Novel suture device for beating-heart mitral leaflet approximation

A novel user-friendly transcatheter edge-to-edge mitral valve repair device in a porcine model

OBJECTIVES

The present study was performed to evaluate the feasibility and safety of the ValveClamp system for transcatheter edge-to-edge mitral valve repair in a porcine model.

BACKGROUND

The ValveClamp system is a novel, transapically delivered edge-to-edge mitral valve repair system designed for ease of operation.

METHODS

Thirteen young adult swine were enrolled in the study. The procedure was performed via the transapical approach under epicardial echocardiography guidance.

RESULTS

The acute procedure success rate was 92.3% (12/13). The catheter manipulation time was just 18.5 ± 8.2 min. Four pigs were explanted on the 14th day after the procedure. One pig died at the 20th day because of pneumonia. The other eight pigs lived to the study endpoint (140 days). No pig had severe mitral valve dysfunction. The gross observation showed that the clamp device was securely attached and created a double-orifice mitral valve in all pigs except the failed one. In the eight pigs living to the endpoint, the clamp device was noted to be completely endothelialized. None of the 13 pigs developed infective endocarditis, thrombosis, thromboembolism, or valve impairment. In two pigs for which mitral regurgitation (MR) was created, the degree of MR was reduced from severe to trace after the device implantation.

CONCLUSIONS

It was feasible and safe to use ValveClamp to perform a catheter-mediated edge-to-edge mitral valve repair in a porcine model. This system is potentially applicable as a novel user-friendly system for the treatment of MR.

Functional and Biomechanical Effects of the Edge-to-Edge Repair in the Setting of Mitral Regurgitation: Consolidated Knowledge and Novel Tools to Gain Insight into Its Percutaneous Implementation

Mitral regurgitation is the most prevalent heart valve disease in the western population. When severe, it requires surgical treatment, repair being the preferred option. The edge-to-edge repair technique treats mitral regurgitation by suturing the leaflets together and creating a double-orifice valve. Due to its relative simplicity and versatility, it has become progressively more widespread. Recently, its percutaneous version has become feasible, and has raised interest thanks to the positive results of the Mitraclip(®) device. Edge-to-edge features and evolution have stimulated debate and multidisciplinary research by both clinicians and engineers. After providing an overview of representative studies in the field, here we propose a novel computational approach to the most recent percutaneous evolution of the edge-to-edge technique. Image-based structural finite element models of three mitral valves affected by posterior prolapse were derived from cine-cardiac magnetic resonance imaging. The models accounted for the patient-specific 3D geometry of the valve, including leaflet compound curvature pattern, patient-specific motion of annulus and papillary muscles, and hyperelastic and anisotropic mechanical properties of tissues. The biomechanics of the three valves throughout the entire cardiac cycle was simulated before and after Mitraclip(®) implantation, assessing the biomechanical impact of the procedure. For all three simulated MVs, Mitraclip(®) implantation significantly improved systolic leaflets coaptation, without inducing major alterations in systolic peak stresses. Diastolic orifice area was decreased, by up to 58.9%, and leaflets diastolic stresses became comparable, although lower, to systolic ones. Despite established knowledge on the edge-to-edge surgical repair, latest technological advances make its percutanoues implementation a challenging field of research. The modeling approach herein proposed may be expanded to analyze clinical scenarios that are currently critical for Mitraclip(®) implantation, helping the search for possible solutions.

Minimally invasive heart valve surgery: already established in clinical routine?

Cardiac valve replacement with the need for open heart surgery still has the highest morbidity and mortality rates among routine cardiac surgery, with the exception of aortic aneurysm repair and surgery for congenital heart defects. Reducing invasiveness is a desirable goal, and different strategies and approaches have been used to achieve this with valve repair or replacement less invasive. Despite the good results reported with minimally invasive techniques, time on extracorporal circulation is always longer compared with the conventional procedures. Since these techniques do not reduce real invasiveness but rather improve the cosmetic results, minimal-access surgery would be a better nomenclature. With the exception of patients at a high risk for sternal infections or redo heart operations, a reduction in postoperative morbidity by the avoidance of a median sternotomy is not yet definitely proven. Meanwhile, most surgeons comply with the demand for minimally invasive surgery posed by patients by reducing the length of the incision in aortic valve replacement and by using a right anterolateral approach with a limited incision for mitral valve operations. However, the use of endoscopic or robotic devices is limited to a few centers, and has not yet found its way into clinical routine. Nonetheless, minimally invasive or minimal-access surgery is now established in many centers, and patients should always be informed of these techniques. When this information is provided objectively and patient selection is carried out accurately, these alternative approaches can help to improve postoperative convalescence.

Multimodality imaging in interventional cardiology

'Multimodality' imaging--the side-by-side interpretation of data obtained from various noninvasive imaging techniques, such as echocardiography, radionuclide techniques, multidetector CT (MDCT), and MRI--allows anatomical, morphological, and functional data to be combined, increases diagnostic accuracy, and improves the efficacy of cardiovascular interventions and clinical outcomes. During the past decade, advances in software and hardware have allowed co-registration of various imaging modalities, resulting in cardiac 'hybrid' or 'fusion' imaging. In this Review, we discuss the roles of both multimodality and hybrid imaging in three broad areas of cardiology--coronary artery disease (CAD), heart failure, and valvular heart disease. In the evaluation of CAD, integration of either single-photon emission computed tomography (SPECT) or PET with CT coronary angiography provides both morphological and functional data in a single procedure. Accordingly, the functional consequences (myocardial hypoperfusion on SPECT or PET) of anatomical pathology (coronary anatomy on MDCT or MRI) can be assessed. Co-registration of PET and MRI data sets to provide cellular and molecular information on plaque composition and stability is now possible. Furthermore, novel imaging modalities have been implemented to guide electrophysiological and transcatheter-based procedures, such as cardiac resynchronization therapy (an established treatment for patients with heart failure), and transcatheter valve repair or replacement procedures.

Mitral Valve Repair: Past, Present, and Future

Mitral valve repair is the operation of choice for mitral valve regurgitation, with appropriate selection. Studies have shown that mitral repair is associated with a decrease in both long-term thromboembolic complications and mortality. Since its initial description, various selection criteria and techniques of mitral valve repair have been discussed in the literature. This review serves as a synopsis of the previous achievements, present status, and possible future directions of mitral valve repair, specifically from an Asian perspective. Vast experience has been amassed in understanding mitral valve pathophysiology, and excellent surgical treatments for mitral regurgitation have been developed. With the efforts of pioneers in the field of mitral valve repair, standard surgical treatment strategies have been proven to restore the life-expectancy of patients with degenerative mitral regurgitation to that of the age-adjusted population. Minimally invasive techniques of mitral valve repair further reduce access trauma, and could potentially benefit patients previously excluded from conventional surgery.

The pre-clinical animal model in the translational research of interventional cardiology

Scientific discoveries for improvement of human health must be translated into practical applications. Such discoveries typically begin at "the bench" with basic research, then progress to the clinical level. In particular, in the field of interventional cardiology, percutaneous cardiovascular intervention has rapidly evolved from an experimental procedure to a therapeutic clinical setting. Pre-clinical studies using animal models play a very important role in the evaluation of efficacy and safety of new medical devices before their use in human clinical studies. This review provides an overview of the emerging role, results of pre-clinical studies and development, and evaluation of animal models for percutaneous cardiovascular intervention technologies for patients with symptomatic cardiovascular disease.

Advances in percutaneous treatment for adult valvular heart disease

Valvular heart disease occurs in 2-3% of the general population with an increase in prevalence with advancing age. The aetiology of valvular heart disease has evolved in recent decades with degenerative aortic and mitral valve disease supplanting rheumatic heart disease as a primary cause. The common valve lesions to be discussed in this article are aortic stenosis and mitral regurgitation. The traditional approach to calcific aortic stenosis when either symptoms or left ventricular impairment develops is surgical aortic valve replacement and it remains a treatment with excellent outcomes. In recent years there has been interest in less invasive approaches, including percutaneous and transapical aortic valve implantation. With refinements in technology these approaches are becoming a potential treatment option, primarily for high-risk patients who may otherwise be unsuitable for traditional open surgical treatment. Catheter-based approaches for mitral valve disease are also evolving. Mitral regurgitation may often be the result of mitral annular dilatation seen in patients with an enlarged left ventricle or left atrium. Percutaneous implantation of a constricting device in the coronary sinus, which lies in close proximity to the mitral annulus, results in a change to the geometry of the mitral valve and reduced regurgitation. Another technique in patients with degenerative mitral regurgitation is the endovascular edge-to-edge repair in which coaptation of the mitral valve leaflets can be improved with a percutaneously deployed clip. Small patient series indicate that these new techniques are promising. As such, advances in percutaneous interventional and surgical approaches have the potential to further improve outcomes for selected patients with valvular heart disease.

Transcatheter cardiac valve interventions

Currently aortic valve replacement is performed for patients with severe aortic stenosis and symptoms or objective pathophysiologic consequences such as left ventricular dysfunction. For transcatheter mitral valve interventions, the complex pathophysiology of mitral regurgitation with varying causes along with challenging imaging and delivery issues has led to slower than anticipated clinical introduction. Transcatheter pulmonary valve intervention was primarily designed to treat the difficult problem of right ventricular to pulmonary artery conduit stenosis in the congenital population. These techniques are reviewed in this article.

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.

The role of the out-of-operating room anesthesiologist in the care of the cardiac patient

Modern invasive cardiovascular procedures require patients to be both comfortable and cooperative. In addition, these procedures demand the complete attention of the attending cardiovascular specialist, and, to a large degree, the outcomes of these procedures depend on the amount of focus and concentration the cardiovascular specialist can give to performing the procedure itself. A team approach using the specialized skills of a cardiologist and an anesthesiologist frequently is required to optimize results. This article clearly delineates the procedures cardiologists perform that might involve anesthesiologists. Mutual knowledge, understanding, and respect are fundamental requirements for integration of cardiology and anesthesia services to optimize patient outcomes.

Effect of Chronotropy and Inotropy on Stitch Tension in the Edge-to-Edge Mitral Repair

Background— Our prior studies suggest that mitral annular septal-lateral (SL) diameter is the chief determinant of “Alfieri stitch” tension, but hemodynamic parameters may also play a role. We approximated the central edge of the mitral leaflets with a miniature force transducer to measure tension (T) at the leaflet approximation point during inotropic and chronotropic stimulation.

Methods and Results— Eight sheep were studied under open-chest conditions immediately after surgical placement of a miniature force transducer to approximate the leaflets and implantation of radiopaque markers on the LV and mitral annulus (MA). Chronotropic stimulation was induced with atrial pacing at 130 minutes −1 (n=5) whereas inotropic state was increased with IV CaCl 2 bolus (n=8). Hemodynamic data, stitch tension, and 3-D marker coordinates were obtained throughout the cardiac cycle before and during each intervention. Peak stitch tension (T MAX ) under all conditions was observed in diastole and temporally correlated with peak annular SL (SL MAX ) size. Atrial pacing did not change peak transducer tension or annular size. Calcium infusion also did not alter peak transducer tension (0.29±0.11 versus 0.32±0.10 N; P =NS) and only slightly reduced SL dimension (29.9±3.3 versus 29.3±3.5 mm; P <0.05).

Conclusion— Isolated increase in heart rate or inotropic state did not alter peak stitch tension whereas enhanced contractile state decreased SL diameter minimally. These data, combined with those from our previous study, suggest that geometric (SL diameter) rather than hemodynamic parameters are the main determinants of “Alfieri stitch” tension. This implies that any interventional or surgical edge-to-edge repair performed without concomitant annular reduction to limit the SL dimension could expose the leaflet junction to forces which could limit repair durability.

Aortic valve surgery: what is the future?

Modern surgical treatment for aortic valve disease has undergone significant improvements in all areas of this procedure. Successful treatment strategies for cardiovascular diseases have often been initiated and driven by surgeons. Radical excision of diseased tissue, repair and replacement strategies lead to long-term successful treatment of the underlying diseases and clearly improved patient outcome. In highly developed nations, valve surgery will be increasing applied in older people, with more co-morbidities and a higher incidence of concomitant coronary artery disease. Cardiovascular surgeons will be facing increased competition from the catheter-based procedures; these are already applied clinically, and their numbers will rise in near future. Right now interventional cardiologists supported by some cardiac surgeons are on their way to transform some conventional open surgical procedures into catheter-based less invasive interventions, such as valve repair and replacement. Cardiovascular surgery is undergoing a rapid transformation; socio-economic factors and recent advances in medical technology contribute to these changes. Further developments will come, and surgeons with all their expertise in the treatment of valvular heart disease need to be part of it. Cardiovascular surgeons have to adapt the exciting new approaches of transapical and transfemoral transcatheter valve implantation techniques.

Proceedings of TCT: current status of catheter-based mitral valve repair therapies

A variety of advances have recently facilitated development of methods to treat mitral regurgitation using catheter techniques via the percutaneous route. These include placing devices into the coronary sinus to support the mitral annulus and direct percutaneous leaflet repair. These approaches are already attractive for use in older patients and will hopefully make treatments available to many with no current options.

Beating-heart percutaneous mitral valve repair using a transcatheter endovascular suturing device in an animal model

BACKGROUND

The edge-to-edge (Alfieri) technique for mitral valve repair is a versatile method of treating mitral insufficiency. Because of its simplicity, it has been applied in minimally invasive surgery, and recently, in the design of endovascular closed-heart devices.

AIM

The purpose of this study was to evaluate the acute in-vivo safety and feasibility of a novel percutaneous mitral valve repair system based on Alfieri technique in an animal model.

METHODS

Under general anesthesia, 11 pigs (90-100 kgs), underwent percutaneous Alfeiri procedure. The right femoral vein was punctured and the mitral valve was approached via a standard transeptal puncture. Combined intracardiac echo and fluoroscopic guidance was used. The procedure included: the positioning of a guide catheter for multiple access to the left atrium and for directing devices; the use of a therapy device to capture the free edge of the mitral valve leaflets using vacuum, and to deliver the suture to the valve and finally the fixation with a Nitinol suture clip, and trimming of the suture with a fastener catheter.

RESULTS

Leaflet capture, suture placement, and suture-clip deployment was successful in all 11 animals. There were no acute cardiac or access site complications. Procedural time (from wire in left atrium to completion of the procedure was 18 +/- 9 min (range 9-30 min). Blood loss was 67 +/- 44 ml (range 0-125 ml). A double orifice configuration was visible by echocardiography at the end of the procedure in all animals.

CONCLUSION

This acute animal study demonstrated the feasibility of a beating heart percutaneous Alfieri procedure in a non-diseased porcine valve using an endovascular suturing device to safely access the mitral valve, place a stitch through the mitral valve leaflets, and deploy a suture-clip that reproduces the surgical technique. Clinical application of this device in humans needs to be evaluated.

Percutaneous Treatment of Valvular Heart Disease: Catheter‐Based Aortic Valve Replacement and Mitral Valve Repair Therapies

Until recently, percutaneous catheter therapy for valvular heart disease was limited to catheter balloon valvuloplasty for aortic, mitral, or pulmonic stenosis. A number of new approaches to percutaneous valve therapy are now developing rapidly, including methods for catheter-based valve replacement and repair. Stent-mounted valve prostheses have been successfully implanted in the pulmonic and aortic positions. These devices have been constructed using pericardial valve leaflets mounted inside balloon-expandable or self-expanding stents and have been used in patients who are high risk for valve replacement surgery. Percutaneous valve repair is also being developed for mitral regurgitation. Direct leaflet repair and percutaneous annuloplasty are being employed in clinical trials. All the percutaneous approaches are based on existing surgical techniques and offer less invasive alternatives. The era of percutaneous valve therapy has clearly arrived, and ongoing trials will define the clinical role for these new therapies.

Percutaneous Mitral Valve Repair

Surgical mitral valve repair is the procedure of choice to treat mitral regurgitation of all etiologies. Whereas annuloplasty is the cornerstone of mitral valve repair, a variety of other surgical techniques are utilized to correct dysfunction of the leaflets and subvalvular apparatus; in most cases, surgical repair entails application of multiple repair techniques in each patient. Preclinical studies and early human experience have demonstrated that some of these surgical repair techniques can be performed using percutaneous approaches. Specifically, there has been great progress in the development of novel technology to facilitate percutaneous annuloplasty and percutaneous edge-to-edge repair. The objectives of this report were to (1) discuss the surgical foundations for these percutaneous approaches; (2) review device design and experimental and clinical results of percutaneous valve repair; and (3) address future directions, including the key challenges of patient selection and clinical trial design.

Future of transcatheter repair of the mitral valve

Percutaneous mitral valve repair is under investigation as a novel method to treat mitral valve insufficiency with a catheter-based, closed-heart, nonsurgical approach. Two techniques of mitral valve reconstruction have been adapted from surgery to the percutaneous approach: edge-to-edge repair and annuloplasty. The devices that have been developed to perform these 2 procedures are described, and preliminary clinical experience is presented. Expectations for the future are discussed.

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.

Percutaneous aortic valve replacement and mitral valve repair

For mitral regurgitation and aortic valve disease warranting replacement, the surgical approach has been the mainstay therapy since the 1960s. Technological advances have provided potentially less invasive alternatives to surgery. Novel catheter-based techniques include aortic valve replacement with a valved stent, and devices aimed at reconfiguring the annulus or approximating a portion of the leaflets for mitral regurgitation. The main considerations regarding aortic valved stents include device anchoring and orientation, potential restriction of coronary flow, optimal method of delivery, ideal leaflet material, stent characteristics, and valve durability. The catheter-based approaches to mitral regurgitation are undergoing further experimental and clinical evaluations, and its success will be partially dependent on a thorough understanding of the underlying valvular pathology. Patient selection will be a critical component in the long-term efficacy of these new therapies. Close collaboration among the cardiovascular specialists and biomedical engineers will enable the development of safe and effective devices.

Beating Heart Catheter-Based Edge-to-Edge Mitral Valve Procedure in a Porcine Model

Background— Surgical edge-to-edge repair has been used in the treatment of mitral regurgitation. We evaluated the ability of a catheter-delivered clip (Evalve, Inc) to achieve edge-to-edge mitral valve approximation without cardiopulmonary bypass and the healing response of this technique.

Methods and Results— Twenty-one pigs underwent general anesthesia and left thoracotomy. A 10F flexible delivery catheter with a clip was placed into the left atrium. With echocardiographic and fluoroscopic guidance, the clip grasped and approximated the mid portion of the anterior and posterior leaflets. After a double orifice had been confirmed, the clip was detached and the catheter withdrawn. All animals survived and had successful clip placement. Three animals were euthanized at 4 weeks, 9 at 12 weeks, 1 at 17 weeks, 7 at 24 weeks, and 1 at 52 weeks. The clip was well positioned, with leaflet approximation in all animals except 1, in which the clip separated from the posterior leaflet at 4 weeks without affecting valve function. The clip was modified and implanted in 4 pigs; all were intact at 12 to 24 weeks. Scanning electron microscopy showed clip encapsulation with complete endothelialization. Mitral stenosis and thromboembolism did not develop. Two animals developed endocarditis (1 at 12 weeks and 1 at 17 weeks). Progressive healing occurred in all other animals.

Conclusions— Edge-to-edge mitral valve approximation can be successfully and reliably achieved with a catheter-delivered clip without cardiopulmonary bypass, resulting in durable healing. The success of this device supports the development of a percutaneous catheter-based system for mitral valve repair.

Midterm results of edge-to-edge mitral valve repair without annuloplasty

OBJECTIVE

Edge-to-edge mitral valve repair is usually performed in association with annuloplasty, with rare exceptions. We retrospectively analyzed the results of ringless edge-to-edge repair, particularly in view of minimally invasive and percutaneous approaches.

METHODS

From November 1993 to December 2001, 81 patients underwent edge-to-edge mitral repair without associated annuloplasty. The cause was degenerative in most patients. In 32 patients the annulus was severely calcified. Type I lesions were present in 6 patients, type II lesions in 60 patients, and type III lesions in 15 patients. A double-orifice repair was done in 69 patients, and paracommissural repair was done in 12 patients. In 5 patients edge-to-edge repair was used as a rescue procedure.

RESULTS

There were 3 hospital and 4 late deaths, for a 4-year survival of 85% +/- 6.7%. At latest follow-up, 63 patients were in New York Heart Association classes I or II, and 9 patients were in classes III or IV. Nine patients required reoperation (89% +/- 3.9% overall freedom from reoperation at 4 years). Annular calcification was associated with a greater reoperation rate (77% +/- 22% vs 95% +/- 4.6% freedom from reoperation, P =.03). Intraoperative water testing and postrepair transesophageal echocardiography predicted late failure. Only 1 of 42 patients required reoperation in the follow-up period when annular calcification, rheumatic disease, or rescue procedure were not present as risk factors.

CONCLUSIONS

Our data confirm overall suboptimal results of the edge-to-edge technique when annuloplasty is not added to the repair. Annular calcification, rheumatic cause, and edge-to-edge repair done as a rescue procedure were associated with the worst outcome. Midterm results in selected patients encourage future developments in catheter-based edge-to-edge procedures.

Feasibility and Short-Term Efficacy of Percutaneous Mitral Annular Reduction for the Therapy of Heart Failure-Induced Mitral Regurgitation

Background— Mitral regurgitation (MR) frequently accompanies congestive heart failure (CHF) and is associated with poorer prognosis and more significantly impaired symptomatic status. Although surgical mitral valve annuloplasty has the potential to offer benefit, concerns about the combined surgical risk and possible effects on ventricular performance have limited progress. We evaluated the feasibility and short-term efficacy of a novel device placed in the coronary sinus to reduce MR in the setting of CHF.

Methods and Results— CHF and MR were induced in 9 adult sheep by rapid ventricular pacing for 5 to 8 weeks. A mitral annular constraint device was implanted percutaneously through the right internal jugular vein in the coronary sinus and great cardiac vein to create a short-term stable reduction (24.9±2.5%) in the mitral annular septal-lateral dimension as assessed echocardiographically. Right and left heart pressures and cardiac output were determined before and 15 minutes after device implantation. MR extent was examined echocardiographically and expressed as a ratio of left atrial area (MR/LAA). After device placement, MR was substantially reduced from an MR/LAA of 42+6% to 4±3% ( P <0.01). In association, mean pulmonary wedge pressure was significantly reduced (26±3 to 18±3 mm Hg; P <0.01) and mean cardiac output significantly increased (3.4±0.3 to 4.3±0.4 L/min; P =0.01).

Conclusions— In this model of CHF, percutaneous placement of a mitral annular constraint device in the coronary sinus resulted in the short-term elimination or minimization of MR and was accompanied in the short term by favorable hemodynamic effects.