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

Transcatheter Coronary Sinus Interventions

The coronary sinus has become a popular route for an increasing number of innovative transcatheter interventions to treat coronary and structural heart diseases. However, interventional cardiologists have limited experience with the cardiac venous system and its highly variable anatomy. In this paper, we review the anatomy of the cardiac veins as it relates to transcatheter interventions. We also provide a contemporary overview of the emerging coronary sinus-based transcatheter therapies and their growing literature.

Anatomical considerations of percutaneous transvenous mitral annuloplasty: a novel procedure for treatment of functional mitral regurgitation

Percutaneous transvenous mitral annuloplasty (PTMA) has evolved as a latest procedure for the treatment of functional mitral regurgitation. It reduces mitral valve annulus (MVA) size and increases valve leaflet coaptation via compression of coronary sinus (CS). Anatomical considerations for this procedure were elucidated in the present study. In 40 formalin fixed adult cadaveric human hearts, relation of the venous channel formed by CS and great cardiac vein (GCV) to MVA and the adjacent arteries was described, at 6 points by making longitudinal sections perpendicular to the plane of MVA, numbered 1-6 starting from CS ostium. CS/GCV formed a semicircular venous channel on the atrial side of MVA. Based on the distance of CS/GCV from MVA, two patterns were identified. In 37 hearts, the venous channel at point 2 was widely separated from the MVA compared to the two ends and in three hearts a nonconsistent pattern was observed. GCV crossed circumflex artery superficially. GCV or CS crossed the left marginal artery and ventricular branches of circumflex artery superficially in 17 and 23 hearts, respectively. As the venous channel was related more to the left atrial wall, PTMA devices probably exert an indirect traction on MVA. The arteries crossing deep to the venous channel may be compressed by PTMA device leading to myocardial ischemia. Knowledge of the spatial relations of MVA and a preoperative and postoperative angiogram may help to reduce such complications during PTMA.

Mitral valve repair over five decades

It has become evident that mitral valve (MV) repair is the preferable treatment for the majority of patients presenting with severe mitral regurgitation (MR). This success clearly testifies that the surgical procedure is accessible, reproducible and is carrying excellent long-lasting results. From the pre-extracorporeal circulation's era to the last percutaneous approaches, a large variety of techniques have been proposed to address the different features of MV diseases. This article aimed at reviewing chronologically the development of these dedicated techniques through their origins and the debates that they generated in the literature.

A Technical Review of Minimally Invasive Mitral Valve Replacements

Mitral regurgitation is one of the most common forms of heart valve disorder, which may result in heart failure. Due to the rapid ageing of the population, surgical repair and replacement treatments, which have represented an effective treatment in the past, are now unsuitable for about half of symptomatic patients, who are judged high-risk. Encouraged by the positive experience with transcatheter aortic valves and percutaneous reconstructive mitral treatments, a number of research groups are currently engaged in the development of minimally invasive approaches for the functional replacement of the mitral valve. The first experiences have clearly demonstrated that the approach is feasible and promising, though significant progress is still required in the prostheses design and implantation procedures before the treatment can establish as a safe and effective solution. This review analyses the devices currently at a most advanced stage of development, describing their main features and the technical solutions that they adopt in order to respond to the functional requirements of the most challenging of the heart valves.

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.

Material properties of aged human mitral valve leaflets

This study aimed to characterize the mechanical properties of aged human anterior mitral leaflets (AML) and posterior mitral leaflets (PML). The AML and PML samples from explanted human hearts (n = 21, mean age of 82.62 ± 8.77-years-old) were subjected to planar biaxial mechanical tests. The material stiffness, extensibility, and degree of anisotropy of the leaflet samples were quantified. The microstructure of the samples was assessed through histology. Both the AML and PML samples exhibited a nonlinear and anisotropic behavior with the circumferential direction being stiffer than the radial direction. The AML samples were significantly stiffer than the PML samples in both directions, suggesting that they should be modeled with separate sets of material properties in computational studies. Histological analysis indicated the changes in the tissue elastic constituents, including the fragmented and disorganized elastin network, the presence of fibrosis and proteoglycan/glycosaminoglycan infiltration and calcification, suggesting possible valvular degenerative characteristics in the aged human leaflet samples. Overall, stiffness increased and areal strain decreased with calcification severity. In addition, leaflet tissues from hypertensive individuals also exhibited a higher stiffness and low areal strain than normotensive individuals. There are significant differences in the mechanical properties of the two human mitral valve leaflets from this advanced age group. The morphologic changes in the tissue composition and structure also infer the structural and functional difference between aged human valves and those of animals.

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.

Characterization of aortic tissue cutting process: experimental investigation using porcine ascending aorta

Understanding biomechanical responses during soft tissue cutting is important for developing surgical simulators and robot-assisted surgery with haptic feedback. The biomechanics involved in the aortic tissue cutting process is largely unknown. In this study, porcine ascending aorta was selected as a representative aortic tissue, and tissue cutting experiments were performed using a novel tissue cutting apparatus. The tissue cutting responses under various cutting conditions were investigated, including differing initial tissue lateral holding force and distance, cutting speed, cutter inclination angle, tissue anatomical orientation and thickness. The results from this study suggest that a "break-in" cutting force of about 4-12 N, a cutter "break-in" distance of 5-15 mm, and a continuous cutting force of 2-4 N were needed to cut through the porcine ascending aorta tissue. For all testing conditions investigated in this study, the cutting force vs. the cutter displacement curves exhibited similar characteristics. More importantly, this study demonstrated that tissue cutting involving one or more of the following conditions: a larger lateral holding force, a smaller lateral hold distance, a higher cutting speed or a larger inclination angle, could result in a smaller "break in" cutting force and a smaller "break-in" distance. In addition, it was found that the cutting force in the vessel longitudinal direction was larger than that in the circumferential direction. There was a strong correlation between the tissue thickness and the cutting force. The experimental results reported in this study could provide a basis for understanding the characteristic response of aortic tissue to scalpel cutting, and offer insight into the development of surgical simulators.

Mitral valve surgery for dilated cardiomyopathy: current status and future roles

There are a large number of patients with functional mitral regurgitation resulting from dilated cardiomyopathy. The decision between surgical correction and medical management of severe mitral regurgitation in heart failure can be difficult. The data regarding long-term benefits and mortality after surgical intervention are contradictory. Recent data suggest that mitral regurgitation can be surgically corrected in heart failure with symptomatic improvements and beneficial reverse remodeling. Contrary to prior beliefs, mitral valve repair can be performed safely with minimal postoperative mortality. Data from multi-institutional, randomized prospective trials will help to elucidate many of the questions and concerns regarding repair of severe functional mitral regurgitation.

Comparison of biaxial mechanical properties of coronary sinus tissues from porcine, ovine and aged human species

Due to its proximity to the mitral valve, the coronary sinus (CS) vessel serves as a conduit for the deployment and implantation of the percutaneous transvenous mitral annuloplasty (PTMA) devices that can potentially reduce the mitral regurgitation. Because CS vessel is a venous tissue and seldom diseased, its mechanical properties have not been well studied. In this study, we performed a multi-axial mechanical test and histological analysis to characterize the mechanical and structural properties of the aged human, porcine and ovine CS tissues. The results showed that the aged human CS tissues exhibited much stiffer and highly anisotropic behaviors compared to the porcine and ovine. Both of the porcine and ovine CS vessel walls were thicker and mainly composed of striated muscle fibers (SMF), whereas the thinner aged human CS had higher collagen, less SMF, and more fragmented elastin fibers, which are possibly due to aging effects. We also observed that the anatomical features of porcine CS vessel might be not suitable for PTMA deployment. These differences between animal and human models raise questions for the validity of using animal models to investigate the biomechanics involved in the PTMA intervention. Therefore, caution must be taken in future studies of PTMA stents using animal models.

Percutaneous approaches to mitral valve regurgitation

Mitral regurgitation is a common problem associated with significant morbidity and mortality. Mitral valve surgery has been the treatment of choice for symptomatic patients with severe mitral regurgitation or asymptomatic patients with high-risk clinical features. However, a significant number of patients remain untreated related mainly due to a projected high surgical risk. Therefore, alternative percutaneous treatments including indirect annuloplasty, which takes advantage of the coronary sinus, and direct annuloplasty have recently been explored. Most recently, promising results of the first randomized trial comparing conventional mitral valve surgery to percutaneous therapy with a clip creating a double orifice much like the surgical Alfieri approach have been presented. Finally, percutaneous mitral valve replacement in an animal model has been pursued. This review serves to familiarize the reader with some anatomical concepts and devices for percutaneous mitral repair.

Is there a role for surgeons in transcatheter mitral valve procedures?

PURPOSE OF REVIEW

The rapid advancement in transcatheter therapies seeks to provide less invasive options compared with conventional surgery in the treatment of acquired valvular heart disease. A number of transcatheter mitral valve devices using a variety of approaches for the treatment of mitral regurgitation are under development or in early clinical application. Although yet to be clearly defined, there is no doubt that transcatheter mitral valve procedures will have a significant role alongside conventional surgery. The question is: will surgeons, who have led the treatment of mitral valve disease for the past 30 years, have a role in these procedures?

RECENT FINDINGS

In order to answer this question, this review discusses key understanding of mitral valve anatomy, function and disorder required to perform transcatheter mitral valve interventions. It assesses the potential role of transcatheter therapies with particular reference to percutaneous edge-to-edge repair using the Mitraclip system (Abbott Vascular Devices, California, USA). The new era in collaboration between surgeons and cardiologists is discussed and the potential role of the surgeon in percutaneous mitral valve procedures is examined.

SUMMARY

Transcatheter mitral valve procedures demand increasing collaboration between cardiologists and surgeons in order to achieve optimal outcomes. Interventional cardiologists will require dedicated training in the specialized field of transcatheter interventions in acquired structural heart diseases. As the delivery of such therapies brings the interface between interventional cardiology and cardiac surgery ever closer, there is the potential for a niche area in cardiac surgery to develop comprising minimally invasive surgical and transcatheter skills.

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.

Advances in mitral valve repair

The results of mitral valve repair for structural disease are durable and are generally accepted to be superior to mitral valve replacement. Following the early pioneering work of Carpentier, most advances in mitral repair have involved performing the same repair through ever smaller incisions in hopes of minimizing tissue trauma. Mitral repair is now possible thru port access with videoscopic and robotic assistance. Transcatheter repair techniques are now being investigated and offer the possibility of mitral repair without the utilization of cardiopulmonary bypass.

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.

Acute outcomes of MitraClip therapy for mitral regurgitation in high-surgical-risk patients: emphasis on adverse valve morphology and severe left ventricular dysfunction

AIMS

We sought to assess the feasibility of catheter-based mitral valve repair using the MitraClip system in high-surgical-risk patients with mitral regurgitation (MR) > or =grade 3+.

METHODS AND RESULTS

MitraClip therapy was performed in 51 consecutive patients [73 +/- 10 years; 34 (67%) men] with symptomatic functional [n = 35 (69%)] or organic MR [n = 16 (31%)]. Mean logistic EuroSCORE was 29 +/- 22%; Society of Thoracic Surgeons score was 15 +/- 11. Left ventricular (LV) ejection fraction was 36 +/- 17%. In 35 patients (69%), adverse mitral valve morphology and/or severe LV dysfunction were present. MitraClip implantation was successful in 49 patients (96%). Most patients [n = 34/49 (69%)] were treated with a single clip, whereas 14 patients (29%) received two clips and one patient received three clips. Mean device and fluoroscopy times were 105 +/- 65 min and 44 +/- 28 min, respectively. Procedure-related reduction in MR severity was one grade in 16 patients (31%), two grades in 24 patients (47%), and three grades in 9 patients (18%). Forty-four of the 49 successfully treated patients (90%) showed clinical improvement at discharge [NYHA functional class > or =III in 48 patients (98%) before and 16 patients (33%) after the procedure (P < 0.0001)]. There were no procedure-related major adverse events and no in-hospital mortality.

CONCLUSION

Mitral valve repair using the MitraClip system was shown to be feasible in patients at high surgical risk primarily determined by an adverse mitral valve morphology and/or severe LV dysfunction.

Mitral cerclage annuloplasty, a novel transcatheter treatment for secondary mitral valve regurgitation: initial results in swine

OBJECTIVES

We developed and tested a novel transcatheter circumferential annuloplasty technique to reduce mitral regurgitation in porcine ischemic cardiomyopathy.

BACKGROUND

Catheter-based annuloplasty for secondary mitral regurgitation exploits the proximity of the coronary sinus to the mitral annulus, but is limited by anatomic variants and coronary artery entrapment.

METHODS

The procedure, "cerclage annuloplasty," is guided by magnetic resonance imaging (MRI) roadmaps fused with live X-ray. A coronary sinus guidewire traverses a short segment of the basal septal myocardium to re-enter the right heart where it is exchanged for a suture. Tension is applied interactively during imaging and secured with a locking device.

RESULTS

We found 2 feasible suture pathways from the great cardiac vein across the interventricular septum to create cerclage. Right ventricular septal re-entry required shorter fluoroscopy times than right atrial re-entry, which entailed a longer intramyocardial traversal but did not cross the tricuspid valve. Graded tension progressively reduced septal-lateral annular diameter, but not end-systolic elastance or regional myocardial function. A simple arch-like device protected entrapped coronary arteries from compression even during supratherapeutic tension. Cerclage reduced mitral regurgitation fraction (from 22.8 +/- 12.7% to 7.2 +/- 4.4%, p = 0.04) by slice tracking velocity-encoded MRI. Flexible cerclage reduced annular size but preserved annular motion. Cerclage also displaced the posterior annulus toward the papillary muscles. Cerclage introduced reciprocal constraint to the left ventricular outflow tract and mitral annulus that enhanced leaflet coaptation. A sample of human coronary venograms and computed tomography angiograms suggested that most have suitable venous anatomy for cerclage.

CONCLUSIONS

Transcatheter mitral cerclage annuloplasty acutely reduces mitral regurgitation in porcine ischemic cardiomyopathy. Entrapped coronary arteries can be protected. MRI provided insight into the mechanism of cerclage action.

Effectiveness and safety of percutaneous coronary sinus-based mitral valve repair in patients with dilated cardiomyopathy (from the AMADEUS trial)

This report presents the procedural results from the AMADEUS trial that support coronary sinus (CS)-based percutaneous mitral annuloplasty. Despite therapeutic advances, functional mitral regurgitation (MR) continues to be a significant clinical problem for patients with dilated cardiomyopathy. CS approaches to mitral valve repair have been viewed with skepticism because of the distance of the CS/great cardiac vein from the mitral valve annulus and the potential to compress a coronary artery. This report presents the procedural results from the AMADEUS trial that support CS-based percutaneous mitral annuloplasty. Patients who met the inclusion criteria were eligible to receive a mitral annuloplasty device. Transesophageal echocardiography was used to assess changes in MR, angiography was used to assess the coronary arteries, and multislice computed tomography was used to evaluate the anatomic relations between the coronary venous system and the mitral valve. Acute MR reduction (grade 3.0 +/- 0.6 to 2.0 +/- 0.8, p <0.0001) and permanent implantation were achieved in 30 of 43 patients in whom an attempt was made. Additional measurements in 20 patients with implants showed reductions in the vena contracta (0.69 +/- 0.29 to 0.46 +/- 0.26 cm, p <0.0001), effective regurgitant orifice area (0.33 +/- 0.17 to 0.19 +/- 0.08 cm(2), p <0.0001), regurgitant volume (40 +/- 20 to 24 +/- 11 ml, p = 0.0005), and jet area/left atrial area (45 +/- 13% to 32 +/- 12%, p <0.0001). The coronary arteries were crossed in 36 patients (84%). Arterial compromise contributed to a lack of implantation in 6 patients (14%). No difference was found in the CS/great cardiac vein position relative to the annulus between the patients who did and did not have a reduction in MR. In conclusion, percutaneous mitral annuloplasty reduces MR and permanent implantation can be achieved in most eligible patients.

[Coronary CTA evaluation of the relationship between mitral valve annulus and coronary circulation: implications for percutaneous mitral annuloplasty]

PURPOSE

To evaluate anatomical relationships between mitral annulus (MA), coronary arteries and coronary sinus (CS) in two groups of patients with and without moderate mitral insufficiency on coronary CTA to identify candidates to percutaneous mitral valve annuloplasty via the coronary sinus without risk of coronary artery occlusion. MATERIALS AND METHODS. Fifty-one ECG-gated coronary CTA examinations, obtained during injection of iodinated contrast material on a 16 MDCT were retrospectively reviewed. The mitral valve annulus diameter, anatomical relationships between CS and coronary arteries and MA-CS distance were compared between both patient groups.

RESULTS

The group with mitral insufficiency included 16 patients and the control group included 35 patients. The AP diameter of the MA was 45,7+/-5,2 mm in the group with mitral insufficiency, significantly larger (p=0.0009) compared to the control group (39,3+/-5,9 mm). In 70.4% of cases, the CS was located next to a coronary artery in an overlapping configuration. The unfavorable anatomical configuration with regards to annuloplasty appeared related to mitral insufficiency (p=0.0539). The distance between MA and CS was greatly variable with the CS routinely extending over the left atrial surface: the distance was significantly (p=0.0002) greater for all patients along the posterior surface (8,1+/-3,8 mm) compared to the lateral surface (5,2+/-4,6 mm) with this différence persisting within both groups: p=0.004 for patients with mitral insufficiency and p=0.0001 for control patients.

CONCLUSION

Our results demonstrate the value of coronary CTA in selecting candidates to percutaneous mitral annuloplasty. In 70.4% of cases, the CS overlaps a coronary artery with risk of compression at the time of annuloplasty.

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.

A novel method of percutaneous mitral valve repair for ischemic mitral regurgitation

OBJECTIVES

This investigation sought to determine the feasibility of a novel method of a percutaneous mitral valve repair.

BACKGROUND

Percutaneous mitral valve repair has emerged as an alternative therapy for patients with functional mitral regurgitation. However, current methods that rely on cannulation of the coronary sinus may not result in direct reduction of the mitral annulus area due to the superior relationship of the sinus to the annulus.

METHODS

A novel device, consisting of helical stainless steel screws connected by a biocompatible tether, was designed for percutaneous mitral valve repair. This device was implanted by implanting the helical screws directly into the myocardium at the posteromedial mitral annulus of 8 anesthetized pigs from the right internal jugular vein.

RESULTS

Implantation of the device resulted in a 19.7 +/- 0.1% reduction in mitral annular area and an 18.8 +/- 0.1% decrease in the mitral anterior-posterior dimension (both p < 0.05 vs. baseline). This annular reduction persisted at 3-month follow-up. Both the coronary sinus and left circumflex coronary artery remained patent in all animals. There was no evidence of device migration, poor wound healing, or tissue thrombosis at the sites of device implantation.

CONCLUSIONS

Percutaneous mitral valve repair targeting the ventricular myocardium from central venous access is feasible. By directly acting on the posteromedial mitral annulus, this methodology targets the mitral annular area most frequently affected by ischemic mitral regurgitation, lessens the risk of coronary artery impingement, promotes coronary sinus patency, and overcomes technical concerns that may arise when the coronary sinus lies significantly superior to the mitral annulus.

Long-term safety and durability of percutaneous septal sinus shortening (The PS(3) System) in an ovine model

OBJECTIVES

Chronic implants of the PS(3) system were conducted in an ovine model to assess durability and safety at up to 1 year follow-up.

BACKGROUND

The long-term durability and safety of emerging percutaneous devices for functional mitral regurgitation remain largely unknown.

METHODS

The PS(3) system (consisting of interatrial septal and great cardiac vein devices connected by an adjustable suture bridge) was placed in eight healthy adult sheep. The mitral annular septal-lateral dimension in systole (SLS) was acutely reduced by 15-20%. Animals were sacrificed at up to 12 months postimplant and characterized by intracardiac echocardiography, cardiac computed tomography (CT), and histopathology. In vivo forces exerted on the PS(3) bridge were measured by means of a novel load cell catheter.

RESULTS

At 3, 6, and 12 months after implantation, intracardiac echocardiographic and CT showed the PS(3) systems to be intact without erosion and with overall sustained reductions in the SLS. Histopathologic assessment revealed each component correctly deployed in its respective target site without evidence of erosion, thrombus, or device fracture. The SLS was 26.5 +/- 1.7 mm preimplant, 22.0 +/- 1.4 mm post-PS(3) (17.0% reduction), and 22.0 +/- 2.1 mm at latest follow-up. Mean forces exerted on the bridge in vivo ranged from 1.16 N to 1.87 N.

CONCLUSIONS

The PS(3) System demonstrated excellent biocompatibility without evidence of erosion, thrombosis, or perforation at up to one-year follow-up in this chronic healthy ovine model. Forces exerted in the PS(3) system were relatively modest and should contribute to the durability of the device.

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.

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.