Introduction
Mitral regurgitation (MR) is the most common valvular regurgitant abnormality, increasing in prevalence with age and affecting approximately 4 million people in the United States alone. , Severe MR eventually leads to left ventricular (LV) dilation and dysfunction resulting in heart failure. Although surgical mitral valve (MV) repair or replacement remains the first-line treatment for MR, a significant fraction of patients are poor surgical candidates and are thus denied surgery. Such patients encounter increased morbidity and mortality, approaching 50% at 5 years. Percutaneous edge-to-edge transcatheter mitral valve repair (TMVR) (also known as the MitraClip® system ) provides a durable alternative in severe (≥3+) MR and was approved by the Food and Drug Administration (FDA) in October 2013 for prohibitive-risk patients with primary MR. Recently published results of the Cardiovascular Outcomes Assessment of the MitraClip® Percutaneous Therapy for Heart Failure Patients with Functional Mitral Regurgitation (COAPT) trial demonstrated the benefit of this technology in secondary MR in terms of lower hospitalization rates and all-cause mortality within 24 months of follow-up. This chapter will review the indications and procedural details, as well as troubleshooting for MitraClip®.
Evidence and indications
The EVEREST II (Endovascular Valve Edge-to-Edge Repair of Mitral Regurgitation Study) trial randomized patients to either surgical or TMVR (MitraClip®). The primary results of the study demonstrated surgery to be superior in terms of efficacy (composite of survival and freedom from recurrent MR), primarily driven by higher rates of repeat intervention for MV dysfunction in the MitraClip® arm at 1 year. MitraClip® therapy, on the other hand, had a better safety outcome and compared favorably in terms of freedom from heart failure symptoms, improvement in quality of life (QoL), and LV reverse remodeling parameters. At 5 years, there was again no difference in mortality between the surgical and percutaneous arms with similar reduction in New York Heart Association (NYHA) class. There was also no difference between surgery and MitraClip® in terms of repeat interventions for residual MR between 1 and 5 years. Additional data from follow-up registries that included higher-risk patients further corroborated significant reduction in MR, improvement in LV dimensions and heart failure symptoms, and reduction in heart failure hospitalizations at 12 months after the MitraClip® procedure. According to the 2014 valvular disease guidelines, TMVR may be considered for severely symptomatic patients (NYHA class III to IV) with chronic severe primary MR (stage D) who have favorable anatomy for the repair procedure and a reasonable life expectancy, but who have a prohibitive surgical risk because of severe comorbidities and remain severely symptomatic despite optimal medical therapy for heart failure (class IIb, level of evidence: B) ( Fig. 15.1 ).
The EVEREST II trial primarily included patients with primary MR. However, in a post hoc analysis involving a small subgroup of patients with secondary MR, MitraClip® was noninferior to surgery in terms of freedom from death, operation for MV dysfunction, or recurrent ≥3 MR grade. Previous data have demonstrated lack of survival benefit and high rate of MR recurrence after surgical repair in patients with LV dysfunction. Given that the majority of secondary MR patients are managed medically, this represents a large group that could potentially benefit from a low-risk transcatheter procedure. Secondary MR represents a larger proportion of patients being treated with the MitraClip® in Europe and constituted 77% of the patients in the ACCESS EU (ACCESS-Europe, A Two-Phase Observational Study of the MitraClip® System in Europe) registry. In fact, the European Society of Cardiology (ESC) Heart Failure and ESC/European Association for Cardio-Thoracic Surgery (EACTS) valvular disease guidelines in 2012 both recommended percutaneous MV repair for patients with symptomatic severe secondary MR despite optimal medical therapy (including cardiac resynchronization therapy if indicated) with anatomic suitability who are judged inoperable or at high surgical risk by a team of cardiologists and cardiac surgeons, and have a life expectancy greater than 1 year (class IIb, level of evidence: C). The results of two randomized trials evaluating the role of MitraClip® in secondary MR were recently published. The French MITRA-FR study showed no difference in the rate of death or unplanned hospitalization for heart failure at 1 year between medical therapy and medical therapy plus MitraClip®. However, the COAPT trial demonstrated significantly lower hospitalization rates (hazard ratio: 0.53; 95% confidence interval [CI], 0.40 to 0.70; P <0.001) and all-cause mortality (hazard ratio: 0.62; 95% CI, 0.46 to 0.82, P <0.001) at 24 months in patients with secondary MR who received MitraClip® in addition to guideline-directed optimal medical therapy. Larger sample size, longer follow-up, more stringent adherence to guideline-directed therapy, and higher success rates with more durable results were some of the plausible reasons for the benefit seen in COAPT as opposed to the MITRA-FR study.
Preprocedural planning
Transthoracic echocardiography (TTE) is a good first modality to evaluate cardiac function and MR severity. However, a transesophageal echocardiogram (TEE) is important to define mitral pathophysiology, MR severity, and anatomic suitability for successful TMVR (see Fig. 15.1 and Fig. 15.2 ). Primary MR includes patients with intrinsic abnormalities of the MV, such as prolapsing or flail leaflets due to myxomatous degeneration or fibroelastic deficiency. Secondary functional MR (FMR) is a consequence of LV enlargement and dysfunction due to ischemic or nonischemic mechanisms, which results in mitral annular dilation and restricted/tethered leaflets. The EVEREST inclusion criteria for MitraClip® therapy included a flail gap of <10 mm, flail length of <15 mm, and, for secondary MR, a coaptation gap of <2 mm and coaptation depth of <11 mm. Moreover, most of the patients included in the trial were central A2-P2 scallop pathologies. Recent experience has shown the ability to successfully treat pathologies outside of these norms, which is discussed later in the chapter.
Procedural details and optimization
The MitraClip® ( Fig. 15.3 ) is a transvenous transfemoral device implanted via a 24F steerable guiding catheter (SGC) (tapers to 22F where it crosses the atrial septum) advanced into the left atrium (LA) after a transseptal procedure. The SGC has an 80-cm working length with a mounted ± knob that allows for flexing (+) and straightening (−) of the catheter. The MitraClip® is a cobalt-chromium, polyester-covered device with movable arms. A fully open clip spans 20 mm, and at 120-degree grasping, it spans 17 mm. The newer XTR model has longer clip arms (an additional 3 mm for each arm) and grippers with two additional rows of frictional elements. It is advanced using the catheter delivery system (CDS) through the SGC into the LV, and the MV leaflets are grasped between Nitinol grippers and the clip arms (see Fig. 15.3 ). The CDS has a steerable sleeve (SS) and a delivery catheter (DC), which is used to advance or retract the clip and to align it perpendicular to the MV coaptation plane. The CDS key material in the current MitraClip® consists of nylon (instead of stainless steel in older iterations), allowing for improved advancement and straddling.
Transseptal puncture
The transseptal puncture is one of the most important aspects of the entire procedure. A good transseptal puncture site for the MitraClip® is superior and posterior along the interatrial septum that ensures an adequate height from the MV ( Fig. 15.4 ). This is usually 4 to 4.5 cm for a prolapsing leaflet and even higher for a flail leaflet. However, it is lower, around 3.5 to 4 cm, for the secondary MR cases, where the coaptation point is below the mitral annular plane. Likewise, the puncture height might need to be adjusted for non–A2-P2 disease—higher for medial and lower for lateral pathologies to allow for adequate space for catheter maneuvering and leaflet grasping. In some acute cases of flail leaflets, the LA may not be enlarged, making it challenging to attain sufficient height from the annular plane. The transseptal puncture usually needs to be extremely posterior to allow sufficient distance from the annular plane. However, care must be taken during the puncture and while advancing the guide and clip to avoid any LA perforation. A counterclockwise turn of the sheath when advancing into the LA turns it anteriorly, away from the posterior wall/LA roof.
Mitraclip® procedure
After transseptal puncture, the transseptal sheath is advanced into the LA. An Amplatz wire is then advanced into the left superior pulmonary vein through this sheath. Alternatively, a Torayguide (Toray) or ProTrack (Baylis Medical) wire can be looped in the LA. The transseptal sheath is then exchanged out over this guidewire for the steerable MitraClip® guide catheter. The fluoroscopic bands at the end of the guide can also be visualized on TEE as having an echogenic double-ring appearance. This allows for careful advancement of the guide catheter under both fluoroscopic and TEE guidance (using short- and long-axis views to visualize the catheter tip), thus avoiding injury to the LA free wall. The clip is then advanced through the guide using the CDS, again under fluoroscopic and TEE guidance. For safe clip advancement, the initial direction of the guide catheter should be oriented posteriorly toward the left superior pulmonary vein because this is the longest distance available in the LA. Once straddled in the LA, medial (M knob) and slight posterior torque (clockwise rotation of SGC) along with retraction of the entire system clears the pulmonary ridge and left atrial appendage, bringing the clip closer to the MV (Video 15.1). Once the MitraClip® arms are opened above the MV, a 3D en face view on TEE allows proper orientation of the clip arms (by rotating the DC handle clockwise or counterclockwise) perpendicular to the MV coaptation line ( Fig. 15.5 ). Importantly, all manipulations and positioning of the clip should be done in the LA above the MV leaflets. Once advanced into the LV to grasp the leaflets, manipulations should be minimized to avoid chordal entrapment, which can potentially worsen MR or result in cardiac injury requiring surgery.
The clip is then advanced into the LV using the DC handle in an open position (some operators might choose to advance in a semiclosed position, sometimes with a breath hold to avoid rotation due to translation). Once in the LV, reexamine the clip carefully under TEE and fluoroscopy to ensure that no rotation of the clip has occurred, which might indicate interaction with the chordal apparatus. The leaflets are usually grasped in the left ventricular outflow tract (LVOT) view ( Fig. 15.6 ). Once the leaflets are appropriately secured between the grippers and clip arms, the arms are closed to plicate the anterior and posterior MV leaflets. An adequate tissue bridge should be confirmed after the grasp in multiple views, including 3D en face view (see Fig. 15.5 ). Significant motion of any leaflet might indicate risk of leaflet escape from the clip and need regrasping.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
