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The MitraClip has performed favorably in the U.S. in the years since FDA approval, per post-market surveillance of patients who've had the device implanted to treat mitral regurgitation.

From the Society of Thoracic Surgery (STS)/American College of Cardiology Transcatheter Valve Therapy Registry, Paul Sorajja, MD, of Abbott Northwestern Hospital in Minneapolis, and colleagues determined that transcatheter mitral valve repair (TMVR) with the MitraClip was associated with low in-hospital mortality (2.7%) and high acute procedural success (91.8%).

Patients who had linkable Centers for Medicare and Medicaid claims data had encouraging outcomes as well, with mortality observed in 5.2% at 30 days and 25.8% at 1 year. By the end of the year, repeat hospitalization for heart failure had reached 20.2%, and the combination of mortality or heart failure rehospitalization 37.9%, Sorajja's group reported in the Journal of the American College of Cardiology.

In all, 95.5% were discharged from hospital with mitral regurgitation grade 2 or lower without cardiac surgery and survived to 30 days.

"Our findings demonstrate that commercial transcatheter mitral valve repair is being performed in the United States with acute effectiveness and safety," the authors concluded. Their study population underwent commercial therapy with the MitraClip after FDA approval in 2013, consisting mainly of those with severe symptoms, degenerative mitral regurgitation, and prohibitive surgical risk.

"These findings, which are consistent with prior reports on the effectiveness and safety of transcatheter mitral valve repair, are important observations as the treatment population expands, new hospital sites for the therapy accrue, and a number of potentially eligible patients remain untreated," Sorajja's group suggested.

On multivariable analysis, the predictors of 1-year mortality or heart failure rehospitalization were:

• Increasing age: HR 1.08 per 5 years (95% CI 1.01-1.15)
• Dialysis: HR 2.09 (95% CI 1.37-3.28)
• Left ventricular ejection fraction: HR 0.92 per 5% (95% CI 0.88-0.95)
• Moderate or severe lung disease: HR 1.28 (95% CI 1.05-1.58)
• Severe tricuspid regurgitation: HR 1.89 (95% CI 1.48-2.39)
• Residual mitral regurgitation grade 3 or 4 after the procedure: HR ~2.0 (95% CI ~1.4-2.0)

"Although these findings are interesting, they are no different from the factors associated with a worse outcome after mitral valve surgery. This affirms that patient-related factors are perhaps more important than the method by which mitral regurgitation is approached, either surgically or percutaneously," commented Steven Bolling, MD, of University of Michigan Health System in Ann Arbor.

In an accompanying editorial, Bolling called MitraClip's confirmed technical success and safety data the most important findings of the analysis.

"In fact, the safety and low biological impact of this left atrial catheter approach may allow practitioners to treat patients with mitral regurgitation much earlier in their disease course," he said. "Perhaps therapeutic mitral regurgitation intervention will be possible even long before congestive heart failure, atrial fibrillation, tricuspid regurgitation, pulmonary hypertension, and other complications of mitral regurgitation occur, which may obscure any benefit of obviating the mitral regurgitation."

The registry used by Sorajja's group included 2,952 TMVR patients who were treated from 2013 to 2015, of which 63.2% had data linked to CMS administrative claims. Participants had a median age of 82 years and were 55.8% men; they presented with a median STS score of 6.1% for mitral repair and 9.2% for mitral replacement.

Rates of safety events were not excessive: 0.1% for device embolization; 3.9% for major or life-threatening bleeding; 0.4% for stroke, and 0.1% for MI. Conversion to open heart surgery was required by 2.7%.

Notably, mortality and heart failure hospitalization at 1 year grew more likely with increasing severity of residual mitral regurgitation after TMVR. Combined, this endpoint was reported in 35.7%, 39.2%, and 54.4% of those leaving the hospital with grade 1-or-below, grade 2, and grade 3-or-higher jets.

This led the investigators to concluded that their findings "support the rationale for achieving significant mitral regurgitation reduction, including minimizing need for future surgical therapy, with procedural expertise when possible, even though the desired therapeutic goal may be less certain when treating patients with limited or no other therapeutic options."

Nevertheless, they admitted that the lack of a comparison arm was a limitation of their single-arm registry study. "Such controls, whether medical or surgical, are necessary to determine the magnitude (or lack thereof) of any clinical benefit of TMVR in these patients, particularly in high-risk individuals in which there may be continued adverse events despite initially successful therapy."

and are two trials that are comparing TMVR with guideline-directed medical therapy in two trials, Sorajja's group said, pointing out that severe tricuspid regurgitation and severe lung disease -- both associated with worse survival in the present study -- are exclusion criteria for these trials.

Another caveat of the study is the lack of reasoning given for hospitalization or surgery after TMVR.

Bolling said that MitraClip is just one component of the triad approach to mitral valve disease -- leaflet grasping, annular ring, and valve replacement -- and together these three components "will certainly remain the gold standard when surgical mitral valve disease therapy inevitably gives way to transcatheter mitral valve disease therapies."

"In the future, we will have all 3 of these gold standard mitral tools in our transcatheter toolbox. MitraClip will probably remain a crucial tool, but perhaps more importantly we will look at the device experience as having been a gateway to the future of catheter-based mitral valve disease therapy," he predicted.