Percutaneous edge-to-edge mitral valve repair using the mitraclip®

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.