Geometric Pattern of Proximal Landing Zones for Thoracic Endovascular Aortic Repair in the Bovine Arch Variant

Objectives: The aim was to investigate whether the \u201cbovine\u201d aortic arch (i.e. arch variant with a common origin of the innominate and left carotid artery (CILCA)) is associated with a consistent geometric configuration of proximal landing zones for thoracic endovascular aortic repair (TEVAR). Methods: Anonymised thoracic computed tomography (CT) scans of healthy aortas were reviewed to retrieve 100 cases of CILCA. Suitable cases were stratified according to type 1 and 2 CILCA, and also based on type of arch (I, II, and III). Further processing allowed calculation of angulation and tortuosity of the proximal landing zones. Centre lumen line lengths of each proximal landing zone were measured in a view perpendicular to the centre line. All geometric features were compared with those measured in healthy patients with a standard arch configuration (n = 60). Two senior authors independently evaluated the CT scans, and intra- and interobserver repeatability were assessed. Results: The 100 selected patients (63% male) were 71.4 \ub1 7.7 years old. Type 1 CILCA (62/100) was more prevalent than type 2 CILCA (38/100), and the two groups were comparable in age (p = .11). Zone 3 presented a severe angulation (i.e. > 60\ub0), which was greater than in Zone 2 (p < .001), and a consistently greater tortuosity than Zone 2 (p = .003). This pattern did not differ between type 1 and type 2 CILCA. A greater tortuosity was also observed in Zone 0, which was related to increased elongation of the ascending aorta (i.e. Zone 0), than the standard configuration. The CILCA had an overall greater elongation, and Zone 2 also was specifically longer. When stratifying by type of arch, reversely from Type III to Type I, the CILCA presented a gradual flattening of its transverse tract, which entailed a consistent progressive elongation (p = .03) and kinking of the ascending aorta, with a significant increase of Zone 0 angulation to even a severe degree (p = .001). Also, from Type III to Type I, Zone 2 presented a progressively shorter length (p = .004), which was associated with increased tortuosity (p < .05). Mean intra- and interobserver differences for angulation measurements were 1.4\ub0 \ub1 6.8\ub0 (p = .17) and 2.0\ub0 \ub1 10.1\ub0 (p = .19), respectively. Conclusions: CILCA presents a consistent and peculiar geometric pattern compared with standard arch configuration, which provides relevant information for TEVAR planning, and may have prognostic implications

Patient-specific computational fluid dynamics analysis of transcatheter aortic root replacement with chimney coronary grafts.

Transcatheter aortic root repair (TARR) consists of the simultaneous endovascular replacement of the aortic valve, the root and the proximal ascending aorta. The aim of the study is to set-up a computational model of TARR to explore the impact of the endovascular procedure on the coronary circulation supported by chimney grafts. Computed tomography of a patient with dilated ascending aorta was segmented to obtain a 3-dimensional representation of the proximal thoracic aorta, including aortic root and supra-aortic branches. Computed assisted design tools were used to modify the geometry to create the post-procedural TARR configuration featuring the main aortic endograft integrated with 2 chimney grafts for coronary circulation. Computational Fluid Dynamics simulations were run in both pre- and post-procedural configurations using a pulsatile inflow and lumped parameter models at the outflows to simulate peripheral aortic and coronary circulation. Differences in coronary flow and pressure along the cardiac cycle were evaluated. After the virtual implant of the TARR device with coronary grafts, the flow became more organized and less recirculation was seen in the ascending aorta. Coronary perfusion was guaranteed with negligible flow differences between pre- and post-procedural configurations. However, despite being well perfused by chimney grafts, the procedure induces an increase of the pressure drop between the coronary ostia and the ascending aorta of 8 mmHg. The proposed numerical simulations, in the specific case under investigation, suggest that the TARR technique maintains coronary perfusion through the chimney grafts. This study calls for experimental validation and further analyses of the impact of TARR on cardiac afterload, decrease of aortic compliance and local pressure drop induced by the coronary chimney grafts

Aortic arch variant with a common origin of the innominate and left carotid artery as a determinant of thoracic aortic disease : a systematic review and meta-analysis

The aim of this study was to investigate whether the 'bovine' arch [i.e. arch variant with a common origin of the innominate and left carotid artery (CILCA)] is associated with an increased risk of thoracic aortic disease (TAD). The study was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The PubMed, EMBASE and Cochrane databases were searched to identify all case series reporting about CILCA arch and TAD between January 2008 and December 2018. A total of 485 studies were screened. The prevalence of CILCA arch was assessed, and data analysis was performed considering the difference in the risk of TAD for presence versus absence of CILCA arch. Eight studies enrolling 11 381 subjects were retrieved for quantitative analysis. The proportion of TAD among CILCA arch patients was higher [41.5% (28.1-56.4)] than the proportion among patients with standard arch configuration 34.0% (20.1-51.4). The odds ratio of developing TAD was 1.4 times higher in subjects with CILCA arch (95% confidence interval 1.068-1.839). The test for an overall effect indicated a significant association between CILCA arch and TAD (P\u2009<\u20090.015). The I2 was 78.1% with a value of P < 0.001 for heterogeneity. The Egger test did not show evidence of publication bias (P\u2009=\u20090.317). In conclusion, our meta-analysis supports the hypothesis of a correlation between the presence of CILCA arch and the onset of TAD. Our results warrant a specific and long-term surveillance for patients with this anatomical variant, and a thorough awareness of its potential clinical implications during image interpretation

Anomalous aortic origin of coronary artery biomechanical modeling: Toward clinical application

Objectives: Anomalous aortic origin of the coronary artery can be associated with sudden cardiac death and ischemic events. Anatomic static characteristics mainly dictated surgical indications, although adverse events are usually related to dynamic physical effort. We developed a computational model able to simulate anomalous coronary behavior, and we aimed to assess its clinical applicability and to investigate coronary characteristics at increasing loading stress conditions. Methods: We selected 5 patients with anomalous aortic origin of the coronary artery and 5 control subjects. For each of them, we construct a 3-dimensional model resembling the aortic root and coronary arteries based on 25 parameters obtained from computed tomography. Structural finite element analysis simulations were run to simulate pressure increasing in the aortic root during exercise (+40 mm Hg, +100 mm Hg with respect baseline condition, assumed at 80 mm Hg) and investigate coronary lumen characteristics. Results: The 25 parameters were obtainable in all subjects with a consistent interobserver agreement. In control subjects, the right coronary artery had a more significant lumen expansion at loading conditions compared with anomalous aortic origin of coronary artery (6%-19.2% vs 1.8%-8.1%, P = .008), which also showed an inability to expand within the intramural segment. Conclusions: The proposed anomalous aortic origin of coronary artery model is able to represent the pathogenic disease mechanism after being populated with patient-specific data. It can assess the impaired expansion of anomalous right coronary at loading conditions, a process that cannot be quantified in any clinical set-up. This first clinical application showed promising results on quantifying pathological behavior, potentially helping in patient-specific risk stratification

The Modified Arch Landing Areas Nomenclature (MALAN) Improves Prediction of Stent Graft Displacement Forces : Proof of Concept by Computational Fluid Dynamics Modelling

Objective: To assess whether the Modified Arch Landing Areas Nomenclature (MALAN), which merges Ishimaru's map with the Aortic Arch Classification, predicts the magnitude of displacement forces and their orientation in proximal landing zones for TEVAR. Methods: Computational fluid dynamic (CFD) modelling was employed to prove the hypothesis. Healthy aorta CT angiography scans were selected based on aortic arch geometry to reflect Types I to III arches equally (each n = 5). CFDs were used to compute pulsatile displacement forces along the Ishimaru's landing zones in each aorta including their three dimensional orientation along the upward component and sideways component. Values were normalised to the corresponding aortic wall area to calculate equivalent surface traction (EST). Results: In Types I and II arches, EST did not change across proximal landing zones (p =.297 and p =.054, respectively), whereas in Type III, EST increased towards more distal landing zones (p =.019). Comparison of EST between adjacent zones, however, showed that EST was greater in 3/II than in 2/II (p =.016), and in 3/III than in 2/III (p =.016). Notably, these differences were related to the upward component, that was four times greater in 3/II compared with 2/II (p <.001), and five times greater in 3/III compared with 2/III (p <.001). Conclusion: CFD modelling suggests that MALAN improves discrimination of expected displacement forces in proximal landing zones for TEVAR, which might influence clinical outcomes. The clinical relevance of the finding, however, remains to be validated in a dedicated post-operative outcome analysis of patients treated by TEVAR of the arch