Analysis of Target Vessel Instability in Fenestrated Endovascular Repair (f-EVAR) in Thoraco-Abdominal Aortic Pathologies.

Objective: The aim of this study was to evaluate the influence of target vessel anatomy and post-stenting geometry on the outcome of fenestrated endovascular aortic repair (f-EVAR). Methods: A retrospective review of data from a single center was conducted, including all consecutive fenestrated endovascular aortic repairs (f-EVARs) performed between September 2018 and December 2023 for thoraco-abdominal aortic aneurysms (TAAAs) and complex abdominal aortic aneurysms (cAAAs). The analysis focused on the correlation of target vessel instability to target vessel anatomy and geometry after stenting. The primary endpoint was the cumulative incidence of target vessel instability. Secondary endpoints were the 30-day and follow-up re-interventions. Results: A total of 136 patients underwent f-EVAR with 481 stented target vessels. A total of ten target vessel instabilities occurred including three in visceral and seven instabilities in renal vessels. The cumulative incidence of target vessel instability with death as the competing risk was 1.4%, 1.8% and 3.4% at 1, 2 and 3 years, respectively. In renal target vessels (260/481), a diameter ≤ 4 mm (OR 1.21, 95% CI 1.035-1.274, p = 0.009) and an aortic protrusion ≥ 5.75 mm (OR 8.21, 95% CI 3.150-12-23, p = 0.027) was associated with an increased target vessel instability. In visceral target vessels (221/481), instability was significantly associated with a preoperative tortuosity index ≥ 1.25 (HR 15.19, CI 95% 2.50-17.47, p = 0.045) and an oversizing ratio of ≥1.25 (HR 7.739, CI % 4.756-12.878, p = 0.049). Conclusions: f-EVAR showed favorable mid-term results concerning target vessel instability in the current cohort. A diameter of ≤4 mm and an aortic protrusion of ≥5.75 mm in the renal target vessels as well as a preoperative tortuosity index and an oversizing of the bridging stent of ≥1.25 in the visceral target vessels should be avoided.

The non to moderately dilated root in acute type A aortic dissection: outcomes of the PENN-BERN registry in young, non-syndromic patients.

OBJECTIVES: There is an ongoing debate regarding whether patients benefit more from root replacement compared to a reconstruction of the sinuses of Valsalva in acute type A aortic dissection (aTAAD). In those with known or suspected connective tissue disorders, root replacement is considered appropriate. However, there are currently no diameter-based guidelines regarding the best approach in patients with minimally to moderately dilated root and no connective tissue disorders. METHODS: From January 2005 to December 2022, a two-centre registry of aTAAD was created. Patients were included based on their age (≤60 years), the absence of root entry and dilatation >50 mm and the absence of syndromic hereditable aortic disease. Patients were divided into 2 groups based on the proximal procedure, root reconstruction and root replacement. Propensity score pair matching was performed based on preoperative characteristics. RESULTS: Cumulative incidence of reintervention at 10 years was slightly higher after root reconstruction 13% vs 3.9% in the matched group (P = 0.040). Survival at 10 years was not affected by the procedure independently of the matching 72.1% vs 71.4% (P = 0.2). Uni- and multivariate Cox regressions showed that a root diameter of >40 mm was associated with a hazard ratio of 7.7 (95% confidence interval 2.6-23) and 5.4 (7-17), respectively, for reoperation for aneurysm and pseudoaneurysm. CONCLUSIONS: Rate of reoperation due to proximal pseudoaneurysm and aneurysm could be significantly reduced with a lower threshold of 40 mm to replace the aortic root in aTAAD than in elective cases.

Outcomes of aortic valve repair with the reimplantation technique and maintenance of commissural orientation.

Background: Debate still persists on whether valve-sparing root reimplantation (VSRR) of a very asymmetric bicuspid aortic valve (BAV) should be completed such that the asymmetry of the native commissural orientation is retained, or if it should be made symmetric (180°-180°). Herein, we present our approach, in which the native asymmetry is preserved, and the valve is reimplanted in a 210°-150° orientation. Methods: A retrospective review was performed of 130 patients with BAV who underwent VSRR between January 1, 2004 and March 1, 2023 at a single institution. Of this total, 37 were reimplanted asymmetrically (210°-150°). The primary outcome was > moderate aortic insufficiency (AI). Secondary outcomes included severe aortic stenosis (AS), reintervention, and survival. Results: The included 37 patients were mostly male [94.6% (35/37)] with mean age of 46.3 years, and with low rates of comorbidities. At least moderate AI was present in 40.5% (15/37) prior to surgery. All BAV in this series were Sievers Type 1 with a mean commissural angle of 128.2°. Leaflet repair was required in 81.1% (30/37), most commonly involving central plication of the conjoined cusp [96.7% (29/30)] and raphe release [73.3% (22/30)]. There was no 30-day mortality or stroke. At 10 years, the cumulative incidences of > moderate AI, severe AS, and reintervention were 7.6% (0-17.2%), 7.1% (0-19.7%), and 5.3% (0.3-22%), respectively. There was no mortality for the entire duration of the study period. Conclusions: This series demonstrates excellent 10-year outcomes of maintaining commissural orientation in asymmetric BAV reimplantation procedures. However, further study with additional patients, longer follow-up, and direct comparison to symmetric reimplantation for similar BAV morphology is required.

Outcome of Stanford type B dissection in patients with Marfan syndrome.

OBJECTIVES: The aim of this study was to determine the outcome of Stanford type B aortic dissection in patients with Marfan syndrome (MFS) and to evaluate aortic diameters at time of dissection as well as the impact of previous aortic root replacement. METHODS: Analysis of all patients with MFS fulfilling Ghent criteria seen at this institution since 1995 until 2022. RESULTS: Thirty-six (19%) out of 188 patients with MFS suffered from Stanford type B aortic dissection during the study period. The Mean aortic diameter at the time of dissection was 39.0 mm [95% confidence interval (CI): 35.6-42.3]. The mean pre-dissection diameter (available in 25% of patients) was 32.1 mm (95% CI: 28.0-36.3) and the mean expansion was 19% (95% CI: 11.9-26.2). There was no correlation between age and diameter at the time of dissection (<20, 21-30, 31-40, 41-50, 51-60, <61 years; P = 0.78). Freedom from intervention after dissection was 53%, 44% and 33% at 1, 5 and 10 years. Aortic growth rate in those patients that had to undergo intervention within the 1st year after dissection was 10.2 mm/year (95% CI: 4.4-15.9) compared to 5.8 mm/year (95% CI: 3.3-8.3, P = 0.109) in those thereafter. The mean time between dissection and intervention was 1.8 years (95% CI: 0.6-3.0). While type B dissection seems more frequent after previous elective aortic repair (58% vs 42%), there was no difference between valve-sparing root replacement (VSRR) compared to Bentall procedures [Hazard ratio (HR) for VSRR 0.78, 95% CI: 0.31-2.0, P-value = 0.61]. The mean age of the entire population at the end of follow-up was 42 years (95% CI: 39.2-44.7). The mean follow-up time was 9 years (95% CI: 7.8-10.4). CONCLUSIONS: Stanford type B dissection in patients with MFS occurs far below accepted thresholds for intervention. Risk for type B dissection is present throughout lifetime and two-thirds of patients need an intervention after dissection. There is no difference in freedom from type B dissection between a Bentall procedure and a VSRR.

Over 8-year survival after ascending endovascular repair of type A intramural haematoma.

Acute type A aortic syndromes are catastrophic events whose management relies primarily on conventional surgery. For several years, various endovascular attempts have been described; however, long-term data are inexistent. We describe a case of stenting of the ascending aorta for a type A intramural haematoma with survival and freedom from reintervention at >8 years postoperatively.

Providing safe perioperative care in cardiac surgery during the COVID-19 pandemic.

The coronavirus disease 2019 (COVID-19) pandemic has potentiated the need for implementation of strict safety measures in the medical care of surgical patients - and especially in cardiac surgery patients, who are at a higher risk of COVID-19-associated morbidity and mortality. Such measures not only require minimization of patients' exposure to COVID-19 but also careful balancing of the risks of postponing nonemergent surgical procedures and providing appropriate and timely surgical care. We provide an overview of current evidence for preoperative strategies used in cardiac surgery patients, including risk stratification, telemedicine, logistical challenges during inpatient care, appropriate screening capacity, and decision-making on when to safely operate on COVID-19 patients. Further, we focus on perioperative measures such as safe operating room management and address the dilemma over when to perform cardiovascular surgical procedures in patients at risk.

Long-term outcome of patients with Marfan syndrome with previous aortic surgery but native aortic roots.

OBJECTIVES: The goal of this study was to report the long-term outcomes of patients with Marfan syndrome who had aortic surgery on any aortic segment except for the replacement of the aortic root itself. METHODS: An observational retrospective single-centre study was conducted with 115 Marfan syndrome patients who underwent 189 major aortic interventions from 1995 until 2018. Patients without aortic root replacement were identified and aortic root growth was analysed over time. RESULTS: Eleven of 115 patients (9.5%) did not have aortic root replacement during a follow-up of 10.5 [standard deviation (SD) 5.7] years and a mean age at last follow-up of 53.9 (SD 13.4) years. Patients without root replacement did not suffer less frequently from any type of acute aortic dissection (type A 27% vs 25%, P = 0.999; type B 36% vs 25%, P = 0.474). Patients with native aortic roots did not undergo fewer aortic interventions than those with aortic root replacement [12/11, mean 1.09 (SD 0.54) operations/patient vs 177/104, mean 1.7 (SD 1.3); P = 0.128]. Progression of the aortic root dimension was 0.5 (SD 0.3) mm/year in the group of patients with native aortic roots. CONCLUSIONS: Current data suggest that 10% of patients with Marfan syndrome with previous aortic surgery will be free from aortic root replacement until the sixth decade of life.

A systemic review and meta-analysis: Bentall versus David procedure in acute type A aortic dissection.

This systemic review of the literature and meta-analysis examined the current state of the evidence in long-term outcomes for and/or against aortic valve reimplantation (RAV) versus composite valve graft (CVG) intervention in patients with an acute type A dissection. Descriptive statistics were used to summarize the baseline characteristics of patients across studies. A random-effects metaregression was performed across study arms with logit-transformed proportions weighted by the study size for each of these outcomes. The results are presented as odds ratios with the RAV procedure as compared to the CVG procedure, including 95% confidence intervals (CIs) and P-values. Further outcomes are summarized with medians, interquartile ranges and the range and number of patients at risk. A total of 27 retrospective studies that included a combined 3058 patients were analysed. In-hospital mortality was in favour of the RAV procedure, which was 2% vs 8% for the CVG procedure. Survival rate at midterm was 98.8% (95% CI 91.7-100%) for RAV and 81.3% (CI 78.5-83.9%) for CVG. Freedom from valve-related reintervention was 100% (CI 93.7-100%) for RAV and 94.6% (CI 86.7-99.1%) for CVG. For an acute type A aortic dissection in the mid-term period, RAV provides a superior outcome over CVG, both in terms of aortic-valve-related reintervention and survival rate.

A systemic review and meta-analysis: long-term results of the Bentall versus the David procedure in patients with Marfan syndrome.

This systemic review of the literature and meta-analysis aimed to evaluate the current state of the evidence for and against reimplantation of the aortic valve (RAV) versus the composite valve graft (CVG) intervention in patients with Marfan syndrome. Random effects meta-regression was performed across the study arms with logit-transformed proportions of in-hospital deaths as an outcome measure when possible. Results are presented as odds ratios with 95% confidence intervals (CIs) and P-values. Other outcomes are summarized with medians, interquartile ranges (IQR) and ranges and the numbers of patients at risk. Twenty retrospective studies that included a combined 2156 patients with long-term follow-up were identified for analysis after a literature search. The in-hospital mortality rate favoured the RAV procedure with an odds ratio of 0.23 [95% CI 0.09-0.55, P = 0.001]. The survival rate at mid-term for the RAV cohort was 96.7% (CI 94.2-98.5) vs. 86.4% (CI 82.8-89.6) for the CVG group and 93.1% (CI 66.4-100) for the RAV group vs. 82.6% (CI 74.9-89.2) for the CVG group for the long term. Freedom from valve-related reintervention (median percentages) for the long term was 97.6% (CI 90.3-100%) for the RAV procedure and 88.6% (CI 79.1-95.5) for a CVG. This systematic review of the literature stresses the advantages of the RAV procedure in patients with Marfan syndrome in regard to long- and short-term results as the treatment of choice in aortic root surgery. The RAV procedure reduces in-hospital as well as long-term deaths and protects against aortic valve reintervention.

Impact of aortic root annuloplasty on 3D aortic root geometry.

BACKGROUND: The aim was to evaluate the impact of aortic root (AoR) annuloplasty on 3D AoR deformation. METHODS: In experimental setup, Yacoub procedure and Yacoub with annuloplasty were performed. Results were compared to native AoR. In each AoR modality, six microsonometric (2 mm, 200 Hz) crystals were implanted at the sinotubular junction (STJ) and at the AoR base (AoB). 3D deformation of the AoR was determined by AoR tilt (α) and rotation (ß) angle changes. RESULTS: Tilt angle in Yacoub AoR with annuloplasty and in Yacoub AoR was maximal at ejection, 26.71 ± 0.18° and 24.91 ± 0.13°, respectively, and minimal at diastole, 25.34 ± 0.15° and 21.90 ± 0.15°, respectively. Rotation angle in Yacoub AoR with and without annuloplasty was maximal at ejection, 27.04 ± 0.25° and 23.53 ± 0.54°, respectively, and minimal at diastole, 24.84 ± 0.14° and 21.62 ± 0.16°, respectively. In native AoR, tilt angle and rotation were minimal at ejection, 14.34 ± 0.81° and 18.1 ± 3.20°, respectively, and maximal at diastole, 18.78 ± 0.84° and 21.23 ± 021°, respectively. AoB and STJ had maximal expansion at ejection; 2.59 ± 2.40% and 6.05 ± 0.66 for Yacoub and 3.75 ± 0.66% and 3.08 ± 0.24% for Yacoub with annuloplasty. In native AoR, the expansion at ejection for AoB was 7.13 ± 2.68% and for STJ was 16.42 ± 0.63%. CONCLUSIONS: AoB annuloplasty reduces AoB deformation and has an impact on STJ dynamics. In both the Yacoub AoR modalities, during ejection, the AoR takes on more of a cone-like geometry, whereas in native AoR, it is of a cylinder-like shape.

Impact of the bicuspid aortic valve on aortic root haemodynamics: three-dimensional computed fluid dynamics simulation.

OBJECTIVES: The aim was to evaluate the impact of a bicuspid aortic valve (BAV) on local shear stress and on the pressure profile on the elements of the aortic root (AoR). METHODS: The experiment setup included a BAV with aortic valve stenosis (n = 5 pigs, 67 ± 3.5 kg) and insufficiency (n = 5 pigs, 66.7 ± 4.4 kg). By implanting 6 high-fidelity microsonometric crystals in each AoR, we determined the 3-dimensional (3D) geometry of the AoR. Experimental and geometric data were used to create a 3D time- and pressure-dependent computed fluid dynamic model of the AoR with the BAV. RESULTS: 3D AoR geometry was determined by AoR tilt (α) and rotation angle (ß). Both values were maximal at the end of diastole: 24.41 ± 1.70° (α) and 20.90 ± 2.11° (ß) for BAV with stenosis and 31.92 ± 11.51° (α) and 20.84 ± 9.80° (ß) for BAV with insufficiency and minimal at peak ejection 23.42 ± 1.65° (α), 20.38 ± 1.61° (ß) for stenosis and 26.62 ± 7.86° (α), 19.79 ± 8.45° (ß) for insufficiency. In insufficiency, low shear stress of 0-0.08 Pa and moderate pressure (60-80 mmHg) were present. In BAV with stenosis, low shear stress of 0-0.5 Pa and moderate pressure (0-20 mmHg) were present at diastole; at peak ejection high shear stress >2 Pa and elevated pressure of >80 mmHg were present. CONCLUSIONS: In a BAV with aortic valve stenosis, the haemodynamics are less favourable. The elevated pressure with elevated shear stress may over the long term promote degenerative processes in the leaflets and consequently valve function failure.

Conservative treatment versus surgery for uncomplicated appendicitis in children: a systematic review and meta-analysis.

OBJECTIVES: To compare conservative treatment with index admission appendicectomy in children with acute uncomplicated appendicitis. DESIGN: Systematic review and meta-analysis. DATA SOURCES: Medline, Embase and the Cochrane Library (CENTRAL) from 1950 to 18 February 2017. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Studies that assessed both appendicectomy and non-operative management of acute uncomplicated appendicitis in children of less than 18 years of age. Endpoints were postintervention complications, readmission and efficacy (successful outcome of the initial therapy). RESULTS: Five studies met the inclusion criteria (conservative treatment n=189; surgical intervention n=253). Compared with patients undergoing index admission appendicectomy, conservative treatment showed a reduced treatment efficacy (relative risk 0.77, 95% CI 0.71 to 0.84; p<0.001) and an increased readmission rate (relative risk 6.98, 95% CI 2.07 to 23.6; p<0.001), with a comparable rate of complications (relative risk 1.07, 95% CI 0.26 to 4.46). Exclusion of patients with faecoliths improved treatment efficacy in conservatively treated patients. One study was randomised, with the remaining four comprising cohorts assembled by patient or physician choice. Different antibiotic regimens were used between investigations. Follow-up varied from 1 to 4 years. CONCLUSIONS: Conservative treatment was less efficacious and was associated with a higher readmission rate. Index admission appendicectomy should in the present still be considered to be the treatment of choice for the management of uncomplicated appendicitis in children.

Aortic Valve Pathology as a Predictive Factor for Acute Aortic Dissection.

BACKGROUND: In this study, the effect of aortic valve (AV) pathology on local hemodynamic conditions was evaluated as a potential trigger for the onset of acute type A and B aortic dissection. METHODS: A time- and pressure-related four-dimensional (4-D) computed fluid dynamic model of the aorta was established. In an experimental setup, AV stenosis and AV insufficiency were created. 4-D pressure-related geometry of the aortic root (AR) with valve insufficiency and valve stenosis were determined by high-fidelity (200 Hz) microsonometric crystals. Flow and pressure were obtained at the left ventricle, ascending aorta, and aortic arch. RESULTS: Expansion of the AR in AV insufficiency was higher with expansion in AV stenosis, at peak ejection, and at the end of systole. In AV insufficiency, there was low shear stress (0 to 0.6 Pa), turbulent flow, and high pressure (80 to 95 mm Hg) at the anterior wall of the ascending aorta, at the proximal aortic arch, and at the aortic isthmus. In stenosis, high shear stress (>2 Pa) and high pressure (>95 mm Hg) were found at the ascending aorta and at the bifurcation of the brachiocephalic trunk. CONCLUSIONS: In AV insufficiency, low shear stresses and turbulent flow regions were documented at the traditional levels of entry tears for acute type A and B dissection. In AV stenosis, high shear stress with elevated pressure at the ascending aorta may be a trigger element for vessel dilatation, aneurysm formation, and intimal tear, which is typical for type A aortic dissection.

Impact of synthetic elements on aortic root haemodynamics: computed fluid dynamics of aortic root reconstruction and valve reimplantation.

Objectives: The aim was to evaluate the impact of the aortic valve reimplantation (David) and of the aortic root (AoR) remodelling (Yacoub) on the AoR haemodynamics. Methods: In an experimental setup where the clinical scenario of Yacoub, ( n = 5, domestic pig) and of David ( n = 5, domestic pig) procedure was performed in each AoR, six high-fidelity (200 Hz) sonomicrometric crystals were implanted. Crystals were positioned at three commissures with their projection at the root base. In post-measurement processing 3D deformation of both AoR was determined and used for computed fluid dynamic modelling in order to evaluate pressure, velocity and shear stress profiles. Results: In David AoR: high pressure (> 150 mmHg) and low to moderate shear stress (0-30 Pa) were found from the period of isovolemic contraction to the closure of the aortic valve. At mid diastole pressure augmentation (> 120 mmHg) a low shear stress (0-10 Pa) was registered at the leaflets, three commissures, and intervalvular triangles. In Yacoub AoR: high pressure (110-130 mmHg) with moderate low shear stress (0-30 Pa) was only registered at isovolemic contraction. Conclusions: The results show that haemodynamic conditions following a David procedure have a less favourable pattern as compared to a Yacoub AoR. In David AoR, high pressure and low shear stress are present during 2/3 of the cardiac cycle, whereas in Yacoub root, these conditions are present only for a short period of isovolemic contraction.

Aortic root haemodynamics following David procedure: numerical analysis of 3-dimensional haemodynamics.

OBJECTIVES: The aim was to determine 3-dimensional (3D) geometrical deformation of the aortic root (AoR) following the David procedure in order to evaluate local haemodynamical conditions of individual AoR elements. METHODS: In the experimental set-up, the David procedure was performed on 10 domestic pigs. Data were compared with the measurements obtained in 10 native AoRs. In each AoR, six high-resolution ultrasonometric crystals (200 Hz) were implanted, being positioned at each commissure and at the AoR base. 3D geometrical deformation of the AoR, torsion and tilt angle was determined. Computed fluid dynamics (CFD) simulation analysis was used to evaluate local pressure, flow and shear stress. RESULTS: In David AoRs, the tilt angle was maximal at a peak ejection of 25.9 ± 1.49° and minimal at the end of isovolemic contraction at 23.5 ± 0.80°. David root rotation was maximal at a peak ejection of 27.93 ± 1.54° and minimal at the end of the isovolemic contraction at 25.7 ± 1.32°. In the native AoR, the opposite was observed. Here, the tilt and rotation angle were maximal at the end of isovolemic contraction (17.25 ± 0.68° and 19.71 ± 0.73°) and decreased to its minimal values at peak ejections (14.1 ± 0.62° and 16.33 ± 0.47°). In David AoR, high pressure (>140 mmHg) combined with low-to-moderate shear stress (0-40 Pa) was found at the leaflet body from the beginning of isovolemic contraction till the opening of the aortic valve. Similar high pressure (>140 mmHg) and shear stress (0-40 Pa) were found in the period from aortic valve closure till the beginning of the isovolemic contraction. In native AoRs, high pressure (>95 mmHg) was conjoined with low-to-moderate shear stress (0-30 Pa) at the leaflets and was registered at the end of isovolemic contraction. CONCLUSIONS: The David AoR is haemodynamically less favourable when compared with the native AoR. During almost two-thirds of the time period of the cardiac cycle, AoR elements are exposed to high pressure and low shear stress. In contrast, in native AoRs, similar conditions were present only during the short period of isovolemic contraction.

Numerical analysis of the 3-dimensional aortic root morphology during the cardiac cycle.

OBJECTIVES: The aim was to define the 3-dimensional (3D) geometrical changes of the aortic root and to determine the local shear stress profile of aortic root elements during the cardiac cycle. METHODS: Six sonomicrometric crystals (200 Hz) were implanted into the aortic root of five pigs at the commissures and at the aortic root base (AoB). 3D aortic root deformation including volume, torsion and tilt angle were determined. Geometrical data with measured local flow and pressure conditions was used for computed fluid dynamics modelling of the aortic root. RESULTS: Compared with end-diastole, the sinotubular junction and AoB have maximal expansion at peak ejection: 16.42 ± 6.36 and 7.60 ± 2.52%, and minimal at isovolaemic relaxation: 2.87 ± 1.62 and 1.85 ± 1.79%. Aortic root tilt and rotation angle were maximal at the end of diastole: 17.7 ± 8.8 and 21.2 ± 2.09°, and decreased to 15.24 ± 8.14 and 18.3 ± 0.1.94° at peak ejection. High shear stress >20 Pa was registered at peak ejection at coaptations, and during diastole at the superior two-thirds of the leaflets and intervalvular triangles (IVTs). The leaflet body, inferior one-third of the IVTs and valve nadir were exposed to moderate shear stress (8-16 Pa) during the cardiac cycle. CONCLUSIONS: Aortic root geometry demonstrates precise 3D changes of tilt and rotation angle. Reduction of angles during ejection results in a straight cylinder with low shear stress that facilitates the ejection; the increase during diastole results in a tilted frustum with elevated shear stress. Findings can be used for comparative analysis of native and synthetic structures with individual compliance.

Fluid dynamics simulation of right ventricular outflow tract oversizing.

OBJECTIVES: Repair of the right ventricular outflow tract (RVOT) in paediatric cardiac surgery remains challenging due to the high reoperation rate. Intimal hyperplasia and consequent arteriosclerosis is one of the most important limitation factors for graft durability. Since local shear stress and pressure are predictive elements for intimal hyperplasia and wall degeneration, we sought to determine in an oversized 12-mm RVOT model, with computed fluid dynamics simulation, the local haemodynamical factors that may explain intimal hyperplasia. This was done with the aim of identifying the optimal degree of oversizing for a 12-mm native RVOT. METHODS: Twenty domestic pigs, with a weight of 24.6 ± 0.89 kg and a native RVOT diameter of 12 ± 1.7 mm, had valve conduits of 12, 16, 18 and 20 mm implanted. Pressure and flow were measured at 75, 100 and 125% of normal flow at RVOT at the pulmonary artery, pulmonary artery bifurcation and at the left and right pulmonary arteries. Three-dimensional computed fluid dynamics (CFD) simulation in all four geometries in all flow modalities was performed. Local shear stress and pressure conditions were investigated. RESULTS: Corresponding to 75, 100 and 125% of steady-state flow, three inlet velocity profiles were obtained, 0.2, 0.29 and 0.36 m/s, respectively. At inflow velocity profiles, low shear stress areas, ranged from 0 to 2 Pa, combined with high-pressure areas ranging from 11.5 to 12.1 mmHg that were found at distal anastomosis, at bifurcation and at the ostia of the left and right pulmonary arteries in all geometries. CONCLUSIONS: In all three oversized geometries, the local reparation of shear stress and pressure in the 16-mm model showed a similar local profile as in the native 12 mm RVOT. According to these findings, we suggest oversizing the natural 12-mm RVOT by not more than 4 mm. The elements responsible for wall degeneration and intimal hyperplasia remain very similar to the conditions present in native RVOT.