Elucidating the mechanisms underlying left ventricular function recovery in patients with ischemic heart failure undergoing surgical remodeling: A 3-dimensional ultrasound analysis.

OBJECTIVE: The study objective was to elucidate the mechanisms of left ventricle functional recovery in terms of endocardial contractility and synchronicity after surgical ventricular reconstruction. METHODS: Real-time 3-dimensional transthoracic echocardiography was performed on 20 patients with anterior left ventricle remodeling and ischemic heart failure before surgical ventricular reconstruction and at 6-month follow-up, and on 15 healthy controls matched by age and body surface area. Real-time 3-dimensional transthoracic echocardiography datasets were analyzed through TomTec software (4D LV-Analysis; TomTec Imaging Systems GmbH, Unterschleissheim, Germany): Left ventricle volumes, ejection fraction, and global longitudinal strain were computed; the time-dependent endocardial surface yielded by 3-dimensional speckle-tracking echocardiography was postprocessed through in-house software to quantify local systolic minimum principal strain as a measure of fiber shortening and mechanical dispersion as a measure of fiber synchronicity. RESULTS: Compared with controls, patients with heart failure before surgical ventricular reconstruction showed lower ejection fraction (P < .0001) and significantly impaired mechanical dispersion (P < .0001) and minimum principal strain (P < .0001); the latter worsened progressively from left ventricle base to apex. After surgical ventricular reconstruction, global longitudinal strain improved from -6.7% to -11.3% (P < .0001); mechanical dispersion decreased in every left ventricle region (P ≤ .017) and mostly in the basal region, where computed mechanical dispersion values were comparable to physiologic values (P ≥ .046); minimum principal strain improved mostly in the basal region, changing from -16.6% to -22.3% (P = .0027). CONCLUSIONS: At 6-month follow-up, surgical ventricular reconstruction was associated with significant recovery in global left ventricle function, improved mechanical dispersion indicating a more synchronous left ventricle contraction, and improved left ventricle fiber shortening mostly in the basal region, suggesting the major role of the remote myocardium in enhancing left ventricle functional recovery.

Non-invasive estimation of vascular compliance and distensibility in the arm vessels: a novel ultrasound-based protocol.

Background: Performance and durability of arterio-venous grafts depend on their ability to mimic the mechanical behavior of the anastomized blood vessels. To select the most suitable synthetic graft, in vivo evaluation of the radial deformability of peripheral arteries and veins could be crucial; however, a standardized non-invasive strategy is still missing. Herein, we sought to define a novel and user-friendly clinical protocol for in vivo assessment of the arm vessel deformability. Methods: A dedicated protocol, applied on 30 volunteers, was specifically designed to estimate both compliance and distensibility of the brachial and radial arteries, and of the basilic and cephalic veins. Bi-dimensional ultrasound imaging was used to acquire cross-sectional areas (CSAs) of arteries in clinostatic configuration, and CSAs of veins combining clinostatic and orthostatic configurations. Arterial pulse pressure was measured with a digital sphygmomanometer, while venous hydrostatic pressure was derived from the arm length in orthostatic configuration. Results: For each participant, all CSAs were successfully extracted from ultrasound images. The basilic vein and the radial artery exhibited the largest (21.5±8.9 mm2) and the smallest (3.4±1.0 mm2) CSAs, respectively; CSA measurements were highly repeatable (Bland-Altman bias <10% and Pearson correlation ≥0.90, for both arteries and veins). In veins, compliance and distensibility were higher than in arteries; compliance was significantly higher (P<0.0001) in the brachial than in the radial artery (3.52×10-4 vs. 1.3×10-4 cm2/mmHg); it was three times larger in basilic veins than in cephalic veins (17.4×10-4 vs. 5.6×10-4 cm2/mmHg, P<0.0001). Conclusions: The proposed non-invasive protocol proved feasible, effective and adequate for daily clinical practice, allowing for the estimation of patient-specific compliance and distensibility of peripheral arteries and veins. If further extended, it may contribute to the fabrication of biohybrid arterio-venous grafts, paving the way towards patient-tailored solutions for vascular access.

Comparison of Four-Dimensional Magnetic Resonance Imaging Analysis of Left Ventricular Fluid Dynamics and Energetics in Ischemic and Restrictive Cardiomyopathies.

BACKGROUND: Time-resolved three-directional velocity-encoded (4D flow) magnetic resonance imaging (MRI) enables the quantification of left ventricular (LV) intracavitary fluid dynamics and energetics, providing mechanistic insight into LV dysfunctions. Before becoming a support to diagnosis and patient stratification, this analysis should prove capable of discriminating between clearly different LV derangements. PURPOSE: To investigate the potential of 4D flow in identifying fluid dynamic and energetics derangements in ischemic and restrictive LV cardiomyopathies. STUDY TYPE: Prospective observational study. POPULATION: Ten patients with post-ischemic cardiomyopathy (ICM), 10 patients with cardiac light-chain cardiac amyloidosis (AL-CA), and 10 healthy controls were included. FIELD STRENGTH/SEQUENCE: 1.5 T/balanced steady-state free precession cine and 4D flow sequences. ASSESSMENT: Flow was divided into four components: direct flow (DF), retained inflow, delayed ejection flow, and residual volume (RV). Demographics, LV morphology, flow components, global and regional energetics (volume-normalized kinetic energy [KEV ] and viscous energy loss [ELV ]), and pressure-derived hemodynamic force (HDF) were compared between the three groups. STATISTICAL TESTS: Intergroup differences in flow components were tested by one-way analysis of variance (ANOVA); differences in energetic variables and peak HDF were tested by two-way ANOVA. A P-value of <0.05 was considered significant. RESULTS: ICM patients exhibited the following statistically significant alterations vs. controls: reduced KEV , mostly in the basal region, in systole (-44%) and in diastole (-37%); altered flow components, with reduced DF (-33%) and increased RV (+26%); and reduced basal-apical HDF component on average by 63% at peak systole. AL-CA patients exhibited the following alterations vs. controls: significantly reduced KEV at the E-wave peak in the basal segment (-34%); albeit nonstatistically significant, increased peaks and altered time-course of the HDF basal-apical component in diastole and slightly reduced HDF components in systole. DATA CONCLUSION: The analysis of multiple 4D flow-derived parameters highlighted fluid dynamic alterations associated with systolic and diastolic dysfunctions in ICM and AL-CA patients, respectively. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY STAGE: 3.

Brugada Syndrome: New Insights From Cardiac Magnetic Resonance and Electroanatomical Imaging.

BACKGROUND: Brugada syndrome (BrS) is considered a purely electrical disease with variable electrical substrates. Variable rates of mechanical abnormalities have been also reported. Whether exists a link between electrical and mechanical abnormalities has never been previously explored. This investigational physiopathological study aimed to determine the relationship between the substrate size/location, as exposed by ajmaline provocation, and the severity of mechanical abnormalities, as assessed by cardiac magnetic resonance in patients with BrS. METHODS: Twenty-four consecutive high-risk patients with BrS (mean age, 38±11 years, 17 males), presenting with malignant syncope and documented polymorphic ventricular tachycardia/ventricular fibrillation, and candidate to implantable cardioverter defibrillator implantation, underwent cardiac magnetic resonance and electroanatomic maps. During each examination, ajmaline test (1 mg/kg over 5 minutes) was performed. Cardiac magnetic resonance findings were compared with 24 age, sex, and body surface area-matched controls. In patients with BrS, the correlation between the electrical substrate extent and right ventricular regional mechanical abnormalities before/after ajmaline challenge was analyzed. RESULTS: After ajmaline, patients with BrS showed a reduction of right ventricular (RV) ejection fraction (P<0.001), associated with decreased transversal displacement (U, P<0.001) and longitudinal strain (ε, P<0.001) localized at RV outflow tract. In patients with BrS significant preajmaline/postajmaline changes of transversal displacement (ΔU, P<0.001) and longitudinal strain (Δε, P<0.001) were found. In the control group, no mechanical changes were observed after ajmaline. The electrical substrate consistently increased after ajmaline from 1.7±2.8 cm2 to 14.2±7.3 cm2 (P<0.001), extending from the RV outflow tract to the neighboring segments of the RV anterior wall. Postajmaline RV ejection fraction inversely correlated with postajmaline substrate extent (r=-0.830, P<0.001). In patients with BrS and normal controls, cardiac magnetic resonance detected neither myocardial fibrosis nor RV outflow tract morphological abnormalities. CONCLUSIONS: BrS is a dynamic RV electromechanical disease, where functional abnormalities correlate with the maximal extent of the substrate size. These findings open new lights on the physiopathology of the disease. Registration: URL: https://clinicaltrial.gov; Unique identifier: NCT03524079.

Blood flow helical pattern in type III arch configuration as a potential risk factor for type B aortic dissection.

OBJECTIVES: Abnormal helical flow (HF) in the aortic arch has been proposed as a causative factor for aortic dilatation and aortic dissections (ADs). Patients with type B AD present a high prevalence of type III arch configuration, which comprises recognized anatomic AD risk factors. Our aim was to assess whether the type III arch configures a consistent secondary HF pattern. METHODS: We employed computational fluid dynamics to compare HF features associated with type I-III arches. The intra-aortic blood flow pattern was regionally assessed through the Modified Arch Landing Areas Nomenclature (MALAN) for planning endovascular aortic repair. Aortic flow pathlines were extracted from the systolic aortic velocity field and objectively characterized through intrinsic shape indices of absolute curvature |κ| and absolute torsion |τ|. Absolute local normalized helicity was computed and mapped on aortic flow pathlines. RESULTS: The tendency of aortic flow pathlines to bend and rotate exacerbated in the isthmus of type III arch (MALAN 3/III), where the highest |κ| values (P < 0.0001) were paralleled by the lowest |τ| values (P = 0.010), demonstrating the persistence of a high rotational HF heavily insisting on 3/III. In 3/III area, local normalized helicity was higher than both 3/I and 3/II (P = 0.053). CONCLUSIONS: Type III arch configuration is associated with a specific, consistent and abnormal secondary HF pattern, which may account for its high prevalence in patients with type B AD.

4D flow evaluation of blood non-Newtonian behavior in left ventricle flow analysis.

Blood is generally modeled as a Newtonian fluid, assuming a standard and constant viscosity; however, this assumption may not hold for the highly pulsatile and recirculating intracavitary flow in the left ventricle (LV), hampering the quantification of fluid dynamic indices of potential clinical relevance. Herein, we investigated the effect of three viscosity models on the patient-specific quantification of LV blood energetics, namely on viscous energy loss (EL), from 4D Flow magnetic resonance imaging: I) Newtonian with standard viscosity (3.7 cP), II) Newtonian with subject-specific hematocrit-dependent viscosity, III) non-Newtonian accounting for the effect of hematocrit and shear rate. Analyses were performed on 5 controls and 5 patients with cardiac light-chain amyloidosis. In Model II, viscosity ranged between 3.0 (-19%) and 4.3 cP (+16%), mildly deviating from the standard value. In the non-Newtonian model, this effect was emphasized: viscosity ranged from 3.2 to 6.0 cP, deviating maximally from the standard value in low shear rate (i.e., <100 s-1) regions. This effect reflected on EL quantifications: in particular, as compared to Model I, Model III yielded markedly higher EL values (up to +40%) or markedly lower (down to -21%) for subjects with hematocrit higher than 39.5% and lower than 30%, respectively. Accounting for non-Newtonian blood behavior on a patient-specific basis may enhance the accuracy of intracardiac energetics assessment by 4D Flow, which may be explored as non-invasive index to discriminate between healthy and pathologic LV.

Computational Fluid Dynamics Modeling of Proximal Landing Zones for Thoracic Endovascular Aortic Repair in the Bovine Arch Variant.

BACKGROUND: To assess the endograft displacement forces (DF), which quantify the forces exerted by the pulsatile blood flow on the vessel wall and transmitted on the terminal fixation site of the endograft after its deployment in proximal landing zones (PLZs) of the bovine aortic arch variant. METHODS: Thirty healthy aortic computed tomographic angiographies of subjects with bovine arch configuration (10 per type of arch, I-III) were selected for the purpose of the study. A 3-dimensional model of the aortic arch lumen was reconstructed. Computational fluid dynamics modeling was then used to compute DF magnitude and orientation (i.e., x, y, and z axes) in PLZs of each case. DF values were normalized to the corresponding aortic wall area to estimate equivalent surface traction (EST). RESULTS: DF were highest in zone 0, consistently with the greater surface area. DF in zone 3 were much greater than in zone 2 because of a 3-fold greater upward component (z axis) (P < 0.001), being therefore mainly oriented orthogonally to the aortic blood flow and to the vessel longitudinal axis in that zone. EST progressively increased from zone 0 toward more distal PLZs, with EST in zone 3 being much greater than that in zone 2 (P < 0.001). The same pattern was observed after stratification by type of arch. CONCLUSIONS: The bovine arch is associated with a consistent fluid dynamic pattern, which identifies in zone 3 an unfavorable biomechanical environment for endograft deployment.

Aortic flow after valve sparing root replacement with or without neosinuses reconstruction.

OBJECTIVES: This study applied advanced 4-dimensional flow magnetic resonance imaging processing to assess differences in aortic flow dynamics after valve sparing root replacement, with and without reconstruction of the Valsalva sinuses. METHODS: We enrolled patients after valve sparing root replacement with a straight tubular prosthesis (n = 10) or with a prosthesis with Valsalva neosinuses (n = 10); age-matched subjects without cardiovascular diseases served as controls (n = 10). 4-Dimensional flow magnetic resonance imaging acquisitions were performed on a 3.0T magnetic resonance imaging unit. In-house processing was used to segment the aortic lumen and extract the volumetric 4-dimensional flow velocity field. Velocity flow streamlines were computed to compare the amount of rotational flow and wall shear stress. Occurrence of abnormal wall shear stress (WSS) was estimated within the descending aorta of each surgical group. RESULTS: Physiologic-like sinus vortices were visible in the aortic root when using the prosthesis with neosinuses, whereas straight tubular graft revealed localized intrados malrotations (P = .003 for organized vortical structures vs neosinuses graft and P < .001 vs control). In the ascending aorta, recreation of the sinuses resulted in significantly lower velocity and WSS than in the straight tubular graft (P < .001) and controls (P < .001), these alterations were attenuated in the mid-descending aorta. Incidence of abnormal WSS was markedly higher in the straight tube grafts than neosinus of Valsalva grafts. CONCLUSIONS: Re-creation of the sinuses of Valsalva during valve-sparing root replacement is associated with more physiologic flow and significantly lower WSS in the aortic root. Lower WSSs in the distal thoracic aorta is a novel finding with potential implications on distal aortic remodeling.

4D flow characterization of aortic blood flow after valve sparing root reimplantation procedure.

Valve-sparing aortic root replacement (VSRR) with reimplantation technique is an effective alternative for young patients with dilated roots and preserved cusps, which avoids the risks of lifelong anticoagulation or valve degeneration. New grafts with anatomically-shaped sinuses have been developed in order to preserve aortic root physiology, which could decrease complication rates and improve durability. However, controversy remains regarding the effect of recreation of the sinuses of Valsalva during VSRR on long-term outcomes. The novel 4D flow technique, exploiting its unique ability to combine anatomical evaluation of the root with fluid-dynamic assessment of aortic flow, enables integrated analysis of the close interaction between graft design, valvular morphology and three-dimensional (3D) flow characteristics. Early experimental studies have shown how graft shape affects the aortic root flow pattern, formation of vortexes and helicity of downstream flow; however, the clinical significance of these findings is yet to be clarified. Various and still unexplored knowledge can be obtained from the qualitative and quantitative analysis of these complex datasets, that could shed more light on which is the best among myriad surgical techniques and grafts adopted in VSRR. The extraordinary potential 4D flow imaging opens new boundless horizons in the perspective of an increasingly patient-tailored surgical planning.

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.

Dynamic and quantitative evaluation of degenerative mitral valve disease: a dedicated framework based on cardiac magnetic resonance imaging.

BACKGROUND: Accurate quantification of mitral valve (MV) morphology and dynamic behavior over the cardiac cycle is crucial to understand the mechanisms of degenerative MV dysfunction and to guide the surgical intervention. Cardiac magnetic resonance (CMR) imaging has progressively been adopted to evaluate MV pathophysiology, although a dedicated framework is required to perform a quantitative assessment of the functional MV anatomy. METHODS: We investigated MV dynamic behavior in subjects with normal MV anatomy (n=10) and patients referred to surgery due to degenerative MV prolapse, classified as fibro-elastic deficiency (FED, n=9) and Barlow's disease (BD, n=10). A CMR-dedicated framework was adopted to evaluate prolapse height and volume and quantitatively assess valvular morphology and papillary muscles (PAPs) function over the cardiac cycle. Multiple comparison was used to investigate the hallmarks associated to MV degenerative prolapse and evaluate the feasibility of anatomical and functional distinction between FED and BD phenotypes. RESULTS: On average, annular dimensions were significantly (P<0.05) larger in BD than in FED and normal subjects while no significant differences were noticed between FED and normal. MV eccentricity progressively decreased passing from normal to FED and BD, with the latter exhibiting a rounder annulus shape. Over the cardiac cycle, we noticed significant differences for BD during systole with an abnormal annular enlargement between mid and late systole (LS) (P<0.001 vs. normal); the PAPs dynamics remained comparable in the three groups. Prolapse height and volume highlighted significant differences among normal, FED and BD valves. CONCLUSIONS: Our CMR-dedicated framework allows for the quantitative and dynamic evaluation of MV apparatus, with quantifiable annular alterations representing the primary hallmark of severe MV degeneration. This may aid surgeons in the evaluation of the severity of MV dysfunction and the selection of the appropriate MV treatment.

Aortic Root Biomechanics After Sleeve and David Sparing Techniques: A Finite Element Analysis.

BACKGROUND: Aortic root aneurysm can be treated with valve-sparing procedures. The David and Yacoub techniques have shown excellent long-term results but are technically demanding. Recently, a new and simpler procedure, the Sleeve technique, was proposed with encouraging results. We aimed to quantify the biomechanics of the initially aneurysmal aortic root (AR) after the Sleeve procedure to assess whether it induces abnormal stresses, potentially undermining its durability. METHODS: Two finite element (FE) models of the physiologic and aneurysmal AR were built, accounting for the anatomical asymmetry and the nonlinear and anisotropic mechanical properties of human AR tissues. On the aneurysmal model, the Sleeve and David techniques were simulated based on the corresponding published technical features. Aortic root biomechanics throughout 2 consecutive cardiac cycles were computed in each simulated configuration. RESULTS: Both sparing techniques restored physiologic-like kinematics of aortic valve (AV) leaflets but induced different leaflets stresses. The time course averaged over the leaflets' bellies was 35% higher in the David model than in the Sleeve model. Commissural stresses, which were equal to 153 and 318 kPa in the physiologic and aneurysmal models, respectively, became 369 and 208 kPa in the David and Sleeve models, respectively. CONCLUSIONS: No intrinsic structural problems were detected in the Sleeve model that might jeopardize the durability of the procedure. If corroborated by long-term clinical outcomes, the results obtained suggest that using this new technique could successfully simplify the surgical repair of AR aneurysms and reduce intraoperative complications.

In vitro and in silico approaches to quantify the effects of the Mitraclip® system on mitral valve function.

Mitraclip® implantation is widely used as a valid alternative to conventional open-chest surgery in high-risk patients with severe mitral valve (MV) regurgitation. Although effective in reducing mitral regurgitation (MR) in the majority of cases, the clip implantation produces a double-orifice area that can result in altered MV biomechanics, particularly in term of hemodynamics and mechanical stress distribution on the leaflets. In this scenario, we combined the consistency of in vitro experimental platforms with the versatility of numerical simulations to investigate clip impact on MV functioning. The fluid dynamic determinants of the procedure were experimentally investigated under different working conditions (from 40bpm to 100bpm of simulated heart rate) on six swine hearts; subsequently, fluid dynamic data served as realistic boundary conditions in a computational framework able to quantitatively assess the post-procedural MV biomechanics. The finite element model of a human mitral valve featuring an isolated posterior leaflet prolapse was reconstructed from cardiac magnetic resonance. A complete as well as a marginal, sub-optimal grasping of the leaflets were finally simulated. The clipping procedure resulted in a properly coapting valve from the geometrical perspective in all the simulated configurations. Symmetrical complete grasping resulted in symmetrical distribution of the mechanical stress, while uncomplete asymmetrical grasping resulted in higher stress distribution, particularly on the prolapsing leaflet. This work pinpointed that the mechanical stress distribution following the clipping procedure is dependent on the cardiac hemodynamics and has a correlation with the proper execution of the grasping procedure, requiring accurate evaluation prior to clip delivery.

Impact of different aortic valve calcification patterns on the outcome of transcatheter aortic valve implantation: A finite element study.

Transcatheter aortic valve implantation (TAVI) can treat symptomatic patients with calcific aortic stenosis. However, the severity and distribution of the calcification of valve leaflets can impair the TAVI efficacy. Here we tackle this issue from a biomechanical standpoint, by finite element simulation of a widely adopted balloon-expandable TAVI in three models representing the aortic root with different scenarios of calcific aortic stenosis. We developed a modeling approach realistically accounting for aortic root pressurization and complex anatomy, detailed calcification patterns, and for the actual stent deployment through balloon-expansion. Numerical results highlighted the dependency on the specific calcification pattern of the "dog-boning" of the stent. Also, local stent distortions were associated with leaflet calcifications, and led to localized gaps between the TAVI stent and the aortic tissues, with potential implications in terms of paravalvular leakage. High stresses were found on calcium deposits, which may be a risk factor for stroke; their magnitude and the extent of the affected regions substantially increased for the case of an "arc-shaped" calcification, running from commissure to commissure. Moreover, high stresses due to the interaction between the aortic wall and the leaflet calcifications were computed in the annular region, suggesting an increased risk for annular damage. Our analyses suggest a relation between the alteration of the stresses in the native anatomical components and prosthetic implant with the presence and distribution of relevant calcifications. This alteration is dependent on the patient-specific features of the calcific aortic stenosis and may be a relevant indicator of suboptimal TAVI results.

Hemodynamic and thrombogenic analysis of a trileaflet polymeric valve using a fluid-structure interaction approach.

Surgical valve replacement in patients with severe calcific aortic valve disease using either bioprosthetic or mechanical heart valves is still limited by structural valve deterioration for the former and thrombosis risk mandating anticoagulant therapy for the latter. Prosthetic polymeric heart valves have the potential to overcome the inherent material and design limitations of these valves, but their development is still ongoing. The aim of this study was to characterize the hemodynamics and thrombogenic potential of the Polynova polymeric trileaflet valve prototype using a fluid-structure interaction (FSI) approach. The FSI model replicated experimental conditions of the valve as tested in a left heart simulator. Hemodynamic parameters (transvalvular pressure gradient, flow rate, maximum velocity, and effective orifice area) were compared to assess the validity of the FSI model. The thrombogenic footprint of the polymeric valve was evaluated using a Lagrangian approach to calculate the stress accumulation (SA) values along multiple platelet trajectories and their statistical distribution. In the commissural regions, platelets were exposed to the highest SA values because of highest stress levels combined with local reverse flow patterns and vortices. Stress-loading waveforms from representative trajectories in regions of interest were emulated in our hemodynamic shearing device (HSD). Platelet activity was measured using our platelet activation state (PAS) assay and the results confirmed the higher thrombogenic potential of the commissural hotspots. In conclusion, the proposed method provides an in depth analysis of the hemodynamic and thrombogenic performance of the polymer valve prototype and identifies locations for further design optimization.

Biomechanical drawbacks of different techniques of mitral neochordal implantation: When an apparently optimal repair can fail.

OBJECTIVES: Intraoperative assessment of the proper neochordal length during mitral plasty may be complex sometimes. Patient-specific finite element models were used to elucidate the biomechanical drawbacks underlying an apparently correct mitral repair for isolated posterior prolapse. METHODS: Preoperative patient-specific models were derived from cardiac magnetic resonance images; integrated with intraoperative surgical details to assess the location and extent of the prolapsing region, including the number and type of diseased chordae; and complemented by the biomechanical properties of mitral leaflets, chordae tendineae, and artificial neochordae. We investigated postoperative mitral valve biomechanics in a wide spectrum of different techniques (single neochorda, double neochordae, and preconfigured neochordal loop), all reestablishing adequate valvular competence, but differing in suboptimal millimetric expanded polytetrafluoroethylene suture lengths in a range of ±2 mm, compared with the corresponding "ideal repair." RESULTS: Despite the absence of residual regurgitation, alterations in chordal forces and leaflet stresses arose simulating suboptimal repairs; alterations were increasingly relevant as more complex prolapse anatomies were considered and were worst when simulating single neochorda implantation. Multiple chordae implantations were less sensitive to errors in neochordal length tuning, but associated postoperative biomechanics were hampered when asymmetric configurations were reproduced. Computational outcomes were consistent with the presence and entity of recurrent mitral regurgitation at midterm follow-up of simulated patients. CONCLUSIONS: Suboptimal suture length tuning significantly alters chordal forces and leaflet stresses, which may be key parameters in determining the long-term outcome of the repair. The comparison of the different simulated techniques suggests possible criteria for the selection and implementation of neochordae implantation techniques.

Is it possible to assess the best mitral valve repair in the individual patient? Preliminary results of a finite element study from magnetic resonance imaging data.

OBJECTIVES: Finite element modeling was adopted to quantitatively compare, for the first time and on a patient-specific basis, the biomechanical effects of a broad spectrum of different neochordal implantation techniques for the repair of isolated posterior mitral leaflet prolapse. METHODS: Cardiac magnetic resonance images were acquired from 4 patients undergoing surgery. A patient-specific 3-dimensional model of the mitral apparatus and the motion of the annulus and papillary muscles were reconstructed. The location and extent of the prolapsing region were confirmed by intraoperative findings, and the mechanical properties of the mitral leaflets, chordae tendineae and expanded polytetrafluoroethylene neochordae were included. Mitral systolic biomechanics was simulated under preoperative conditions and after 5 different neochordal procedures: single neochorda, double neochorda, standard neochordal loop with 3 neochordae of the same length and 2 premeasured loops with 1 common neochordal loop and 3 different branched neochordae arising from it, alternatively one third and two thirds of the entire length. RESULTS: The best repair in terms of biomechanics was achieved with a specific neochordal technique in the single patient, according to the location of the prolapsing region. However, all techniques achieved a slight reduction in papillary muscle forces and tension relief in intact native chordae proximal to the prolapsing region. Multiple neochordae implantation improved the repositioning of the prolapsing region below the annular plane and better redistributed mechanical stresses on the leaflet. CONCLUSIONS: Although applied on a small cohort of patients, systematic biomechanical differences were noticed between neochordal techniques, potentially affecting their short- to long-term clinical outcomes. This study opens the way to patient-specific optimization of neochordal techniques.