Mitral valve repair in complex anatomy and challenging patients: the versatility of the edge to edge concept.

The edge-to-edge technique was introduced into the surgical armamentarium of mitral valve repair in the early 1990s and, from the beginning, it appeared to be an attractive approach because of its simplicity, reproducibility and effectiveness even in complex settings [1,2,3]. The technique is used to treat both organic and functional mitral regurgitation (MR). The surgical repair consists of the suture of the free edge of the leaflets at the site of regurgitation, creating a valve with 2 orifices when the regurgitation originates from the middle scallops. As opposed to conventional techniques, MR is corrected by obliteration of the regurgitant orifice at the leaflet level, regardless the anatomical lesion. This concept implies that the same technique can be applied to different anatomical and functional conditions [1,2,3,4,5].

We predicted many years ago, that the edge to edge repair, due to its simplicity and versatility, could open the perspective of percutaneous correction of MR [3]. In the last years, the prediction became reality, and nowadays the edge to edge concept is the basis of the MitraClip therapy, which represents currently most widespread and successful catheter-based method of correcting MR.

The value of the technique has been long debated in the surgical arena, initially with several detractors, mainly because of the perceived non-physiological consequences. Currently, the technique has been demonstrated safe, effective, and durable and several institutions around the world adopted this surgical method in selected patients with MR due to different causes and mechanisms [6,7,8,9,10].

The current indications and major contraindications for the edge-to-edge repair are mainly based on the surgical results obtained with this approach in the different settings of mitral insufficiency [11] and are summarized in Table 1.

Current indications and contraindications to the edge-to-edge technique.

Bileaflet prolapse. The clinical and echocardiographic very long-term results of the edge-to-edge repair for bileaflet prolapse have been recently reported by De Bonis et al. At 12 years, freedom from recurrence of MR ≥3+ was 86.3±3.54%. Mitral stenosis requiring reoperation was detected in 0.7% of the total. The only predictor of recurrence of MR at follow-up was residual regurgitation greater than mild at hospital discharge. Those long term results (up to 17 years) confirm that the double orifice technique combined with ring annuloplasty provides excellent late outcomes in patients with degenerative mitral regurgitation and bileaflet prolapse [12].

Segmental prolapse of the anterior leaflet. If only one scallop (usually A2) is prolapsing, the edge-to-edge repair is very effective in restoring mitral valve competence in a rapid, standardized and easily reproducible manner. Long-term results are very satisfactory, with a freedom from reoperation at 10 years of 96±2.3% and a rate of echocardiographic recurrence MR ≥3+ of only 2.2% at a mean follow-up of 4.5±3.12 years (range 1 month-13.2 years); these results were comparable to those obtained in patients submitted to standard quadrangular resection for prolapse of the posterior leaflet [13].

Commissural prolapse. Different and often technically challenging methods of repair have been suggested for the treatment of commissural prolapse. The absence of a unique and standardized approach in this context demonstrates the challenging feature of ‘commissural mitral regurgitation’. Complete suturing of the entire commissural area of prolapse (paracommissural edge-to-edge) followed by annuloplasty, effectively eliminates prolapse, regardless of the fact that the anterior, posterior or both leaflets are involved. In the Cleveland Clinic experience, more than 100 patients with commissural MR were treated with paracommissural edge to edge, with no instances of mitral stenosis, suture dehiscence or recurrent prolapse in the follow-up [14]. Excellent long term results results have been reported also in a recent retrospective analysis performed in our institution [15] echocardiographic freedom from MR ≥3+ at 11 years was 96.3±1.7%. Those results, up to 15 years after the operation, confirm that the edge-to-edge technique is probably the simplest and most reproducible method to repair isolated commissural prolapse.

Functional MR. Restrictive annuloplasty using a complete rigid ring is the standard operation in functional MR; however, in patients with a more advanced degree of leaflet tethering, the edge-to-edge technique may play an important role in addiction to annuloplasty to enhance the likelihood of a durable repair [16]. The results of the edge-to-edge in the context of functional MR have been the object of great debate. The Cleveland Clinic group reported a disappointing 24% recurrence rate of moderately severe mitral regurgitation about 2 years after surgery [9]. However, in that series, the concomitant annuloplasty was always performed with a posterior flexible band. Conversely, when the edge-to-edge has been associated with a complete rigid/semirigid ring annuloplasty, in patients with advanced tethering (coaptation depth >1 cm), the durability of mitral repair has been significantly increased compared with annuloplasty alone [16].

Other situations. It has been demonstrated that the use of the edge to edge technique is very effective in eliminating postoperative systolic anterior motion (SAM) in patients undergoing mitral valve repair [17]. Recent data showed that this method has also a role in preventing the occurrence of SAM in patients with echocardiographic predictors of SAM and in patients with hypertrophic obstructive cardiomyopathy and residual SAM after myectomy [18,19].

An extremely interesting indication of the edge to edge is represented by the use of this technique to ‘rescue’ patients with significant residual MR after conventional mitral repair (‘rescue edge-to-edge’). In our experience long-term durability of those ‘rescued’ mitral valves is very satisfactory, with only a short additional cross-clamp time (15.2±5.6): at hospital discharge all patients showed no or mild mitral regurgitation, and freedom from MR≥3+ at 10 years was 96.9±2.9% [20].

The edge to edge repair may be useful also in other very selected situation, such us children with complex congenital heart disease associated with atrioventricular valve incompetence [21], patients in which mitral valve exposure is extremely difficult and in patients with severe left ventricular dysfunction or need for concomitant multiple procedures, in which the edge-to-edge can be particularly convenient due to the short aortic cross-clamp time required [11].

Transcatheter edge to edge repair with MitraClip System. The EVEREST study (Endovascular Valve Edge-to-edge REpair of mitral regurgitation STudy) comprises a series of trials, including the first randomized controlled trial in which the percutaneous treatment was compared to surgical treatment in selected patients with MR (mainly with degenerative etiology). The study results concluded that, one year after the procedure, surgery was superior to percutaneous treatment in terms of efficacy (measured as freedom from recurrence of MR and survival), whereas the percutaneous treatment was associated with higher safety than surgery [22]. However, patients treated with percutaneous edge to edge in the real world are different from patients enrolled in the EVEREST trial. The ACCESS-EU registry offers a reliable snapshot of the characteristics of patients who currently undergo the procedure in the European post-market real-word: they are mainly elderly patients with comorbidities, with high surgical risk or inoperable and a high prevalence of FMR (more than 70% of the total). The recently reported 1 year results from the ACCESS-EU registry showed in 567 high risk patients (mean Logistic EuroScore 23±18.3) an implant rate of 99.6%, with a 3.4% of 30 days mortality after the MitraClip procedure and 1 year actuarial survival of 81.8%. An improvement in the severity of MR at 12 months compared to baseline was observed, with 78.9% of patients free from MR severity of >2+ at 12 months and significant clinical and quality of life improvements, confirming that in high risk patients population, the MitraClip procedure is effective with low rates of hospital mortality and adverse events [23].

In conclusions, 20 years after its introduction, the edge-to-edge technique remains an effective and versatile method to treat MR due to different etiologies and mechanisms. Simplicity, reliability and reproducibility even in complex diseases are the main advantages of the edge to edge repair. Recently, very long-term durability has been definitely demonstrated [12]. If the well-established technical aspects of the procedure and the correct indications are observed, results with this type of repair are similar or even superior to those obtained with other reconstructive techniques. Moreover, from a historical perspective, edge to edge repair had the great merit to open the perspective of percutaneous correction of MR, which became reality in the last years.