Re-creation of a sinuslike graft expansion in Bentall procedure reduces stress at the coronary button anastomoses: A finite element study

Fluid-Structure Interaction Simulations of Repaired Type A Aortic Dissection: a Comprehensive Comparison With Rigid Wall Models

This study aimed to evaluate the effect of aortic wall compliance on intraluminal hemodynamics within surgically repaired type A aortic dissection (TAAD). Fully coupled two-way fluid-structure interaction (FSI) simulations were performed on two patient-specific post-surgery TAAD models reconstructed from computed tomography angiography images. Our FSI model incorporated prestress and different material properties for the aorta and graft. Computational results, including velocity, wall shear stress (WSS) and pressure difference between the true and false lumen, were compared between the FSI and rigid wall simulations. It was found that the FSI model predicted lower blood velocities and WSS along the dissected aorta. In particular, the area exposed to low time-averaged WSS (≤0.2 Pa) was increased from 21 cm² (rigid) to 38 cm² (FSI) in patient 1 and from 35 cm² (rigid) to 144 cm² (FSI) in patient 2. FSI models also produced more disturbed flow where much larger regions presented with higher turbulence intensity as compared to the rigid wall models. The effect of wall compliance on pressure difference between the true and false lumen was insignificant, with the maximum difference between FSI and rigid models being less than 0.25 mmHg for the two patient-specific models. Comparisons of simulation results for models with different Young’s moduli revealed that a more compliant wall resulted in further reduction in velocity and WSS magnitudes because of increased displacements. This study demonstrated the importance of FSI simulation for accurate prediction of low WSS regions in surgically repaired TAAD, but a rigid wall computational fluid dynamics simulation would be sufficient for prediction of luminal pressure difference.

Giant Distal Anastomotic Pseudoaneurysm 35 Years after Bentall Operation Mimicking an “Elephant Trunk”

We present the case of a giant distal aortic pseudoaneurysm 35 years after a classic mechanical Bentall operation. Computed tomography and coronary angiography showed that this originated from the distal suture line. The proximal suture and coronary ostia appeared to be intact. At reoperation, we found a complete dehiscence of distal suture line: the graft was floating in the pseudoaneurysm, mimicking an “elephant trunk” procedure. This complication suggested a systematic and accurate follow-up of patients who underwent an original Bentall procedure.

The Skirt and Collar of The Valsalva Graft: One Dress Fits All

In the original pre-formed Valsalva graft, the skirt is the defining feature. It is a self-expanding portion, obtained by 90° rotation of the Dacron fabric corrugation with respect to the rest of the graft. Due to this manufacturing feature, the skirt length is equal to the graft diameter and, once pressurized, it expands by 25-30% (up to 10 mm) from the nominal size. Proximal to this bulged portion, a small collar completes the prosthesis. By virtue of this anatomical design, the Valsalva graft is recommended for most aortic root surgeries including valve-sparing and Bentall procedures. The skirt, by recreating the pseudo-sinuses, represents the key feature of the graft when used for aortic valve-sparing procedures (remodeling and reimplantation). However, in the Bentall procedure, the graft collar is an important feature because it is useful to attach the Valsalva graft to the valve prosthesis sewing ring when making a valved conduit. Moreover, once the graft is pressurized, the whole volume of the skirt better accommodates the struts and the leaflets of biological and mechanical prostheses. Furthermore, the expanded skirt reduces the distance and the tension on the coronary button anastomosis, increasing safety and possibly reducing complication rates. This review demonstrates the versatility of the Valsalva graft in various scenarios of aortic root surgery, with special emphasis on different uses of the skirt and the collar.

Optimized use of the "skirt" of the Valsalva graft for the completion Bentall

We report the case of a patient with an aortic root aneurysm who had previously undergone aortic valve replacement with a large mechanical prosthesis which proved to be normally functioning at the time of reoperation. We describe a new technique of replacing the aortic root while retaining the existing aortic valve similar to the "completion Bentall" procedure using a 32 mm Valsalva graft by suturing the skirted portion of the graft to the sewing ring of the mechanical valve. The ability of the skirt to increase its diameter was the key of this approach.

Fate of a coronary artery intramural haematoma complicating aortic root surgery: a case report

Background

Coronary intramural haematoma (CIH) is an uncommon but potentially life-threatening complication during aortic root surgery (such as Bentall procedure). Depending on its extension it can lead to cardiogenic shock. Documented reports of this complication are lacking in literature.

Case summary

In the report we present a case of CIH and its management and we show a stepwise imaging of the healing process that gives an insight of the fate of CIHs.

Discussion

This case raises awareness of CIH as differential diagnosis for myocardial ischaemia during aortic root surgery. It underlines the effectiveness of immediate surgical revascularization, highlights the potential temporary role of coronary artery bypass graft that can stabilize the acute coronary syndrome and may give time to the CIH to reabsorb and native coronary circulation to re-establish.

Long-term follow-up of Bentall procedure using the Perimount bioprosthesis and the Valsalva graft

OBJECTIVES

Bentall procedure is the gold standard for aortic root pathologies when valve repair is not feasible. The development of durable bioprosthetic valves and improved vascular conduits allowed the implementation of bioprosthetic composite grafts; hereby, we performed a retrospective analysis of long-term follow-up of Bentall procedure using the Valsalva graft and the Perimount Magna Ease prosthesis.

METHODS

From June 2000 to March 2019, 309 patients received an aortic root and valve replacement with a bioprosthetic composite graft. The mean age was 69 ± 6.9 years, and the majority were men (88%); most of them were affected by aortic stenosis (86%) and the mean aortic root diameter was 48.6 ± 5.5 mm.

RESULTS

Freedom from cardiac death was 76.8% [confidence interval (CI) 32.5-94.0] at 16 years. Freedom from thromboembolism, haemorrhage, structural valve deterioration and infective endocarditis was 98.2% (CI 96.0-98.9), 95.2% (CI 87.1-98.2), 87.5% (CI 63.2-97.1) and 79.6% (CI 45.3-95.6) at 16 years, respectively. Freedom from reoperation was 74.7% (CI 41.9-90.6).

CONCLUSIONS

These data indicate that, in experienced centres, the Bentall procedure is a safe and effective intervention. This is the first long-term follow-up that analyses the results after implantation of a composite graft made with the Perimount Magna Ease aortic valve and the Valsalva graft.

Aortic root surgery with the CARDIOROOT vascular graft: results of a prospective multicenter post-market surveillance study

BACKGROUND

Sparing Aortic Valve procedure requires to reproduction of the geometry of the physiologic anatomy of the aortic root. Thus, the materials adopted may make a difference. CARDIOROOT is a one-piece collagen-coated woven vascular graft with pseudo-sinuses, which was designed for use in the treatment of aortic root disease. We report the results of a prospective, multicenter, observational post-market surveillance study evaluating the safety and performance of the CARDIOROOT in patients requiring aortic root surgery.

METHODS

Patients with aortic root disease suitable for treatment with a vascular graft with pseudo-sinuses CARDIOROOT graft were eligible for participation. The enrolled patients were assessed intraoperatively, post-operatively, at discharge and at 1-year. Sites assessed complications at each visit, and recorded any reported adverse events. The study endpoint was mortality and complications through 1-year post-procedure.

RESULTS

Fifty-two patients were enrolled from 6 European centers. All procedures were technically successful. Operative mortality was 1.9%: one patient suffered hemorrhagic shock unrelated to the graft 1 day following surgery. At 1-year follow-up the survival rate was 96.2%, with a late death due to pneumonia 5 months post-procedure. Eleven serious adverse events occurred in 7 patients, which included cardiac complications (pericardial effusion, myocardial infarction and ventricular arrhythmia), infection (pericardial infection, deep sternal infection and superficial sternal infection), vascular disorders, including hemorrhagic shock and pleural effusion requiring drainage. Nine of the 11 events were deemed procedure-related by the local investigator, and all were deemed unrelated to the device. There were no reports of graft-related adverse events, infection, occlusion or graft failure.

CONCLUSIONS

The results of this 1-year follow-up study showed that the CARDIOROOT vascular graft is safe and effective for the treatment of aneurysmal aortic root in immediate and mid-term follow-up. However, longer term follow-up is needed before conclusions can be made on the long-term safety and effectiveness.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01609270. Registered 31 May 2012.

Surgical anatomy of the aortic valve and root-implications for valve repair

The aortic root is an important anatomical structure positioned at the center of the heart, making it critical to the functioning of the major cardiac chambers. Deep knowledge of the anatomical "surroundings" of the aortic root is crucial for surgeon attempting to spare or repair a leaking aortic valve. In fact, root dissection is a necessary step to "skeletonize" the aortic valve, allowing the surgeon to work on the critical components of its structure, namely the aorto-ventricular junction, the virtual basal ring (VBR) and the sino-tubular junction (STJ). These three components, along with the insertion of the leaflet to the aortic wall, form the skeleton of the aortic valve that is essential in guaranteeing valve competence. A good anatomical proportion between the various component of the skeleton of the aortic valve need to be verified, or re-established in order to set the basis for an optimal aortic valve repair. Once the skeleton of the heart has been correctly addressed, the condition of the valve leaflets need to be considered. Excess of leaflet tissue is treated by leaflet plication or resection and lack of leaflet tissue is addressed by tissue extension with autologous or heterologous materials. In the present manuscript, we highlight the principal structure of the aortic root and describe in detail each anatomical component. This basic anatomical knowledge is also important for a through understanding of the normal function of the valve and root structure during the cardiac cycle. The close boundaries existing between the left ventricular cavity and the aorta are important in explaining the sophisticated function of opening and closing of the aortic valve. Similarly, the role played by the sinuses of Valsalva in regulating the blood flow exiting the ventricle underline the concept that "form follows function" and emphasizes the importance of a good anatomical reconstruction for an optimal and long-lasting valve function.

Novel insights by 4D Flow imaging on aortic flow physiology after valve-sparing root replacement with or without neosinuses

OBJECTIVES

This study was undertaken to evaluate the flow dynamics in the aortic root after valve-sparing root replacement with and without neosinuses of Valsalva reconstruction, by exploiting the capability of 4D Flow imaging to measure in vivo blood velocity fields and 3D geometric flow patterns.

METHODS

Ten patients who underwent valve-sparing root replacement utilizing grafts with neosinuses or straight tube grafts (5 cases each) were evaluated by 4D Flow imaging at a mean of 46.5 months after surgery. We used in-house processing tools to quantify relevant bulk flow variables (flow rate, stroke volume, peak velocity and mean velocity), wall shear stresses and the amount of flow rotation characterizing the region enclosed by the graft and the aortic valve leaflets.

RESULTS

Despite bulk flows with similar peak velocities, flow rates and stroke volumes (P = 0.31-1.00), the neosinuses graft was associated with a lower mean velocity (P < 0.03) and magnitude of wall shear stress along the axial direction of the vessel wall (P < 0.05) at the proximal root level but remained comparable along the circumferential direction (P = 0.22-1.0) to the straight tube graft. Flow rotation was evidently and systematically higher in the neosinuses grafts, characterized by streamline rotations higher than 270°, nearly triple that of tubular grafts (10.3 ÷ 14.0% of all aortic streamline vs 2.2 ÷ 5.7%, P = 0.008).

CONCLUSIONS

Recreation of the sinuses of Valsalva during valve-sparing root replacement is associated with significantly lower wall shear stress and organized vortical flows at the level of the sinus that are not evident using the straight tube graft. These findings need confirmation in larger studies and could have important implications in terms of aortic valve durability.

The evidence in a Bentall procedure with Valsalva graft: is this standard of care?

Background

Biologic valved-conduits avoids the need for anticoagulation and can exploit the excellent hemodynamic performance of stentless valves. Incorporation of the sinuses of Valsalva into the neoaortic root can improve the function and longevity of stentless valves. We report our experience in performing the Bentall procedure with a self-prefabricated composite valved-conduit and review the published experience with the Valsalva graft.

Methods

From Feb 2005 through Sep 2017, 428 patients underwent aortic root replacement utilizing a composite graft constructed from a 27-29-mm Freestyle MS valve (Medtronic) sutured into a 28-30-mm Gelweave Valsalva prosthesis (Sulzer Vascutek, Renfrewshire, Scotland). Data were retrospectively analyzed.

Results

Mean age was 58±13 years, with a male predominance (337, 79%). Additional surgical procedures included a mitral valve repair/replacement in 10 patients (2%), coronary artery bypass graft (CABG) in 114 patients (27%), and aortic arch (hemi or total) replacement in 252 patients (59%). Average cardiopulmonary bypass, cross-clamp, and circulatory arrest times were 210±57, 180±44, and 29±15 min, respectively. Thirty-day mortality was 7% (31 patients). Mean echocardiography follow-up was 27.2±29.0 months (range, 1-138 months). Pressure gradients (mean, peak) across the aortic valve on latest echocardiography were 5.59, 10.57 mmHg respectively. Freedom from >2+ aortic insufficiency (AI) at 6 and 9 years was 96%, and 87% respectively. Freedom from aortic valve replacement (AVR) at 6 and 9 years was 99%, and 95% respectively. To date, 4 (1%) patients required an additional aortic valve intervention secondary to structural valve degeneration.

Conclusions

Use of the Valsalva graft combined with the Freestyle valve for Bentall procedures is associated with favorable results. Clinical outcomes are excellent and in longitudinal follow-up, valve-related complications are minimal.

Comparison of mid-term haemodynamic performance between the BioValsalva and the BioIntegral valved conduits after aortic root replacement

OBJECTIVES

We retrospectively compared the haemodynamic performance of the BioValsalva (BV) and BioIntegral (BI) biological aortic-valved conduits in the aortic root position.

METHODS

Between July 2008 and June 2014, a total of 55 patients underwent aortic root replacement using the BV conduit (n = 27) or the BI conduit (n = 28). The primary study endpoints were haemodynamic performance during follow-up, including mean pressure gradients (MPGs) and effective orifice areas (EOAs). Secondary study endpoints were early postoperative outcomes within 30 days and survival.

RESULTS

Both groups did not differ in regard to demographics (BV: median age 71 years, 70.4% female; BI: median age 66 years, 85.7% female, P = 0.15 and P = 0.17) and risk profile (median EuroSCORE-II BV: 3.8 vs 5.3% for BI, P = 0.38). A total of 20% of the total patients (BV 5/27, 18.5% vs BI 6/28, 21.4%) presented with acute type-A aortic dissection. During follow-up, both groups showed no difference in MPGs for all valve sizes [BV, 11.0 mmHg (8.3-14.8 mmHg) vs BI, 11.5 mmHg (9.0-13.0), P = 0.82]. Similar results were achieved for EOAs for all valve sizes [BV, 1.85 cm(2) (1.55-2.21) vs BI, 1.80 cm(2) (1.64-1.83), P = 0.24]. Moreover, there was no statistically significant difference in aortic regurgitation (AR) with none/trace AR in (21/23) 91.3% in BV patients versus (16/21) 76.2% in BI patients (P = 0.23) at follow-up. Both groups showed a high rate of concomitant procedures (BV: 59.3% vs BI: 71.4%, P = 0.40) and emergency indication (BV: 18.5% vs BI: 21.4%, P = 0.79), resulting in an overall 30-day mortality rate of 7.3% (4/55 patients).

CONCLUSIONS

The present small single-centre study is one of the first to evaluate and compare the BioValsalva and BioIntegral biological aortic-valved conduit in the aortic root position. Both conduits showed optimal haemodynamic results with a low incidence of aortic regurgitation.

Biomechanical properties of the Marfan's aortic root and ascending aorta before and after personalised external aortic root support surgery

Marfan syndrome is an inherited systemic connective tissue disease which may lead to aortic root disease causing dilatation, dissection and rupture of the aorta. The standard treatment is a major operation involving either an artificial valve and aorta or a complex valve repair. More recently, a personalised external aortic root support (PEARS) has been used to strengthen the aorta at an earlier stage of the disease avoiding risk of both rupture and major surgery. The aim of this study was to compare the stress and strain fields of the Marfan aortic root and ascending aorta before and after insertion of PEARS in order to understand its biomechanical implications. Finite element (FE) models were developed using patient-specific aortic geometries reconstructed from pre and post-PEARS magnetic resonance images in three Marfan patients. For the post-PEARS model, two scenarios were investigated-a bilayer model where PEARS and the aortic wall were treated as separate layers, and a single-layer model where PEARS was incorporated into the aortic wall. The wall and PEARS materials were assumed to be isotropic, incompressible and linearly elastic. A static load on the inner wall corresponding to the patients' pulse pressure was applied. Results from our FE models with patient-specific geometries show that peak aortic stresses and displacements before PEARS were located at the sinuses of Valsalva but following PEARS surgery, these peak values were shifted to the aortic arch, particularly at the interface between the supported and unsupported aorta. Further studies are required to assess the statistical significance of these findings and how PEARS compares with the standard treatment.

In-vivo assessment of the morphology and hemodynamic functions of the BioValsalva™ composite valve-conduit graft using cardiac magnetic resonance imaging and computational modelling technology

BACKGROUND

The evaluation of any new cardiac valvular prosthesis should go beyond the classical morbidity and mortality rates and involve hemodynamic assessment. As a proof of concept, the objective of this study was to characterise for the first time the hemodynamics and the blood flow profiles at the aortic root in patients implanted with BioValsalva™ composite valve-conduit using comprehensive MRI and computer technologies.

METHODS

Four male patients implanted with BioValsalva™ and 2 age-matched normal controls (NC) underwent cardiac magnetic resonance imaging (MRI). Phase-contrast imaging with velocity-mapping in 3 orthogonal directions was performed at the level of the aortic root and descending thoracic aorta. Computational fluid dynamic (CFD) simulations were performed for all the subjects with patient-specific flow information derived from phase-contrast MR data.

RESULTS

The maximum and mean flow rates throughout the cardiac cycle at the aortic root level were very comparable between NC and BioValsalva™ patients (541 ± 199 vs. 567 ± 75 ml/s) and (95 ± 46 vs. 96 ± 10 ml/s), respectively. The maximum velocity (cm/s) was higher in patients (314 ± 49 vs. 223 ± 20; P = 0.06) due to relatively smaller effective orifice area (EOA), 2.99 ± 0.47 vs. 4.40 ± 0.24 cm2 (P = 0.06), however, the BioValsalva™ EOA was comparable to other reported prosthesis. The cross-sectional area and maximum diameter at the root were comparable between the two groups. BioValsalva™ conduit was stiffer than the native aortic wall, compliance (mm2 • mmHg(-1) • 10(-3)) values were (12.6 ± 4.2 vs 25.3 ± 0.4.; P = 0.06). The maximum time-averaged wall shear stress (Pa), at the ascending aorta was equivalent between the two groups, 17.17 ± 2.7 (NC) vs. 17.33 ± 4.7 (BioValsalva™ ). Flow streamlines at the root and ascending aorta were also similar between the two groups apart from a degree of helical flow that occurs at the outer curvature at the angle developed near the suture line.

CONCLUSIONS

BioValsalva™ composite valve-conduit prosthesis is potentially comparable to native aortic root in structural design and in many hemodynamic parameters, although it is stiffer. Surgeons should pay more attention to the surgical technique to maximise the reestablishment of normal smooth aortic curvature geometry to prevent unfavourable flow characteristics.

Annular dilatation and loss of sino-tubular junction in aneurysmatic aorta: implications on leaflet quality at the time of surgery. A finite element study

OBJECTIVES

In the belief that stress is the main determinant of leaflet quality deterioration, we sought to evaluate the effect of annular and/or sino-tubular junction dilatation on leaflet stress. A finite element computer-assisted stress analysis was used to model four different anatomic conditions and analyse the consequent stress pattern on the aortic valve.

METHODS

Theoretical models of four aortic root configurations (normal, with dilated annulus, with loss of sino-tubular junction and with both dilatation simultaneously) were created with computer-aided design technique. The pattern of stress and strain was then analysed by means of finite elements analysis, when a uniform pressure of 100 mmHg was applied to the model. Analysis produced von Mises charts (colour-coded, computational, three-dimensional stress-pattern graphics) and bidimensional plots of compared stress on arc-linear line, which allowed direct comparison of stress in the four different conditions.

RESULTS

Stresses both on the free margin and on the 'belly' of the leaflet rose from 0.28 MPa (normal conditions) to 0.32 MPa (+14%) in case of isolated dilatation of the sino-tubular junction, while increased to 0.42 MPa (+67%) in case of isolated annular dilatation, with no substantial difference whether sino-tubular junction dilatation was present or not.

CONCLUSIONS

Annular dilatation is the key element determining an increased stress on aortic leaflets independently from an associated sino-tubular junction dilatation. The presence of annular dilatation associated with root aneurysm greatly decreases the chance of performing a valve sparing procedure without the need for additional manoeuvres on leaflet tissue. This information may lead to a refinement in the optimal surgical strategy.

Opening of a wall-mounted leaflet by a single flow pulse

The opening of a leaflet by one flow pulsation is studied here in an ideal system made of a rigid door, initially vertical, mounted on a horizontal wall. The dependence of the fluid-structure interaction on the leaflet inertia and flow parameters has been analyzed. The system has been solved by numerical integration of the Navier-Stokes equations coupled with the body dynamics. The behavior of the movable leaflet and resulting vortex formation has been conditioned through the range of Strouhal numbers and body inertia. When inertia is relatively large, the flow pulsation is unable to significantly move the leaflet. When inertia is relatively low, the degree of opening smoothly increases with lowering the Strouhal number (that corresponds, for example, to either a longer pulsation period or a higher flow velocity). The analysis also demonstrated the existence of a critical intermediate range where the body opens completely and impacts onto the lower wall at high speed.

Evaluation of prosthetic-valved devices by means of numerical simulations

The in vivo evaluation of prosthetic device performance is often difficult, if not impossible. In particular, in order to deal with potential problems such as thrombosis, haemolysis, etc., which could arise when a patient undergoes heart valve replacement, a thorough understanding of the blood flow dynamics inside the devices interacting with natural or composite tissues is required. Numerical simulation, combining both computational fluid and structure dynamics, could provide detailed information on such complex problems. In this work, a numerical investigation of the mechanics of two composite aortic prostheses during a cardiac cycle is presented. The numerical tool presented is able to reproduce accurately the flow and structure dynamics of the prostheses. The analysis shows that the vortical structures forming inside the two different grafts do not influence the kinematics of a bileaflet valve or the main coronary flow, whereas major differences are present for the stress status near the suture line of the coronaries to the prostheses. The results are in agreement with in vitro and in vivo observations found in literature.

Fluid-structure interaction of deformable aortic prostheses with a bileaflet mechanical valve

Two different aortic prostheses can be used for performing the Bentall procedure: a standard straight graft and the Valsalva graft that better reproduces the aortic root anatomy. The aim of the present work is to study the effect of the graft geometry on the blood flow when a bileaflet mechanical heart valve is used, as well as to evaluate the stress concentration near the suture line where the coronary arteries are connected to graft. An accurate three-dimensional numerical method is proposed, based on the immersed boundary technique. The method accounts for the interactions between the flow and the motion of the rigid leaflets and of the deformable aortic root, under physiological pulsatile conditions. The results show that the graft geometry only slightly influences the leaflets dynamics, while using the Valsalva graft the stress level near the coronary-root anastomoses is about half that obtained using the standard straight graft.