Postimplant biological aortic prosthesis degeneration: challenges in transcatheter valve implants.

Surgical aortic valve replacement (SAVR) is highly effective and can be achieved with relatively low risk in patients with severe aortic stenosis. Bioprostheses have been used most frequently during the past 60 years. However, the function of biological valves usually declines after 10-15 years from implant when structural valve degeneration occurs often mandating a reoperation once valve dysfunction becomes haemodynamically significant. Known for many years by surgeons and cardiologists taking care of patients with SAVR, the issue of postimplant structural valve degeneration has been recently highlighted also in patients with transcatheter aortic valve implant (TAVI). There is growing concern that TAVI valves exhibit structural valve degeneration due to inherent challenges of the deployment mode. The impact on postimplant degeneration of TAVI valves compared to SAVR has still to be understood and defined. Based on the ongoing process of expanding TAVI indications, several potential shortcomings and caveats, learned during the last 60 years of SAVR experience, should be taken into consideration to refine this technique.

Traumatic leaflet injury: comparison of porcine leaflet self-expandable and bovine leaflet balloon-expandable prostheses.

OBJECTIVES: The main goal of this study was to compare the occurrence of post-deployment leaflet injury between prostheses made of porcine and bovine pericardium. METHODS: Two types of prostheses, self-expandable prostheses with porcine pericardial leaflet on one side and balloon-expandable prostheses with bovine pericardial leaflet on the other side, were used. In each group, crimped prostheses were compared with control non-crimped prostheses. Following a 15-min period of crimping, prostheses were deployed, and their leaflets were removed and subjected to analyses. The analyses included determination of global and local hydraulic conductance of the leaflets, leaflet plasma insudation and microscopic analysis. The results were expressed as percentage (standard error of the mean) or median (interquartile range). RESULTS: A significant increase in the global hydraulic conductance was only observed in the crimped balloon-expandable prostheses: 20.1 (15.5-41.2) ml/h/m2/mmHg vs 12.3 (9.0-15.6) ml/h/m2/mmHg (P = 0.021). Similarly, areas of marked staining (a marker of local hydraulic conductance) were only seen in the bovine pericardium balloon-expandable prostheses. The incidence of leaflet plasmatic insudation was increased in the crimped prostheses compared with the control prostheses. The microscopic study revealed a higher occurrence of traumatic lesions in the crimped prostheses in comparison with the control prostheses: 33.3 ± 21.1% vs 5.5 ± 5.5% (P = 0.039) and 44.4 ± 20.5% vs 5.5 ± 5.5% (P = 0.017) in the bovine and the porcine leaflets, respectively. CONCLUSIONS: Post-deployment leaflet injury occurred in both types of prostheses. However, alteration of the global and local hydraulic conductance was important in the bovine pericardium balloon-expandable prostheses.

A Novel Method for Optical High Spatiotemporal Strain Analysis for Transcatheter Aortic Valves In Vitro.

The transcatheter aortic valve implantation (TAVI) valve is a bioprosthetic valve within a metal stent frame. Like traditional surgical bioprosthetic valves, the TAVI valve leaflet tissue is expected to calcify and degrade over time. However, clinical studies of TAVI valve longevity are still limited. In order to indirectly assess the longevity of TAVI valves, an estimate of the mechanical wear and tear in terms of valvular deformation and strain of the leaflets under various conditions is warranted. The aim of this study was, therefore, to develop a platform for noncontact TAVI valve deformation analysis with both high temporal and spatial resolutions based on stereophotogrammetry and digital image correlation (DIC). A left-heart pulsatile in vitro flow loop system for mounting of TAVI valves was designed. The system enabled high-resolution imaging of all three TAVI valve leaflets simultaneously for up to 2000 frames per second through two high-speed cameras allowing three-dimensional analyses. A coating technique for applying a stochastic pattern on the leaflets of the TAVI valve was developed. The technique allowed a pattern recognition software to apply frame-by-frame cross correlation based deformation measurements from which the leaflet motions and the strain fields were derived. The spatiotemporal development of a very detailed strain field was obtained with a 0.5 ms time resolution and a spatial resolution of 72 µm/pixel. Hence, a platform offering a new and enhanced supplementary experimental evaluation of tissue valves during various conditions in vitro is presented.

Comparison of two antiplatelet therapy strategies in patients undergoing transcatheter aortic valve implantation.

Dual antiplatelet therapy is commonly used in patients undergoing transcatheter aortic valve implantation (TAVI), but the optimal antiplatelet regimen is uncertain and remains to be determined. The objective of this study was to compare 2 strategies of antiplatelet therapy in patients undergoing TAVI. A strategy using monoantiplatelet therapy (group A, n = 164) was prospectively compared with a strategy using dual antiplatelet therapy (group B, n = 128) in 292 consecutive patients undergoing TAVI. The primary end point was a combination of mortality, major stroke, life-threatening bleeding (LTB), myocardial infarction, and major vascular complications at 30 days. All adverse events were adjudicated according to the Valve Academic Research Consortium. The primary end point occurred in 22 patients (13.4%) in the group A and in 30 patients (23.4%) in the group B (hazard ratio 0.51, 95% confidence interval 0.28 to 0.94, p = 0.026). LTB (3.7% vs 12.5%, p = 0.005) and major bleedings (2.4% vs 13.3%, p <0.0001) occurred less frequently in the group A, whereas the incidence of stroke (1.2% vs 4.7%, p = 0.14) and myocardial infarction (1.2% vs 0.8%, p = 1.0) was not significantly different between the 2 groups. The benefit of a strategy using mono versus dual antiplatelet therapy persisted after multivariate adjustment and propensity score analysis (hazard ratio 0.53, 95% confidence interval 0.28 to 0.95, p = 0.033). In conclusion, a strategy using mono versus dual antiplatelet therapy in patients undergoing TAVI reduces LTB and major bleedings without increasing the risk of stroke and myocardial infarction. The results of our study question the justification of dual antiplatelet therapy and require confirmation in a randomized trial.

Crimping and deployment of balloon-expandable valved stents are responsible for the increase in the hydraulic conductance of leaflets.

OBJECTIVES: Leaflet injury has been documented to occur during the deployment of valved stents (VSs). The pathological aspects, however, of this injury are difficult to quantify. Conversely, the hydraulic conductance of a (pericardial) membrane may be easily determined. The impact of crimping and deployment of VS on this parameter was therefore investigated. METHODS: Bovine pericardial square (25 × 25 mm) patches were placed within a pressure chamber and their hydraulic conductance was determined. The influence of the pressure gradient and tissue thickness on this parameter was analysed. Six balloon-expandable VS were constructed. The hydraulic conductance of their bovine pericardial leaflets was determined before and after VS crimping and deployment in four of them. Pericardial leaflets of non-crimped VS were used as controls. RESULTS: Hydraulic conductance increased insignificantly with the pressure level within the chamber: from 128 ± 26.9 ml/h/m(2)/mmHg at a pressure of 50 mmHg to 232.3 ± 51.9 ml/h/m(2)/mmHg at a pressure of 250 mmHg (P = 0.117). Hydraulic conductance was not correlated to pericardial thickness, for thickness measurements ranging from 0.34 to 0.76 mm. The hydraulic conductance of VS leaflets significantly increased immediately after crimping from 45.2 ± 7.6 to 667.9.0 ± 527.2 ml/h/m(2)/mmHg (P < 0.001). This increase was still observed 24 h after VS deployment. No change in hydraulic conductance occurred in the control group. CONCLUSIONS: The determination of the hydraulic conductance of pericardial patches was easy to perform, reproducible and not influenced by tissue thickness. The hydraulic conductance of pericardial leaflets dramatically increased after VS crimping and deployment. This parameter might be, in the future, a useful noninvasive tool in studying leaflet trauma.

Traumatic leaflet injury during the use of percutaneous valves: a comparative study of balloon- and self-expandable valved stents.

OBJECTIVES: No comparison of balloon- or self-expandable valved stents (VSs) regarding tissue injury (if any) has been reported yet. The objective was to evaluate the occurrence and compare the severity of traumatic injury to leaflets from balloon- or self-expandable VSs. METHODS: Twelve homemade VSs were used for this experiment. These three-leaflet bovine pericardial bioprostheses had either a stainless steel (Group A) or a nitinol stent (Group B). After a 30-min period of compression (external diameter of VS reduced to 7 mm), the prostheses were deployed by balloon inflation (Group A) or by unsheathing (Group B). After H&E staining, pericardial leaflets were subsequently analyzed qualitatively and quantitatively for microscopic lesions. Non-crimped pericardial leaflets were used as a control group (Group C). RESULTS: All deployed VSs had microscopic lesions evocating traumatic injury to pericardial leaflets. Transverse fractures and longitudinal cleavages were the two main lesions encountered. Transverse fractures (no. per field) were significantly more frequent in the VS in comparison with the control group: 5 (range: 0-13), 4 (range: 0-9) and 0 (range: 0-1) in Groups A, B and C, respectively (P < 0.001). Cleavages (no. per field) were also more frequent with balloon-expandable VSs compared with self-expandable VSs [3 (range: 0-7) vs 1(range: 0-8); P = 0.03]. CONCLUSIONS: Traumatic injury to the pericardial leaflets does occur during crimping and deployment of balloon- or self-expandable VSs. Injury may be more severe with the balloon-expandable VSs. The impact of such an injury on prosthesis durability requires a further investigation.

Detecting aortic valve bicuspidy in patients with severe aortic valve stenosis: high diagnostic accuracy of colour Doppler transoesophageal echocardiography.

OBJECTIVES: The diagnostic accuracy of multiplane bi-dimensional transoesophageal echocardiography (TEE) in detecting aortic valve bicuspidy is good, but is less reliable when the leaflets are moderately or severely calcified. We hypothesized that systolic colour Doppler analysis might improve the accuracy of diagnosing aortic bicuspidy by TEE in patients with severe symptomatic aortic stenosis (AS). METHODS: Two colour Doppler images of a stenotic aortic valve were defined in a preliminary study using multiplane TEE. In type I, the valve opening had a linear, angular or 'hanger-like' configuration and in type II it was more star-like or 'stellar'. The accuracy of this classification in detecting bicuspidy was evaluated. Fifty-one patients (mean age 71 years (range 40-90 years); 52% male) with severe symptomatic AS (defined as aortic valve area ≤1 cm(2)), requiring surgical aortic valve replacement, were included in this prospective study. The surgical findings were compared with the echocardiographic data. RESULTS: The incidence of aortic bicuspidy was 43%. The presence of type I colour Doppler configuration was significantly higher for bicuspid than for tricuspid aortic valves (95.5 vs 3.5%, respectively; P < 0.001). Diagnostic accuracy in detecting bicuspidy was high (sensitivity 95.5%; specificity 96.5%; positive predictive value 95.5%). Intra- and inter-observer agreements were excellent (Kappa coefficient = 0.88 and 0.92, respectively). CONCLUSIONS: Aortic valve bicuspidy may be accurately diagnosed by colour Doppler valve analysis during TEE in patients with severe AS. Larger prospective studies are required to confirm our results.

Transfemorally or transapically deployed Sapien Edwards bioprosthesis is always deformed.

OBJECTIVE: To study the impact of femoral compared to apical access on the Sapien-Edwards (SE) prosthesis deployment and geometry in patients treated with transcatheter aortic valve implantation (TAVI) for aortic stenosis. BACKGROUND: SE prosthesis deformation exists after its deployment through transfemoral (TF-TAVI) approach. However, no study comparing the deformation between TF-TAVI and transapical (TA-TAVI) approaches has yet been published. METHODS: Forty consecutive patients received TAVI with the SE prosthesis (TF-TAVI n = 25; TA-TAVI n = 15). A fluoroscopic analysis of the prosthesis was then performed. The stent frame geometry was assessed during deployment in the profile view, and after implantation in the profile and frontal views. RESULTS: Expansion kinetics revealed a triphasic stent deployment with both approaches; the aortic extremity being the first to open. After implantation, on the profile view, the stent shape was never rectangular (therefore never cylindrical) in both groups. It had a biconic shape in most of the patients (76% vs. 93.3% for TF-TAVI and TA-TAVI patients, respectively, P = 0.224) with a wider aortic extremity relative to the ventricular one. The frontal view analysis showed that circular deployment of the stent was never achieved. A greater leaflet to stent mismatch was noted in TA-TAVI patients, however, the difference was not statistically significant (12% vs. 33.3%, P = 0.126). CONCLUSION: Fluoroscopically assessed, the geometry of SE prosthesis was never cylindrical after deployment, whatever the access for implantation was. Longitudinal deformation was greater after TF-TAVI whereas leaflet to stent mismatch tended to be more pronounced after TA-TAVI.

Elliptical shape of a SAPIEN XT prosthesis deployed in a patient with bicuspid aortic valve stenosis.

Transcatheter aortic valve implantation (TAVI) has been shown as an effective procedure in patients considered at high risk for surgery. Aortic valve bicuspidy, as encountered in up of 50% of patients with severe aortic stenosis, has been considered a contraindication to TAVI. One reason for this is that stent deformation is likely to occur after prosthesis deployment, but this has been refuted by recent observations with the SAPIEN prosthesis. Herein is reported the first case of a severely deformed SAPIEN XT prosthesis after TAVI in a patient with severe symptomatic aortic stenosis, and known to have a bicuspid native aortic valve.

Complications of the access during aortic valve implantation through transfemoral access.

BACKGROUND: Aortic valve implantation (AVI) is a booming therapeutic option in high-risk patients with calcific aortic stenosis. Retrograde femoral approach drawbacks include vascular complications owing to the size of the introduction system (22- and 24-F).The aim of this study was to retrospectively analyze the incidence and the treatment of vascular complications in the first 2 years of transfemoral AVI experience with the first generation of Edwards SAPIEN transcatheter heart valves. METHODS: Since December 2007, AVI has been performed in 71 patients, 21 times by the transapical route and 50 times by the transfemoral route through an inguinal approach with the first generation of Edwards SAPIEN transcatheter heart valves (23 and 26 mm). The incidence and the treatment of vascular complications were evaluated as main criteria for transfemoral AVI. RESULTS: All the procedures could be successfully performed by a femoral route, except for three cases when the introducing device could not be fixed on the thoracic aorta because of vascular access problems. Vascular access-related complications occurred in nine patients (18%), including three iliac dissections, two aortic dissections, three femoral lesions, and one thoracic aorta rupture. These complications were treated either in a conservative way (n = 2), or in an endovascular way using a contralateral approach (n = 3), or surgically through an inguinal approach (n = 3). A traumatic rupture of the thoracic aorta resulted in the death of a female patient. CONCLUSION: In our experience, transfemoral AVI gives a satisfying technical success rate in the selected patients. The incidence of complications involving the vascular access remains an important limitation of this new technique. Although a conservative or endovascular treatment can be applied in most cases, improving the introduction devices is highly expected because it would reduce the complications rate of vascular access.

Aortic biological valve thrombosis in an HIV positive patient.

Biological aortic valve thrombosis is an exceptional complication. A 64-year-old patient positive for human immunodeficiency virus presented for syncope on exertion, 2 years after an aortic bioprosthetic valve replacement and double coronary artery bypass. Transvalvular aortic mean gradient was approximately 50 mm Hg on echocardiogram and catheterization. Cardiac computed tomography scan showed a limited opening of the bioprosthesis cusps. Surgical exploration revealed thrombosis of the three cusps on the aortic side, limiting the opening of the valve. No relation could be established between the patient's human immunodeficiency virus status and valve thrombosis.

Pericardial patch anterior leaflet extension in rheumatic mitral insufficiency.

This report describes a technique for anterior leaflet extension using an autologous pericardial patch in patients suffering from rheumatic mitral regurgitation. The technique has recently evolved and now enables us to correct both vertical and transversal fibrotic leaflet retraction.

Evidence of leaflet injury during percutaneous aortic valve deployment.

It has been suggested that valved stent deployment during transcatheter aortic valve implantation may be responsible for traumatic injury to pericardial leaflets, especially with balloon expandable valved stents. However, such an injury has not been described nor reported so far. We here report the microscopic analysis of 4 Sapien-Edwards prostheses, 2 of which have been implanted in humans. There was no macroscopic evidence of traumatic injury to the pericardial leaflets of the percutaneous valves. However, pathological microscopic findings were observed in all of them. These mainly consisted of collagen fibers fragmentation and disruption. Areas of non- or mildly affected tissue were adjacent to areas of severely damaged tissue. The entire thickness of the leaflets might be involved. The severity of the lesions also differed among leaflets from a same prosthesis. Areas of plasmatic insudation were identified in one case. The disruption index was significantly higher in the Sapien group in comparison to the control group: 42.4% (14-63.5%) versus 17.5% (9.2-31%) (p < 0.001). Although of limited size sample, this study does prove that traumatic injury to leaflets occurs during percutaneous valves implantation. This should prompt physicians to wait for the long-term results of this new technology before extending the indications to low-risk patients.

Partitioning of exhaled NO in ventilated patients undergoing cardiac surgery.

The change in exhaled NO after cardio-pulmonary bypass remains controversial. The aims were to determine whether exhaled NO sources (alveolar or bronchial) are modified after bypass, and whether mechanical ventilation (MV) settings during bypass modify exhaled NO changes. Thirty-two patients were divided into three groups: without MV during bypass and positive end-expiratory pressure (PEEP) (n=12), dead space MV without PEEP (n=10) and dead space MV with PEEP (n=10). Alveolar NO concentration and bronchial NO flux were calculated before and 1h after surgery using a two-compartment model of NO exchange developed in spontaneous breathing patients. Whereas a significant decrease in bronchial NO was found after bypass in the two groups without PEEP during bypass, this decrease was not observed in patients with dead space ventilation with PEEP. Alveolar NO was not significantly modified whatever the ventilation settings. In conclusion, the impairment of bronchial NO seemed related to airway closure since dead space mechanical ventilation with PEEP prevented its decrease.

Increased radial force improves stent deployment in tricuspid but not in bicuspid stenotic native aortic valves.

BACKGROUND: Stent deployment within stenotic native aortic valves has been shown to depend on valve anatomy (presence of bicuspid valve or not). This study investigated the influence of stent stiffness on stent expansion. METHODS: The study included 88 patients with severe aortic stenosis, and 36 (41%) had bicuspid aortic valves. Two self-expandable stents with different radial force were deployed intraoperatively inside stenotic aortic valves before surgical aortic valve replacement. Patients in group B received a stent stiffer than that in group A. Effect of stent radial force on stent shape and incidence of paraprosthetic gaps was determined. RESULTS: Noncircular stent deployment was more frequent in bicuspid (81%) than in tricuspid aortic valves (33%; p < 0.0001). Increasing stent radial force significantly improved stent shape in tricuspid valves (circular shape: 60% in group A vs 93% in group B; p = 0.005) but had no significant effect in bicuspid valves (12.5% in group A vs 27% in group B;p = 0.394). Likewise, incidence of paraprosthetic gaps was significantly reduced with the stiff stent in tricuspid valves (64% in group A vs 30% in group B, p = 0.025) but not in bicuspid valves (50% in group A vs 60% in group B; p= 0.722). CONCLUSIONS: Increased stent radial force had a favorable effect on stent deployment in tricuspid but not in bicuspid valves. In bicuspid valves, stent maldeployment was constant. Leaflet distortion of implanted valved stent might be a concern in this setting.

A new endovascular size reducer for large pulmonary outflow tract.

Around 75% of patients with severe pulmonary insufficiency requiring valvular replacement are excluded from percutaneous pulmonary valve implantation (PPVI) due to a large ventricular outflow tract. To extend the indication of PPVI to these patients, a new size reducer has been designed. This 35-mm size reducer was successfully deployed inside the main pulmonary artery through a 21-Fr delivery catheter in six sheep. A 20-mm pericardial valved stent was subsequently deployed inside the size reducer to restore pulmonary valve continence. We successfully verified the efficiency of the delivery catheter by controlling the deployment precisely and reversibly. In all six cases, device positioning was satisfactory. There was no post-procedural residual stenosis in the right ventricular outflow tract in haemodynamic (9.5+/-3 mm Hg), echocardiographic and angiographic studies. After 8-12 weeks of follow-up, no prosthetic migration occurred. The transprosthetic systolic gradient remained low (4+/-2.5 mm Hg) during follow-up. There was one trivial persistent paraprosthetic leak. This study confirmed the feasibility and the effectiveness of this new size reducer to reduce the size of the pulmonary artery.