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Mitral Valve Repair With the MitraClip
Mitral valve regurgitation is a common disease, traditionally treated with valve repair or replacement using open cardiac surgery.
MitraClip a new device for transcatheter mitral valve repair, in patients with symptomatic degenerative mitral valve regurgitation who are deemed to be prohibitive risk surgical candidates.
Mitral regurgitation (MR), either from primary valve disease (degenerative) or secondary (functional) to left ventricular dysfunction, affects more than 4 million Americans, or almost one in ten people over age 75 years.
When MR progresses and results in the deterioration of left ventricular function resulting in congestive heart failure, increased mortality and a significant decrease in quality of life.
Chronic MR also increases the risk of atrial fibrillation and stroke, both of which can have a debilitating impact on patients.
Definitive treatment traditionally requires surgical intervention, either with repair or replacement of the diseased valve through a median sternotomy or a lateral thoracotomy.
Minimally invasive open-heart techniques such as endoscopic repair through the right chest or robotic mitral valve repair are available but are less frequently used; all surgical approaches require cardiopulmonary bypass.
Transcatheter mitral valve repair with MitraClip uses femoral venous access to repair the mitral valve without requiring cardiac arrest.
Repair has recently been favored over mitral valve replacement in order to preserve as much of the native valve and subvalvular apparatus as possible.
Additionally, the most common mitral valve pathologies includes flail or billowing leaflets that are amenable to resection or repair using artificial chords.
Durable repair is associated with reduced mortality, reduce risk of endocarditis and obviate the need for life-long anticoagulation.
Techniques to repair the prolapsing mitral valve: traditional quadrangular and triangular resection techniques, replacement of the ruptured chordae with artificial neochordae, placement of an edge-to-edge stitch to anchor the prolapsing leaflet cusp to the opposing stable cusp, and implantation of a mitral annuloplasty ring to improve leaflet coaptation and avoid future annular dilatation.
Unlike primary MR, secondary or functional MR remains a surgical challenge, and is often treated with implantation of an undersized annuloplasty ring or valve replacement.
The durability of these repairs is suboptimal, with recurrence rates of 15-60% reported in the literature.
Transcatheter mitral valve replacement technologies have limited success because percutaneous access to the mitral valve is more challenging than the aortic valve, and the mitral annulus is large, irregularly shaped, and is intimately involved in left ventricle (LV) geometry.
The most common mitral valve abnormality resulting in severe symptomatic MR is myxomatous degeneration of the posterior leaflet, and is most often managed with mitral valve repair.
A partial resection of the posterior leaflet of the mitral valve, is a technique that is used frequently today.
The Alfieri mitral repair, treats MR by fixing the cusps of the anterior and posterior leaflets together using a double stitch placement at the point of maximal regurgitation.
The MitraClip is a single-size clip device that has been used to treat patients with functional, mixed and degenerative MR.
The MitraClip has a dual arm structure, with grippers to assist with capture of the mitral valve leaflets while the heart is beating.
The MitraClip system is introduced via the femoral vein access and uses trans-septal puncture to enter the left atrium.
The system includes the Steerable Guide Catheter (SGC) through which the Clip Delivery System (CDS) is introduced.
The Clip at the end of delivery system is made of cobalt-chromium and is covered with polypropylene fabric to promote tissue in-growth, and can be used in an MRI.
It is implanted in a percutaneous procedure using both fluoroscopic and echocardiographic guidance.
First, femoral venous access is obtained, and then trans-septal puncture of the interatrial septum.
Transmission-septal puncture is ideally performed at the fossa ovalis to gain access to the left atrium.
The patient is anticoagulated during the procedure.
The device can be oriented perpendicular to the mitral valve under echocardiographic visualization including real-time 3D transesophageal echocardiographic guidance.
The device is positioned above the regurgitant jet and is advanced across the mitral valve into the LV, with the two arms of the Clip perpendicular to the valve leaflets.
The Clip is then retracted so it can engage the appropriate segments of the mitral valve.
The arms and grippers of the Clip are then closed and the leaflet insertion is judged if it is acceptable by transesophageal echocardiography.
When the reduction of mitral regurgitation is adequate, the Clip is released from the delivery system.
If after releasing the Clip, mitral regurgitation of greater than mild is apparent and the mean gradient is less than 5 mmHg, another Clip can be implanted.
Multiple Clips are implanted in about 50% of patients.
Protamine is often administered to reverse the heparinization.
9% having a major adverse events including: death, myocardial infarction, nonelective cardiac surgery for adverse events, renal failure, transfusion of greater than two units of blood, reoperation for failed surgery, stroke, gastrointestinal complications requiring surgery, ventilation for greater than 48 h, deep wound infection, septicemia and new onset of permanent atrial fibrillation, and partial Clip detachments at 30 days
In a Phase II clinical trial (EVEREST II) comparing the MitraClip directly to mitral valve surgery in a randomized trial: included patients with both degenerative and functional MR.
In the above study the primary outcome was freedom from death, surgery for mitral valve dysfunction, or ?3+ MR, for which surgery was found to be superior.
In the short-term only 15% of patients experience a major adverse event.
45% of the patients in the surgical group received a transfusion of ?2 units of blood.
Prolonged mechanical ventilation was also more common in the surgical patients
Blood transfusions associated with worse early and late outcomes in cardiac surgery patients.
The degree of MR reduction is larger in the surgical patients.
Nearly 80% of patients are free from 3+ or 4+ MR after Clip placement and thus avoid surgery in 12-month follow-up.
Recovery from the MitraClip procedure is rapid, with patients typically only staying in the hospital for 2-3 days.
Approval of the MitraClip was granted in for patients with severe symptomatic degenerative MR that are considered to be too high risk for conventional mitral valve surgery.
There is little data to support that mitral valve surgery for functional MR improves symptoms over time or life expectancy.
Used in patients with heart failure and secondary mitral regurgitation with a dysfunctional heart valve lowered the 50% annualized rate of heart failure hospitalizations and 40% lower all-cause mortality at 24 months and significantly improved Quality of life and exercise performance at 12 months than patients treated with medical therapy alone (Stone GW).
Among patients with severe secondary mitral regurgitation, the rate of death or unplanned hospitalizations for heart failure at one year did not differ significantly between patients who underwent percutaneous mitral valve repair in addition to receiving medical therapy in those who receive medical therapy alone (Obadia JF)
In a multicenter, randomized controlled trial involving patients with severe secondary mitral regurgitation, the rate of primary outcome of death or unplanned hospitalization for heart failure at 12 months did not differ significantly between a percutanouus mitral clip repair and a control group (MITRA-FR investigators.
Among many patients with heart failure and moderate to severe secondary mitral regurgitation trans catheter mitral repair resulted in lower rate of hospitalization for heart failure, lower mortality and better quality of life and functional capacity within 24 months of follow up then medical therapy alone (COAPT investigators)
The five year follow up for the COAPT trial showed the annualized hospital hospitalization rate for heart failure was 33.1% per year in the device group and 57.2% per year in a control group.
While the benefits of transcatheter intervention are substantial, the residual risk among patients with heart failure and secondary mitral regurgitation are high-by five years almost 3/4 of patients in the intervention group had been hospitalized for heart failure, or died, and 57% had died.
There is a correlation between pulmonary hypertension (pHTN) and increased mortality after transcatheter mitral valve repair (TMVr) using the MitraClip.
pHTN is associated with increased mortality and readmission for heart failure in patients undergoing TMVr using the MitraClip system for severe mitral regurgitation.