An indirect approach to the MV annulus consists in the transmission of traction forces on the MV annulus by modifying the perivalvular tissue without a direct contact with the annular fibers. This can be achieved in several manners.

The coronary sinus (CS) reshaping techniques or percutaneous transvenous mitral annuloplasty (PTMA) devices represent the first attempts to reduce MR by indirectly approaching the mitral annulus through the close CS. These techniques consist in the introduction in the CS of a steerable catheter, which delivers two anchors (proximal and distal). Once the anchors are expanded and fixed on site, the nitinol “bridge” between the two anchors is shortened, deflecting the posterior annulus anteriorly, thereby reducing the septo-lateral dimension. The MONARC (Edwards Lifesciences Corporation, Irvine, CA, USA) and the Carillon (Cardiac Dimensions, Kirkland, WA, USA; Fig. 10.1) are two similar devices that use the CS reshaping technique. Both devices went through a reengineering process in order to reduce complications (coronary artery compressions, coronary sinus dissections/perforations), to reduce implantation failure and to improve grade of MR reduction [2, 3]. Nevertheless, according to the Transcatheter Implantation of Carillon Mitral Annuloplasty Device (TITAN), device implantation rate remains only 68 %, with high rate of implantation failure and transient coronary compromise [4]. Carillon device obtained CE Mark in 2011. The results of the TITAN trial showed a significant reduction in FMR grade with a reduction in LV diastolic and systolic volumes compared to a control group composed of non-implanted patients. In addition, functional and performance status markedly improved for the implanted patients. The REDUCE FMR randomized trial will compare the Carillon device to optimal medical therapy in 120 heart failure patients with FMR. The first patient has been enrolled in June 2015.

The MONARC device is actually abandoned.

Another critic addressed to PTMA devices was that the partial obliteration of CS might theoretically jeopardize future attempts at implanting cardiac resynchronization devices. Nevertheless, initial experience has been reassuring about this [5].

The so-called asymmetric approach to CS reshaping is a complex approach where a PTMA is connected to an Amplatzer PFO occluder anchored in the atrial septum. The device that has been engineered using this method is the Percutaneous Septal Sinus Shortening System (PS3 System, Ample Medical, Foster City, California). Tension on the bridge reduced septo-lateral dimension.

The direct approach differs from the indirect one, because the reshaping of the mitral annulus is achieved without the occupation of the CS. In this case, the use of mechanical forces or heat energy applied directed on the mitral annulus will permit a cinching of the annular fibers.

The direct approach to the mitral annulus could be from the ventricular or the atrial side.

Techniques based on mechanical traction forces are, at the time, the most promising.

The Mitralign (Mitralign, Tewksbury, MA, USA) is a device based on anchors, which approach the posterior mitral annulus from the LV side. The anchors, connected to each other by a suture, are able to cinch the annulus by traction. Similarly, the Accucinch (Guided Delivery Systems, Santa Clara, CA, USA; Fig. 10.2) uses also a ventricular approach to place circumferentially 9–12 anchors that are able to cinch the posterior annulus.

The Cardioband (Valtech Cardio, Or Yehuda, Israel) is a transcatheter mitral sutureless and adjustable posterior direct annuloplasty system. This device represents the real percutaneous adaptation of the surgical annuloplasty with an incomplete ring. Through a transseptal approach, the placement of a variable number of small retrievable corkscrews permits the fixation of the adjustable Dacron sleeve in supra-annular position (Fig. 10.3). Annular dimensions are then tuned using the adjustment tool. Short- and midterm (up to 90 days) preclinical outcomes in porcine model are very promising [6]. First-in-man implantation has been recently reported [7].

The main concern pointed out against the direct TMVA devices is the risk of accidental damage or perforation of neighboring cardiac structures (coronary sinus, left atrium, and MV leaflets). However, preliminary results showed that direct annuloplasty is a very safe approach. Moreover, compared to CS annuloplasty, direct approach bases on a solid surgical background.

On the other hand, the energy-mediated cinching approach for direct TMVA applies heat to cause the fibrosis and the cinching of the mitral annulus. This category includes:

In this case, the limitation reported is a not precise control of the energy distribution and a possible resulting mitral stenosis.

Several devices have been developed in order to reintegrate or sometimes enhance leaflet coaptation.

Taking again in consideration the Carpentier’s classification for MR [1], an insufficient leaflet coaptation resulting in a significant MR may be secondary to several mechanisms: a dilated annulus (type I), an excessive leaflet motion in case of MV prolapse/flail (type II), or a limited systolic leaflet motion due to chordal tethering by LV dilation (type IIIb). The first and the third features depict mainly a functional disease, while the second feature is more consistent of a myxomatous or damaged valve. In all these cases, an intervention addressed at increasing leaflet coaptation may represent a valid solution in reducing MR.

Conversely, in the remaining type of MR (type IIIa), an impaired systolic and diastolic leaflet motion results in most cases in an enhanced leaflet coaptation and in elevated transvalvular gradient measures that could represent a contraindication to a percutaneous approach aimed at increase leaflet coaptation.

Most of the devices operating on leaflet coaptation basically work by “clipping” two MV scallops together. In this way, the regurgitant orifice is partially obliterated. The final result is the creation of a double orifice valve. This concept comes directly from the surgical edge-to-edge technique, also worldwide known as Alfieri’s technique [8]. The only device clinically available in this category is the MitraClip (Evalve, Menlo Park, CA, USA); the Mobius device (Edwards Lifesciences, Irving, California) has been abandoned secondary to serious suture dehiscence and technical difficulties occurred [9], and the MitraFlex (TransCardiac Therapeutics, Atlanta, Georgia) is still in a preclinical phase. The latter one could also be used to deliver a neochorda to the MV (see further).

The MitraClip system represents the transcatheter conversion of the surgical Alfieri’s stitch [8]. This percutaneous treatment consists in the union of free edges (edge to edge) of the leaflet by applying a cobalt-chromium mixture clip (Fig. 10.4) on the beating heart. The clip includes two arms and two “grippers” adjacent to each arm to independently secure the leaflets following grasping. Arms and grippers are covered with polyester to enhance healing.

The procedure is performed under general anesthesia and is guided by transesophageal real-time 3D echocardiography and fluoroscopy. Conscious sedation and intracardiac echocardiographic guidance may be considered in selected patients [10, 11].

The MitraClip is implanted through a sequence of standardized steps via peripheral venous access at the groin (Fig. 10.5). After transseptal puncture (see Box 10.1), a 24-Fr steerable clip delivery system (CDS) delivers the clip on the left atrium. The device is then advanced to the annular level through a sophisticated triaxial remote catheter control system (Fig. 10.4), which allows the CDS to move in four directions.

An optimal coaxial alignment with the annular plane is critical for an optimal MitraClip implantation. At the regurgitant orifice, clip arms are opened and positioned perpendicular to the line of coaptation. Then, the clip is advanced in the LV and then slowly retracted again toward the valvular level. By doing this, a progressive contact with the MV leaflet is achieved. In the following, the barbed grippers are lowered and the clip arms are closed. A consensual movement of the MitraClip and MV leaflet indicates a successful leaflet engagement. If a satisfactory reduction of MR is achieved without a significant increase in transvalvular mitral gradient, the clip can be deployed. Otherwise, arms and grippers can be reopened at any time before device deployment and the device can be repositioned. In some cases, the implantation of one or two additional clips could be indicated. Once the procedure is completed, vascular closure is performed, and the patient is weaned from general anesthesia.

With more than 20,000 implantation worldwide, randomized trials and national registries demonstrated safety, feasibility, and efficacy of the MitraClip procedure in selected high surgical risk patients with both degenerative and functional etiologies [12–14], and the latest European and North American guidelines recommend (see Table 10.2) this device in symptomatic severe mitral regurgitation in high surgical risk patients on optimal medical treatment [15–18].

ThermoCool (Biosense Webster, Inc., Diamond Bar, California) is a radiofrequency ablation catheter that through regional fibrosis reduces the excessive leaflet motion in a degenerated MV. Severe damage to leaflets and adjacent cardiac structures might occur [19].