Minimally Invasive Mitral Valve Surgery Earns Confidence in Expert Hands

NEW ORLEANS -- There is no single best surgical approach for mitral valve repair (MVr) after minimally invasive mini thoracotomy was shown to be as safe and effective as conventional sternotomy in a randomized trial.

People who had degenerative mitral regurgitation (MR) treated with either procedure had similar changes in physical function, according to SF-36v2 physical functioning scale scores from baseline to 12 weeks, according to the U.K. Mini Mitral presentation by Enoch Akowuah, MD, of James Cook University Hospital in Middlesbrough, England, at the annual meeting of the American College of Cardiology.

Between treatment arms, surgeons produced a similar quality of MVr. There was little moderate or severe MR at 12 weeks and 1 year, and patients experienced no differences in adverse events (e.g., death, stroke, heart failure hospitalization, repeat intervention on the mitral valve).

"It doesn't seem like either [mini thoracotomy or sternotomy] is better. It's not the journey, it's the destination that matters. If you correct the primary problem, the patient will do well," commented Thomas MacGillivray, MD, of MedStar Washington Hospital Center in Washington, D.C., a cardiac surgeon and discussant at the late-breaking trial session.

Akowuah said that "the emergence of percutaneous strategies to treat [degenerative MR] and the need for trials to determine which procedures benefit specific patients groups make defining the optimum surgical approach an urgent priority."

These findings should give confidence to patients and clinicians and aid adoption of minimally invasive MVr, he concluded.

Although results at 1 year were comparable, trial data suggested faster recovery with mini thoracotomy. Physical function recovered within 6 weeks after mini thoracotomy but not sternotomy, and patients resumed moderate-to-vigorous physical activity and enjoyed better sleep efficiency at 6 weeks with the minimally invasive procedure.

Moreover, there were small differences in quality-of-life metrics favoring mini thoracotomy at all time points, Akowuah reported.

As for resource utilization, this approach was associated with hospital stays that were 1 day shorter than with conventional sternotomy (5 vs 6 days).

However, the tradeoff was longer aortic cross clamp (+11 minutes), cardiopulmonary bypass (+30 min), and total procedure times (+44 min). This was the result even in the hands of the 28 experienced participating surgeons who were said to be over the learning curve for mini thoracotomy.

"Expertise is extremely important," as mini thoracotomy is a "complex operation," Akowuah stressed during a press conference. "Clearly the results only apply to surgeons with expertise."

Akowuah and colleagues had set the bar of expertise at a "not unreasonable" minimum 50 procedures per participating operator in the trial. "Most mitral surgeons should achieve this in a year or two," he said.

Yet David Moliterno, MD, of University of Kentucky Medical Center in Lexington, observed that the U.K. Mini Mitral surgeons had performed a median 86 career mini thoracotomies over 7.5 years before the trial.

"Even though those are experts, it looks like they were doing one procedure a month," he pointed out. "That's relatively infrequent."

Moliterno also suggested it is only going to get harder to find that level of MVr expertise in the real-world now that MitraClip transcatheter edge-to-edge repair (TEER) is gaining traction.

A nationwide study from 2011 to 2018 found a downtrend in both intermediate-risk and high-risk surgical MVr volumes at centers that adopted TEER for degenerative MR, though the median annualized institutional MVr volume nevertheless stayed around 30 per center.

Important questions remain regarding the relative net clinical benefit, or detriment, of shifting large volumes of surgical MVr to TEER.

The U.K. Mini Mitral trial was conducted at 10 sites in the U.K. Participants were adults with degenerative (or primary) mitral valve disease requiring isolated MVr who were deemed suitable for both conventional and minimally invasive approaches by a local heart team.

After screening 1,167 surgical candidates, 330 were ultimately randomized in the study. The difficulty enrolling was partly due to lack of equipoise among patients and surgeons, as many had strong preference for one treatment over the other, according to Akowuah.

Baseline characters were similar between groups. Average age was 67 years, and women accounted for 30% of the cohort. Transthoracic echocardiography showed that the vast majority of participants had severe MR and type II mitral valve pathology.

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