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In the 2 years since the FDA-approved MitraClip for the treatment of mitral regurgitation, it appears to have demonstrated efficacy based on U.S. registry data.

Using the clip to repair malfunctioning mitral valves successfully reduced regurgitation to moderate severity or better (grade 2 or below) in 93% of patients. But recipients also had a 2.3% rate of in-hospital mortality and overall procedural complications were seen in 8% of patients.

Nonetheless, with a -- or the composite of successful reduction of mitral regurgitation without conversion to open cardiac surgery and death -- the data still "support the effectiveness of this therapy in appropriately selected high-risk patients in a commercial setting," , of Minneapolis Heart Institute in Minn., and colleagues concluded online in the Journal of the American College of Cardiology.

The initial commercial experience of the MitraClip, consisting "predominantly of patients with symptomatic, degenerative mitral regurgitation and prohibitive surgical risk," has been "favorable," they added, expressing contentment that "the commercial U.S. outcomes are comparable with those reported in Europe, where rates of procedural success typically have exceeded 90%, with a low incidence of in-hospital mortality."

Indeed, the investigators should be "complimented" for providing these findings, which are "very encouraging and mirror data obtained from other centers throughout the world," wrote , of Atlanta's Marcus Heart Valve Center, in an accompanying editorial.

Martin also emphasized that "the heart team taking care of and/or performing mitral valve replacement procedures should not only involve skilled imagers and interventional cardiologists, but also surgeons experienced in mitral valve surgery. By bringing the expertise of this team to each case, the field will advance and, most importantly, our patients will be properly and better served," he concluded.

Sorajja's study included 564 patients who were enrolled in the Society of Thoracic Surgeons/American College of Cardiology Transcatheter Valve Therapy (TVT) Registry between 2013 and 2014. The majority of patients (90.8%) had degenerative mitral regurgitation. Functional mitral regurgitation was reported in 14.4% of cases.

At 30 days, stroke occurred 1.8% of the time, death 5.8%, life-threatening bleeding 2.6%, and device-related complications 1.4%.

Interestingly, the successful reduction of mitral regurgitation to moderate-to-low severity (grade 2 or below) was equally likely at institutions with or without precommercial MitraClip experience (93.8% versus 91.1%, P=0.26), but precommercial sites had better odds of producing drastically lower degrees of mitral regurgitation (grade 1 or below, 66.5% versus 57.4%, P=0.04).

This may be because, "as we learned from transcatheter aortic valve replacement, education of new implanters by more experienced colleagues is critical to successful outcomes of the procedure in patients who are symptomatically ill with severe mitral regurgitation," according to Martin.

He continued, writing that by providing proctoring physicians, clinical specialists, and tutorial courses at reference centers, "Abbott has made a major push to improve the technical skills and clinical judgment needed to make commercial insertion a safe and appropriate therapy."

Sorajja and colleagues conceded that their study was limited by the voluntary nature of the TVT Registry and the missing core laboratory assessment of key echocardiographic variables. Another shortcoming was the lack of 1-year data, Martin added.

The editorialist pointed out several important questions still left unanswered: "Are there patients who should not be considered for a mitral valve repair procedure? For example, those with severe dementia or marked immobility/frailty?" and "What are the predictors of those patients who might have very minimal, if any, reduction in mitral regurgitation from the clip procedure,?" he added.

To that end, "the TVT Registry, as a scientific tool, will enable the collection of these data for analysis and outcome reporting and will lead to further insight into the impact of this important therapy," according to Sorajja and colleagues.