Leaflet Mechanical Stress in Different Designs and Generations of Transcatheter Aortic Valves: An in Vitro Study.

Background: It is unknown whether bioprostheses used for transcatheter aortic valve implantation will have similar long-term durability as those used for surgical aortic valve replacement. Repetitive mechanical stress applied to the valve leaflets, particularly during diastole, is the main determinant of structural valve deterioration. Leaflet mechanical stress cannot be measured in vivo. The objective of this in vitro/in silico study was thus to compare the magnitude and regional distribution of leaflet mechanical stress in old vs new generations of self-expanding (SE) vs balloon expandable (BE) transcatheter heart valves (THVs). Methods: A double activation simulator was used for in vitro testing of two generations of SE THV (Medtronic CoreValve 26 mm and EVOLUT PRO 26 mm) and two generations of BE THV (Edwards SAPIEN 23 mm vs SAPIEN-3 23 mm). These THVs were implanted within a 21-mm aortic annulus. A noncontact system based on stereophotogammetry and digital image correlation with high spatial and temporal resolution (2000 img/sec) was used to visualize the valve leaflet motion and perform the three-dimensional analysis. A finite element model of the valve was developed, and the leaflet deformation obtained from the digital image correlation analysis was applied to the finite element model to calculate local leaflet mechanical stress during diastole. Results: The maximum von Mises leaflet stress was higher in early vs new THV generation (p < 0.05) and in BE vs SE THV (p < 0.05): early generation BE: 2.48 vs SE: 1.40 MPa; new generation BE: 1.68 vs SE: 1.07 MPa. For both types of THV, the highest values of leaflet stress were primarily observed in the upper leaflet edge near the commissures and to a lesser extent in the mid-portion of the leaflet body, which is the area where structural leaflet deterioration most often occurs in vivo. Conclusions: The results of this in vitro/in silico study suggest that: i) Newer generations of THVs have ∼30% lower leaflet mechanical stress than the early generations; ii) For a given generation, SE THVs have lower leaflet mechanical stress than BE THVs. Further studies are needed to determine if these differences between new vs early THV generations and between SE vs BE THVs will translate into significant differences in long-term valve durability in vivo.

An Anatomically Shaped Mitral Valve for Hemodynamic Testing.

In vitro modeling of the left heart relies on accurately replicating the physiological conditions of the native heart. The targeted physiological conditions include the complex fluid dynamics coming along with the opening and closing of the aortic and mitral valves. As the mitral valve possess a highly sophisticated apparatus, thence, accurately modeling it remained a missing piece in the perfect heart duplicator puzzle. In this study, we explore using a hydrogel-based mitral valve that offers a full representation of the mitral valve apparatus. The valve is tested using a custom-made mock circulatory loop to replicate the left heart. The flow analysis includes performing particle image velocimetry measurements in both left atrium and ventricle. The results showed the ability of the new mitral valve to replicate the real interventricular and atrial flow patterns during the whole cardiac cycle. Moreover, the investigated valve has a ventricular vortex formation time of 5.2, while the peak e- and a-wave ventricular velocities was 0.9 m/s and 0.4 m/s respectively.

In vitro Doppler versus catheter transvalvular pressure gradients in balloon-expandable versus self-expanding transcatheter aortic valves.

OBJECTIVES: The objective of this in vitro study was to compare Doppler versus catheter transvalvular pressure gradients (TPG) in third generations balloon-expandable (BE) versus self-expanding (SE) transcatheter heart valves (THV). BACKGROUND: TPG is a key parameter to assess and follow valve hemodynamic function following transcatheter aortic valve implantation (TAVI). It remains uncertain and debated whether, and to which extent, TPGs differ according to the type of THV, that is, BE versus SE and to the method used for TPG measurement, that is, Doppler echocardiography versus cardiac catheterization. METHODS: The CoreValve EVOLUT PRO 26 mm and the SAPIEN 3 23 mm THVs were tested in a left heart simulator using a 21 mm aortic annulus under following conditions: heart rate: 70 bpm, mean aortic pressure: 100 mmHg, stroke volume: 30, 70 and 100 ml. Mean TPGs were measured by continuous-wave Doppler and by micro-tip pressure catheters positioned in the left ventricle and at 50 mm downstream to the tip of the THV leaflets. RESULTS: Doppler TPGs (9.5 ± 3.9 mmHg) were on average 40.5 ± 13.9% higher (p < 0.001) than catheter TPGs (6.3 ± 3.4 mmHg). Both Doppler and catheter TPGs were lower (p = 0.003) in the SE versus BE THVs (Doppler: 8.7 ± 3.5 vs. 10.7 ± 4.6; catheter: 5.0 ± 1.7 mmHg vs. 7.1 ± 2.2). The Doppler versus catheter difference in TPG increased with the higher flow conditions. The Doppler versus catheter difference in TPG was similar in BE versus SE THVs (3.6 ± 1.1 vs. 3.7 ± 1.4 mmHg or 42 ± 9 vs. 47 ± 9%; p = 0.58) overall and in each flow conditions. CONCLUSION: The Doppler TPGs are, on average, 40% higher than the catheter TPGs for both BE and SE THVs. The SE THV had lower Doppler and catheter TPGs compared to the BE THV, at normal and high flow states. The absolute and percent differences between Doppler versus catheter TPGs were similar in BE versus SE THVs.

Leaflet stress quantification of porcine vs bovine surgical bioprostheses: an in vitro study.

Calcified aortic stenoses are among the most prevalent form of cardiovascular diseases in the industrialized countries. This progressive disease, with no effective medical therapy, ultimately requires aortic valve replacement - either a surgical or very recently transcatheter aortic valve implantation. Increase leaflet mechanical stress is one of the main determinants of the structural deterioration of bioprosthetic aortic valves. We applied a coupled in vitro/in silico method to compare the timing, magnitude, and regional distribution of leaflet mechanical stress in porcine versus pericardial bioprostheses (Mosaic and Trifecta). A double activation simulator was used for in vitro testing of a bioprosthesis with externally mounted pericardium (Abbott, Trifecta) and a bioprosthesis with internally mounted porcine valve (Medtronic, Mosaic). A non-contact system based on stereophotogammetry and digital image correlation (DIC) with high spatial and temporal resolution (2000 img/s) was used to visualize the valve leaflet motion and perform the three-dimensional analysis. A finite element model of the valve was developed, and the leaflet deformation obtained from the DIC analysis was applied to the finite element model calculate local leaflet mechanical stress throughout the cardiac cycle. The maximum leaflet stress was higher with the pericardial versus the porcine bioprosthesis (2.03 vs. 1.30 MPa) For both bioprostheses the highest values of leaflet stress occurred during diastole and were primarily observed in the upper leaflet edge near the commissures and to a lesser extent in the mid-portion of the leaflet body. In conclusion, the coupled in vitro/in silico method described in this study shows that the highest levels of leaflet stress occur in the regions of the commissures and mid-portion of the leaflet body. This method may have important insight with regard to bioprosthetic valve durability. Our results suggest that, compared to porcine bioprostheses, those with externally mounted pericardium have higher leaflet mechanical stress, which may translate into shorter durability.

In vitro correlation between the effective and geometric orifice area in aortic stenosis.

BACKGROUND: Planimetry of aortic stenosis can be performed when Doppler measurements are unavailable. We sought to evaluate if, as advised in guidelines, the geometric orifice area (GOA) threshold value of 1 cm² was concordant with the threshold of 1 cm² of the effective orifice area (EOA), and the factors influencing the contraction coefficient (EOA/GOA ratio). METHODS: In an in vitro mock circulatory system, we tested 6 degrees of AS severity (3 severe and 3 non-severe), and 3 levels of flow (<150 ml/s, 150-200 ml/s, >250 ml/s). The EOA was calculated by Doppler-echocardiography, and the GOA was measured with dedicated software after camera acquisition. RESULTS: In all but the very low flow condition, an EOA of 1 cm² corresponded to a GOA of 1.2 cm². The contraction coefficient increased with both the flow and the stenosis severity. For very severe stenoses, the EOA and the GOA were interchangeable. CONCLUSION: As observed in clinical studies, the GOA was larger than the EOA, and a GOA between 1 and 1.2 cm² should not discard the possibility of severe aortic stenosis.

Impact of Mitral Regurgitation on the Flow in a Model of a Left Ventricle.

PURPOSE: Mitral regurgitation (MR) is the second most common valve disease in industrialized countries. Despite its high prevalence, little is known about its impact on the flow dynamics in the left ventricle (LV). Because of the interdependence between valvular function and hemodynamics in the heart chambers, an exploration of the dynamics in the LV could lead to a diagnosis of MR. This in vitro study aimed to develop an advanced left heart simulator capable of reproducing several conditions of MR and to evaluate their impact on the LV flow dynamics in terms of flow structures and viscous energy dissipation (VED). METHODS: A simulator, previously developed to test mechanical and biological valves, was upgraded with an original anatomically-shaped mitral valve made from a hydrogel. The valve can be used in healthy or pathological configurations. The nature and severity of the disease was controlled by applying specific strain to the chordae. In this study, in addition to a healthy condition, two different severities of MR were investigated: moderate MR and severe MR. Planar time-resolved particle image velocimetry measurements were performed in order to evaluate the velocity field in the LV and the VED induced by each condition. RESULTS: Our results showed that MR led to flow disturbances in the LV that were characterized by an increase in mitral inflow velocity and by elevated values of VED. Interestingly VED increased in proportion to the severity of MR and with a dissipation predominating during systole. CONCLUSION: Considering these results, the introduction of new parameters based on LV VED could provide crucial information regarding the coupling between the mitral valve and the LV and allow for a better stratification of patients with MR.

In Vitro Quantification of Mitral Regurgitation of Complex Geometry by the Modified Proximal Isovelocity Surface Area Method.

BACKGROUND: Doppler echocardiographic methods, such as the proximal isovelocity surface area (PISA) method, are used to quantify mitral regurgitations (MRs). However, their accuracy and reproducibility are still being discussed, especially in the case of MR of complex geometry. The aim of this study was to evaluate the accuracy of the PISA method depending on the shape and number of regurgitant flows. METHODS: First, various MR shapes and severities (central, oblong, and multiple-jet MR) were mimicked in a left heart simulator. The effective regurgitant orifice area (EROA) was calculated using the standard and modified PISA methods and was compared to a reference value obtained from an electromagnetic flowmeter. Second, in order to clinically validate the in vitro findings, 16 patients were examined with two-dimensional (2D) echocardiography. The results were analyzed by comparing the PISA method and the echocardiographic 2D quantitative volumetric method. RESULTS: Both hemicylindrical and hemiellipsoidal PISA assumptions improved the quantification of the EROA for oblong MR compared with the traditional PISA method (hemispherical PISA assumption: 11 ± 4.6 mm2, P < .01; hemicylindrical PISA assumption: 2 ± 0.8 mm2, P = .83; hemiellipsoidal PISA assumption: 6 ± 3.7 mm2, P = .05). In the case of multiple jets of different sizes, an improved EROA calculation was measured when both jets were considered (single hemispherical PISA assumption: 4.5 ± 0.7 mm2, P < .01; double hemispherical PISA assumption: 2 ± 1.1 mm2, P = .64). CONCLUSION: For a correct diagnosis of MR, the PISA geometry must be considered. A measurement of both PISA radius and PISA width is necessary for an accurate quantification of an oblong MR. In the case of a double-jet MR, a measurement of the two radii is recommended.

Effects of hemodynamic conditions and valve sizing on leaflet bending stress in self-expanding transcatheter aortic valve: An in vitro study.

Transcatheter aortic valve (TAV) replacement has become a viable alternative to surgery for high and intermediate risk patients with severe aortic stenosis. This technology may extend to the younger and lower risk patients. In this population, long-term durability of the TAV is key. Increased leaflet mechanical stress is one of the main determinants of valve structural deterioration. This in vitro study aims at evaluating leaflet bending stress (LBS) in the self-expanding TAV for different valve sizes, stroke volumes (SV), and degrees of valve oversizing (OS). Three different sizes (23, 26, and 29 mm) of CoreValve (CV) were tested on a pulse duplicator in annulus size ranging from 17 to 26 mm. Leaflet bending stress and bending of the leaflet coaptation line in diastole pinwheeling index (PI) were measured using high-speed camera imaging (1000 images/s). For each given CV and annulus size, geometric orifice area (GOA) increased significantly with OS (P < .001) and SV (P = .001). LBS decreased with increasing prosthesis size and aortic annulus (AA) size while increasing with SV (P < .03). The largest value of peak LBS (3.79 MPa) was obtained with the CV 23 mm in AA of 17 mm (%OS = 35%), SV 90 mL and the smallest value (0.99 MPa) for the CV 29 mm in AA of 26 mm (%OS = 12%), SV 30 mL. On multivariable analysis, LBS increased independently with larger OS, smaller AA size and higher SV. The PI increased with decreasing AA size and increasing OS. Moderate valve OS, such as generally used for transcatheter aortic valve implantation, is associated with increased LBS during valve opening and closing, especially in small annuli. Hence, TAV OS may negatively impact long-term valve durability.

A bench test study of bioprosthetic valve fracture performed before versus after transcatheter valve-in-valve intervention.

AIMS: Bioprosthetic valve fracture (BVF) may improve transvalvular gradients and transcatheter heart valve (THV) expansion during VIV interventions. However, the optimal timing of BVF is unknown. We assessed the impact of timing of BVF (before versus after) for valve-in-valve (VIV) intervention, on hydrodynamic function and THV expansion. METHODS AND RESULTS: Three THV designs were assessed, a 23 mm SAPIEN 3 (S3), small ACURATE neo (ACn) and 23 mm Evolut R, deployed into 21 mm Mitroflow bioprosthetic surgical valves. We evaluated each THV in three groups: 1) no BVF, 2) BVF before VIV, and 3) BVF after VIV. Hydrodynamic testing was performed using a pulse duplicator to ISO 5840:2013 standard. Transvalvular gradients were lower when BVF was performed after VIV for the S3 (no BVF 15.5 mmHg, BVF before VIV 8.0 mmHg, BVF after VIV 5.6 mmHg), and the ACn (no BVF 9.8 mmHg, BVF before VIV 8.4 mmHg, BVF after VIV 5.1 mmHg). Transvalvular gradients were similar for the Evolut R, irrespective of performance of BVF or timing of BVF. BVF performed after VIV resulted in better expansion in all three THV designs. The ACn and Evolut R samples all had a mild degree of pinwheeling, and BVF timing did not impact on pinwheeling severity. The S3 samples had severe pinwheeling with no BVF, and significant improvement in pinwheeling when BVF was performed after VIV. CONCLUSIONS: BVF performed after VIV was associated with superior THV expansion in all three THV designs tested, with lower residual transvalvular gradients in the S3 and ACn THVs. The Evolut R had similar hydrodynamic performance irrespective of BVF timing. Timing of BVF has potential implications on THV function.

A novel method to quantitate bioprosthetic valve leaflet mechanical stress: a numerical and in vitro study.

An original in vitro/in silico method was developed to estimate the local and global mechanical stress applied on the bioprosthetic valve leaflet, which can be important for better understanding of the valve durability. A non-contact system based on stereophotogammetry and digital image correlation enabled filming and studying the valve leaflet movement frame by frame and performing three-dimensional analysis. The deformation was applied in a finite element model in order to calculate the local mechanical stress applied. High stress regions were primarily observed in the upper leaflet edge and belly and to a lesser extent at the free leaflet edge.

Valve-in-Valve Transcatheter Aortic Valve Replacement and Bioprosthetic Valve Fracture Comparing Different Transcatheter Heart Valve Designs: An Ex Vivo Bench Study.

OBJECTIVES: The authors assessed the effect of valve-in-valve (VIV) transcatheter aortic valve replacement (TAVR) followed by bioprosthetic valve fracture (BVF), testing different transcatheter heart valve (THV) designs in an ex vivo bench study. BACKGROUND: Bioprosthetic valve fracture can be performed to improve residual transvalvular gradients following VIV TAVR. METHODS: The authors evaluated VIV TAVR and BVF with the SAPIEN 3 (S3) (Edwards Lifesciences, Irvine, California) and ACURATE neo (Boston Scientific Corporation, Natick, Massachusetts) THVs. A 20-mm and 23-mm S3 were deployed in a 19-mm and 21-mm Mitroflow (Sorin Group USA, Arvada, Colorado), respectively. A small ACURATE neo was deployed in both sizes of Mitroflow tested. VIV TAVR samples underwent multimodality imaging, and hydrodynamic evaluation before and after BVF. RESULTS: A high implantation was required to enable full expansion of the upper crown of the ACURATE neo and allow optimal leaflet function. Marked underexpansion of the lower crown of the THV within the surgical valve was also observed. Before BVF, VIV TAVR in the 19-mm Mitroflow had high transvalvular gradients using either THV design (22.0 mm Hg S3, and 19.1 mm Hg ACURATE neo). After BVF, gradients improved and were similar for both THVs (14.2 mm Hg S3, and 13.8 mm Hg ACURATE neo). The effective orifice area increased with BVF from 1.2 to 1.6 cm2 with the S3 and from 1.4 to 1.6 cm2 with the ACURATE neo. Before BVF, VIV TAVR with the ACURATE neo in the 21-mm Mitroflow had lower gradients compared with S3 (11.3 mm Hg vs. 16 mm Hg). However, after BVF valve gradients were similar for both THVs (8.4 mm Hg ACURATE neo vs. 7.8 mm Hg S3). The effective orifice area increased from 1.5 to 2.1 cm2 with the S3 and from 1.8 to 2.2 cm2 with the ACURATE neo. CONCLUSIONS: BVF performed after VIV TAVR results in improved residual gradients. Following BVF, residual gradients were similar irrespective of THV design. Use of a small ACURATE neo for VIV TAVR in small (≤21 mm) surgical valves may be associated with challenges in achieving optimum THV position and expansion. BVF could be considered in selected clinical cases.

Overexpansion of the SAPIEN 3 Transcatheter Heart Valve: An Ex Vivo Bench Study.

OBJECTIVES: This study assessed the effect of overexpansion beyond labeled size (diameter) of transcatheter heart valves through an ex vivo bench study. BACKGROUND: Transcatheter heart valves function optimally when expanded to specific dimensions. However, clinicians may sometimes wish to overexpand balloon-expandable valves to address specific clinical challenges. The implications of overexpansion have assumed considerable importance, and objective information to guide practice is limited. METHODS: We evaluated SAPIEN 3 transcatheter heart valves (Edwards Lifesciences, Irvine, California). Valves (diameters of 23, 26, and 29 mm) were expanded to nominal dimensions, and then incrementally overexpanded with balloons sized 1-, 2-, and 3-mm larger than the recommended diameter. Valves underwent visual, microcomputed tomography, and hydrodynamic evaluation at various degrees of overexpansion. RESULTS: SAPIEN 3 valves with labeled diameters of 23, 26, and 29 mm could be incrementally overexpanded to midvalve diameters of 26.4, 28.4, and 31.2 mm, respectively. With overexpansion, there was visible restriction of the valve leaflets, which was particularly evident with the smaller valves. After maximal overexpansion of a 26-mm valve a leaflet tear was observed. High-speed video demonstrated impaired leaflet motion of both the 23- and 26-mm valves and hydrodynamic testing documented a regurgitant fraction for the 23- and 26-mm valves above accepted international standards. The maximally overexpanded 29-mm SAPIEN 3 still had relatively normal leaflet motion and excellent hydrodynamic function. Durability was not specifically evaluated. CONCLUSIONS: Overexpansion of balloon-expandable valves is possible. However, excessive overexpansion may be associated with impaired hydrodynamic function, acute leaflet failure, and reduced durability. Smaller valves may be at greater risk with overexpansion than larger valves. Overexpansion is best avoided unless clinical circumstances are compelling.

Haemodynamic outcomes following aortic valve-in-valve procedure.

Background and objectives: Transcatheter aortic valve-in-valve implantation (ViV) has emerged as a valuable technique to treat failed surgical bioprostheses (BPs) in patients with high risk for redo surgical aortic valve replacement (SAVR). Small BP size (≤21 mm), stenotic pattern of degeneration and pre-existing prosthesis-patient mismatch (PPM) have been associated with worse clinical outcomes after ViV. However, no study has evaluated the actual haemodynamic benefit associated with ViV. This study aims to compare haemodynamic status observed at post-ViV, pre-ViV and early after initial SAVR and to determine the factors associated with worse haemodynamic outcomes following ViV, including the rates of high residual gradient and 'haemodynamic futility'. Methods: Early post-SAVR, pre-ViV and post-ViV echocardiographic data of 79 consecutive patients who underwent aortic ViV at our institution were retrospectively analysed. The primary study endpoint was suboptimal valve haemodynamics (SVH) following ViV defined by the Valve Academic Research Consortium 2 as the presence of high residual aortic mean gradient (≥20 mm Hg) and/or at least moderate aortic regurgitation (AR). Haemodynamic futility of ViV was defined as <10 mm Hg decrease in mean aortic gradient and no improvement in AR compared with pre-ViV. Results: SVH was found in 61% of patients (57% high residual gradient, 4% moderate AR) after ViV versus 24% early after SAVR. Pre-existing PPM and BP mode of failure by stenosis were independently associated with the primary endpoint (OR: 2.87; 95% CI 1.08 to 7.65; p=0.035 and OR: 3.02; 95% CI 1.08 to 8.42; p=0.035, respectively) and with the presence of high residual gradient (OR: 4.38; 95% CI 1.55 to 12.37; p=0.005 and OR: 5.37; 95% CI 1.77 to 16.30; p=0.003, respectively) following ViV. Criteria of ViV haemodynamic futility were met in 7.6% overall and more frequently in patients with pre-existing PPM and stenotic BP (18.5%) compared with other patients (2.0%). ViV restored haemodynamic function to early post-SAVR level in only 34% of patients. Conclusion: Although ViV was associated with significant haemodynamic improvement compared with pre-ViV in >90% of patients, more than half harboured SVH outcome. Furthermore, only one-third of patients had a restoration of valve haemodynamic function to the early post-SAVR level. Pre-existing PPM and stenosis pattern of BP degeneration were the main factors associated with SVH and haemodynamic futility following ViV. These findings provide strong support for the prevention of PPM at the time of initial SAVR and careful preprocedural patient screening.

Effect of size and position of self-expanding transcatheter valve on haemodynamics following valve-in-valve procedure in small surgical bioprostheses: an in vitro study.

AIMS: The valve-in-valve (ViV) procedure has become a valuable alternative for the treatment of failed surgical bioprostheses (BP) in high-risk patients. However, in small BP, the clinical outcomes have been suboptimal due to high post-procedural gradients. We aimed to examine the effect of size and position of the self-expanding transcatheter heart valve (THV) CoreValve on the haemodynamics of ViV within small BP. METHODS AND RESULTS: Sizes 23 and 26 mm of the CoreValve were implanted in sizes 19 and 21 mm of three BP models: Trifecta, Mitroflow and Epic Supra. The THV was tested in three positions -normal (manufacturer recommendation), low (4 mm below normal) and high (4 mm above normal)- using a pulse duplicator. Haemodynamics were assessed by Doppler echocardiography and flowmeter, and GOA with a high-speed camera. Higher implantation was associated with lower residual gradients (normal position: -9%, high: -25% versus low). High position was, however, associated with increased risk of regurgitation in the Mitroflow and embolisation in the Epic Supra. Using a 26 mm THV instead of a 23 mm was associated with larger EOAs in the Trifecta, smaller in the Mitroflow, and increased risk of embolisation in the Epic Supra. CONCLUSIONS: Supra-annular positioning of the CoreValve THV is associated with improved post-ViV haemodynamics in small surgical BP. The haemodynamic outcomes are highly dependent on the model and size of surgical BP.

Characterization of Effective Orifice Areas of Mitral Prosthetic Heart Valves: An In-Vitro Study.

BACKGROUND: Reference values of hemodynamic parameters for the assessment of prosthetic heart valves are necessary, and ideally need to be provided by entities independent of the valve manufacturers. Thus, the study aim was to provide, in vitro, normal reference values of the effective orifice area (EOA) for different models and sizes of mitral prosthetic valve, and to assess the determinants of EOA and mean transvalvular pressure gradient (mTPG). METHODS: Four models of mechanical prostheses were tested (one mono-leaflet, three bi-leaflet) and four models of bioprostheses (two bovine pericardial, two porcine) on a double-activation pulsed duplicator that was specifically designed and optimized for assessing the hemodynamic performance of mitral prosthetic valves. The hemodynamic conditions were standardized and included for bioprostheses: two mitral flow volumes, three mean aortic pressures, two heart rates, and three E/A ratios. The EOAs were measured with Doppler echocardiography, using the same method (continuity equation) as was used in the clinical setting. Overestimation in term of EOA was defined according to guidelines as >0.25 cm2. RESULTS: EOA reference values were recorded. For mono-leaflet prostheses (Medtronic Hall 7700, size 25 to 31 mm) 2.29 and 3.49; for bi-leaflet prostheses (St. Jude Medical Master and Master HP, sizes 25 to 33 mm and On-X valve, sizes 27-29 mm) 1.34 and 4.74 cm2; for porcine bioprostheses (Medtronic Mosaic CINCH, sizes 25 to 31 mm and St. Jude Epic 100, sizes 25 to 33 mm) 1.35 and 3.56 cm2; for bovine pericardial bioprosthetic valves (Edwards Perimount 6900P and Magna Ease 7300, sizes 25 to 33 mm) 1.67 and 2.36 cm2. There were some discrepancies between the normal reference EOAs measured compared to those provided by the prosthesis manufacturers, or in published reports. The bioprosthetic EOAs were shown to be smaller than the manufacturers' values in 32% of valves (by an average of 0.57 ± 0.28 cm2) versus in 7% of valves when compared to values reported elsewhere (by an average of 0.43 ± 0.17 cm2). The relationship between EOA and internal orifice area (IOA) varied according to the type of prosthesis. The EOA was close to the IOA in mechanical valves (regression slopes 0.87-0.99) but was much smaller than the IOA in bioprosthetic valves (slopes 0.25-0.30). The EOA was influenced by prosthesis diameter, prosthesis stent diameter and height, while the mTPG was influenced by EOA and heart rate. CONCLUSIONS: The present study has provided normal reference values of EOAs for several frequently used mitral prostheses. This information may be helpful for identifying and quantifying prosthetic valve dysfunction and prosthesis-patient mismatch.

Are the Current Doppler Echocardiography Criteria Able to Discriminate Mitral Bileaflet Mechanical Heart Valve Malfunction? An In Vitro Study.

Malfunction of bileaflet mechanical heart valves in the mitral position could either be due to patient-prosthesis mismatch (PPM) or leaflet obstruction. The aim of this article is to investigate the validity of current echocardiographic criteria used for diagnosis of mitral prosthesis malfunction, namely maximum velocity, mean transvalvular pressure gradient, effective orifice area, and Doppler velocity index. In vitro testing was performed on a double activation left heart duplicator. Both PPM and leaflet obstruction were investigated on a St. Jude Medical Master. PPM was studied by varying the St. Jude prosthesis size (21, 25, and 29 mm) and stroke volume (70 and 90 mL). Prosthesis leaflet obstruction was studied by partially or totally blocking the movement of one valve leaflet. Mitral flow conditions were altered in terms of E/A ratios (0.5, 1.0, and 1.5) to simulate physiologic panel of diastolic function. Maximum velocity, effective orifice area, and Doppler velocity index are shown to be insufficient to distinguish normal from malfunctioning St. Jude prostheses. Doppler velocity index and effective orifice area were 1.3 ± 0.49 and 1.83 ± 0.43 cm(2) for testing conditions with no malfunction below the 2.2 and 2 cm(2) thresholds (1.19 cm(2) for severe PPM and 1.23 cm(2) for fully blocked leaflet). The mean pressure gradient reached 5 mm Hg thresholds for several conditions of severe PPM only (6.9 mm Hg and mean maximum velocity value: 183.4 cm/s) whereas such value was never attained in the case of leaflet obstruction. In the case of leaflet obstruction, the maximum velocity averaged over the nine pulsed-wave Doppler locations increased by 38% for partial leaflet obstruction and 75% for a fully blocked leaflet when compared with normal conditions. Current echocardiographic criteria might be suboptimal for the detection of bileaflet mechanical heart valve malfunction. Further developments and investigations are required in order to further improve current guidelines.

Effect of oversizing and elliptical shape of aortic annulus on transcatheter valve hemodynamics: An in vitro study.

BACKGROUND: Transcatheter aortic valve implantation (TAVI) is often performed in patients with non-circular aortic annulus and in oversizing (OS) conditions. The impact of elliptical annulus shape and the consequences of oversizing/underdeployment on the hemodynamic performance are still debated. OBJECTIVE: This in-vitro study aims to assess and compare the valve hemodynamic performances of the Edwards SAPIEN transcatheter heart valve (THV) in the different current conditions of use: important oversizing in small circular annuli and in elliptical annuli, moderate oversizing in circular and in elliptical annuli of various degrees of eccentricity. METHODS: A pulsed cardiovascular simulator was used. Edwards SAPIEN 23 and 26 (mm) were implanted in different circular and elliptical annuli of various sizes and eccentricity. Transvalvular mean pressure gradients (TPGm), effective orifice area (EOA) after implantation of Edwards SAPIEN THV were measured by Doppler-echocardiography and the performance index (PI=100 × EOA/Annulus Area) was calculated. Para and transvalvular regurgitation was assessed by color-Doppler and leakage volume was quantified by flowmeter measurement. RESULTS: For a given aortic annulus area, EOAs after implantation of Edwards SAPIEN THV were generally larger and TPGms lower with elliptical annuli compared to circular annuli. The PI was higher (p=0.047) for elliptical (48 ± 3%) than for circular annuli (43 ± 5%). Paravalvular regurgitation occurred only in the case of the SAPIEN 26 implanted in the elliptical annulus with highest eccentricity. CONCLUSION: The results of this in-vitro study suggest that the EOAs of Edwards SAPIEN are better in elliptical than in circular annuli. No transvalvular regurgitation occurred and only one paravalvular regurgitation was observed after implantation of SAPIEN 26 in the highly eccentric annulus.

Mitral valve-in-valve hemodynamic performance: An in vitro study.

OBJECTIVES: The valve-in-valve (VinV) procedure may be used in high-risk patients with failed mitral surgical bioprostheses. The objective of this in vitro study was to assess the hemodynamic function of different VinV configurations. METHODS: A double activation duplicator was used to test 11 valve configurations (surgical bioprostheses alone) and 15 VinV configurations (Sapien [Edwards Lifesciences, Irvine, Calif] implanted within the surgical bioprosthesis) under 8 different hemodynamic conditions. The internal orifice diameter (IOD) of the surgical bioprosthesis was measured with a Smartscope (OGP Multi Sensor Measuring Instruments, Singapore). RESULTS: The VinV procedure was associated with significant deterioration in antegrade hemodynamic parameters compared with valve configuration (effective orifice area, 1.51 ± 0.21 cm(2) vs 1.65 ± 0.37 cm(2); P < .001 and regurgitant fraction, 11.5% ± 7.2% vs 4.8% ± 3.8%; P < .001). Among the 120 tested experimental VinV situations, moderate or greater mitral stenosis occurred in 52 situations and mild or greater regurgitation occurred in 28 situations. The IOD of the surgical bioprosthesis was the main independent determinant of effective orifice area and regurgitant fraction. An IOD < 22 mm was associated with higher risk of significant mitral stenosis, particularly when the oversizing was >20%, and IOD > 23 mm was associated with higher risk of paravalvular regurgitation when oversizing was <8%. CONCLUSIONS: This in vitro study shows that VinV within mitral surgical bioprostheses provides satisfactory hemodynamic results in the majority of patients. However, significant mitral stenosis is more likely to occur when the IOD of the surgical bioprosthesis is <22 mm, and particularly when the percentage of oversizing is >20%. Significant paravalvular regurgitation is rare and occurs with larger IODs and lower percentage of oversizing (8%).

Longitudinal compression behaviour of coronary stents: a bench-top comparative study.

AIMS: The aim of this study was to characterise the coronary stent longitudinal resistance of new coronary stents under worst case clinical crossing simulated configurations. METHODS AND RESULTS: Six coronary balloon-expandable stents were evaluated using two different tests. The first was a direct parallel plates longitudinal crush resistance test: it was conducted on stents deployed to 3 mm diameter, and three samples of each model were used. The second was performed by tracking over the wire and deploying the stents in two types of coronary model: good and malapposition models. Two samples of each model were used for this test. After deployment, a PTCA balloon was advanced over the wire. For each stent, the force required for balloon tracking and the stent shortening were recorded. In the first crush test, three out of six stent models demonstrated higher longitudinal crush rates compared to the Resolute Integrity (Medtronic, Minneapolis, MN, USA): PROMUS Element™ (Boston Scientific, Natick, MA, USA) p<0.0001, Coroflex® Blue (B. Braun, Melsungen, Germany) p<0.0001, and Orsiro (Biotronik, Berlin, Germany) p=0.038. In the simulation test, there were no statistical differences when comparing all good and malapposition groups. CONCLUSIONS: Lower resistance to mechanical longitudinal compression of some stents did not correlate to significantly higher crush rates in simulated clinical conditions. Nevertheless, it would be useful for cardiologists to be aware of the actual mechanical characteristics of new stents to take them into account and thus minimise longitudinal compression during difficult stent implantations.

Doppler vortography: a color Doppler approach to quantification of intraventricular blood flow vortices.

We propose a new approach to quantification of intracardiac vorticity based on conventional color Doppler images -Doppler vortography. Doppler vortography relies on the centrosymmetric properties of the vortices. Such properties induce particular symmetries in the Doppler flow data that can be exploited to describe the vortices quantitatively. For this purpose, a kernel filter was developed to derive a parameter, the blood vortex signature (BVS), that allows detection of the main intracardiac vortices and estimation of their core vorticities. The reliability of Doppler vortography was assessed in mock Doppler fields issued from simulations and in vitro data. Doppler vortography was also tested in patients and compared with vector flow mapping by echocardiography. Strong correlations were obtained between Doppler vortography-derived and ground-truth vorticities (in silico: r2 = 0.98, in vitro: r2 = 0.86, in vivo: r2 = 0.89). Our results indicate that Doppler vortography is a potentially promising echocardiographic tool for quantification of vortex flow in the left ventricle.