By Sachin Goel and Samir Kapadia
Uncorrected severe symptomatic mitral regurgitation is associated with worsening heart failure and mortality. There are two main mechanisms of mitral regurgitation–degenerative mitral valve disease (including prolapse and flail) and functional mitral regurgitation (characterised by apical tethering of anatomically normal mitral leaflets in the presence of left ventricular dilatation with regional or global systolic dysfunction).
Mitral valve surgery is recommended in patients with moderately severe or severe (3+ or 4+) mitral regurgitation in the presence of symptoms outlined in the current guidelines for valvular heart disease1. Additionally, the indications for mitral valve surgery are clear in patients with degenerative severe mitral regurgitation and symptoms. However, mitral valve surgery in patients severe symptomatic mitral regurgitation secondary to severe left ventricular dysfunction (left ventricular ejection fraction <30%), which mostly represents patients with functional mitral regurgitation1, has a class IIb indication. This recommendation is based on studies demonstrating no survival benefit of surgical correction of severe functional mitral regurgitation and high recurrence rate of mitral regurgitation2,3. Although there does not appear to be survival benefit in these patients, they do appear to derive benefit from mitral valve surgery in terms of symptoms, rehospitalisation for heart failure and changes in left ventricular geometry. Consequently, a significant number of patients with severe symptomatic functional mitral regurgitation do not undergo surgery due to advanced age, left ventricular dysfunction or comorbidities that place them at high risk for morbidity and mortality with mitral valve surgery. In this context, various percutaneous catheter based mitral valve repair techniques have been developed in order to provide an alternative minimally invasive option for these patients to reduce mitral regurgitation severity and improve their outcomes.
Leaflet based repair
Significant clinical data exists thus far only on the MitraClip device (Abbott Vascular), which is based on the surgical edge-to-edge repair technique. This device is advanced into the left side of the heart via femoral venous and transseptal approach and the two arms of the clip grasp the mitral valve leaflets from beneath, creating a double orifice and reducing mitral regurgitation severity.
The randomised EVEREST (Endovascular Valve Edge-to-Edge Repair Study) II study proved safety and efficacy of the MitraClip device in patients with severe mitral regurgitation who were candidates for mitral valve surgery4. Furthermore, the EVEREST II high risk study showed significant improvement in symptoms and left ventricular size in high surgical risk patients at 12 months after being treated with the MitraClip5, and the COAPT (Clinical Outcomes Assessment of the MitraClip Percutaneous Therapy for High Surgical Risk Patients) trial is enrolling high surgical risk patients with severe functional mitral regurgitation and will provide data on effectiveness of MitraClip in these patients. Other leaflet based approaches include the NeoChord (NeoChord), which involves transapical chordal replacement for degenerative mitral regurgitation and Percu-Pro device (Cardiosolutions) wherein a spacer is deployed across the mitral valve and anchored at the apex.
Annuloplasty based repair
Indirect mitral annuloplasty using coronary sinus-based approach has been studied in the AMADEUS trial with the Carillon mitral contour system (Cardiac Dimension), which demonstrated its safety and efficacy. Direct mitral annuloplasty techniques that reshape the annulus directly without using the coronary sinus include: the Mitralign device (Mitralign) where pledgets are delivered to the mitral annulus via retrograde transfemoral approach and plicated and locked to cinch the annulus; the Accucinch device (Guided Delivery Systems), which uses a small adjustable ring of anchors placed under the valve via retrograde femoral approach, and the Millipede system (Millipede), which involves placement of a mitral annuloplasty ring percutaneously.
Transcatheter mitral valve replacement
Efforts are already underway in developing exciting transcatheter mitral valve replacement techniques, either via transseptal or transapical approach, such as the CardiAQ prosthesis (CardiAQ Valve Technologies) and the Endovalve-Hermann prosthesis (Endovalve).
Various transcatheter mitral valve devices for repair and valve replacement have emerged and have the potential of fulfilling the unmet need for minimally invasive strategies in these patients with severe MR at high risk for morbidity and mortality.
Sachin S Goel and Samir R Kapadia are at the Department of Cardiovascular Medicine, Cleveland Clinic Foundation, Cleveland, USA
1. Bonow et al. J Am Coll Cardiol 2008; 52:e1–142
2. Wu AH et al. J Am Coll Cardiol 2005; 45:381–87
3. McGee et al. J Thorac Cardiovasc Surg 2004; 128: 916–24
4. Feldman et al. N Engl J Med 2011; 364:1395–406
5. Whitlow et al. J Am Coll Cardiol 2012; 59:130–9