Edge-to-edge technique

The percutaneous edge-to-edge technique reproduces the surgical technique described by Dr Alfieri, which consists of a suture of the mid part of both mitral leaflets to create a double mitral orifice. The surgical technique has been used mainly in organic MR but cases have also been performed in patients with functional MR .

The percutaneous edge-to-edge technique uses a transseptal approach to insert a device, which aims to secure both leaflets. The technique currently used involves the MitraClip (Abbott Inc.), in which a metallic clip is positioned at the free edge of the valve and then closed to grasp both leaflets. The procedure is technically demanding, not only because of the required expertise for transseptal catheterization, but also because of the difficulties in catching the appropriate part of the leaflets under transoesophageal echocardiography.

The MitraClip has been used in more than 2000 patients in the USA and in Europe, where CE marking has been obtained this year. The most relevant evaluation of the MitraClip is the Endovascular Valve Edge-to-Edge REpair Study (EVEREST) II randomized trial, which was presented at the American College of Cardiology Meeting in 2010 but has not yet been published. In this trial, 279 patients with severe MR were randomized in 37 centres to MitraClip ( n = 184) or surgical valve repair or replacement ( n = 95). Mean age was 66 years and 73% of the patients had organic MR. Procedural success was achieved in 74% of patients. Intention-to-treat analysis showed a 30-day major adverse event rate of 15% in the MitraClip group and 48% in the surgical group ( p < 0.0001 for superiority). The superiority of the MitraClip can be partially explained by lower rates of atrial fibrillation and, mainly, blood transfusions. The 12-month clinical success rate was 67% in the MitraClip group and 74% in the surgical group ( p = 0.0005 for non-inferiority). According to per-protocol analyses, i.e. considering patients who actually had an effective procedure, the 1-year residual rate of MR grade greater than 2/4 was 18% in the MitraClip group and 3% in the surgical group. Respective 1-year rates of New York Heart Association (NYHA) class I or II were 98 vs. 88% and quality of life improved in both groups.

At present, published MitraClip experience is limited to an observational series from the EVEREST registry involving 107 patients and two series from Germany and Italy comprising, respectively, 51 and 31 patients . These series differ particularly with regard to the aetiologies of MR, since the European series included a majority of patients with functional/ischaemic MR, whereas they accounted for only 21% of cases in the EVEREST registry. Patients from the European series also had a higher risk profile. Despite these differences, these three series consistently showed high procedural success rates, with a successful implantation of the clip in greater or equal to 90% of patients and a final MR less or equal to two in at least three of four patients.

Coronary sinus annuloplasty

The other percutaneous approach used to treat MR consists of inserting a retractable device into the coronary sinus to shrink the mitral annulus. The procedure reproduces the principle of surgical valve repair in functional MR, which consists of a remodelling annuloplasty using an undersized prosthetic ring. The rationale is the vicinity between the coronary sinus and the mitral annulus, but there are also limitations. Firstly, there is some distance between the coronary sinus and the mitral annulus. Secondly, the coronary sinus corresponds only to approximately half of the circumference of mitral annulus so that the annuloplasty is not circumferential, unlike with prosthetic rings. Finally, the circumflex artery often crosses the coronary sinus and may be compromised by the retracting device.

At the present time, three devices have been tested in humans:

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  the MONARC™ device (Edwards Lifesciences Inc.) consists of a proximal and a distal stent connected by a bridge that retracts progressively during the months following implantation ;

  
  
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  the CARILLON™ Mitral Contour System (Cardiac Dimensions Inc.) device comprises a proximal and a distal nitinol self-expandable anchor. The bridge connecting the two anchors is positioned by manual traction under echocardiographic and fluoroscopic control ;

  
  
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  the Viacor PTMA ^© (PTMA Viacor Inc.) system is based on a different approach and uses the implantation of several nitinol rods through a multilumen catheter, enabling the stiffness of the coronary sinus to be adjusted according to the reduction of MR .

Published experience in functional/ischaemic MR concerns 72 patients treated with the MONARC™ device, 48 with the CARILLON™ device and 27 with the Viacor PTMA ^© device. Implantation success rates vary between 48 and 82%, but included MR reduction in one series. Thirty-day death rates are low, between 0 and 2%. The two main complications are tamponade due to coronary sinus perforation, in 3–6% of cases, and myocardial infarction in up to 6% of cases. Complication rates are low for early feasibility trials but they illustrate the specific risks of this approach. Compression of the circumflex artery by the device, although seldom leading to myocardial infarction, is frequently observed when using a computed tomography scan during follow-up, in 30% of patients with the MONARC™ device, resulting in coronary stenosis greater than 50% in 8% .

Efficacy has been evaluated in only small non-randomized series using surrogate endpoints. There was a decrease of at least one grade of MR in 50% of patients at 1 year with the MONARC™ device and in 22% of patients at 6 months with the Viacor PTMA ^© device. Within the first year, the effective regurgitant orifice area decreased by approximately 30% and the regurgitant volume by 20–25%. The response was heterogeneous and certain patients experienced more marked reductions of MR. Series analysing functional results within the first year reported an improvement in NYHA class and/or 6-minute walk test .