Percutaneous Mitral Valve Repair Technique

Updated: Jan 21, 2015
  • Author: Ramin Assadi, MD; Chief Editor: Richard A Lange, MD, MBA  more...
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Technique

Approach Considerations

The technologies of percutaneous transcatheter mitral valve repair (MVR), the field of which is evolving exponentially, 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 [CS] approach)
  • Percutaneous chordal implantation
  • Remodeling of the left ventricle (LV)

Several other technologies, including a variety of direct and indirect annuloplasty and devices for remodeling the LV, are in preclinical testing or have been used in humans. 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. Despite the significant challenges, several prototypes for percutaneous MVR are being developed.

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Leaflet-Directed Procedures

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

The technology of leaflet plication is based on the surgical Alfieri technique, [13] in which the posterior and anterior leaflets are joined with a suture, creating a “double-orifice mitral valve.” This restores coaptation of the leaflets, reducing mitral regurgitation (MR).

A randomized trial has found this technique to yield results that are not inferior to those of surgery. Percutaneous edge-to-edge leaflet repair is most appropriate for degenerative mitral regurgitation, although it could also be used to treat functional mitral regurgitation.

With the MitraClip system, a steerable catheter is used transseptally to deliver a clip to the anterior and posterior leaflets.

With the MOBIUS device, a double-orifice mitral valve is created with a suture. Although this device was feasible in an animal model, it was abandoned because of technical difficulties and suture dehiscence in initial human experience. [14]

The MitraFlex, in which a clip is deployed to the leaflets transapically (also allowing implantation of an artificial chord during the same procedure), is undergoing preclinical testing.

Annuloplasty is typically performed with a surgical Alfieri technique. Without annuloplasty, results are typically suboptimal, with significant rates of mitral regurgitation recurrence and necessary reoperation, [15] especially in patients with annular calcification [15] or ischemic mitral regurgitation. [16] Iatrogenic mitral stenosis is also a risk.

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 (a radiofrequency ablation [RFA] catheter) is advanced into the LV via femoral artery access in a retrograde fashion. RFA 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. [17]

Note that scarring and fibrosis caused by RFA 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 currently being studied in phase 1 trials, is anchored at the apex through the MV (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.

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Direct Annuloplasty

Percutaneous mechanical cinching approach

The percutaneous mechanical cinching approach to direct annuloplasty is used to directly reshape the mitral annulus (MA) without use of the CS. The left atrium (LA) side or the LV side is used for the approach. The MA 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 may be able to overcome the potential limitations of indirect annuloplasty (see below).

With the Mitralign system, the MA is approached transventricularly, and the posterior MA is fitted with anchors placed directly and connected with a suture, cinching the MA with a purse-string. 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 a transventricular approach. 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 MA 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, since 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 MA, 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 MA with RF energy. Its loop tip contains thermocouples and electrodes to regulate the amount of energy delivered. The Quantumcor has been shown to reduce MA distances and nonischemic mitral regurgitation in animal models. [18]

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 MA).

The problem with this 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 CS), although these complications were not observed in animal models. [18]

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 this 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.

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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. [19]

Percutaneous devices may represent an alternative 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 (coronary sinus reshaping)

With the CS approach, devices are implanted within the CS in order to push the posterior annulus anteriorly, thereby reducing the septal-lateral (anteroposterior) dimension of the MA. This improves leaflet coaptation and decreases mitral regurgitation. [20]

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 CS and distal great cardiac vein closer, indirectly displacing the posterior MA 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 CS 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 MA anteriorly.

The Viacor Percutaneous Transvenous Mitral Annuloplasty device is used to deliver nitinol rods of varying stiffnesses and lengths to the CS 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 MA and CS in 16% of persons, while the figure was 64%-80% for the left circumflex artery. [21, 22, 23, 24] Therefore, evaluation of the anatomy, including the relationships among the CS, coronary artery, and MA, is required before consideration of these devices. MA calcification is another potential risk.

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

Asymmetric approach

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

With the PS3 system, whose development has since been abandoned, a CS anchor was positioned behind the posterior leaflet, and a cinching wire (bridge) was used to connect the CS anchor to an atrial septal anchor. Tension applied to the bridge reduced the lateral-septal dimension and decreased mitral regurgitation. [25]

The St Jude adjustable annuloplasty ring is composed of 4 helical anchors (2 distal and 2 proximal), 2 loading spacers, a tether rope, and a locking mechanism. The distal pair of anchors is delivered into the LV myocardium through the CS, in close proximity to the posterior leaflet scallop. The proximal pair of anchors is implanted into the posteromedial trigone via the right atrium. A cable is used to connect the two pairs of anchors to cinch the posteromedial MA. Manual, reversible dynamic shortening can be performed; the locking mechanism (a self-retracting nitinol structure) is used to maintain the cinched load. [26]

With the experimental National Institutes of Health (NIH) cerclage technology, a guidewire is directed into the first septal perforator of the great cardiac vein via the CS. 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. [27]

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

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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 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 the 3 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 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.

This 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 thrombus may form on the device.

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Left Ventricular Remodeling

With 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.

With percutaneous iCoapsys technology, which is based on the Coapsys surgical system, pads are placed on both sides of the LV, and a cord is passed through the LV cavity to apply tension to the MA and basal LV wall; thus, the posterior leaflet can be moved for better coaptation with the anterior leaflet. Surgical data have demonstrated implantation safety, reduced mitral regurgitation, and positive LV remodeling. Although percutaneous implantation of the device transpericardially via a subxiphoid approach was feasible in animal models, device development has been discontinued.

The BACE device requires minithoracotomy but 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 MA, reshaping the MA for better leaflet coaptation. It can be adjusted remotely adjusted 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 unknown.

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