefully monitored, as they are likely to require future reoperation for AR.

Aortic Valve Engineering Advancements: Precision Tuning with Laser Sintering Additive Manufacturing of TPU/TPE Submillimeter Membranes

Synthetic biomaterials play a crucial role in developing tissue-engineered heart valves (TEHVs) due to their versatile mechanical properties. Achieving the right balance between mechanical strength and manufacturability is essential. Thermoplastic polyurethanes (TPUs) and elastomers (TPEs) garner significant attention for TEHV applications due to their notable stability, fatigue resistance, and customizable properties such as shear strength and elasticity. This study explores the additive manufacturing technique of selective laser sintering (SLS) for TPUs and TPEs to optimize process parameters to balance flexibility and strength, mimicking aortic valve tissue properties. Additionally, it aims to assess the feasibility of printing aortic valve models with submillimeter membranes. The results demonstrate that the SLS-TPU/TPE technique can produce micrometric valve structures with soft shape memory properties, resembling aortic tissue in strength, flexibility, and fineness. These models show promise for surgical training and manipulation, display intriguing echogenicity properties, and can potentially be personalized to shape biocompatible valve substitutes.

Complete Aortic Valve Reconstruction with Autologous Pericardium: Analysis of Mid-Term Results of Single-Center Experience with AVNeo Procedure

PURPOSE

Aortic valve neocuspidization (AVNeo) is a relatively recent advancement in surgical AV replacement. Data on its performance beyond the short term are limited. We assessed the mid-term outcomes in patients undergoing AVNeo, focusing on feasibility, perioperative details, and its role in AV pathology treatment.

METHODS

Sixty-five consecutive patients underwent AVNeo between December 2016 and February 2018. Clinical data were prospectively collected and retrospectively analyzed. Tricuspid reconstruction with autologous pericardium was performed in all cases. Echocardiographic follow-up was conducted post-discharge, at 6 and 12 months, and annually thereafter.

RESULTS

The mean age was 62.6 ± 18.7 years. AVNeo was feasible in all cases. Concomitant procedures were performed in 43 (66.2%) patients. Mean bypass and cross-clamp times were 119.2 ± 30.3 and 87.1 ± 22.9 minutes, respectively. Postoperative transvalvular hemodynamics was excellent. There was one (1.5%) in-hospital death. Follow-up (mean 66.72 ± 12.77 months) was complete in 58 patients (89.2%). There were no detected valve-related or thromboembolic events. Transvalvular hemodynamic parameters were stable during the observation period: peak pressure gradient at discharge and follow-up was 15.3 ± 4.6 mmHg and 15.01 ± 6.3 mmHg, respectively (ρ = 0.346).

CONCLUSIONS

AVNeo demonstrated the feasibility and favorable mid-term outcomes. Studies with longer-term observation are warranted to evaluate its durability.

The Ozaki Procedure: Standardized Protocol Adoption of a Complex Innovative Procedure

Background

The Ozaki procedure using autologous pericardium is an interesting but complex alternative for aortic valve replacement. We present a standardized approach to minimize the learning curve and confirm reproducibility.

Methods

After careful preparation, from May 2015 to February 2021, an Ozaki procedure was performed on 46 patients age 51 ± 14 years. Seven had unicuspid (15%), 29 bicuspid (63%), and 10 tricuspid (22%) aortic valves, and 2 patients had endocarditis. Endpoints were operative learning curves, perioperative outcomes, intermediate-term valve hemodynamics, reintervention, health-related quality of life (MacNew Heart Disease Health-Related Quality of Life questionnaire), and mortality.

Results

Cardiopulmonary bypass and aortic clamp times decreased from 145 to 125 ​minutes and 120 to 100 ​minutes, respectively, over the first 20 cases, reflecting the learning curve. There was no major perioperative morbidity or mortality. Median postoperative stay was 6.9 days. Aortic regurgitation was mild or less in all but 2 patients who developed moderate aortic regurgitation. Mean aortic valve gradient was 7.9 mmHg postoperatively, 9.2 mmHg by 6 months, and constant thereafter. Left ventricular ejection fraction was 58% preoperatively, 60% at 6 months, and remained stable thereafter. One patient developed infective endocarditis 7 months postoperatively, failed medical management, and underwent valve replacement at 14 months. Two-year survival was 96%, with 1 noncardiac death at 16 months. Health-related quality of life in mental, physical, and emotional domains was better than matched norms, global 6.2 vs. 5.0 (p < 0.0001).

Conclusions

Using a well-prepared standardized approach, the Ozaki procedure is reproducible with a short learning curve, excellent hemodynamic performance, and good quality of life.

Ozaki procedure-re-construction of aortic valve leaflets using autologous pericardial tissue: a review

The Ozaki procedure has emerged as a valuable option for treating various aortic valve pathologies. This review article delves into the intricacies of this innovative surgical approach by exploring its adaptation to the complex anatomy and physiology of the aortic root. The diverse etiologies of aortic valve diseases, ranging from congenital anomalies to degenerative changes, make treatment selection a complex challenge. Aortic valve replacement has traditionally been the gold standard, but emerging evidence supports valve repair techniques, emphasizing the importance of preserving native tissue. Nevertheless, issues like lifelong anticoagulation with mechanical valves and patient-prosthetic mismatch remain. The Ozaki procedure offers a compelling alternative by utilizing autologous pericardium or a tissue substitute to construct new aortic valve leaflets. This technique, standardized by Dr. Ozaki in 2007, provides a customizable and adaptable solution. The article highlights the anatomy of the aortic root, emphasizing the critical role of the sinus of Valsalva and interleaflet triangles in maintaining proper valve function. The procedure's unique adaptation to aortic root dynamics allows for reduced mechanical stress during systole and diastole, mimicking the natural valve's behavior. Furthermore, Ozaki leaflets exhibit promising hemodynamics and reduced risks of complications, such as permanent pacemaker implantation and patient-prosthetic mismatch. The use of autologous pericardium in the Ozaki procedure presents advantages, including enhanced tissue strength, minimal immunogenicity, and reduced risk of immune-mediated calcification. These factors contribute to the longevity and resilience of the reconstructed valve. This comprehensive review aims to shed light on the procedure's intricacies, its alignment with aortic root anatomy and physiology, and its potential as a valuable tool in the armamentarium of aortic surgeons.

Past, present, and future options for right ventricular outflow tract reconstruction

The pulmonary valve is the most frequently replaced cardiac valve in congenital heart diseases. Whether the valve alone or part of the right ventricular outflow tract have to be repaired or replaced depends on the specific pathological anatomy of the malformation. Once the decision to replace the pulmonary valve has been made, two options are available: the isolated transcatheter pulmonary valve replacement and the surgical implantation of a prosthetic valve either isolated or in combination with a procedure on the right ventricular outflow tract. In this paper, we will focus on the different past and present surgical options and present a new concept called "endogenous tissue restoration," a promising alternative to the hitherto existing implants. From a general point of view, neither the transcatheter nor the surgical valvular implants are magic bullets in the arsenal for the management of valvular diseases. Smaller valves have to be frequently replaced because of outgrowth of the patients, larger tissue valves may present late structural valve deterioration, while xenograft and homograft conduits may calcify and therefore become narrowed within unpredictable incidence and interval following implantation. Based on long-term research efforts combining the knowledge of supramolecular chemistry, electrospinning, and regenerative medicine, endogenous tissue restoration has emerged most recently as a promising option to create long-term functioning implants. This technology is appealing because following resorption of the polymer scaffold and timely replacement through autologous tissue, no foreign material remain at all in the cardiovascular system. Proof-of-concept studies as well as small first-in-man series have been completed and have demonstrated favorable anatomic and hemodynamic results, comparable to currently available implants in the short term. Based on the initial experience, important modifications to improve the pulmonary valve function have been initiated.