Abstract
Improvements in procedural technique and intra-procedural imaging have progressively expanded the indications of percutaneous edge-to-edge technique. To date in higher volume centres and by experienced operators MitraClip is used for the treatment of complex anatomies and challenging cases in high risk-inoperable patients. This progressive step is superimposable to what observed in surgery for edge-to-edge surgery (Alfieri’s technique). Moreover, the results of clinical studies on the treatment of patients with high surgical risk and functional mitral insufficiency have confirmed that the main goal to be achieved for improving clinical outcomes of patients with severe mitral regurgitation (MR) is the reduction of MR itself. The MitraClip should therefore be considered as a tool to achieve this goal in addition to medical therapy. Nowadays, evaluation of patient’s candidacy to MitraClip procedure, discussed in local Heart Team, must take into account not only the clinical features of patients but even the experience of the operators and the volume of the centre, which are mostly related to the probability to achieve good procedural results. This ‘relative feasibility’ of challenges cases by experienced operators should always been taken into account in selecting patients for MitraClip. Here, we present a review of the literature available on the treatment of complex and challenging lesions.
Advances in procedural tools in MitraClip procedure allow safety and versatility
First described by Alfieri et al.1 in 1995, E2E technique has demonstrated its efficacy and durability in treatment of different anatomical complex settings and functional conditions and even in more compromised patients thanks to short cardiopulmonary run period.2–4 The MitraClip system (Abbott Vascular, Santa Clara, CA, USA) is the catheter-based mitral valve repair (MVP)5 method inspired by the surgical E2E technique. Patient selection for MitraClip procedure is provided by echocardiographic characteristics obtained by two-dimensional (2D) transthoracic echocardiography (TTE) and/or transoesophageal echocardiography (TOE) in order to define the mechanism of MR and to evaluate the anatomic suitability for a MitraClip implantation. Since procedural success is the most important factor affecting outcomes of patients, this factor should always be considered before referring each patient for MitraClip (Figure 1). Since it was first approved for the treatment of symptomatic degenerative mitral regurgitation (DMR) in high-risk patients there has been an increasing interest in extending the use of the MitraClip system to patients that do not meet the inclusion criteria of the EVEREST trials.6–8 Currently, learning curve has been completed in many centres in the world, allowing to reach a good global expertise. Moreover, since it was developed and approved by Food and Drug Administration in 2008, MitraClip device has been widely modified to make operator more comfortable with its different aspects. Last generation of MitraClip system provides cardiologists with advanced steering, navigation, and positioning capabilities for the clip and the additional clip available size (XTR MitraClip) has 3 mm longer arms that are supposed to allow the operator to grasp better leaflets, increasing the length of grasping zone, and ensuring more durability of the device. All these facts let the operators being more comfortable with the treatment of MV pathologies that have been considered ‘unsuitable’ for many years.9 Indeed, operators’ skills and experience influence directly the type of anatomies that can be treated with MitraClip with acceptable results.
Criteria for patients selection for MitraClip procedure.
Intra-procedural guidance for MitraClip in 2020
Because of the fact that residual MR and trans-valvular diastolic gradient are associated with increased risk of mortality after MitraClip implantation10,11 the decision-making and the procedural strategy during the intervention assume a crucial importance. Intraoperative TOE still remains the cornerstone of intra-procedural guidance of MitraClip procedure as it allows a ‘dynamic step-by-step guidance’ in many complex procedures.12,13 Echocardiographic tools and the challenges in treatment of complex anatomies are summarized in Table 1. MV complex lesions usually require more than one clip, different size, different manoeuvre before clip deployment. At each step, a complete reassessment of the ‘changed MV pathology’ is needed, with precise evaluation of efficacy and ‘safety’ concerns. Figure 2 represents this conceptual framework acting during MitraClip procedure. The continuous communication and feedback from echo specialist to interventionist is pivotal for complex procedures since the anatomy of the MV is changing all the time. Recent evidence suggests that a more integrated approach is needed to guide intra-procedural decision-making. Invasive haemodynamic measurements should be mandatory for results assessment, shifting the paradigm of evaluation of MitraClip results from an echocardiography-based colour-Doppler evaluation to a haemodynamic-based approach.14 Live monitoring of haemodynamic changes during procedure has been related to outcomes independently from residual colour jet, and it represents a valuable tool to guide decision-making. This tool can be even more important in case of dealing with complex anatomies, in which several procedural steps make it challenging and final geometrical shape of jets can be very eccentric.15
Intraprocedural decision making. TSP: Transeptal Puncture; LAP: left atrial pressure; MV: mitral valve; MR: mitral regurgitatiom.
Special consideration for echocardiographic guidance of procedures in case of complex MV pathologies
| Procedural steps | Echocardiographic and procedural tools for ‘normal anatomies’ | Specific challenges for complex anatomies |
|---|---|---|
| Transseptal puncture | Usually should be posterior and inferior; always posterior to the coaptation line of MV seen from 3D-surgical view (3D volume sample should include IAS displayed at 3 o’clock from the LA-view point and MV in the surgical view) | More inferior in case of medial commissure pathologies; height from MV plane should be highest as possible to avoid aorta hugging and allow all manoeuvres for complex cases |
| SGC insertion into the LA and CDS insertion into the LA | Insertion of the SGC should be carefully monitored with 2D and 3D TOE (short-axis, long-axis, and four-chamber views are recommended) and fluoroscopic imaging to avoid injuries of the LA wall | No specific challenges |
| MitraClip positioning in the LA and LV and grasping of the leaflets and verification of adequate leaflet insertion |
|
|
| Evaluation of results/decision-making | Assessment of symmetry of the valve is needed to ensure durability and avoid distortion evaluation of residual jet, MV area, and double orifice | The final result can be a triple orifice or a single asymmetric orifice when complex anatomies are approached. Integrated approach with haemodynamic evaluation is even more important for decision-making in complex anatomies |
| Procedural steps | Echocardiographic and procedural tools for ‘normal anatomies’ | Specific challenges for complex anatomies |
|---|---|---|
| Transseptal puncture | Usually should be posterior and inferior; always posterior to the coaptation line of MV seen from 3D-surgical view (3D volume sample should include IAS displayed at 3 o’clock from the LA-view point and MV in the surgical view) | More inferior in case of medial commissure pathologies; height from MV plane should be highest as possible to avoid aorta hugging and allow all manoeuvres for complex cases |
| SGC insertion into the LA and CDS insertion into the LA | Insertion of the SGC should be carefully monitored with 2D and 3D TOE (short-axis, long-axis, and four-chamber views are recommended) and fluoroscopic imaging to avoid injuries of the LA wall | No specific challenges |
| MitraClip positioning in the LA and LV and grasping of the leaflets and verification of adequate leaflet insertion |
|
|
| Evaluation of results/decision-making | Assessment of symmetry of the valve is needed to ensure durability and avoid distortion evaluation of residual jet, MV area, and double orifice | The final result can be a triple orifice or a single asymmetric orifice when complex anatomies are approached. Integrated approach with haemodynamic evaluation is even more important for decision-making in complex anatomies |
CDS, catheter delivery system; 3D, three-dimensional; IAS, interatrial septum; LA, left atrium; SGC, Steerable Guide Catheter.
Special consideration for echocardiographic guidance of procedures in case of complex MV pathologies
| Procedural steps | Echocardiographic and procedural tools for ‘normal anatomies’ | Specific challenges for complex anatomies |
|---|---|---|
| Transseptal puncture | Usually should be posterior and inferior; always posterior to the coaptation line of MV seen from 3D-surgical view (3D volume sample should include IAS displayed at 3 o’clock from the LA-view point and MV in the surgical view) | More inferior in case of medial commissure pathologies; height from MV plane should be highest as possible to avoid aorta hugging and allow all manoeuvres for complex cases |
| SGC insertion into the LA and CDS insertion into the LA | Insertion of the SGC should be carefully monitored with 2D and 3D TOE (short-axis, long-axis, and four-chamber views are recommended) and fluoroscopic imaging to avoid injuries of the LA wall | No specific challenges |
| MitraClip positioning in the LA and LV and grasping of the leaflets and verification of adequate leaflet insertion |
|
|
| Evaluation of results/decision-making | Assessment of symmetry of the valve is needed to ensure durability and avoid distortion evaluation of residual jet, MV area, and double orifice | The final result can be a triple orifice or a single asymmetric orifice when complex anatomies are approached. Integrated approach with haemodynamic evaluation is even more important for decision-making in complex anatomies |
| Procedural steps | Echocardiographic and procedural tools for ‘normal anatomies’ | Specific challenges for complex anatomies |
|---|---|---|
| Transseptal puncture | Usually should be posterior and inferior; always posterior to the coaptation line of MV seen from 3D-surgical view (3D volume sample should include IAS displayed at 3 o’clock from the LA-view point and MV in the surgical view) | More inferior in case of medial commissure pathologies; height from MV plane should be highest as possible to avoid aorta hugging and allow all manoeuvres for complex cases |
| SGC insertion into the LA and CDS insertion into the LA | Insertion of the SGC should be carefully monitored with 2D and 3D TOE (short-axis, long-axis, and four-chamber views are recommended) and fluoroscopic imaging to avoid injuries of the LA wall | No specific challenges |
| MitraClip positioning in the LA and LV and grasping of the leaflets and verification of adequate leaflet insertion |
|
|
| Evaluation of results/decision-making | Assessment of symmetry of the valve is needed to ensure durability and avoid distortion evaluation of residual jet, MV area, and double orifice | The final result can be a triple orifice or a single asymmetric orifice when complex anatomies are approached. Integrated approach with haemodynamic evaluation is even more important for decision-making in complex anatomies |
CDS, catheter delivery system; 3D, three-dimensional; IAS, interatrial septum; LA, left atrium; SGC, Steerable Guide Catheter.
In the following paragraphs, we try to collect available evidence about treatment of complex anatomies and unsuitable cases (Figure 3).
Examples of different MV lesions considered ‘not ideal anatomies’ for MitraClip procedure; red arrows indicate the ‘target lesion’ for MitraClip of each MV pathology. (A) Complex prolapse of two scallops with complete eversion of P2–M2 (diastasis) causing a discontinuity in the MV leaflet tissue similar to a cleft (pseudo-cleft); (B) ‘cleft of P2’; (C and D) medial and commissural flail; (E) flail caused by rupture of artificial chordae with failure of previous MVP; (F) SAM of MV anterior leaflet causing latent obstruction.
Barlow disease with multi-segmental prolapse
.Barlow’s disease is characterized by an abnormal matrix structure and multiple leaflet scallops prolapsing into the left atrium. This pathology can lead to a single-dual-jets MR or to multiple-jets MR; when a severe MR is detected, usually the main lesion is a flail with chordae rupture and the coaptation gap can be extreme with a single scallop eversion in left atrium (diastasis cleft like). The major challenge of using MitraClip in treating multiple flail segments is the residual mitral valve area after the repair. Another important challenge can be the quality of the grasping due to the thickening of the leaflets. As a result, patients with Barlow’s disease are not considered ideal candidate for the MitraClip procedure. Despite this fact, Barlow disease can be asymptomatic for a long period so that patients can be candidate with delay and open-heart surgery may not be feasible for patients with higher and prohibitive risk. Isolated experience about treatment of Barlow has been reported and specific tricks have been described. Three tricks have been described to complete a procedure of MitraClip in a Barlow patient: (i) application of a positive end-expiratory pressure (PEEP) by mechanical ventilation; (ii) adenosine-induced asystole; and (iii) anchoring strategy.
The first trick was described by Patzelt et al.16 and consists in application of positive PEEP and stopping ventilation at forced expirations. This fact increases intra-thoracic pressure, reduce preload, MV annulus antero-posterior coaptation gap. The injection of 13 mg of adenosine with mechanical ventilation support has been published in a case report by Borgia et al.17, to allow the positioning of the clip.
The anchor technique was described by Singh et al. and by Ching et al. and it consists in a stabilization of the extreme fail (with huge coaptation gap) by positioning a clip in adjacent regions that reduces immediately the coaptation gap (anchoring strategy), allowing the positioning of further multiple clips with a satisfactory grasping for treating the flail.18,19 Most of these available case series were performed with NTR clip. Preliminary data from the EXPAND study have showed a slight preference of XTR clips over NTR (48% vs. 36%) in treatment of prolapse. In our experience, the choice between NTR or XTR does not hang only on the leaflet length but also on the leaflet tissue quality, frailty, and calcification. XTR gives more tension to the edges of leaflets, therefore it may be less safe when leaflet tissue has lost its elastic properties.
Beyond the redundancy of tissue chronic stress on mitral valve leaflets in Barlow disease leads to focal and semi circumferential mitral valve degeneration and calcification;20 moreover, with progressive chordal rupture, the diastasis of the prolapsing scallops occurs frequently, increasing normal indentations of mitral valve. Therefore, during such a procedure operators should often deal also with pseudo-cleft lesions or opened indentations after the successful placement of the first MitraClip21 (Figure 4).
Treatment of complex Barlow. (A) Complex prolapse of posterior mitral leaflet 8PLM) , with complete eversion of P2; (B) identification of main lesions; (C) result after clipping: residual MR is seen with 2D for checking the color and 3D for assessing final new anathomy.
‘Cleft-like’ lesions
Sub-commissures or clefts of MV are deep indentations involving at least 50% of the leaflet body (from the edge towards the hinge-line). The indentation involving <50% of the leaflet is categorized as a pseudo-cleft providing a definition of sub-scallops or lobes, which may receive chordae insertion of the opposite papillary muscles.22 Three-dimensional TOE is more accurate in diagnosing mitral valve cleft (MVC) and indentation than 2D TOE.23,24
Deep MVC extending from the free edge to the annulus are rare (<1%) site of regurgitation and consequently classified among the possible causes of primary MR. Surgical repair of MR can be accomplished with direct suturing of the cleft21,25 or with an Alfieri-type repair. In percutaneous repair, cleft represents a challenge as leaflet grasping may worsen the regurgitation because of lack of enough tissue and it was considered an exclusion criteria in most studies.26
Moreover, the presence of cleft-like indentations is a frequent cause of residual MR after MitraClip implantation, mainly in functional MR when the implantation of one clip in the central position may open a cleft-like indentation, or in DMR when a clip is implanted close to a cleft-like indentation. Some clinical cases and case series reporting the treatment of ‘cleft-like’ lesions have been published.27–31 Three main techniques have been successfully performed (Figure 5). ‘Zipping by clipping’ technique has been described by Kische et al.29 in a case of advanced heart failure patient with huge coaptation gap in functional mitral regurgitation; this technique consists in reducing the extreme gap by a sequential parallel clipping of MV with a series of clips that are parallel to each other and perpendicular to MV coaptation line, placed from medial (A3–P3) or lateral (A1–P1) commissure, towards the central segments of MV. Final result is a single smaller mitral valve orifice rather than in a double mitral valve orifice (Figure 5A). Another approach is the convergent clips technique, described by Taramasso and Maisano30 (Figure 5B). In this technique, the clips are not perpendicular to the coaptation line and not parallel to each other: lateral clip is oriented slightly more clockwise than the line of coaptation and the medial one is oriented slightly counter-clockwise. Finally, a single oblique/asymmetric clip (e.g. between A2 and P3) can be implanted31 (Figure 5C).
Convergent clips technique for treating MV cleft with MitraClip.
Commissural lesions
Surgical experience has demonstrated the feasibility and efficacy of the edge-to-edge technique to non-central MR.1,32 Despite initial restricted indication for central mitral pathology33 more than 20% of the cases included in the Society of Thoracic Surgeons/American College of Cardiology Transcatheter Valve Therapy Registry dealt with non-central lesions.34
A2–P2 area of MV is the ‘chordal free zone’ and for this reason it is an ideal space for MitraClip deployment, while medial or lateral lesions may limit manoeuvring and may increase the risk of clip entanglement or chordal rupture. The first criterion of feasibility of MitraClip only on central segments referred to the concerns of device interference with the sub-valvular apparatus and difficulties in image guidance.35,36 In a series of patients undergoing MitraClip procedure, Estévez-Loureiro et al.35 reported similar procedural success rates and sustained effects on clinical outcomes for central vs. non-central MR and no entanglement (defined as manipulation of the system for >120 s to free the MitraClip) or chordal rupture for the patients with non-central MR. It is also notable that approximately one-third (38%) of patients with degenerative MR had non-central MR, highlighting the significant prevalence of non-central MR. Clip entanglement might be solved by experienced operators by inverting the clip and retracting it into the left atrium or by undoing the manoeuvres leading to the entanglement. Sometimes clip deployment should be considered while surgical conversion occurs rarely.36 Actually, even if the choice of the clip remains to operator, in case of commissural lesions it is recommended to prefer NTR clip over the XTR clip whereas the latter should be considered in case of large commissural flail. Regarding transseptal puncture, the only caution to be highlighted in case of A3–P3 lesions is to aim at posterior and inferior puncture in order to reach easily the medial commissure (Figure 6). In order to treat residual commissural primary MR after MitraClip implantation, Amplatzer Vascular Plug II occluder has been implanted between the commissure and the MitraClip with acute satisfactory results mainly in terms of reduction of MR. Raphael et al.37 showed the results in six patients of which three had medial commissure MR while the remaining three had A1–P1 lesion. All cases were successful with significant MR and invasive left atrial pressure reduction. At 30-day follow-up, all patients were alive and persisting good echocardiographic result was reported. In contrast to the first enthusiasm about success of this procedure, our group have previously published the mid-term outcome of this method for treatment of ‘intra-clip’ commissural jet and ‘intra-clip’ cleft-like indentation of leaflet perforation on 13 high-risk patients who previously underwent MitraClip.
Treatment of commissural flail (A1–P1).
Despite satisfactory procedural results, in-hospital mortality was 23% and according to the Mitral Valve Academic Research Consortium (MVARC) definition, device success and procedural success at 30 days were achieved only in 38%. After 8 months of follow-up poor outcomes were achieved. Based on such evidence, this technique has been abandoned in some centres and should be generally avoided. Only in case no other therapeutic options are feasible, it should be taken in consideration as bailout strategy.38
Previous annuloplasty
Mitral annuloplasty performed during conventional mitral surgery serves several purposes: to restore a normal ratio between the leaflet surface area and the annular area; to improve the leaflet coaptation and prevents progressive annular dilatation and, consequently, recurrent MR after surgery;39 and to reduce the stress forces acting on the valve leaflet, protecting from tissue tear and dehiscence.40,41 When recurrence of severe MR occurs in patients with previous annuloplasty, this is usually due to the long-term failure of the associated leaflet repair (neo-chordae, resection, edge-to-edge). Once clarified the mechanism with TOE and the feasibility of MitraClip in such cases, the main challenge is represented by the presence of the ring. This determines: (i) suboptimal visualization of the posterior leaflet (shadows) (Figure 7) and (ii) increased transmitral diastolic gradients. Also the depth of leaflet coaptation can be a challenge for grasping manoeuvres. Recently, some cases of ‘edge-to-ring’ have been described in which the grasp results in capture of the anterior mitral valve leaflet and the posterior mitral annular ring.42,43
MitraClip in failure of previous surgery.
Mitral valve systolic anterior motion
Left ventricular outflow tract obstruction (LVOTO) caused by systolic anterior motion (SAM) of MV occurs in patients with hypertrophic obstructive cardiomyopathy (HCM) and in selected patients after MVP for degenerative disease.44
Sorajja et al.45 reported the first series of percutaneous mitral valve plication in the management of severely symptomatic, obstructive HCM patients confirming that it could be useful for treating patients considered to be at very high risk for surgical myectomy or patients not having the anatomical criteria indicating surgical myectomy. Evidence suggests that placement of a single clip at the A2–P2 segments is usually sufficient to treat pathological SAM. Intraoperative haemodynamic invasive assessment shows the immediate effect of removal of LVOTO: LV pressure decreases and aortic pressure increase after grasping manoeuvre (Figure 8). When the procedure is performed for latent LVOTO, the intraoperative use of catecholamine can help to assess at baseline the presence of significant gradient and, after procedure, the procedural outcome. MitraClip can therefore represent bailout solution in selected cases of post-operative SAM after mitral repair.
MitraClip in SAM with latent LVOTO in a patient without indication for myectomy in hypertrophic cardiomyopathy. With one XTR MitraClip, the plicature of anterior leaflet was obtained allowing to remove the LVOTO and restoring normal haemodynamic conditions.
Real challenging anatomies
In light of the spread of MitraClip even for all these difficult anatomies, nowadays few anatomical contraindications to MitraClip remain: the presence of severe calcification in the grasping area, the length of posterior leaflet <7 mm, active endocarditis, and haemodynamically relevant mitral stenosis. Rheumatic valve disease is no more an absolute contraindication per se and this can be due to the fact that using XTR allows to reduce the leaflet gap also in case of increase thickness of MV leaflets (MV rheumatic disease).46
Conceiving MitraClip as a tool
This overview of current published evidence on treatment of challenging anatomies raises the point that is currently no longer appropriate to consider the MitraClip as a procedure. A procedure is an interventional therapeutic process that is defined by certain plan and certain steps that are usually well defined. Different operators can perform procedures in the same way when they are in the same phase of the learning curve. On the contrary, for MitraClip the standardization of techniques is currently possible only when dealing with more simple anatomies and in case of beginner operators. The learning curve allows to be confident with this tool so that it widens the spectrum of pathologies that can be treated. For these reasons, MitraClip may be conceived more as a tool to obtain the procedural success which is the durable reduction of MR. As consequence, when judging the indications to percutaneous MVP, especially when dealing with more complex anatomies and challenges cases, the expertise of the operators and the imaging specialists must be considered as a factor that mostly affects the probability to reach adequate and durable results.
Conflict of interest: Dr Gavazzoni is consultant for Biotronik and Abbott. Dr. Miura is a consultant for Japan Lifeline. Prof.Zuber is consultant for Abbott. Dr. Taramasso is a consultant for Abbott Vascular and 4 Tech, Boston CoreMedical, speaker for Edwards. Francesco Maisano received Grant and/or Research Support from Abbott, Medtronic, Edwards Lifesciences, Biotronik, Boston Scientific Corporation, NVT, Terumo; receives Consulting fees, Honoraria from Abbott, Medtronic, Edwards Lifesciences, Swissvortex, Perifect, Xeltis, Transseptal solutions, Cardiovalve, Magenta; has Royalty Income/IP Rights Edwards Lifesciences and is Shareholder, Cardiogard, Magenta, SwissVortex, Transseptalsolutions, 4 Tech, Perifect. Dr. Pozzoli and Dr. Russo have nothing to declare.
