Catheter-Based Approach to Mitral Regurgitation

Effects of Transcatheter Mitral Valve Repair Using MitraClip® Device on Sleep Disordered Breathing in Patients with Mitral Valve Regurgitation

Sleep disordered breathing (SDB) is common among patients with valvular heart disease, and successful valve surgery could reduce SDB severity. However, data about the effects of transcatheter mitral valve repair on SDB are scarce. Therefore, mitral regurgitation (MR) patients undergoing MitraClip-placement were prospectively enrolled. Before MitraClip-placement, daytime sleepiness and sleep quality were assessed using the Epworth Sleepiness Scale (ESS) and Pittsburgh Sleep Quality Index (PSQI), respectively; and all patients underwent SDB screening using five-channel respiratory polygraphy. After 3-6 months, patients had a similar reassessment including: ESS, PSQI, and respiratory polygraphy. 67 patients were included (77 ± 8years). Despite normal sleepiness scores, 41 patients (61%) had SDB with apnea-hypopnea-index (AHI) ≥ 15 h before MitraClip-placement, of whom only three patients had known SDB previously. Compared to patients without SDB, patients with SDB had similar sleepiness scores but higher NT-proBNP values at baseline (4325 vs. 1520 pg/mL, p < 0.001). At follow-up, there were significant AHI improvements among patients with SDB (p = 0.013). However, there were no significant sleepiness score changes. In conclusion, the prevalence of SDB among MitraClip candidates is very high even in those without daytime sleepiness. MR patients with SDB have higher NT-proBNP values, which may reflect a worse prognosis. MitraClip-placement may improve the underlying SDB, which could be an additional benefit of the procedure.

Percutaneous Edge-to-Edge Mitral Valve Repair

Percutaneous edge-to-edge mitral valve repair, using the MitraClip device for severe mitral regurgitation (MR) was first introduced in 2003. Since then, more than 100,000 cases have been performed worldwide and it remains the most established percutaneous therapy available for the treatment of severe MR. Currently, it is indicated for severe, symptomatic functional MR in patients who continue to have significant symptoms despite optimal guideline directed medical therapy, as well as in symptomatic patients with severe degenerative MR who are deemed too high risk for conventional surgical therapy in the opinion of the heart team. In this paper, we discuss the evolution of the MitraClip device, the clinical studies supporting its use as well as the important concept of proportionate and disproportionate MR.

An investigation of regional variations in the biaxial mechanical properties and stress relaxation behaviors of porcine atrioventricular heart valve leaflets

The facilitation of proper blood flow through the heart depends on proper function of heart valve components, and alterations to any component can lead to heart disease or failure. Comprehension of these valvular diseases is reliant on thorough characterization of healthy heart valve structures for use in computational models. Previously, computational models have treated these leaflet structures as a structurally and mechanically homogenous material, which may not be an accurate description of leaflet mechanical response. In this study, we aimed to characterize the mechanics of the heart valve leaflet as a structurally heterogenous material. Specifically, porcine mitral valve and tricuspid valve anterior leaflets were sectioned into six regions and biaxial mechanical tests with various loading ratios and stress-relaxation test were performed on each regional tissue sample. Three main findings from this study were summarized as follows: (i) the central regions of the leaflet had a more anisotropic nature than edge regions, (ii) the mitral valve anterior leaflet was more extensible in regions closer to the annulus, and (iii) there was variance in the stress-relaxation behavior among all six regions, with mitral valve leaflet tissue regions exhibiting a greater decay than the tricuspid valve regions. This study presents a novel investigation of the regional variations in the heart valve biomechanics that has not been comprehensively examined. Our results thus allow for a refinement of computational models for more accurately predicting diseased or surgically-intervened condition, where tissue heterogeneity plays an essential role in the heart valve function.

Mitral valve disease

In industrially developed countries, moderate or severe mitral valve disease is relatively common and is usually caused by prolapse or is secondary to left ventricular disease. Mitral stenosis (MS), however, is uncommon and usually a sequela of rheumatic fever. This article discusses the natural history of mitral regurgitation and MS and their medical and surgical management.

Tension to passively cinch the mitral annulus through coronary sinus access: an ex vivo study in ovine model

INTRODUCTION

The transcatheter mitral valve repair (TMVR) technique utilizes a stent to cinch a segment of the mitral annulus (MA) and reduces mitral regurgitation. The cinching mechanism results in reduction of the septal-lateral distance. However, the mechanism has not been characterized completely. In this study, a method was developed to quantify the relation between cinching tension and MA area in an ex vivo ovine model.

METHOD

The cinching tension was measured from a suture inserted within the coronary sinus (CS) vessel with one end tied to the distal end of the vessel and the other end exited to the CS ostium where it was attached to a force transducer on a linear stage. The cinching tension, MA area, septal-lateral (S-L) and commissure-commissure (C-C) diameters and leakage was simultaneously measured in normal and dilated condition, under a hydrostatic left ventricular pressure of 90 mm Hg.

RESULTS

The MA area was increased up to 22.8% after MA dilation. A mean tension of 2.1 ± 0.5 N reduced the MA area by 21.3 ± 5.6% and S-L diameter by 24.2 ± 5.3%. Thus, leakage was improved by 51.7 ± 16.2% following restoration of normal MA geometry.

CONCLUSION

The cinching tension generated by the suture acts as a compensation force in MA reduction, implying the maximum tension needed to be generated by annuloplasty device to restore normal annular size. The relationship between cinching tension and the corresponding MA geometry will contribute to the development of future TMVR devices and understanding of myocardial contraction function.

Advances in percutaneous valvular intervention

We are entering a new era in the percutaneous treatment of valvular heart disease. Novel techniques and devices have given rise to the possible treatment of a range of valvular heart diseases that previously necessitated surgical therapies, including aortic stenosis, pulmonary regurgitation and mitral regurgitation. Despite the enormous potential of these percutaneous therapies, enthusiasm needs to be balanced by an understanding of the challenges that need to be overcome before such therapies can be widely embraced. This review provides a critical assessment of the status of the major developments in percutaneous valvular intervention to date, and provides the authors' perspective on the current role and future potential of these techniques.

Echocardiographic guidance for diagnostic and therapeutic percutaneous procedures

Echocardiographic guidance has an important role in percutaneous cardiovascular procedures and vascular access. The advantages include real time imaging, portability, and availability, which make it an effective imaging modality. This article will review the role of echocardiographic guidance for diagnostic and therapeutic percutaneous procedures, specifically, transvenous and transarterial access, pericardiocentesis, endomyocardial biopsy, transcatheter pulmonary valve replacement, pulmonary valve repair, transcatheter aortic valve implantation, and percutaneous mitral valve repair. We will address the ways in which echocardiographic guidance provides these procedures with detailed information on anatomy, adjacent structures, and intraprocedural instrument position, thus resulting in improvement in procedural efficacy, safety and patient outcomes.

Finite element analysis of the biomechanical interaction between coronary sinus and proximal anchoring stent in coronary sinus annuloplasty

Recent clinical studies of the percutaneous transvenous mitral annuloplasty (PTMA) devices have shown a short-term reduction of mitral regurgitation after implantation. However, adverse events associated with the devices such as compression and perforation of vessel branches, device migration and fracture were reported. In this study, a finite element analysis was carried out to investigate the biomechanical interaction between the proximal anchor stent of a PTMA device and the coronary sinus (CS) vessel in three steps including: (i) the stent release and contact with the CS wall, (ii) the axial pull t the stent connector and (iii) the pressure inflation of the vessel wall. To investigate the impact of the material properties of tissues and stents on the interactive responses, the CS vessel was modelled with human and porcine material properties, and the proximal stent was modelled with two different Nitinol materials with one being stiffer than the other. The results indicated that the vessel wall stresses and contact forces imposed by the stents were much higher in the human model than the porcine model. However, the mechanical differences induced by the two stent types were relatively small. The softer stent exhibited a better fatigue safety factor when deployed in the human model than in the porcine model. These results underscored the importance of the CS tissue mechanical properties. Vessel wall stress and stent radial force obtained in the human model were higher than those obtained in the porcine model, which also brought up questions as to the validity of using the porcine model to assess device mechanical function. The quantification of these biomechanical interactions can offer scientific insight into the development and optimisation of the PTMA device design.

Echocardiography in transcatheter aortic valve implantation and mitral valve clip

Transcatheter aortic valve implantation and transcatheter mitral valve repair (MitraClip) procedures have been performed worldwide. In this paper, we review the use of two-dimensional and three-dimensional transesophageal echo for guiding transcatheter aortic valve replacement and mitral valve repair.

Relationship between mitral leaflets angles, left ventricular geometry and mitral deformation indices in patients with ischemic mitral regurgitation: imaging by echocardiography and cardiac magnetic resonance

Chronic ischemic mitral regurgitation (IMR) is associated with a markedly worse prognosis after myocardial infarction (MI).The study aimed to evaluate the relationship between anterior and posterior mitral leaflet angle (MLA) values, left ventricle remodeling and severity of ischaemic mitral regurgitation (IMR).

METHODS

Forty-two patients (age 63.5 ± 9.7 years, 36 men) with chronic IMR (regurgitant volume, RV > 20 ml; >6 months after MI) underwent transthoracic echocardiography (TTE) and cardiovascular magnetic resonance (CMR) imaging. Anterior and posterior MLA, determined by echocardiography, were correlated with indices of LV remodeling, mitral apparatus deformation and IMR severity by CMR. The anterior and posterior MLA was 25.41 ± 4.28 and 38.37 ± 8.89° (mean ± SD). In 5 patients (11.9%) the posterior MLA was ≥45°. There was a significant correlation between anterior MLA and RV (r = 0.74, P = 0.01). For patients with RV > 30 ml this correlation was stronger (r = 0.97, P = 0.005) and, in addition, there was a correlation between the RV and posterior MLA (r = 0.90, P = 0.037), between tenting area and posterior MLA (r = 0.90, P = 0.04), and between tenting area and anterior MLA (r = 0.82, P = 0.08). With regard to LV remodeling parameters, there was weaker but significant correlation between posterior MLA and LV end-diastolic volume index (r = 0.35, P = 0.031), LV end-systolic volume index (r = 0.37, P = 0.021), stroke volume (r = 0.35, P = 0.03), sphericity index (r = 0.33, P = 0.041). Anterior MLA correlated with wall motion score index (r = 0.41, P = 0.019). Besides, there was a correlation between posterior MLA and left atrial volume (r = 0.41, P = 0.012). Measurement of anterior and posterior MLA may play an important role in evaluating patients with IMR.

Characterization of the mechanical properties of the coronary sinus for percutaneous transvenous mitral annuloplasty

The coronary sinus (CS) vessel serves as a conduit for the deployment of percutaneous transvenous mitral annuloplasty (PTMA) devices for the treatment of functional mitral regurgitation. Characterization of the mechanical response of the CS is an important step towards an understanding of tissue-device interaction in PTMA intervention. The purpose of this study was to investigate the mechanical properties of the porcine CS using the pressure-inflation test and constitutively model the wall behavior using a four fiber family strain energy function (SEF). The results showed that the CS exhibited an S-shaped pressure-radius response and could be dilated up to 88% at a pressure of 80mmHg. Excellent results from model fitting indicated that the four fiber family SEF could capture the experimental data well and could be used in future numerical simulations of tissue-device interaction. In addition, a histological study was performed to identify the micro-structure of the CS wall. We found a high content of striated myocardial fibers (SMFs) surrounding the CS wall, which was also mainly composed of SMFs, while the content of smooth muscle cells was very low. Elastin and collagen fibers were highly concentrated in the luminal and outer layers and sparsely distributed in the medial layer of the CS wall. These structural and mechanical properties of the CS should be taken into consideration in future PTMA device designs.

Percutaneous valve procedures: Present and future

Percutaneous mitral commissurotomy and aortic valvuloplasty have been being performed since the mid-1980s. Balloon commissurotomy has been used in thousands of cases worldwide and it provides good short- and long-term results in a wide range of patients. It has virtually replaced surgical commissurotomy in the treatment of mitral stenosis. In contrast, percutaneous aortic valvuloplasty is almost abandoned worldwide due to its lack of efficacy and the risks involved. The new techniques of percutaneous valve intervention: aortic valve replacement and mitral valve repair are at an early stage: the first in-man applications of these fledgling techniques started in 2002. Preliminary series show that they are feasible; however, they need to be further evaluated in comparison with contemporary treatment to assess accurately how efficient they are and the risks involved. Currently potential applications concern high-risk patients, however, in the future, after thorough evaluation, this may be extended to others. Thus, percutaneous interventions already play an important role in treatment of valvular heart disease, a role that seems set for future expansion.

The future of interventional cardiology lies in the left atrium

The historic focus of interventional cardiology has been on treating atherosclerotic coronary artery disease. Balloons, stents, and debulking devices have been the mainstay tools of the interventionalist. However, as engineering skills have developed and clinical techniques have improved, new clinical avenues for the interventionalist beyond the coronary vessels are starting to evolve. One of the most opportunistic areas in cardiology for the interventionalist is the left atrium where treatment of clinically important issues such as mitral regurgitation, left atrial thrombus, atrial fibrillation, patent foramen ovale, and atrial septal defect may be approached. Additionally, the left atrium is a source of important hemodynamic information that can be captured with new implantable devices. While in the past the trans-septal puncture has been infrequently used, the future may hold this technique as one of the most common. The following manuscript describes the status of some of the newest opportunities for interventionalists that lie beyond atherosclerotic disease and within the left atrium.

Percutaneous mitral annuloplasty through the coronary sinus: an anatomic point of view

OBJECTIVE

We assessed the anatomic relationships among the mitral annulus, coronary sinus, and circumflex artery in human cadaver hearts.

METHODS

Percutaneous posterior mitral annuloplasty has been proposed to treat functional mitral regurgitation on the basis of the proximity of the coronary sinus to the mitral annulus. However, concern remains about the ability to perform a trigone-to-trigone posterior annuloplasty and the potential for compromise of the circumflex coronary artery. Ten hearts were studied after injection of expansible foam into the coronary sinus and circumflex artery. The mitral annulus perimeter, posterior intertrigonal (T1-T2) and intercommissural (C1-C2) distance, and coronary sinus projection on the native annulus (S1-S2) were measured. The spatial geometry of the coronary sinus was correlated with the circumflex artery route and the distance with the native mitral annulus.

RESULTS

The projection of coronary sinus annuloplasty achieves at best a commissure-to-commissure annuloplasty 14.5 (6-24) mm behind each trigone: T1-T2: 74 (56-114) mm, C1-C2: 62.2 (48-80) mm, S1-S2: 59.5 (40-80) mm. The coronary sinus was distant from the native annulus (8-14 mm at the coronary sinus ostium, 13.7-20.4 mm at the middle of the coronary sinus, 6.9-14 mm at the level of the great coronary vein). The circumflex artery was located between the coronary sinus and the mitral annulus in 45.5% of cases.

CONCLUSIONS

This anatomic study highlights the 3-dimensional structure of the coronary sinus and its distance from the native mitral annulus and fibrous trigones. Human anatomic studies are mandatory for the further development of percutaneous mitral repair technology.

Echocardiographic Guidance and Assessment of Percutaneous Repair for Mitral Regurgitation With the Evalve MitraClip: Lessons Learned From EVEREST I

OBJECTIVE

Percutaneous mitral repair is rapidly developing as an alternative to cardiac surgery in select patients. The Evalve percutaneous E2E system uses the MitraClip to replicate the surgical suture-based approach. This procedure requires real-time echocardiographic guidance in a unique and significant collaboration between echocardiographer and interventionalist. transesophageal echocardiography (TEE) is used as the primary imaging modality to guide this procedure and is essential to its success.

METHODS

In EVEREST I, the US multicenter phase I safety and feasibility trial, 47 patients with 3 or 4+ mitral regurgitation (MR) were enrolled. The trial involved a standardized echocardiographic imaging protocol with a standardized anatomic-based vocabulary, predetermined standard TEE views, preprocedural strategy meetings, and display of echocardiographic aids to optimize communication and procedural efficiency during placement of the clip.

RESULTS

TEE guidance facilitated the creation of a double-orifice mitral valve in all 47 patients enrolled (100%), and 40 patients were discharged with 1 or more clips (85%). At discharge, successful placement of a clip and <or= 2+ MR was present in 34 patients (74%). The standardized approach contributed to a reduction in the time to perform the procedure over the course of the trial at both initial and new sites.

CONCLUSIONS

TEE is essential to the guidance of percutaneous MitraClip E2E repair. A streamlined approach to echocardiographic guidance, using predetermined standardized views, a common anatomic-based vocabulary, preprocedural strategy meetings, and a display of echocardiographic aids in the catheterization laboratory shortens the procedure time and allows for efficient percutaneous repair.

Percutaneous mitral valve annuloplasty for ischemic mitral regurgitation: First in man experience with a temporary implant

OBJECTIVE

This study evaluated human feasibility and acute efficacy of a novel percutaneous transvenous mitral annuloplasty (PTMA) device (Viacor) placed temporarily in the coronary sinus (CS): the implant allows in-situ incremental adjustment to optimally reduce the anterior-posterior mitral annulus (MA) dimension, and improve leaflet co-aptation and reducing mitral regurgitation (MR).

BACKGROUND

Surgical annuloplasty remains the standard treatment of severe ischemic MR but its application is limited by high morbidity and mortality. The effectiveness of PTMA device (Viacor) to reduce MR in the short-term has been demonstrated in animals studies but not in humans.

METHODS

Symptomatic patients with ischemic MR graded 2+ to 4+ requiring surgical mitral annuloplasty were screened. Patients with any mitral leaflet or mitral apparatus abnormality were excluded. Preoperatively, under general anesthesia and transesophageal echocardiography guidance, a temporary PTMA device was placed via the right internal jugular or subclavian vein.

RESULTS

Four patients were studied. After device placement and adjustment, regurgitant volume was substantially reduced (45.5 +/- 24.4 to 13.3 +/- 7.3 ml) via MA anterior-posterior diameter reduction (40.75 +/- 4.3 to 35.2 +/- 1.6 mm) in 3 patients. In one patient, the PTMA device could not be deployed due to extreme angulated anatomy.

CONCLUSIONS

PTMA in human is feasible and reduces ischemic MR (to grade 1+) by reducing MA anterior-posterior diameter. Temporary placement of the PTMA device may assist in the development of permanent implants and ensure optimal efficacy.

Current status of percutaneous valvular procedures

OPINION STATEMENT

During the past few decades, percutaneous valvular procedures have been used in mitral and aortic stenosis. Percutaneous mitral commissurotomy, which has virtually replaced surgical commissurotomy in the treatment of mitral stenosis, has been performed since the mid-1980s and has provided good results in thousands of patients worldwide. Percutaneous balloon aortic valvuloplasty has largely been abandoned due to its limited efficacy and the risks involved. New percutaneous procedures are currently being developed in mitral regurgitation and aortic stenosis, which represent the two most frequent valve diseases in industrialized countries. They are in the early stages of development but have opened a very exciting field of investigation. Two percutaneous mitral valve treatment techniques have been used: the edge-to-edge technique and the prosthetic ring annuloplasty. Preliminary series show that they are feasible; however, they need to be further evaluated in comparison with contemporary treatment to accurately assess their effectiveness and the risks involved. Since 2003, percutaneous aortic valve replacement has been performed in approximately 100 compassionate cases with end-stage aortic stenosis, formally declined for surgery. It results in hemodynamic and clinical improvement, with an acceptable risk in this highly selected population. The evaluation of these new percutaneous procedures requires a close collaboration between interventionalists, echocardiographers, engineers, and surgeons. It is probable that they will play an important role in the treatment of valve disease in the future.

Chronic Ischemic Mitral Regurgitation: Repair, Replace or Rethink?

Ischemic mitral regurgitation (IMR) is a common complication of coronary artery disease and is the focus of a rapidly increasing amount of research. Mechanistic studies have determined that IMR is caused by apical displacement and tethering of the mitral valve leaflets after myocardial infarction, resulting in incomplete coaptation. Despite the relatively high prevalence of IMR, most centers have only a small surgical experience with this disorder. The result is that a number of different procedures have been recently developed without clear improvement in patient outcomes. The current review will examine the myriad surgical options for IMR with a focus on clinical outcomes.

Percutaneous transvenous mitral annuloplasty: initial human experience with device implantation in the coronary sinus

BACKGROUND

Mitral annuloplasty is the most common surgical procedure performed for ischemic mitral regurgitation (MR). Surgical mitral annuloplasty is limited by morbidity, mortality, and MR recurrence. We evaluated the safety and feasibility of a transvenous catheter-delivered implantable device to provide a percutaneous alternative to surgical mitral annuloplasty.

METHODS AND RESULTS

Five patients with chronic ischemic MR underwent percutaneous transvenous implantation of an annuloplasty device in the coronary sinus. Implantation was successful in 4 patients. Baseline MR in the entire group was grade 3.0+/-0.7 and was reduced to grade 1.6+/-1.1 at the last postimplantation visit when the device was intact or the last postprocedural visit in the patient in whom the device was not successfully implanted. Separation of the bridge section of the device occurred in 3 of 4 implanted devices and was detected at 28 to 81 days after implantation. There were no postprocedural device-related complications.

CONCLUSIONS

Percutaneous implantation of a device intended to remodel the mitral annulus is feasible. Initial experience suggests a possible favorable effect on MR. Percutaneous transvenous mitral annuloplasty warrants further evaluation as a less invasive alternative to surgical annuloplasty.

Percutaneous closure of prosthetic paravalvular leaks: Case series and review

BACKGROUND

Paravalvular leaks (PVLs) are a well-recognized complication of prosthetic valve replacement. Most are asymptomatic and benign, but some may cause symptoms due to a large regurgitant volume or hemolysis. Medical therapy is palliative, while reoperation carries significant morbidity and mortality. Percutaneous transcatheter closure techniques, now routinely applied in the management of pathological cardiac and vascular communications, may be adaptable to PVL closure, potentially offer symptomatic relief.

METHODS

We reviewed our experience with attempted percutaneous closure of PVLs, using data from medical and procedural records.

RESULTS

Between 2001 and 2004, 14 procedures were performed in 10 patients, all under general anesthesia, with transesophageal and radiographic guidance. Mitral (9) and aortic (1) valve replacements were involved, both mechanical and bioprosthetic. A variety of devices were used, including atrial septal occluders, patent ductus arteriosus occluders, and coils (all of label use). Six had a single procedure, which was technically successful in four: in two, the PVL could not be crossed. Four underwent a second procedure, which was technically successful in three; in one the previously deployed device was dislodged necessitating urgent, but ultimately uneventful, surgical removal and leak repair. One patient had transient severe hemolysis, which resolved after 1 week. At 1-year follow-up (9/10 pts) three had died, five had sustained symptomatic improvement while 1 patient with a residual leak still required regular blood transfusions.

CONCLUSIONS

Percutaneous closure of PVLs is time-consuming but feasible in selected patients, with a reasonable degree of technical and clinical success. A second procedure may be necessary and a variety of complications can occur.

Mechanical Device–Based Methods of Managing and Treating Heart Failure

Despite advances in pharmacological treatments aimed at neurohormonal blockade for heart failure in the setting of left ventricular pump dysfunction, there is still a growing number of patients with advanced symptoms who suffer significant morbidity and mortality. Mechanical stresses and chronic neurohormonal activation conspire to propagate maladaptive ventricular remodeling responsible for the insidious nature of this disease. Recent studies suggest that further pharmacological neurohormonal blockade may not be safe or effective, which has driven development of devices for this patient population. Furthermore, such devices may target fundamental pathophysiological abnormalities that are largely hemodynamic and mechanical in nature that are not addressed by available pharmacological agents. The profound reverse remodeling routinely associated with left ventricular assist device use, reviewed in detail, further validates device-based approaches and should inspire research to find ways to make this recovery more complete and permanent. Accordingly, this review focuses on the multitude of mechanical device–based approaches currently being investigated to manage and treat this population. From devices for monitoring patient status to anticipate congestive heart failure exacerbations and preemptively adjust therapy to devices to support preterminal patients with end-stage disease, it is recognized that these device-based approaches will assume an increasingly important role in treating the growing number of patients with advanced heart failure.

Percutaneous valve procedures: what is the future?

PURPOSE OF REVIEW

Since its introduction 27 years ago by Andreas Gruntzig, interventional cardiology has expanded its scope from coronary disease to peripheral, congenital, and also valve diseases.Percutaneous mitral commissurotomy and aortic valvuloplasty have been performed since the mid 1980s. Balloon commissurotomy has been used in tens of thousands of patients worldwide and provides good short- and long-term results in a wide range of patients. It has virtually replaced surgical commissurotomy in the management of mitral stenosis. On the other hand, percutaneous aortic valvuloplasty is almost abandoned worldwide due to its lack of efficacy and the risks involved.

RECENT FINDINGS

The new techniques of percutaneous valve intervention are aortic valve replacement, and mitral valve repair. Both are at an early stage since the first in-man applications only started in 2002. Preliminary series show that these techniques are feasible; however, they must be further evaluated in comparison with contemporary treatment to accurately assess efficacy and risks. Today potential applications concern high-risk patients, however, after thorough evaluation this may be extended to others in the future.

SUMMARY

Therefore, percutaneous interventions already play an important role in management of valvular heart disease, which is likely to grow in the future.

Techniques for percutaneous closure of prosthetic paravalvular leaks

Percutaneous transcatheter closure techniques are now routinely applied in the management of atrial and ventricular septal defects, patent ductus arteriosus, and other pathological cardiac and vascular communications. Recently, these same techniques have been applied to paravalvular defects. Reports are few; success variable and techniques vary widely. We review the current considerations and techniques of percutaneous transcatheter closure of paravalvular leaks.

[Percutaneous correction of acquired aortic stenosis and mitral insufficiency in adults]

Aortic stenosis and mitral regurgitation are the most common valvular diseases in western countries. Surgical treatment, aortic valve replacement or mitral valve repair, is the treatment of choice. Innovative technologies could offer an alternative therapeutic option to the patients with increased operative risk. This article will report the early experience with these promising techniques as presented at the High-Tech 2004 meeting.

Acetyl-coenzyme A synthetase (AMP forming)

Acetyl-coenzyme A synthetase (AMP forming; Acs) is an enzyme whose activity is central to the metabolism of prokaryotic and eukaryotic cells. The physiological role of this enzyme is to activate acetate to acetyl-coenzyme A (Ac-CoA). The importance of Acs has been recognized for decades, since it provides the cell the two-carbon metabolite used in many anabolic and energy generation processes. In the last decade researchers have learned how carefully the cell monitors the synthesis and activity of this enzyme. In eukaryotes and prokaryotes, complex regulatory systems control acs gene expression as a function carbon flux, with a second layer of regulation exerted posttranslationally by the NAD+/sirtuin-dependent protein acetylation/deacetylation system. Recent structural work provides snapshots of the dramatic conformational changes Acs undergoes during catalysis. Future work on the regulation of acs gene expression will expand our understanding of metabolic integration, while structure/function studies will reveal more details of the function of this splendid molecular machine.