The MitraClip procedure represents a cutting edge way to fix a leaky mitral valve. For a broad overview of the procedure and the type of patients who need it, see our article The MitraClip – Treatment for a Leaky Heart Valve. The following article is meant for all levels of those wishing to learn about the details of the MitraClip procedure itself. It will be useful for patients who simply want to know more about the procedure, but because the article goes in to great depth, it will also be useful for advanced structural heart specialists wishing to learn the technical aspects of the MitraClip procedure.
The Mitraclip Procedure for Severe Mitral Regurgitation
The image below shows severe mitral regurgitation, which is the leaky mitral valve.
Getting Access to the Vein of the Leg
A small needle is used to obtain access to the femoral vein. This is done under fluoroscopic and ultrasound guidance usually as seen in fluoro image 1. A wire being passed through the needle in to the vein in fluoro image 2. Tubes that the procedure is performed through are then passed over wires and in to the vein as required.
Trans-septal Puncture and MitraClip Guide Catheter Advancement In to the Left Atrium
What is a Trans-septal Puncture?
The MitraClip procedure is performed through a tube that is inserted the veins of the leg. To get to the mitral valve we have to go up the vein to the right side of the heart, and then puncture through the membrane that separates the left and right chambers of the heart known as the intra-atrial septum. This is known as a Trans-septal puncture.
The Most Critical Step in the Whole Procedure
Many people would say that this is the most critical step in the MitraClip procedure. An optimally positioned Trans-septal puncture will not only markedly increase chances of success but it will reduce the chance of complication. A poorly positioned Trans-septal puncture can add hours to a MitraClip procedure and lead to the need for shortcuts that could have been avoided. If the Trans-septal puncture is felt to be in the wrong position then rather than simply proceeding, the Trans-septal system should be retracted and the puncture re-performed in a more appropriate position.
Ideal Puncture Site
The Mitraclip delivery system is a large and bulky device when compared to any other device used in the left atrium. Positioning of the device above the valve relies on using a series of levers and knobs that require adequate working space and height above the valve to allow steering. In general we prefer a high and posterior position for the puncture. The puncture should be in the region of 4cm above the mitral annular plane to allow for an adequate working space. The puncture should be relatively posterior to allow grasping of the leaflets in the plane of coaptation of the mitral valve. No matter how tempting, it is critical not to use a patent foramen tunnel to obtain left atrial access.
Imaging Guidance for Transseptal
Fluoroscopic and echocardiographic guidance can be used in guiding trans-septal puncture in general. In the clip procedure it is essentially echo guided as exact positioning is critical and cannot be done with fluoroscopy.
Fluoroscopy is used to place a guide wire in the superior vena cava. Over this guidewire a sheath is placed in the superior vena cava. The wire is removed and the trans-septal needle advanced to almost the tip of the sheath dilator. The sheath is torqued until the flange on the handle is in the 4-5 o’clock position, thus posterior, in the direction of the septum.
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Bicaval View for Superior – Inferior positioning
At this point I turn to echocardiography almost exclusively. The echo of the sheath is searched for in the bi-caval view (90 degrees). So as we retract the system we will go from superior to inferior, that is right to left on the echo view. The system is pulled down as a whole, under echo guidance until the dilator tip is seen to approach the region of the thin portion of the septum. It should still be superior and towards the right of the echo image. At this point the echocardiographer should look for tenting of the septum by the tip of the dilator. If tenting is seen in a superior location of the thin septum, then we move to assess the anterior-posterior orientation.
Short Axis View for Anterior – Posterior Positioning
At this point we swing to a short axis (45 degrees) orientation where the aortic valve and septum are seen. Remember that the aorta is an anterior structure therefore toward aorta is posterior and away is posterior. Look for tenting of the septum in this view. We want to be relatively posterior, so if the tenting is seen to be in an anterior position near the aorta, posterior torque should be applied to the trans-septal system. This means going clockwise. In general we start around 4 o clock, so posterior would mean going to 5 then 6 etc. As this is done, the echo is directly observed and the tenting is seen to move posteriorly.
4 Chamber View For Checking Adequacy of Height Above Valve
Next we will assess the height of the puncture point above the mitral valve. This is done in the standard 4-chamber view (0-10 degrees). Here the echocardiographer will look for the tenting. Then a line is drawn in this plane and another line drawn in the mitral annular plane. The distance between these two planes is measured. We want this to be 3.5 – 4cm. If it is too high or low then the system will need to be re-positioned higher or lower as described in the steps above.
Proceeding to Puncture the Septum
Once we are satisfied we are in the correct position in all the above-described views, then we can proceed with the puncture. The trans-septal needle is advanced to the tip of the dilator and gently advanced beyond until it punctures through the tented septum and goes in to the left atrium. Care must be taken not to push too hard or fast as that could result in the needle jumping forward and causing damage to the atrial walls or tissue, or worse case scenario a through and through perforation. There are several ways to assess for the needle being in the left atrium. Firstly is feel, secondly is on the echocardiogram the needle tip should be monitored and micro-bubbles can be seen to appear in the left atrium. I prefer pressure monitoring also, a transduced attached to the trans-septal system will show a right atrial pressure tracing become a left atrial one.
Advancing the Trans-septal System to the Left Atrium
Once we are confident that we are in the left atrium then the needle is gently advanced with the dilator, the sheath is then gently advanced over the dilator as the needle is retracted. We now have a sheath in the left atrium. At this point heparin should be given for systemic anticoagulation to ensure no clot formation in the left atrium.
2D vs. 3D Imaging for the Transseptal
Above I described the 2D approach; I personally prefer a 3D integrated approach for several reasons. Although I’m generally guided by 2D, intermittent 3D datasets are acquired. This clearly increase field of view, for example it may be hard to see tenting in a certain view, whereas this may become easily apparent in a 3D view. I find that this improves communication and understanding between the echocardiographer and the interventionalist. The interventionalist will more easily appreciate orientation with good 3D images, and the imager will gain an understanding of the equipment and technique used in the interventional part.
State of the art 3D-technology allows excellent quality, large field of view images with real time imaging and good temporal resolution. Finally 3D imaging has been described to help pick up complications that have been missed by 2D imaging that could lead to bad outcomes if the approach is not altered. An example is intramural placement of a trans-septal wire.
Preferred Trans-septal System
The two main systems I use are the standard trans-septal system (BRK) and the inbuilt radiofrequency system (such as the Bayliss). Of course the latter being higher in cost. The advantage of a radiofrequency system is that is basically makes it easier to cross the septum as it burns its way across. This can mean less pushing, higher chances of crossing a thick, fibrous, or calcified septum. Its of course also possible to apply radiofrequency to the end of a standard needle by applying cautery to the flange handle, this does have a few disadvantages however such as less needle control.
I approach it as follows. The septum should been interrogated thoroughly beforehand on the preoperative evaluation. If the septum appears straightforward and there is no aneurysm, redundancy or good sized patent foramen ovale tunnel and there has been no prior intracardiac surgery then I will proceed with the standard needle with cautery backup. If there is any evidence of the above then I prefer to use a radiofrequency system.
Difficult Trans-septal – Tips and Tricks
Trans-septal puncture can be difficult for many reasons. As described above, some atrial septum may be calcified or fibrous and thick either due to ongoing disease or previous surgery. Radiofrequency may be used to get through these. In the case of distorted anatomy or overly large atria it may be difficult to reach the septum with the standard needle and shape. In this instance the needle can be shaped to exaggerate the curve prior to insertion. Sometimes the longer needle and an extra curve may be required. If the system continually slips through a patent foramen ovale when pushing it, then a slightly higher puncture with use of the radiofrequency needle will generally work.
Guidewire Insertion into the Left Atrium
Once the trans-septal sheath is in the left atrium the next step is to get the MitraClip guide catheter in to the left atrium. Through the trans-septal sheath a suitable 0.038 stiff type wire is advanced in to the left upper pulmonary vein ideally as this provides stability and a relatively straight shot. Another pulmonary vein may be an option if this isn’t possible although it almost always should be. Other options would include having a friendly wire loop against the wall in the left atrium or the use of an Inoue type wire although that will add often-unneeded expense to the procedure. A wire in to the left atrial appendage should be avoided due to the risk of injury and perforation. As mentioned above it’s important after the trans-septal puncture to ensure adequate anticoagulation.
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Guide Catheter Insertion into the Left Atrium
Next the guide catheter is inserted over the wire. The catheter has a dilator in it, and the dilator tip is of course just beyond the guide catheter. When accessing the body the curve is taken out of the sheath using the steering feature. This is first negotiated through the skin at the groin. Usually dilation of the femoral access site isn’t needed and the dilator serves the purpose. It may occasionally be required however with intermediate sized sheaths and dilators. Negotiating the sheath through the femoral access and up to the atrium should be done under fluoroscopic guidance. Of course care needs to be taken to ensure the wire remains in position in the left atrium during this process. When reaching the atrium the curve is added back to the guide catheter using the steering feature.
Advancement of the dilator and the MitraClip guide catheter in to the left atrium should be done under echocardiographic guidance. The dilator has echogenic coils in the tip and the guide catheter is also echogenic. The aim is to get the guide catheter about 1-2cm in to the atrium and no further, so that the clip delivery system can be manipulated with adequate room. Usually the guide catheter can be negotiated through the septum over the dilator however occasionally it is difficult and wont advance.
Tips and Tricks for Difficult Guide Catheter Insertion
If the catheter can’t be negotiated across the septum a few steps can be taken. It is important at this point to ensure an adequately stiff wire was used. Sometimes controlled to and fro anterior/posterior rocking of the system can be applied and may help advance the guiding sheath. If this doesn’t work options include use of a long dilator advanced through the septum or balloon dilation of the septum. Once the guide catheter is across the septum it’s a good idea to confirm its position and orientation with 3D. Importantly, once the catheter is in correct position, the dilator and the wire are removed in a specific manner with continuous sheath aspiration that ensures adequate de-airing of the system.
Securing the Guide Catheter
Once the guide catheter is in position 1-2 cm in to the left atrium the control box is secured in to the MitraClip support table and clip securing system. These would have already been placed during preparation; the table is typically placed over the right thigh. The guide box will have ability to have plus/minus bend applied from a Knob on the guiding catheter and also the box can be turned clockwise and counterclockwise for anterior and posterior torque.
Positioning the Clip Delivery System
Clip Advancement to Guide Catheter Tip
Next we have to introduce the clip in to the atrium and position it over the mitral valve. The clip is advanced to the guide catheter tip under fluoroscopic guidance and the clip advanced in to the atrium just beyond the tip. From this point on advancement of the clip needs to be closely monitored under echocardiographic guidance.
Next comes straddling. There are two marker rings on the clip delivery system that are close together and the goal is to advance the clip so that the tip of the guide catheter is in the middle of these two marker rings. This is known as straddling. This is important in allowing the clip to be steered in to position appropriately. While advancing the clip to allow straddling care needs to be taken to watch the tip of the clip and ensure it isn’t in contact with atrial tissue otherwise further pushing would be prohibited without appropriate movements. Sometimes anterior or posterior torque or other steering will need to be applied to ensure there is enough room to advance the clip to straddling position. From an echocardiographic perspective, the remainder of the procedure will be spent flipping between LVOT (120 degrees) and intercommissural views (60 degrees).
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Pointing The Clip Delivery System Down to the Valve
Once the clip is out in the left atrium and the delivery system straddled, the clip is essentially pointing laterally towards the atrial wall. Maneuvers are then made to bring the clip down towards the mitral valve. We are essentially trying to bring the clip perpendicular to the valve plane as in towards the left ventricular apex. The exact description of the manipulation of the knobs is individualized and needs to be learned through experience. For those starting out, although a familiarity and understanding of the system is needed, the associated clinical representative will be heavily involved in the process.
Appropriate Positioning Above the Valve
Now the clip is pointing down towards the valve fine movements are made to position the clip above the desired area. Anterior – posterior manipulations are made in the LVOT (120 degree view). Towards the aorta, the right side of the echo will be anterior and away from that will be posterior. This is done by torqueing the guide catheter box. Medial – lateral manipulations are performed in the intercommissural view (60 degrees). Lateral is toward the appendage and medial toward the septum. With this positioning we essentially want to be able to split the regurgitant jet with the final position.
At this point we also check the trajectory of the clip by advancing it forward towards the valve. In an ideal world we would be pointing straight toward the desired area with the delivery system and advancing the clip would be in a straight line towards the targeted area, however angulations may mean that when we advance the clip it veers off course. In that case further manipulations are made to ensure a good trajectory.
Opening Clip Arms and Positioning Appropriately
The clip arms are then opened. Remember we want to one clip arm to grab the anterior leaflet and the other clip arm to grab the posterior leaflet at the area of maximal regurgitation. To do this, the clip generally needs to be placed in a 12 o’clock – 6 o’clock position. An example being for A2-P2, A2 would be 12 o’clock and P2 would be 6 o’clock. In a 10 o’clock – 4 o’clock position, the 10 o’clock would be directed towards A1 and the 4 o’clock towards P3. This orientation is best checked under real-time 3D imaging with an enface view above the valve. In this view, real time manipulations can be made.
Lets say the clip was in a 10 o’clock – 4 o’clock position, we would need to rotate it clockwise to achieve the desired 12-6 position. To do this the clip system is rotated clockwise from the most proximal portion and while doing this, the clip is jogged forward and backward, above but not through the valve, to allow translation of the torque and also to remove built up torque in the system. Another way of checking this throughout the steps where the clip is in the ventricle is by looking in the LVOT view where both the clip arms should be seen and then looking in the intercommissural view where no arms should be seen. Once we are happy with the positioning above the valve, the clip, with arms open is advanced in to the ventricle below the valve. Its important to minimize adjustments to clip position when in the ventricle to avoid entrapment in chordae.
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Grasping the Leaflets
Retracting the Clip Until The Leaflets Fall In
The clip is now in the ventricle with both arms open and the next step is to retract the clip in a manner that allows the anterior leaflet to fall on one arm and the posterior leaflet to fall on the other. The clip is closed a little to around 120 degrees to facilitate the capture and then retracted slowly until the leaflets fall on to the arms. This may need to be repeated several times until both leaflets are clearly seen to be on the clip arms. This is performed in the 120 degree LVOT view. When the clip is below the leaflets and being retracted there may need to be some minor torquing of the system in an anterior or posterior direction as dictated by the echocardiographic images. For example if the retraction of the clip to the leaflets shows the anterior leaflet is falling in but not the posterior, the clip may be advanced forward a littler, then posterior torque applied, then the clip pulled back up towards the leaflet to see if this leads to both the anterior and the posterior leaflet falling into the clip arms.
Lowering The Grippers
Once both the anterior and posterior leaflets are confirmed to have fallen in to the clip arms the grippers are lowered which essentially leads to the leaflets being trapped down on the clip arms.
At this point the clip is still open so we close it to around 60 degrees. Before closing the clip further, a comprehensive echocardiographic assessment is performed to answer several questions. Leaflet insertion is checked to ensure an adequate grasp of both leaflets 3D imaging should demonstrate a double orifice mitral valve. The leaflets where inserted should be stable without excessive motion. The degree of mitral regurgitation should be significantly reduced although it can typically be expected to reduce further once the clip is fully closed.
In some circumstances the preoperative evaluation would have already determined the likelihood of needing more than 1 clip and in those cases even if there is residual MR after the 1st clip insertion then the clip may still be inserted strategically and another clip placed in proximity.
Closing the Clip
If it has been decided that the position of the clip is satisfactory then the next step is to proceed to close the clip. This is typically performed in the intercommissural view. Once the clip is full closed and the reduction in MR is seen as satisfactory it’s important to check a gradient across the mitral valve, typically with TEE to ensure no significant stenosis has appeared. The threshold for acceptable gradient is not set in stone, rather it depends on valve characteristics, patient activity levels, pre-procedural gradients, hemodynamic conditions etc. It’s important to make sure mitral regurgitation is not replaced by mitral stenosis however.
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Releasing the Clip
Releasing Clip From Delivery System
Now that a satisfactory clip position has been achieved, the clip can be released from the delivery system. A series of checks is performed to ensure the clip is firmly closed. Importantly until the next steps nothing is set in stone and if required the clip can still be removed. If everything appears in order however the clip can be deployed involving a series of steps including removal of the gripper and clip caps, and removal of the gripper and clip lines, then finally retraction of the insertion pin.
Retracting the Delivery System
The clip is inserted to the delivery system on a fairly sharp pin that will be exposed in the atrium once the clip is deployed. This needs to be removed very carefully as its essentially a very sharp object. This is removed under direct echocardiographic guidance to ensure it is away from atrial tissue as the system is straightened and retracted in to the sheath. The guiding catheter should remain in the left atrium, of course if another clip is deployed or simply as a way to measure left atrial pressure at the end of the case. After clip deployment, as the clip delivery system is retracted care needs to be taken to de-air the system appropriately.
Managing the Access Site
Typically, anticoagulation can be reversed at this point if desired. I personally use a figure of 8 suture tied down as the guiding catheter is removed to secure hemostasis. With the figure of 8 sutures the sutures must be removed the next morning. Some people have described the use of perclose pre-closure and others have simply used manual pressure.
Complications and How To Manage Them
It is important to limit clip movement once it has been advanced in to the ventricle, particularly in the case of more complex repairs involving the lateral or medial leaflet. The reason is there is an increased chance of clip entrapment in the subvalvular structures, such as the chordae. If clip entrapment is suspected, movement should be minimized and close attention paid to echocardiography and fluoroscopy. The clip arms should be inverted before attempting to pull back and careful maneuvers made as to not to worsen the situation.
Fortunately this is rare and can be avoided if care is taken do ensure good grasp of the leaflet and not too much tension on the system prior to deployment. If partial leaflet detachment is noted, another immediately adjacent clip may be deployed to stabilize it. In some instances surgery may need to be considered.
Of course if tamponade occurs, the mechanism should be sought, and also pericardiocentesis performed. It is important that the echocardiographer continually be searching for effusion through the case and also at case termination.
Atrial Septal Defect
This is not usually an issue and I have found the vast majority will be of no significance and will decrease or just close over time. In certain cases however, for example in desaturation or known unfavorable hemodynamics with evidence of significant shunting by echocardiography and saturation check, closure may be considered. This may be more applicable in high-risk subsets with known severe elevation of right-sided pressures.
Acute LV dysfunction
This would be of most concern in those patients with tenuous LV function prior to the procedure, where the regurgitant orifice acted as a low-pressure pathway to ejection. Correcting the regurgitation will of course lead to altered loading conditions that can overwhelm the LV. In these circumstanced the patient should be treated in a manner similar to high-risk surgical patients with close attention to hemodynamic support in an intensive care setting. In the majority of cases however, forward cardiac output should be preserved or improve.
This is rare and would likely be the result of entanglement. If this occurs of course the flail segment should be identified. It would theoretically be possible to attempt to deploy a clip in this position, however if this cant be done then emergent surgery would likely be required.
Descriptions of More Atypical Uses of the MitraClip
Successful treatment of post-acute ischemic papillary muscle rupture and cardiogenic shock.
Successful treatment of systolic anterior motion with obstructive physiology with clip placement.
Use of two simultaneous clip systems in severe mal-coaptation whereby the first is used to grasp and approximate leaflets allowing placement of a second clip after which the first one is released and optimized.
Clip treatment of post surgical mitral valve repair mitral regurgitation.