In Europe, mitral regurgitation (MR) is the second most common form of valvular heart disease needing surgery.1 Studies have shown that up to 50 % of patients with severe symptomatic MR are not referred to surgery, even if a surgical indication exists.1–3 Reasons for denying surgery include impaired left ventricular ejection fraction, a high operative risk, multiple comorbidities or advanced age.2
When surgery is performed, mitral valve repair, rather than replacement, has become the preferred surgical treatment for severe MR.4 The mainstay of surgical repair is annuloplasty, which is associated with excellent outcome.5 In 1991, a simple technique for mitral valve repair was introduced by Otavio Alfieri, involving the placement of a surgical suture in the mid-portion of the anterior and posterior leaflets, creating a double-orifice mitral valve.6 This technique ensures a fixed area of coaptation during systole, without disturbing the subvalvular and annular function, preserving left ventricular function. This seems to be associated with improved functional status and freedom from re-operation.7,8 However, most patients treated with the ‘Alfieri-stitch’ also needed an annuloplasty. The surgical literature suggests that the absence of a ring is associated with suboptimal results and the frequent need for reoperation in patients with more severe MR.9 Therefore, the technique was used in patients who are not candidates for conventional surgical repair.
Since the introduction of the percutaneous mitral valve repair system (Mitraclip; Abbott Vascular, Menlo Park, CA), this surgical suture-based repair can be replicated to accomplish the double orifice repair. Using the trans-septal approach, a clip device is delivered into the left atrium. The free edges of the mitral valve can be grasped simultaneously. The guidance of this sophisticated procedure requires a unique collaboration between echocardiographer and interventionalist and is mainly driven by real-time transoesophageal echocardiography (TEE). Fluoroscopy is used primarily for assessing the opening angle of the clip arms and plays a lesser role in the steering and positioning of the clip. Three-dimensional (3D) TEE is not mandatory for this procedure. However, it increases the safety and efficacy and reduces the procedural times.10,11
This procedure is divided into different procedural steps: trans-septal catheterisation and advancement of the guide; positioning and orientation of the guide and clip in the left atrium; alignment of clip arms perpendicular to the line of coaptation; leaflet grasping and assessment of leaflet capture; post-clip placement assessment; and, if necessary, placement of another clip.12 We will review all these different procedural steps and the role of echocardiography.
Trans-septal Catheterisation and Advancement of the Guide
Access to the left atrium from the femoral vein is accomplished using a trans-septal puncture. This trans-septal puncture is different from the standard trans-septal puncture (i.e. for electrophysiological examinations) since it has to be done in a precise location in the fossa ovalis. This position is superior (to get an adequate height above the mitral valve annulus for sufficient steering of the clip) and (mid-) posterior (since the line of coaptation of the mitral valve is situated posterior in the heart). Puncturing at a different site can significantly delay the procedure, because difficult catheter manipulations are needed to obtain an adequate position of the clip. This specific location is found with TEE guidance. First, the bicaval view is needed for visualisation of the superior and inferior part of the fossa ovalis. The trans-septal needle is placed in the superior vena cava and pulled back towards the fossa ovalis. The preferred puncture site is recognised by tenting. When the needle is in the superior part of the fossa ovalis the echocardiographer switches to the short axis at the base view for visualisation of the anterior and posterior part of the septum. When the needle is (mid-) posterior, the midoesophageal four- or five-chamber is necessary for assessing the height of the trans-septal puncture. The height should be around 3.5–4 cm above the mitral valve annulus. In patients with a degenerative MR where the leaflets prolapse above the mitral valve, a higher puncture is recommended. In patients with a functioning MR, the coaptation depth can be deep in the left ventricle and a lower puncture is recommended.
After the correct position of the needle is confirmed, a trans-septal puncture is performed and a stiff exchange guidewire is placed in the left upper pulmonary vein. Over this guidewire, a dilator and steerable guide catheter are slowly advanced in the left atrium. The dilator can be recognised by several echo-bright markers and the guide by one echo-bright (and radiopaque) ring at the tip of the guide catheter. These different parts can also easily be visualised with 3D-TEE (see Figures 1A–C).
After the guide is placed in the left atrium, the guidewire and dilator are retracted and the clip delivery system is advanced through this guide catheter. During the introduction of the clip, it is important for the echocardiographer to visualise the tip of the clip in the short axis at the base view to prevent traumatic contact with the posterior or lateral wall. The clip is advanced until straddling position and then positioned above the mitral valve by medial deflection and posterior torque of the guide. Again, the tip of the clip is visualised on TEE to avoid contact with the left atrium wall. This can be difficult, since the clip is frequently moving out of plane. This can be overcome by using the 3D-TEE left atrial view, where the clip and the left atrial wall are shown in one image without switching between 2D views (see Figures 1D and E).
Positioning and Orientation of the Guide and Clip in the Left Atrium
After the clip is positioned above the mitral valve, it has to be axial aligned and positioned above the origin of the MR jet. This is done with two orthogonal views: the intercommissural view (60°), used for medial and lateral positioning of the clip and the left ventricular outflow tract (LVOT)-view (145°), used for anterior and posterior positioning of the clip. Both can be seen at the same time when using the X-plane mode on the 3D-TEE probe. Since manipulations made to the clip in a medial-lateral direction also influence the anterior-posterior position of the clip and vice versa, it is helpful to use X-plane. Steering can also be done with live 3D left atrial view (with colour). After positioning the clip above the origin of the MR, it is important to check the trajectory of the clip before it is advanced into the left ventricle. It has to be axially aligned when it is advanced towards the mitral valve.
Alignment Clip Arms Perpendicular to the Line of Coaptation
When the clip is axially aligned in the intercommissural and LVOT-view and positioned above the origin of the MR-jet, the clip will be opened to 180°. This is necessary to check perpendicularity to the line of coaptation. Not being perpendicular to the line of coaptation, might lead to inadequate leaflet grasp and leaflet-insertion, increasing the chance of partial detachment or torsion on the valve. The clip is considered perpendicular to the line of coaptation, if the two clip arms are of equal length in the LVOT-view and shown as a ‘bar’ in the intercommissural view. If not, the interventionalist has to translate and rotate the delivery catheter handle to torque the clip until the clip arms are of equal length.
Both views can be obtained at the same time using the X-plane mode (see Figure 2A). A third view to check perpendicularity is the transgastric short-axis view at the level of the mitral valve leaflets, however this is not possible in every patient. Using this view, it is important to lower the clip to the level of the mitral valve. Live 3DTEE might be helpful to visualise both the clip and the line of coaptation in the same view (see Figure 2B). In cases where the clip should be placed in a lateral or medial position, 3D-TEE can be extremely helpful. In the latter, the clip is not visible in the LVOT- or intercommissural view (the clip is not in these planes).
Leaflet Grasping and Assessment of Leaflet Capture
Once the clip is in the perpendicular position, it will be advanced into the left ventricle until the tip of the grippers are below the mitral valve leaflets in the LVOT-view (or X-plane). It is important to check if the clip does not rotate during this step. When this occurs, the clip should be inverted and retracted into the left atrium, since rotating in the left ventricle is not allowed, because the clip can get entangled between the chordae. When the clip is in the ventricle, perpendicularity can again be checked with a transgastric short-axis view or a 3D left ventricle view of the mitral valve. Finally, in the ventricle, the clip is closed to grasping position (approximately 120–140°) and pulled back slowly towards the mitral valve until the mitral valve leaflets are resting on the clip arms. At that point, the grippers are lowered and the clip is closed. It can be helpful to acquire a film during the grasping, so this step can be reviewed. After leaflet grasping, a quick check is done in the LVOT position using colour Doppler to see if the grasp reduced the MR. If this looks satisfactory, the next step is the leaflet insertion assessment while the clip is reopened a little. The first view for leaflet assessment is the LVOT-view, in which especially the posterior mitral valve leaflet is best seen. After a proper grasp, both leaflets will go over the tip of the clip arms and are fully inserted towards the centre of the clip. Systolic and diastolic motion of the leaflets should be limited or non-existent. The same items are checked in the four-chamber view in which especially the anterior mitral valve leaflet is best seen. In the intercommissural view, the echocardiographer checks if the leaflets bisect the clip in the centre at equal height and if the chordae are moving freely. In the transgastric short-axis view or left atrial view using live 3D-TEE, the double orifice can be visualised (see Figure 3) if the clip isplaced centrally. In these views, the perpendicularity of both clip arms should be checked and if the clip is not favouring the anterior or the posterior leaflet.
Post-clip Placement Assessment
The adequacy of the grasp is evaluated by closing the clip with colour Doppler to assess the MR reduction. Insufficient MR reduction may be due to suboptimal placement of the clip in relation to the origin of the MR-jet, unintended capturing of chordae, insufficient leaflet insertion or the need for a second clip. During this step the diastolic transmitral gradient is measured to exclude mitral stenosis. Therefore, a careful assessment is important. If necessary, the clip can be reopened to release the leaflets to perform a new grasp or to reposition the clip. Repositioning of the clip is done in the left atrium following inversion and withdrawal from the ventricle. If clip position is satisfactory and MR reduction is sufficient, the clip can be released (see Figure 4). After clip release, the clip delivery system must be withdrawn into the guide catheter without contacting the atrial wall.
Management of Complications
Live 3D-TEE can be helpful during the management of complications of the percutaneous mitral clip procedure, such as the placement of a second clip in the unfortunate case of a partial detachment of the first clip, visualisation of ruptured chordae or tearing of the mitral valve leaflets.13,14
The percutaneous mitral valve repair is a sophisticated procedure which requires an unique collaboration between the interventionalist and echocardiographer since this procedure is mainly driven by real-time 3D-TEE.