Mitraclip

The major technology in this category, MitraClip (Abbott Vascular), was also the first transcatheter mitral valve repair technology to receive CE Mark approval ( Figure 22-2). This system has its roots in the Alfieri stich operation, in which the middle scallops of the posterior and anterior leaflets (P2 and A2, respectively) are sutured together to create a double-orifice mitral valve. This operation, though usually performed with adjunctive ring annuloplasty, has proved effective and durable in a wide variety of pathologies and even in selected patients without annuloplasty.^21,22

The concept of a percutaneous replicate of an Alfieri stich was initially conceived by St. Goar and subsequently developed as MitraClip by Evalve, Inc. (which was later acquired by Abbott Vascular). ²³ A series of trials with this device confirmed its feasibility (Endovascular Valve Edge-to-Edge Repair Study [EVEREST] I), and its safety and efficacy were compared with those of surgical repair in a randomized trial (EVEREST II), providing a wealth of data on this technology as described later.^24,25

The procedure is performed with standard catheterization techniques utilizing a transseptal approach from the right femoral vein. ²⁶ The clip delivery system is introduced through a 24F sheath into the left atrium, where it can be guided using a series of turning knobs under transesophageal (both two- and three-dimensional) echocardiography guidance through the mitral valve into the left ventricle. A properly aligned and oriented clip can be placed on the P2 and A2 segments of leaflets, grasping them from the ventricular side to create leaflet opposition. Once leaflet insertion is confirmed by echocardiography, the clip can be released. If a suboptimal grasp occurs, the leaflet can be released, allowing repositioning prior to a second grasp attempt. Additionally, a second or more clips can be placed as needed for optimal MR reduction ( Figure 22-3). ²⁶

In the 2 : 1 randomized EVEREST II trial, 184 patients were designated to receive MitraClip therapy and 95 to undergo surgical repair or replacement. These patients were almost a decade older (mean age 67 years) than in usual surgical series and had more comorbidities. Major adverse events at 30 days were significantly less frequent with MitraClip therapy (9.6% versus 57% with surgery; P < 0.0001), although much of the difference could be attributed to the greater need for blood transfusions with surgery ²⁷ ( Figure 22-4). The freedom from the combined outcome of death, mitral valve surgery, and MR severity greater than 2+ at 12 months was higher with surgery (73%) than with MitraClip therapy (55%; P = 0.0007). Importantly, in patients with acute MitraClip therapy success, the result appears durable with a very low rate of later mitral valve surgery ( Figure 22-5).

Subsequent analyses of this rich database have demonstrated persistent reductions in MR grade, improvement in New York Heart Association (NYHA) functional class, and reduction in LV dimensions ²⁷ with MitraClip therapy. Other studies have demonstrated a lack of mitral stenosis, no effect of initial rhythm on results, and benefit in higher-risk subjects.^28–30

In the EVEREST II High-Risk Study, 78 patients with an estimated surgical mortality rate of 12% or higher (mean 14%) were treated with MitraClip, with an actual 30-day mortality of 8%. Survival at 12 months was 76% and significantly better than that of a concurrently screened comparison group, the majority of whom (86%) were treated medically. Patients treated with MitraClip had improved MR grade at 12 months (78% ≤2+), LV dimensions, New York Heart Association functional class, and quality of life, and a reduced need for hospitalization. ³⁰ Similar benefit was demonstrated in another series of extreme-risk patients. ³¹ In addition, a group of European investigators have demonstrated the feasibility of MitraClip therapy in a group of 51 severely symptomatic patients with secondary ischemic or functional MR that failed to respond to cardiac resynchronization therapy. ³²

The future of MitraClip therapy and its role in the management of patients with MR remains unclear in the United States because of its investigational status. The EVEREST II trial failed to demonstrate efficacy equivalent to that of surgery for a diverse group of patients with varied risk and etiology. The EVEREST High-Risk Registry and experience outside the United States point to a more appropriate role in high-risk patients with secondary functional and ischemic MR. A new randomized trial (Clinical Outcomes Assessment of the MitraClip Percutaneous Therapy for High Surgical Risk Patients [COAPT]) is under way to compare the device with medical therapy in these patients.

Other Devices

Other devices discussed in this category are NeoChord, Mitra-Spacer, and MitraFlex ( Figure 22-6). The NeoChord DS1000 system is a transapically inserted tool that can capture a flail leaflet segment and pierce it with a semidull needle to attach a standard polytetrafluoroethylene (PTFE) artificial chord, which is then anchored to the apical entry site with a pledgeted suture. A first-in-human case has been reported, ³³ and the device is currently undergoing a phase 1 evaluation in Europe in the Transapical Artificial Chordae Tendineae (TACT) trial.

Mitra-Spacer (Cardiosolutions, Inc.) is an occluder device that is anchored in the LV apex via transseptal or transapical insertion with an anchor fixed outside the heart. The tethered “balloon-like” spacer floats in the mitral inflow pathway, providing a space occluder around which the mitral leaflets coalesce. This device has entered outside US first-in-human evaluation and has been deployed in four patients, with a reported reduction of one to two MR grades. ³⁴ The MitraFlex device (Transcardiac Therapeutics) is designed as a transapically inserted thorascopic device to implant artificial chordae tendineae and is in preclinical development.