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.

Correlation between structural changes and acute thrombogenicity in transcatheter pericardium valves after crimping and balloon deployment

INTRODUCTION

Transcathether heart valve replacement has gained considerable acceptance during the last decades. It is now part of the armamentarium for aortic valve replacement. The procedure proved to be highly efficient. However the issues of the blood compatibility and tissue durability were not raised and the adverse events were probably under-reported, according to observations of thrombosis after deployment.

MATERIAL AND METHOD

Bovine pericardium leaflets were sewn inside a 26mm diameter stainless steel stent to manufacture these valves (one control and two experimental). The correlation between the trauma and the acute thombogenicity of bovine pericardium leaflets, after crimping and ballooning, was investigated via an in vitro blood flow with labeled platelets. These leaflets were processed for histology: scanning electron microscopy, light microscopy, and transmission electron microscopy.

RESULTS

The control specimens showed a regular pericardium structure with some blood cells deposited on the collagen fibrous surface (inflow) and scarce blood cells deposited on the serous surface (outflow). After crimping and ballooning, the structure of the pericardium was severely injured, eventually with delaminations and ruptures. The blood cell uptake was considerably increased compared to the control.

CONCLUSION

It would therefore be appropriate to pay more attention to the design of the valves. Specifically, the incorporation of a buffer tissue or fabric between the pericardium and the metallic stent is suggested. The issue of ballooning deserves detailed and in depth investigation regarding the lifetime of the device.

Transcatheter heart valve crimping and the protecting effects of a polyester cuff

INTRODUCTION

Prior to deployment, the percutaneous heart valves must be crimped and loaded into sheaths of diameters that can be as low as 6mm for a 23mm diameter valve. However, as the valve leaflets are fragile, any damage caused during this crimping process may contribute to reducing its long-term durability in vivo.

MATERIAL AND METHOD

Bovine pericardium percutaneous valves were manufactured as follows. The leaflets were sutured on a nitinol frame. A polyester cuff fabric served as a buffer between the pericardium and the stent. Two valves were crimped and one valve was used as control. The valves were examined in gross observation and micro-CT scan and then the leaflets were processed for histology and analyzed in scanning electron microscopy, light microscopy and transmission electron microscopy.

RESULT

Crimping of the valves resulted in the increase thickness of the leaflets and there was no evidence of additional delamination. The heavy prints of the stents were irregularly distributed on the outflow surface in the crimped devices and were shallow and did not penetrate throughout the thickness of the leaflets. However, the wavy microscopy of collagen fiber bundles was well preserved. They were found to remain individualized without any agglutination as shown by the regular banding appearance.

CONCLUSION

Crimping of self-deployable valves per se caused only minor damages to the leaflets. However, the procedure could be refined in order to minimize areas of high pressure and swelling of the tissue that can be accompanied with flow surface disruption and increase of the hydraulic conductance. The incorporation of a polyester buffer serves to prevent the deleterious effects that may be caused if the pericardium tissue were in direct contact with the nitinol stent.

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.

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.

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.

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.

Ultrasonographic diagnostic criterion for severe diaphragmatic dysfunction after cardiac surgery

BACKGROUND

Severe diaphragmatic dysfunction can prolong mechanical ventilation after cardiac surgery. An ultrasonographic criterion for diagnosing severe diaphragmatic dysfunction defined by a reference technique such as transdiaphragmatic pressure measurements has never been determined.

METHODS

Twenty-eight patients requiring mechanical ventilation > 7 days postoperatively were studied. Esophageal and gastric pressures were measured to calculate transdiaphragmatic pressure during maximal inspiratory effort and the Gilbert index, which evaluates the diaphragm contribution to respiratory pressure swings during quiet ventilation. Ultrasonography allowed measuring right and left hemidiaphragmatic excursions during maximal inspiratory effort. Best E is the greatest positive value from either hemidiaphragm. Twenty cardiac surgery patients with uncomplicated postoperative course were also evaluated with ultrasonography preoperatively and postoperatively. Measurements were performed in semirecumbent position.

RESULTS

Transdiaphragmatic pressure during maximal inspiratory effort was below normal value in 27 of the 28 patients receiving prolonged mechanical ventilation (median, 39 cm H(2)O; interquartile range [IQR] 28 cm H(2)O). Eight patients had Gilbert indexes <or= 0 indicating severe diaphragmatic dysfunction. Best E was lower in patients with Gilbert index <or= 0 than > 0 (30 mm; IQR, 10 mm; vs 19 mm; IQR, 7 mm, respectively; p = 0.001). Best E < 25 mm had a positive likelihood ratio of 6.7 (95% confidence interval [CI], 2.4 to 19) and a negative likelihood ratio of 0 (95% CI, 0 to 1.1) for having a Gilbert index <or= 0. None of the patients with uncomplicated course had Best E < 25 mm either preoperatively or postoperatively.

CONCLUSIONS

Ultrasonographic-based determination of hemidiaphragm excursions in patients requiring prolonged mechanical ventilation after cardiac surgery may help identify those with and without severe diaphragmatic dysfunction as defined by the Gilbert index.

Late posterior failure after mitral valve repair in degenerative disease

OBJECTIVES

Little is known regarding the mechanisms, the feasibility and the long-term results of re-repair in 'posterior failure' of a previous mitral valve repair performed for severe degenerative mitral regurgitation. We report our 16-year experience in redo surgery for late posterior failure of mitral valve repair in degenerative disease.

METHODS

From 1991 to 2004, 13 consecutive patients (10 males; median age: 65 years) were reoperated for late posterior failure of mitral valve repair. All patients had grade > or =3+ mitral regurgitation. Repair was mainly performed using Carpentier's techniques.

RESULTS

Repair failure was due to posterior leaflet prolapse, leaflet retraction or leaflet dehiscence in eight (62%), three (23%) and two (15%) patients, respectively. Repair was performed in nine patients (69%). There was no perioperative death. During follow-up (median: 105 months; range: 40-170 months) one late death occurred in the mitral valve replacement group. One (11%) patient underwent mechanical mitral valve replacement 125 months after re-repair. Congestive heart failure occurred in one patient in each group. At the latest follow-up, all but one patient in the mitral valve repair group were in NYHA functional class I or II and all were in sinus rhythm. Doppler echocardiographic studies of the re-repaired valves (n=8) showed no or trivial, grade 1+ and grade 2+ residual mitral regurgitation in 6 (75%), 1 and 1 patients, respectively. Mean transmitral gradient was 3 mmHg (2-8 mmHg) and left ventricular ejection fraction was 59% (43-77%).

CONCLUSION

In case of late posterior failure of mitral valve repair for severe degenerative, re-repair is feasible in about 70% of the patients with encouraging results at 10 years.

Is it reasonable to treat all calcified stenotic aortic valves with a valved stent? Results from a human anatomic study in adults

OBJECTIVES

This study was designed to study the behavior of a stent deployed inside human stenotic aortic valves.

BACKGROUND

Endovascular valved stent (VS) implantation is a promising new therapy for patients with severe calcific aortic stenosis (AS). The precise characteristics of stent deployment in humans have been poorly studied so far.

METHODS

Thirty-five patients with severe AS were included in the study. Sixteen patients (46%) had bicuspid aortic valves. A self-expandable stent specifically designed for VS implantation was deployed intraoperatively inside the aortic valve before surgical aortic valve replacement.

RESULTS

In tricuspid aortic valves, the shape of stent deployment was circular, triangular, or elliptic in 68%, 21%, or 11%, respectively. Noncircular stent deployment was frequent in bicuspid aortic valves (the elliptic deployment being the rule [79%]), and stent underdeployment was constant. The incidence of gaps between the stent external surface and the aortic valve did not differ between tricuspid and bicuspid valves (58% vs. 43%; p = 0.49). Sharp calcific excrescences protruding inside the stent lumen were present in 3 cases (9%). Ex vivo study of a homemade VS confirmed that the regularity of the coaptation line of the leaflets was critically dependent on the presence or the absence of stent misdeployment.

CONCLUSIONS

Stent misdeployment was constant in bicuspid valves and occurred in one-third of cases of tricuspid valves. Premature failure of implanted VS (secondary to valve distortion or traumatic injury to the leaflets by calcific excrescences) might be an important concern in the future.

Unilateral pulmonary edema after pulmonary embolism in a bilateral lung transplant patient

We report a case of unilateral pulmonary edema due to the decompensation of an asymptomatic ipsilateral pulmonary venous stenosis by a contralateral pulmonary embolism. Emergency surgery included pulmonary embolectomy and refashioning of the stenotic pulmonary venous anastomosis.

Carbon monoxide can prevent acute lung injury observed after ischemia reperfusion of the lower extremities

BACKGROUND

Pulmonary expression of heme oxygenase has been observed in multiple studies. This expression has been found beneficial in decreasing the severity of acute lung injury (ALI) post ischemia-reperfusion (I/R). The aim of this study was to assess the role of exogenous administration of the end-products of heme oxygenase reaction, carbon monoxide, and bilirubin, in the severity of ALI.

STUDY DESIGN

We compared five groups of rats (n = 7/group) including a sham group and four I/R of the lower extremities by clamping the abdominal aorta for 2 h followed by reperfusion for 2 h. The four I/R groups included a control group, one pretreated with bilirubin (50 micromol/kg IV), another with inhaled carbon monoxide (CO) (250 ppm), and the last pretreated with both. The severity of ALI has been evaluated by a histological assay grading neutrophilic infiltration, as well as a study of the microvascular permeability using the Evans blue.

RESULTS

The administration of CO prevented pulmonary microvascular permeability alteration noted after I/R of the lower limbs (pulmonary content of Evans blue: 141 +/- 23 microg/g of tissue in the isolated I/R group versus 68 +/- 34 microg/g of tissue in CO group; P < 0.001). Histologically CO administration inhibited neutrophilic sequestration observed after I/R. On the other hand, treatment by bilirubin alone (50 micromol/kg IV) did not modify the extent of pulmonary injury.

CONCLUSION

Exogenous administration of carbon monoxide by inhalation at low doses prevented ALI post-I/R in this model.

Posterior Leaflet Extension With an Autologous Pericardial Patch in Rheumatic Mitral Insufficiency

We describe our technique of posterior leaflet extension with an autologous pericardial patch in patients suffering from rheumatic mitral regurgitation. Several simple rules have allowed us to achieve satisfying long-term results.

[Systolic anterior motion (SAM): a rare cause of late failure in mitral valve repair]

Systolic anterior motion (SAM) of the mitral valve is a rare complication of mitral valve repair. The treatment of the large majority of cases is purely medical. Nevertheless, an early degradation may require reoperation (revision of the repair or valve replacement). The authors report two cases of post-repair SAM with a poor outcome with medical therapy which required reoperation after several years. In both cases, an excess of bivalvular tissue with respect to the size of the mitral orifice was observed. A second repair was possible (sliding valvuloplasty associated with an oval resection of the anterior leaflet) with satisfactory long-term results. The identification of the risk factors and careful analysis of the lesions in cases of SAM after mitral valve repair may lead to a repeat repair and the avoidance of mitral valve replacement.

A Repositionable Valved Stent for Endovascular Treatment of Deteriorated Bioprostheses

OBJECTIVES

We report our animal experience of endovascular valve replacement (VR) of failed bioprosthesis (BP) using an original delivery catheter allowing repositioning of the valved stent (VS).

BACKGROUND

Among the different devices designed for percutaneous VR, none has the potential for repositioning of a fully deployed VS.

METHODS

Five sheep underwent, on beating heart, tricuspid VR with a stented BP. Prolapse of 1 leaflet was induced by tearing. For the endovascular tricuspid VR, we used a VS constructed with a nitinol self-expandable stent and a porcine stentless aortic valve. We also used an original delivery catheter, allowing repositioning of the VS through a compression or relaxation mechanism of the stent.

RESULTS

Epicardial echocardiography and right ventriculography showed severe tricuspid regurgitation, with a regurgitant jet extending to the inferior vena cava. After surgical exposure to the infrarenal inferior vena cava, the VS was successfully implanted inside the failed BP in all cases. Repositioning of the fully deployed VS was always possible. Echocardiographic and macroscopic studies revealed adequate VS positioning, excellent leaflet opening, and absence of any intraprosthetic or periprosthetic leak.

CONCLUSIONS

Endovascular VR was easily performed in sheep with failed BP in the tricuspid position. The novel delivery catheter allowed adequate repositioning of our fully deployed VS before its definitive release. One may anticipate that the safety improvement conferred by this new technology will certainly favor the development of percutaneous VR in clinical practice.

Management of commissural lesions in native mitral valve endocarditis: long-term results of valve repair and partial homograft replacement

BACKGROUND AND AIM OF THE STUDY

Commissural lesions in the context of native mitral valve endocarditis are a technically challenging condition for conservative surgery. Herein are reported the authors' 10-year results for mitral valve repair (MVRep) or partial homograft replacement (PHR) performed in this setting.

METHODS

Data were reviewed from 19 consecutive patients who underwent MVRep using either Carpentier's technique (n = 14) or PHR (n = 5) for endocarditis at the authors' institution between 1989 and 1994.

RESULTS

There was one operative death (5%; 95% CI 0-15.5%). Two reoperations were performed in each subgroup for recurrence of endocarditis (n = 2) and mitral valve failure (n = 2). The 10-year survival rate and freedom from mitral valve reoperation were 95% (95% CI 84-100%) and 78% (95% CI 59-97%), respectively. At 10 years, 13 (93%) surviving and non-reoperated patients were in good functional status (NYHA class I-II), and 14 (100%) were in sinus rhythm. Although echocardiographic results were excellent in the MVRep group, all PHR patients had moderate or severe mitral valve dysfunction.

CONCLUSION

Commissural reconstruction using Carpentier's techniques demonstrated excellent long-term results in patients with native mitral valve endocarditis. In contrast, the results for PHR were rather disappointing.

The induction of heme oxygenase 1 decreases contractility in human internal thoracic artery and radial artery grafts

OBJECTIVE

Spasm remains a potential problem encountered during the use of arterial grafts in coronary artery bypass surgery. Heme oxygenase plays a role in the control of arterial vasoreactivity. Heme oxygenase exists in 2 constitutive isoforms (heme oxygenase 2 and 3) and an inducible isoform (heme oxygenase 1). The aim of our study was to induce heme oxygenase 1 by using hemin in human internal thoracic and radial arteries and to evaluate the effect of this induction on the contractility of these arterial grafts.

METHODS

Segments of human arterial grafts obtained from patients undergoing isolated coronary artery bypass surgery were incubated in organ chambers for 4 hours in the presence of 10(-4) mol/L hemin. Concentration-response curves to norepinephrine were obtained in control and hemin-treated arterial rings. Heme oxygenase 1 expression was evaluated by using enzyme-linked immunosorbent assays and immunohistochemical staining.

RESULTS

The contractility of the arterial rings to norepinephrine was significantly reduced after incubation with hemin. Zinc protoporphyrin (an inhibitor of heme oxygenase) reversed the effect of hemin, whereas the inhibitor of nitric oxide synthase had no effect. The inhibitor of soluble guanylate cyclase blocked the decrease in contractility induced by hemin. Immunohistochemical staining revealed a large expression of heme oxygenase 1 in all vascular layers of hemin-treated internal thoracic artery and radial artery rings. Enzyme-linked immunosorbent assay studies showed a significant increase in heme oxygenase 1 levels in hemin-treated internal thoracic artery and radial artery rings.

CONCLUSION

Hemin caused in vitro induction of heme oxygenase 1 in human internal thoracic artery and radial artery grafts. This induction resulted in a reduced contractility to norepinephrine, partially through the cyclic guanosine monophosphate-dependent pathway. This effect was independent from nitric oxide synthesis.

Pulmonary expression of inducible heme-oxygenase after ischemia/reperfusion of the lower extremities in rats

BACKGROUND

Expression of inducible heme-oxygenase (HO-1) has been shown to be increased in various inflammatory disorders, which may confer a protective role. The aim of our study was to assess pulmonary expression of HO-1 after ischemia/reperfusion (I/R) of the lower limbs in rats.

MATERIALS AND METHODS

We compared three groups of rats (n = 5/group): one Sham group, and two I/R groups (aorta cross-clamped for 2 h followed by 2 h of reperfusion), one of which pre-treated with Zn-protoporphyrin (Zn-PP), a competitive inhibitor of HO (50 micromol/kg, i.p.). At the end of experiment, lungs were harvested for determination of HO activity and HO-1 expression by Western blot and immunohistochemistry. Lung injury was assessed by bronchoalveolar lavage, histological study, and determination of the lung Evans Blue dye content, an index of microvascular permeability.

RESULTS

I/R of the lower limbs was responsible for acute lung injury (ALI), characterized by neutrophilic infiltration (87 +/- 20 x 10(3) neutrophils/mm(3), Sham group versus 191 +/- 38 x 10(3) neutrophils/mm(3), I/R group; P < 0.002) and an increase in lung Evans blue dye content: (74 +/- 6 microg/g, Sham group versus 122 +/- 48 microg/g, I/R group; P < 0.05). Pre-treatment with Zn-PP further increases the Evans Blue content (122 +/- 48 microg/g, I/R group versus 179 +/- 23 microg/g Zn-PP group P < 0.05) and the neutrophilic infiltration. Pulmonary heme-oxygenase activity, and HO-1 content were increased after I/R. (10.5 +/- 12 pmol bilirubin/mg protein/h, Sham group versus 101.2 +/- 66 pmol bilirubin/mg protein/h, I/R group; P < 0.02). Immunohistochemistry revealed that the expression of HO-1 was mainly localized to inflammatory cells.

CONCLUSIONS

ALI following I/R of the lower limbs in rats is associated with an increase of pulmonary expression of HO-1, inhibition of this expression increase the severity of ALI.