Percutaneous Mitral Valve Repair

Updated: May 04, 2021
Author: Ramin Assadi, MD; Chief Editor: Richard A Lange, MD, MBA 

Overview

Background

Percutaneous mitral valve repair (MVR) is used to treat mitral regurgitation (see the image below). Percutaneous procedures used to treat valvular heart disease were first developed decades ago; the first pulmonic balloon valvuloplasty was reported in 1982, which was quickly followed by applications to the aortic and mitral valves.[1, 2] Mitral stenosis was the first pathologic condition of a heart valve to be treated both surgically[3] and percutaneously.[4]

Percutaneous Mitral Valve Repair. Mitral regurgita Percutaneous Mitral Valve Repair. Mitral regurgitation.

Over the past 20 years, percutaneous mitral balloon valvuloplasty used to treat mitral stenosis has yielded excellent success rates in patients with suitable valvular and subvalvular morphology.[5] However, clinically viable percutaneous treatments for mitral regurgitation have become available only relatively recently.

Newer approaches have progressed far beyond balloon valvuloplasty to include catheter techniques for emulating surgical annuloplasty and edge-to-edge repair of regurgitant mitral valves.

A multinational study by Nickenig et al of transcatheter MVR in 628 patients in Europe found that such treatment had a high acute procedural success rate (95.4%) and that reduction in the severity of mitral regurgitation persisted at 1 year.[6] The study also determined that the acute procedural success rate was similar between patients with functional mitral regurgitation and those with degenerative mitral regurgitation, as were the in-hospital (2.9%) and estimated 1-year mortality (15.3%). However, the patients with functional mitral regurgitation had a significantly higher estimated 1-year rate of heart failure-related rehospitalization than did the other group (25.8% versus 12.0%, respectively).[6]

In a study of the initial US commercial experience with transcatheter MVR using the MitraClip, Sorajja et al analyzed data from the Society of Thoracic Surgeons/American College of Cardiology Transcatheter Valve Therapy Registry on patients commercially treated with the MitraClip (N = 564).[7] Procedural success was achieved in 90.6% of patients, and the majority of patients were discharged home with a moderate or lesser degree of mitral regurgitation. The results support the effectiveness of MitraClip therapy in the treatment of appropriately selected, high-risk patients in a commercial setting.[7]

In a prospective, observational study, Scandura et al compared 1-year outcomes of MitraClip therapy in high surgical risk patients with moderate-to-severe or severe mitral regurgitation between patients aged up to 75 versus those 75 years or older (total N: 180 patients) and found that the primary efficacy endpoint occurred in 41 patients, with similar rates between groups.[8] The groups showed no significant differences in cumulative mortality or in the rates of rehospitalization for acute heart failure within 1 year after the MitraClip procedure. Relative to baseline, both groups showed a significant reduction in severity of mitral regurgitation achieved after the procedure at 1-year follow-up and a significant improvement in New York Heart Association (NYHA) functional class.[8]

The COAPT (Cardiovascular Outcomes Assessment of the MitraClip Percutaneous Therapy for Heart Failure Patients with Functional Mitral Regurgitation) trial randomized 614 patients with heart failure with moderate-to-severe or severe secondary mitral regurgitation and symptoms despite maximally tolerated medical therapy to transcatheter MVR (with MitraClip) plus medical therapy versus medical therapy alone. Transcatheter MVR was safe; provided a durable reduction in mitral regurgitation+, heart failure hospitalizations (51%) and mortality (33%); and improved quality of life and functional capacity compared with medical therapy alone through 36 months.[9]

In the near term, percutaneous valve intervention will probably have several indications, as follows:

  • Severe disease deemed inoperable or at high risk of surgical complications owing to comorbid disease

  • Treatment of secondary mitral regurgitation in patients with severe symptomatic heart failure refractory to medical therapy

  • Early-stage regurgitant lesions if less-invasive valve repair may prevent progressive ventricular enlargement

Various percutaneous approaches are being evaluated and used. The field will develop rapidly over the next several years, with refinement of the above approaches, emergence of still newer technologies, and better identification of which patients are most likely to derive benefit.

If these percutaneous techniques are to be considered as alternatives to traditional surgical methodologies in low-risk to medium-risk patients, they must demonstrate hemodynamic effects, safety, and durability comparable to those of the current highly refined surgical techniques. Conversely, these percutaneous techniques may be best applied to patients at the margins of current surgical indications.

See also Percutaneous Valve Therapies for more information.

Relevant anatomy

The human heart has four valves. The left atrium (LA) is connected to the left ventricle (LV) via the mitral valve, which opens during diastole to allow blood to flow from the LA to the LV. During ventricular systole, the mitral valve closes and prevents backflow to the LA. The normal function of the mitral valve depends on its six components, which include the LA wall, the annulus, the leaflets, the chordae tendineae, the papillary muscles, and the LV wall.

For more information about the relevant anatomy, see Mitral Valve Anatomy and Cardiovascular System Anatomy.

Indications

Despite the general enthusiasm generated by emerging percutaneous devices, establishing which patient populations are suitable for such technologies is important. Degenerative (primary) and functional (secondary) etiologies are two causes of mitral regurgitation most amenable to surgical repair.

Surgical annuloplasty is the main invasive technique for treating functional mitral regurgitation, whereas leaflet repair is also usually performed to treat degenerative mitral regurgitation.

The excellent results and low perioperative mortality associated with surgical repair in selected patients emphasize the need for a thoughtful approach to percutaneous mitral valve repair.

For more details, see the Percutaneous Mitral Valve Repair section in the Percutaneous Valve Therapies topic.

 

Periprocedural Care

Preprocedural Planning

Pathologic conditions that affect the mitral annulus, papillary muscle, leaflets, chordae tendineae, left ventricle (LV), and left atrium (LA) can all produce or contribute to mitral regurgitation.[10] The goals of surgical techniques are mainly to correct the etiologic mechanism(s) (eg, prolapsed leaflet, annular dilatation) of mitral regurgitation. Broadly, the targets of these surgical techniques include the leaflets, mitral annulus, commissures, chordae, papillary muscles, and LV.[11, 12, 13, 14, 15]

Percutaneous technologies for mitral valve repair were developed based on some of the same principles as the standard open approaches. These technologies may be conveniently grouped into the following categories:

  • Interventions addressing the leaflets

  • Direct annuloplasty

  • Indirect annuloplasty (eg, via the coronary sinus)

  • Chordal implantation

  • LV remodeling

A combination of techniques may be used to obtain the best outcome.

Equipment

The equipment included below serve as examples of the available devices; a comprehensive list of equipment is beyond the scope of this topic.

Equipment options for leaflet plication include the following:

  • Abbott MitraClip

  • TransCardiac MitraFlex

Equipment used for leaflet ablation includes the following:

  • BioSense Webster ThermoCool irrigation ablation catheter

Equipment used as a leaflet space occupier includes the following:

  • Cardiosolutions Percu-Pro

Equipment options for the percutaneous mechanical cinching approach to direct annuloplasty include the following:

  • Mitralign Percutaneous Annuloplasty System

  • Guided Delivery Systems Accucinch Annuloplasty System

  • Boston Scientific Millipede system

Equipment options for the percutaneous energy-mediated cinching approach to direct annuloplasty include the following:

  • QuantumCor device

  • ReCor device

Equipment options for the hybrid approach to direct annuloplasty include the following:

  • Mitral Solutions Adjustable Annuloplasty Ring

  • MiCardia Dynamic Annuloplasty Ring System

Equipment options for the coronary sinus approach to indirect annuloplasty include the following:

  • Edwards MONARC device

  • Cardiac Dimensions Carillon Mitral Contour System

  • Viacor Percutaneous Transvenous Mitral Annuloplasty device

Equipment options for the asymmetrical approach to indirect annuloplasty include the following:

  • St Jude Medical Attune Adjustable Annuloplasty Ring

  • National Institutes of Health (NIH) cerclage technology

Equipment options for chordal implantation include the following:

  • TransCardiac Therapeutics MitraFlex device

  • NeoChord DS1000 device

  • Babic device

Equipment options for left ventricle remodeling includes the following:

  • Mardil BACE (Basal Annuloplasty of the Cardia Externally) device

 

Technique

Approach Considerations

The technologies of percutaneous transcatheter mitral valve repair (MVR) can be classified according to their device mechanism and site of action, as follows:

  • Therapies that target the leaflets (leaflet ablation, leaflet plication, leaflet coaptation)

  • Direct annuloplasty (truly percutaneous or hybrid)

  • Indirect annuloplasty (asymmetric or coronary sinus approach)

  • Percutaneous chordal implantation

  • Remodeling of the left ventricle (LV)

A combination of these technologies will probably be necessary for satisfactory MVR. However, for many patients, percutaneous repair will not be possible, and surgical MVR will be required.

Leaflet-Directed Procedures

Percutaneous leaflet plication (edge-to-edge leaflet repair)

The technology of leaflet plication is based on the surgical Alfieri technique,[16] in which the posterior and anterior leaflets are joined with a suture, creating a “double-orifice mitral valve.” This restores coaptation of the leaflets, thereby reducing mitral regurgitation.

A randomized trial has found this technique to yield results that are not inferior to those of surgery. Percutaneous edge-to-edge leaflet repair can be appropriate for degenerative mitral regurgitation or functional mitral regurgitation.

The MitraClip system is a steerable catheter advanced transseptally to deliver a clip to the anterior and posterior leaflets.

The MitraFlex, in which a clip is deployed to the leaflets transapically (also allowing implantation of an artificial chord during the same procedure), and the Cardica Mitral Repair system, are undergoing preclinical testing.[17]

The PASCAL (PAddles Spacer Clasps ALfieri) implant is delivered via a transseptal approach, connecting a 10-mm central spacer to the mitral valve leaflets using two wide paddles and clasps.[17] Simultaneous or independent use of the clasps allows the option of grasping each mitral valve separately. A first-in-human trial with the PASCAL system showed a high rate of technical success and reduction of mitral regurgitation.[17, 18]

Annuloplasty is typically performed concomitantly with a surgical Alfieri technique.[17] Without annuloplasty, results are typically suboptimal, with significant rates of mitral regurgitation recurrence and necessary reoperation,[19] especially in patients with annular calcification[19] or ischemic mitral regurgitation.[20] Iatrogenic mitral stenosis is a potential complication.

Leaflet ablation

Leaflet ablation is designed to treat degenerative mitral regurgitation. In this procedure, the leaflet(s) are targeted with radiofrequency (RF) energy to alter structure (fibrosis) or function (reduced motion).

The ThermoCool irrigation ablation electrode (an RF ablation catheter) is advanced into the left ventricle (LV) via femoral artery access in a retrograde fashion. RF ablation is delivered to the anterior leaflet upon contact by the catheter; this causes fibrosis, scarring, and reduced motion of the leaflet. An earlier animal study was used to demonstrate proof of concept.[21]

Note that scarring and fibrosis caused by RF ablation may be imprecise, potentially leading to a postablation leaflet that is too short or too long, with residual or even worsened mitral regurgitation. In addition, the leaflet(s) may be perforated and/or adjacent cardiac structures damaged.

Leaflet space occupier

A device whose function is similar to that of a buoy is placed across the mitral valve orifice to provide a surface against which the leaflets can coapt, reducing mitral regurgitation. This can be used in degenerative or functional mitral regurgitation.

The Percu-Pro, a space-occupying polyurethane-silicone polymer buoy under investigation, is anchored at the apex through the mitral valve (using a transseptal approach), acting as a spacer in the mitral orifice. Note that risks associated with this approach include thrombus formation on the device, iatrogenic mitral stenosis, and residual mitral regurgitation.

Direct Annuloplasty

Percutaneous mechanical cinching approach

The percutaneous mechanical cinching approach to direct annuloplasty is used to directly reshape the mitral annulus without use of the coronary sinus. The left atrium (LA) side or the left ventricular (LV) side is used for the approach. The mitral annulus is cinched directly with implantation of sutures or some other device. These technologies are most suitable for functional mitral regurgitation (but could also be used to treat degenerative mitral regurgitation), and they may be able to overcome the potential limitations of indirect annuloplasty (see below).

With the Mitralign system, the mitral annulus is approached from the ventricular side of the valve (through the aortic valve), and the posterior mitral annulus is fitted with anchors placed directly and connected with a suture, cinching the mitral annulus with a purse-string suture. The periannular space has been accessed via a retrograde LV approach reliably, with successful results in humans.

With the Accucinch system, mitral regurgitation is treated by cinching the posterior annulus circumferentially from trigone to trigone via the ventricular side (which is accessed through the aortic valve). This has also been tested in humans.

With the Millipede system, a novel retrievable and repositionable annular ring is placed with a unique attachment system via percutaneous (transseptal) or minimally invasive methods.

Only the posterior mitral annulus is cinched with the Mitralign and Accucinch devices, which represents a limitation. Currently, annuloplasty with a complete ring (as opposed to a partial ring) is generally considered the optimal surgical correction, because the intertrigonal distance is not fixed as was once believed. The Millipede system overcomes this limitation, but the feasibility and stability of annular fixation are unproven.

Percutaneous energy-mediated cinching approach

The percutaneous energy-mediated approach is used to apply heat energy to the mitral annulus, thereby causing scarring and shrinking the annulus. Devices include QuantumCor and ReCor.

The QuantumCor is placed transatrially (transseptally) to achieve direct annuloplasty by creating scarring and constricting the mitral annulus with RF energy. Its loop tip contains thermocouples and electrodes to regulate the amount of energy delivered. The QuantumCor has been shown to reduce mitral annulus distances and nonischemic mitral regurgitation in animal models,[22] and it is undergoing preclinical testing.[17]

The ReCor is used to deliver high-intensity focused ultrasound to the catheter shaft circumferentially and perpendicularly, heating the tissue and shrinking the collagen (and thus mitral annulus).

The problem with this percutaneous energy-mediated cinching approach is that the scarring caused by these devices may be imprecise, resulting in the potential complications of overconstriction (with resultant mitral stenosis) or undercorrection (with residual mitral regurgitation). This approach also has the potential to damage or perforate neighboring cardiac structures (including the coronary sinus), although these complications were not observed in animal models.[22]

Hybrid approach

A hybrid approach is used to surgically implant an annuloplasty ring, which is then adjusted transseptally if mitral regurgitation recurs or worsens. The Dynamic Annuloplasty Ring System, which has been tested in humans, is adjusted with RF energy, whereas the Adjustable Annuloplasty Ring is adjusted with a mechanical rotating cable. Both devices are in preclinical development.

Although the hybrid approach seems to be an effective method to tailor the device shape and size to each patient under real-life loading conditions, initial surgical implantation is necessary. As such, the approach used with these devices is a hybrid rather than a purely percutaneous technique. However, these may one day evolve into true percutaneous technologies.

Indirect Annuloplasty

Indirect annuloplasty mimics surgical placement of annuloplasty rings, which are commonly used to repair both functional and degenerative mitral regurgitation. Because surgical annuloplasty necessitates cardiac bypass, it is usually performed in conjunction with another procedure, such as coronary artery bypass grafting.[23]

Percutaneous devices may represent an alternative option in patients who are at excessive surgical risk or who do not require another cardiac surgical procedure. Several percutaneous devices are undergoing clinical testing, mainly to treat functional mitral regurgitation.

Coronary sinus approach (reshaping)

With the coronary sinus approach, devices are implanted within the coronary sinus to push the posterior annulus anteriorly, thereby reducing the septal-lateral (anteroposterior) dimension of the mitral annulus. This improves leaflet coaptation and decreases mitral regurgitation.[24]

The MONARC (previously Viking) system is composed of an outer guide catheter, a smaller delivery catheter, and a nitinol implant, which consists of distal and proximal self-expanding anchors and a springlike “bridge” that has shortening forces. This system is used to draw the proximal coronary sinus and distal great cardiac vein closer, indirectly displacing the posterior mitral annulus anteriorly.

The Carillon Mitral Contour System is composed of self-expandable nitinol proximal and distal anchors connected by a nitinol bridge. These are placed in the proximal coronary sinus and great cardiac vein with a catheter-based system. Tension is applied to the system, which cinches the posterior periannular tissue and deflects the posterior mitral annulus anteriorly.

The Viacor Percutaneous Transvenous Mitral Annuloplasty device is used to deliver nitinol rods of varying stiffness and lengths to the coronary sinus via a catheter. This device displaces the posterior annulus anteriorly by exerting outward force.

The principal risk with these devices is potential coronary artery compression. Studies have shown that a diagonal or ramus branch crosses between the mitral annulus and coronary sinus in 16% of persons, whereas the figure is 64-80% for the left circumflex artery.[25, 26, 27, 28] Therefore, evaluation of the coronary anatomy, including the relationships among the coronary sinus, coronary artery, and mitral annulus, is required before consideration of these devices.

Although initial experience has been reassuring, the coronary sinus approach could jeopardize later attempts at implanting cardiac resynchronization devices.

Asymmetric approach

With the asymmetric approach, the proximity of the mitral annulus to the coronary sinus is leveraged in an attempt to reshape the annulus while exerting traction on another portion of the right atrium (RA) or left atrium (LA), thereby causing asymmetric forces. The goal of this approach is to minimalize the lateral-septal dimension and to decrease mitral regurgitation.

The St Jude adjustable annuloplasty ring is composed of four helical anchors (two distal and two proximal), two loading spacers, a tether rope, and a locking mechanism. The distal pair of anchors is delivered into the left ventricle myocardium through the coronary sinus, in close proximity to the posterior leaflet scallop. The proximal pair of anchors is implanted into the posteromedial trigone via the RA. A cable is used to connect the two pairs of anchors to cinch the posteromedial mitral annulus. Manual, reversible dynamic shortening can be performed; the locking mechanism (a self-retracting nitinol structure) is used to maintain the cinched load.[29]

The experimental National Institutes of Health (NIH) cerclage technology directs a guidewire into the first septal perforator of the great cardiac vein via the coronary sinus. With imaging guidance, the guidewire is then directed across the myocardium to reenter a right heart chamber. The wire is then ensnared and exchanged for a suture and tension-fixation device. Results in initial animal models have shown promise in reducing mitral regurgitation.[30]

One potential limitation of the asymmetric approach is that the mitral annulus and coronary sinus may not lie in the same plane, preventing true annuloplasty. Another limitation is that no long-term data are yet available to study the long-term consequences of the unequal tension exerted on the LA or coronary sinus. Device erosion or fracture is also theoretically possible, and a thrombus may form on the connecting cable.

Chordal Implantation

Chordal implantation, which is mainly used to treat degenerative mitral regurgitation, involves transseptal or transapical implantation of synthetic sutures or chords. They are anchored onto the left ventricle (LV) myocardium at one end and the leaflet at the other. The chord length is then adjusted to achieve optimal leaflet coaptation and to reduce mitral regurgitation.

The MitraFlex, NeoChord, and Babic are three devices currently in development for this approach.

With the MitraFlex and NeoChord devices, one anchor is placed in the inner LV myocardium and another on the leaflet transapically; the two anchors are then connected with a synthetic chord.

The Babic device is used to create two continuous suture tracks from the LV puncture site through the puncture of the target leaflet; they are then exteriorized transseptally. A pledget is apposed onto the exteriorized venous sutures and anchored onto the atrial side of the leaflet upon retraction of the guiding sutures from the epicardial end. A polymer tube is then interposed between the leaflet and the free myocardial wall and secured at the epicardial surface with an adjustable knob.

The chordal implantation approach may be limited by residual leaflet prolapse (ie, artificial chords that are too long) or leaflet restriction (ie, chords that are too short). In addition, residual mitral regurgitation may persist, and a thrombus may form on the device.

Left Ventricular Remodeling

With left ventricular (LV) remodeling, the anteroposterior dimension of the LV is reduced, which indirectly decreases the septal-lateral annular distance and moves the LV papillary muscles closer to the leaflets. This approach seems most appropriate for functional mitral regurgitation due to cardiomyopathy or ischemia.

The BACE device requires a mini-thoracotomy and is implanted on a beating heart. With this technique, a silicone band is placed around the atrioventricular groove, and built-in inflatable chambers are placed on the mitral annulus, reshaping the mitral annulus for better leaflet coaptation. It can be adjusted remotely following implantation. Studies in animals showed no coronary artery compromise, and proof of concept was shown in 15 human patients, although no further details were made available.

Available clinical data on this approach are sparse, and longer-term outcomes and adverse event frequencies are yet unknown.