Sutureless Biological Aortic Valve Replacement (Su-AVR) in Redo operations: a retrospective real-world experience report of clinical and echocardiographic outcomes.

OBJECTIVE: This retrospective study aimed to compare the outcomes of sutureless aortic valve replacement (su-AVR) and conventional bioprosthetic sutured AVR (cAVR) in high-risk patients undergoing redo surgery. METHODS: A total of 79 patients who underwent redo AVR between 2014 and 2021 were included in the study. Of these, 27 patients underwent su-AVR and 52 underwent cAVR. Patient characteristics and clinical outcomes were analysed using multivariate regression and Kaplan Meier survival test. RESULTS: The groups were similar in terms of age, gender, left ventricular function, and number of previous sternotomies. In cases of isolated AVR, su-AVR had significantly lower cross clamp times than cAVR (71 vs. 86 min, p = 0.03). Postoperatively, 4 cAVR patients required pacemaker compared to zero patients in the su-AVR group. There were no significant differences between the two groups in terms of postoperative complications, intrahospital stay (median 9 days, IQR 7-20), or in-hospital mortality (1 su-AVR; 2 cAVR). The long-term survival rate was similar between the su-AVR (90%) and cAVR (92%) groups (log rank p = 0.8). The transvalvular gradients at follow-up were not affected by the type of valve used, regardless of the valve size (coef 2.68, 95%CI -3.14-8.50, p = 0.36). CONCLUSION: The study suggests that su-AVR is a feasible and safe alternative to cAVR in high-risk patients undergoing redo surgery. The use of su-AVR offers comparable outcomes to cAVR, with reduced cross clamp times and a lower incidence of postoperative pacemaker requirement in isolated AVR cases. The results of this study contribute to the growing body of evidence supporting the use of su-AVR in high-risk patients, highlighting its feasibility and safety in redo surgeries.

Current Status of Simulation in Thoracic Surgical Training.

BACKGROUND: Simulation is playing an increasingly important role in surgical training but is not yet a mandatory part of most surgical curricula. A simulator must undergo rigorous validation to verify it as a reliable tool. The aim of this study was to review the literature to identify simulators that are currently available to augment thoracic surgical training and to analyze any evidence supporting or validating them. METHODS: A literature search of the MEDLINE (1946 to November 2022) and Embase (1947 to November 2022) databases was performed to identify simulators for basic skills and procedures in thoracic surgery. A selection of keywords were used to perform the literature search. After identification of appropriate articles, data were extracted and analyzed. RESULTS: Thirty-three simulators were found in 31 articles. Simulators for basic skills (n = 13) and thoracic lobectomy (n = 13) were most commonly described, followed by miscellaneous (n = 7). Most models were of a hybrid modality (n = 18). Evidence of validity was established in 48.5% (n = 16) of simulators. In total, 15.2% (n = 5) of simulators had 3 or more elements of validity demonstrated, and only 3.0% (n = 1) accomplished full validation. CONCLUSIONS: Numerous simulators of varying modality and fidelity exist for a variety of thoracic surgical skills and procedures, although validation evidence is frequently inadequate. Simulation models may be able to provide training in basic surgical and procedural skills; however, further assessment of validity needs to be undertaken before consideration of their integration into training programs.

Consensus statement on aortic valve replacement via an anterior right minithoracotomy in the UK healthcare setting.

The wide uptake of anterior right thoracotomy (ART) as an approach for aortic valve replacement (AVR) has been limited despite initial reports of its use in 1993. Compared with median sternotomy, and even ministernotomy, ART is considered to be less traumatic to the chest wall and to help facilitate quicker patient recovery. In this statement, a consensus agreement is outlined that describes the potential benefits of the ART AVR. The technical considerations that require specific attention are described and the initiation of an ART programme at a UK centre is recommended through simulation and/or use of specialist instruments in conventional cases. The use of soft tissue retractors, peripheral cannulation, modified aortic clamping and the use of intraoperative adjuncts, such as sutureless valves and/or automated knot fasteners, are important to consider in order to circumvent the challenges of minimal the altered exposure via an ART.A coordinated team-based approach that encourages ownership of the programme by team members is critical. A designated proctor/mentor is also recommended. The organisation of structured training and simulation, as well as planning the initial cases are important steps to consider.

Data-driven generation of 4D velocity profiles in the aneurysmal ascending aorta.

BACKGROUND AND OBJECTIVE: Numerical simulations of blood flow are a valuable tool to investigate the pathophysiology of ascending thoratic aortic aneurysms (ATAA). To accurately reproduce in vivo hemodynamics, computational fluid dynamics (CFD) models must employ realistic inflow boundary conditions (BCs). However, the limited availability of in vivo velocity measurements, still makes researchers resort to idealized BCs. The aim of this study was to generate and thoroughly characterize a large dataset of synthetic 4D aortic velocity profiles sampled on a 2D cross-section along the ascending aorta with features similar to clinical cohorts of patients with ATAA. METHODS: Time-resolved 3D phase contrast magnetic resonance (4D flow MRI) scans of 30 subjects with ATAA were processed through in-house code to extract anatomically consistent cross-sectional planes along the ascending aorta, ensuring spatial alignment among all planes and interpolating all velocity fields to a reference configuration. Velocity profiles of the clinical cohort were extensively characterized by computing flow morphology descriptors of both spatial and temporal features. By exploiting principal component analysis (PCA), a statistical shape model (SSM) of 4D aortic velocity profiles was built and a dataset of 437 synthetic cases with realistic properties was generated. RESULTS: Comparison between clinical and synthetic datasets showed that the synthetic data presented similar characteristics as the clinical population in terms of key morphological parameters. The average velocity profile qualitatively resembled a parabolic-shaped profile, but was quantitatively characterized by more complex flow patterns which an idealized profile would not replicate. Statistically significant correlations were found between PCA principal modes of variation and flow descriptors. CONCLUSIONS: We built a data-driven generative model of 4D aortic inlet velocity profiles, suitable to be used in computational studies of blood flow. The proposed software system also allows to map any of the generated velocity profiles to the inlet plane of any virtual subject given its coordinate set.

Geometry and flow in ascending aortic aneurysms are influenced by left ventricular outflow tract orientation: Detecting increased wall shear stress on the outer curve of proximal aortic aneurysms.

BACKGROUND: The geometrical characterization of ascending thoracic aortic aneurysms in clinical practice is limited to diameter measurements. Despite growing interest in hemodynamic assessment, its relationship with ascending thoracic aortic aneurysm pathogenesis is poorly understood. This study examines the relationship between geometry of the ventriculo-aortic junction and blood flow patterns in ascending thoracic aortic aneurysm disease. METHODS: Thirty-three patients with ascending thoracic aortic aneurysms (exclusions: bicuspid aortic valves, connective tissue disease) underwent 4-dimensional flow magnetic resonance imaging. After image segmentation, geometrical parameters were measured, including aortic curvature, tortuosity, length, and diameter. A unique angular measurement made by the trajectory of the left ventricular outflow tract axis and the proximal aorta was also conducted. Velocity profiles were quantitatively and qualitatively analyzed. In addition, 11 patients (33%) underwent wall shear stress mapping of the ascending thoracic aortic aneurysm region using computational fluid dynamics simulation. RESULTS: Greater left ventricular outflow tract aortic angles were associated with larger aortic diameters at the levels of the sinus (coefficient = 0.387, P = .014) and ascending aorta (coefficient = 0.284, P = .031). Patients with left ventricular outflow tract aortic angles greater than 60° had marked asymmetric flow acceleration on the outer curvature in the proximal aorta, ascertained from 4-dimensional flow analysis. For patients undergoing computational fluid dynamics assessment, regression analysis found that higher left ventricular outflow tract aortic angles were associated with significantly higher wall shear stress values in the outer curve of the aorta (coefficient 0.07, 95% confidence interval 0.04-0.11, P = .002): Angles greater than 50° yielded time-averaged wall shear stress values greater than 2.5 Pa, exhibiting a linear relationship. CONCLUSIONS: Our findings strengthen the hypothesis of flow-mediated ascending thoracic aortic aneurysm disease progression and that left ventricular outflow tract aortic angle may be a predictor of disease severity.

The genetic basis of thoracic aortic disease: The future of aneurysm classification?

The expansion in the repertoire of genes linked to thoracic aortic aneurysms (TAA) has revolutionised our understanding of the disease process. The clinical benefits of such progress are numerous, particularly helping our understanding of non-syndromic hereditary causes of TAA (HTAAD) and further refinement in the subclassification of disease. Furthermore, the understanding of aortic biomechanics and mechanical homeostasis has been significantly informed by the discovery of deleterious mutations and their effect on aortic phenotype. The drawbacks in genetic testing in TAA lie with the inability to translate genotype to accurate prognostication in the risk of thoracic aortic dissection (TAD), which is a life-threatening condition. Under current guidelines, there are no metrics by which those at risk for dissection with normal aortic diameters may undergo preventive surgery. Future research lies with more advanced genetic diagnosis of HTAAD and investigation of the diverse pathways involved in its pathophysiology, which will i) serve to improve our understanding of the underlying mechanisms, ii) improve guidelines for treatment and iii) prevent complications for HTAAD and sporadic aortopathies.

Comparison of outcomes between aortic root replacement and supra-coronary interposition graft for type A aortic dissection: A retrospective case series.

BACKGROUND: The decision to conserve or replace the native aortic valve following acute type-A aortic dissection (ATAAD) is an area of cardiac surgery without standardized practice. This single-center retrospective study analysed the long-term performance of the native aortic valve and root following surgery for ATAAD. METHODS: Between 2009 and 2018 all cases ATAAD treated at Royal Brompton and Harefield NHS Foundation Trust were analysed. Patients were divided into two groups: (a) ascending aorta (interposition) graft (AAG) without valve replacement and (b) nonvalve-sparing aortic root replacement (ARR). Preoperative covariates were compared, as well as operative characteristics and postoperative complications. Long-term survival and echocardiographic outcomes were analysed using regression analysis. RESULTS: In total, 116 patients were included: 63 patients in the AAG group and 53 patients in the ARR group. In patients where the native aortic valve was conserved, nine developed severe aortic regurgitation and two patients developed dilation of the aortic root requiring subsequent replacement during the follow-up period. Aortic regurgitation at presentation was not found to be associated with subsequent risk of developing severe aortic regurgitation or reintervention on the aortic valve. Overall mortality was observed to be significantly lower in patients undergoing AAG (17.5% vs. 41.5%, p = .004). CONCLUSIONS: With careful patient selection, the native aortic root shows good long-term durability both in terms of valve competence and stable root dimensions after surgery for ATAAD. This study supports the consideration of conservation of the aortic valve during emergency surgery for type-A dissection, in the absence of a definitive indication for root replacement, including in cases where aortic regurgitation complicates the presentation.

Determining the genetic contribution in patients with non-syndromic ascending thoracic aortic aneurysms: Correlation with findings from computational pathology.

OBJECTIVES: This study aims to identify the clinical utility of targeted-genetic sequencing in a cohort of patients with TAA and establish a new method for regional histological characterisation of TAA disease. METHODS: Fifty-four patients undergoing surgery for proximal TAA were recruited. EXCLUSIONS: connective tissue disease, bicuspid aortic valves, redo surgery. All patients underwent next generation sequencing (NGS) using a custom gene panel containing 63 genes previously associated with TAA on Illumina MiSeqor NextSeq550 platforms. Explanted TAA tissue was obtained en-bloc from 34/54 patients, and complete circumferential strips of TAA tissue processed into whole slides which were subsequently digitalised. Computational pathology methods were employed to quantify elastin, cellularity and collagen in six equally divided regions across the whole aneurysm circumference. RESULTS: Of 54 patients, clearly pathogenic or potentially pathogenic variants were found in 7.4%: namely LOX, PRKG1, TGFBR1 and SMAD3 genes. 55% had at least one variant of unknown significance (VUS) and seven of the VUSs were in genes with a strong disease association (category A) genes, whilst 15 were from moderate risk (category B) genes. Elastin and collagen abundance displayed high regional variation throughout the aneurysm circumference. In patients with <60% total elastin, the loss of elastin was more significant on the outer curve (38.0% vs 47.4%, p = 0.0094). The presence of VUS, higher pulse wave velocity and advancing age were predictors of elastin loss (regression analysis: p < 0.05). CONCLUSIONS: These findings demonstrate the heterogeneity of TAA disease microstructure and the potential link between histological appearance and clinical factors, including genetic variation.

Regional variation in biomechanical properties of ascending thoracic aortic aneurysms.

OBJECTIVES: This study aims to characterize the material properties of ascending thoracic aortic aneurysmal tissue, using regional biomechanical assessment of both tensile and dissection propagation peel strength. METHODS: Thirty-four aneurysm specimens (proximal thoracic aorta) were harvested en-bloc from patients undergoing surgery for aneurysm replacement. Specimens were processed into regional samples of similar shapes covering the whole aneurysm isosurface, according to a structured protocol, in both orientations (longitudinal and circumferential). Thickness mapping, uniaxial tensile and peel tests were conducted, enabling calculation of the following parameters: true stress/strain, tangential modulus, tensile strength, peeling force and dissection energy. Two constitutive material models were used (hyperelastic models of Delfino and Ogden) to fit the data. A circumferential strip of tissue was also obtained for computational histology [regional quantification of (i) elastin, (ii) collagen and (iii) smooth muscle cells]. RESULTS: The aortic wall was thinner on the outer curve (2.21, standard deviation (SD) 0.4 mm vs inner curve 2.50, SD 0.12 mm). Advanced patient age and higher pulse wave velocity (externally measured) were predictors of increased aortic wall thickness. Tensile strength was higher in the circumferential versus longitudinal direction when analysed according to anatomical regions. Both peel force (35.5, 22 N/m) and dissection energy (88.5, 69 J/m2) were on average lowest at the outer curve of the aneurysm in the longitudinal orientation. Delfino and Ogden model constants varied throughout anatomical regions, with the outer curve being associated a higher ɑ constant (Delfino) and lower µ1 constant (Ogden) (P < 0.05) indicating increased stiffness. Histologically, collagen abundance was significantly related to circumferential and longitudinal strength (P= 0.010), whilst smooth muscle cell count had no relation with any mechanical property (P > 0.05). CONCLUSIONS: Our results suggest that the outer aortic curve is more prone to dissection propagation and perhaps less prone to rupture than the inner aortic curve. This strengthens the notion of disease heterogeneity in ascending thoracic aortic aneurysms and has implications for the pathogenesis of aortic dissection.

Converging rapid deployment prostheses with minimal access surgery: analysis of early outcomes.

BACKGROUND: Sutureless prostheses may have added benefit when combined with minimal access surgery, although this has not been fully assessed in the literature. This study aims to provide a comparative analysis of the Perceval valve comparing median sternotomy (MS) with mini-sternotomy (MIS). METHODS: A retrospective analysis of prospectively collected data was conducted for all isolated aortic valve replacement (AVR), using the Perceval valve, for severe aortic stenosis cases in the period 2014 to 2019. Patients undergoing concomitant valve or revascularisation surgery were excluded. RESULTS: A total of 78 patients were included: MS group 41; MIS group 37. Operatively, bypass times were comparable between MS and MIS groups (mean 89.3 vs 83.4, p = 0.307), as were aortic cross clamp times (58.4 vs 55.9, p = 0.434). There were no operative deaths or new onset post-operative neurology. MIS was a predictor of reduced stay in the intensive care unit (coef - 3.25, 95% CI [- 4.93, - 0.59], p = 0.036) and hospital stay overall (p = 0.004). Blood transfusion units were comparable as were the incidence of heart block (n = 5 vs n = 3, p = 0.429) and new onset atrial fibrillation (n = 15 vs n = 9, p = 0.250). Follow-up echocardiography found a significant improvement in effective orifice area, left ventricular dimension and volume indices, and LVEF (p > 0.05) for all patients. Multivariate analysis found mini-sternotomy to be a predictor for reduced LV diastolic volume (coef - 0.35, 95% CI [- 1.02, - 0.05], p = 0.05). CONCLUSIONS: The combination of minimal access surgery and sutureless AVR may enhance patient recovery and provide early LV remodelling.

High Wall Shear Stress can Predict Wall Degradation in Ascending Aortic Aneurysms: An Integrated Biomechanics Study.

Background: Blood flow patterns can alter material properties of ascending thoracic aortic aneurysms (ATAA) via vascular wall remodeling. This study examines the relationship between wall shear stress (WSS) obtained from image-based computational modelling with tissue-derived mechanical and microstructural properties of the ATAA wall using segmental analysis. Methods: Ten patients undergoing surgery for ATAA were recruited. Exclusions: bicuspid aortopathy, connective tissue disease. All patients had pre-operative 4-dimensional flow magnetic resonance imaging (4D-MRI), allowing for patient-specific computational fluid dynamics (CFD) analysis and anatomically precise WSS mapping of ATAA regions (6-12 segments per patient). ATAA samples were obtained from surgery and subjected to region-specific tensile and peel testing (matched to WSS segments). Computational pathology was used to characterize elastin/collagen abundance and smooth muscle cell (SMC) count. Results: Elevated values of WSS were predictive of: reduced wall thickness [coef -0.0489, 95% CI (-0.0905, -0.00727), p = 0.022] and dissection energy function (longitudinal) [-15,0, 95% CI (-33.00, -2.98), p = 0.048]. High WSS values also predicted higher ultimate tensile strength [coef 0.136, 95% CI (0 0.001, 0.270), p = 0.048]. Additionally, elevated WSS also predicted a reduction in elastin levels [coef -0.276, 95% (CI -0.531, -0.020), p = 0.035] and lower SMC count ([oef -6.19, 95% CI (-11.41, -0.98), p = 0.021]. WSS was found to have no effect on collagen abundance or circumferential mechanical properties. Conclusions: Our study suggests an association between elevated WSS values and aortic wall degradation in ATAA disease. Further studies might help identify threshold values to predict acute aortic events.

Recommendations for the use of coronary and valve simulators in cardiac surgical training: a systematic review.

OBJECTIVES: The aim of this study was to systematically review the simulators that are currently available for coronary artery bypass graft and valve surgery and, in addition, to review the validation evidence supporting them and to recommend several simulators for training based on the analysis of results. METHODS: A systematic literature search of the MEDLINE® (1946 to May 2021) and EMBASE® (1947 to May 2021) databases was performed to identify simulators for coronary artery and valvular procedures in cardiothoracic surgery. A selection of keywords and MeSH terms was used to execute the literature search. After identification of relevant articles, data were extracted and analysed. RESULTS: Thirty-seven simulators were found in 31 articles. Simulators were found for coronary artery bypass graft (n = 24) and valve surgery (n = 13). The majority of models were either benchtop (n = 28) or hybrid (n = 8) modalities. Evidence of validity was demonstrated in 15 (40.5%) simulators. Twenty-two (59.5%) simulators had no validation evidence, and 1 (2.7%) simulator had 3 or more elements of validity established. CONCLUSIONS: Two simulators were recommended for supplemental training in cardiothoracic surgery. Low-fidelity models can provide a broad foundation for surgical skills' development whereas high-fidelity simulators can be used for immersive training scenarios and appraisals. These should be utilized in early training, at which point the learning curve of trainees is steepest.

Surgical management of misdeployed transcatheter aortic valve due to eccentric leaflet calcification.

A serious complication of transcatheter valves is the mechanistic failure of the deployment system and prosthesis migration. We report the case of a transcatheter aortic valve implantation which failed during implantation resulting in dislodgement of the prosthesis. Emergency surgery to retrieve the deployment system and surgically replace the native valve was the only option to salvage the patient.

Validation of markerless strain-field optical tracking approach for soft tissue mechanical assessment.

Strain measurement during tissue deformation is crucial to elucidate relationships between mechanical loading and functional changes in biological tissues. When combined with specified loading conditions, assessment of strain fields can be used to craft models that accurately represent the mechanical behavior of soft tissue. Inhomogeneities in strain fields may be indicative of normal or pathological inhomogeneities in mechanical properties. In this study, we present the validation of a modified Demons registration algorithm for non-contact, marker-less strain measurement of tissue undergoing uniaxial loading. We validate the algorithm on a synthetic dataset composed of artificial deformation fields applied to a speckle image, as well as images of aortic sections of varying perceptual quality. Initial results indicate that Demons outperforms recent Optical Flow and Digital Image Correlation methods in terms of accuracy and robustness to low image quality, with similar runtimes. Demons achieves at least 8% lower maximal deviation from ground truth on 50% biaxial and shear strain applied to aortic images. To illustrate utility, we quantified strain fields of multiple human aortic specimens undergoing uniaxial tensile testing, noting the formation of strain concentrations in areas of rupture. The modified Demons algorithm captured a large range of strains (up to 50%) and provided spatially resolved strain fields that could be useful in the assessment of soft tissue pathologies.

BISMICS consensus statement: implementing a safe minimally invasive mitral programme in the UK healthcare setting.

Disseminating the practice of minimally invasive mitral surgery (mini-MVS) can be challenging, despite its original case reports a few decades ago. The penetration of this technology into clinical practice has been limited to centres of excellence, and mitral surgery in most general cardiothoracic centres remains to be conducted via sternotomy access as a first line. The process for the uptake of mini-MVS requires clearer guidance and standardisation for the processes involved in its implementation. In this statement, a consensus agreement is outlined that describes the benefits of mini-MVS, including reduced postoperative bleeding, reduced wound infection, enhanced recovery and patient satisfaction. Technical considerations require specific attention and can be introduced through simulation and/or use in conventional cases. Either endoballoon or aortic cross clamping is recommended, as well as femoral or central aortic cannulation, with the use of appropriate adjuncts and instruments. A coordinated team-based approach that encourages ownership of the programme by the team members is critical. A designated proctor is also recommended. The organisation of structured training and simulation, as well as planning the initial cases, is an important step to consider. The importance of pre-empting complications and dealing with adverse events is described, including re-exploration, conversion to sternotomy, unilateral pulmonary oedema and phrenic nerve injury. Accounting for both institutional and team considerations can effectively facilitate the introduction of a mini-MVS service. This involves simulation, team-based training, visits to specialist centres and involvement of a designated proctor to oversee the initial cases.

The risk of misdiagnosis in acute thoracic aortic dissection: a review of current guidelines.

Acute aortic syndrome and in particular aortic dissection (AAD) persists as a cause of significant morbidity and mortality despite improvements in surgical management. This clinical review aims to explore the risks of misdiagnosis, outcomes associated with misdiagnosis and evaluate current diagnostic methods for reducing its incidence.Due to the nature of the pathology, misdiagnosing the condition and delaying management can dramatically worsen patient outcomes. Several diagnostic challenges exist, including low prevalence, rapidly propagating pathology, non-discrete symptomatology, non-specific signs, analogy with other acute conditions and lack of management infrastructure. A similarity to acute coronary syndromes is a specific concern and risks patient maltreatment. AAD with malperfusion syndromes are both a cause of misdiagnosis and marker of disease complication, requiring specifically tailored management plans from the emergency setting.Despite improvements in diagnostic measures, including imaging modalities and biomarkers, misdiagnosis of AAD remains commonplace and current guidelines are relatively limited in preventing its occurrence. This paper recommends the early use of AAD risk scoring, focused echocardiography and most importantly, fast-tracking patients to cross-sectional imaging where the suspicion of AAD is high. This has the potential to improve the diagnostic process for AAD and limit the risk of misdiagnosis. However, our understanding remains limited by the lack of large patient datasets and an adequately audited processes of emergency department practice.