Surgical Volume Matters When It Comes to Repair of Primary MR

Patients treated at centers with the lowest versus highest volumes have worse operative and 1-year outcomes.

Surgical Volume Matters When It Comes to Repair of Primary MR

SAN FRANCISCO, CA—Patients who require a surgical fix for primary mitral regurgitation (MR) would be better off getting treated at a hospital—or by a surgeon—performing a higher volume of operations, US national registry data indicate.

Annual volume of mitral valve repair or replacement at both the hospital and surgeon levels was inversely related to the successful mitral valve repair rate, operative mortality, 30-day mortality/morbidity, and 1-year mortality, according to Vinay Badhwar, MD (West Virginia University, Morgantown).

The improvement in outcomes associated with higher volumes appeared to flatten out at around 75 procedures at the hospital level and 35 at the surgeon level, he reported here at TCT 2019.

“These findings may further inform guideline-directed efforts to define access to experienced hospitals and surgeons for primary MR or advanced complex mitral valve disease,” he concluded.

Robert Bonow, MD (Northwestern University Feinberg School of Medicine, Chicago, IL), speaking at a press conference, said that the finding of a volume-outcome relationship in this setting is not surprising but that it fills a gap in the literature. Previous research has examined volumes among centers and operators, repair rates, and technical success, “and now you’ve got the outcomes data, which we’ve been looking for,” Bonow said. “This ties it together that there really is an impact on patient outcome, and so this does help us begin to think about . . . how we can identify centers and surgeons where patients should go.”

STS Adult Cardiac Surgery Database

Badhwar noted that early surgical correction of severe primary degenerative MR is recommended in the guidelines as long as optimal outcomes is possible. Durable repair has been shown to be superior to replacement for primary MR, he added.

But whether procedural volume influences the outcomes of mitral valve surgery “has yet to be clearly defined by large contemporary national clinical data,” Badhwar said.

He and his colleagues examined data from the Society of Thoracic Surgeons Adult Cardiac Surgery Database to find out. Their analysis included 55,311 patients with primary MR who underwent isolated mitral valve repair or replacement at 1,094 US hospitals. One-year outcomes were assessed through linkage with Centers for Medicare & Medicaid Services (CMS) data.

Median annual procedural volume was 23 at the hospital level (11 for repairs only) and 12 at the surgeon level (5 for repairs only). Hospitals in the lowest quartile for volume performed fewer than 10.9 operations per year, whereas those in the highest quartile were doing more than 46.4. The figures for surgeons were roughly half of those.

There were some noteworthy differences in patient characteristics between the lowest-volume and highest-volume groups. Patients treated at the lowest-volume centers were more likely to have no insurance, to be black or Hispanic, and to have class III/IV symptoms. In addition, Badhwar said, “it is of interest that despite mitral valve repair being a guideline-directed therapy for minimally symptomatic patients, this was less than 5% of the [referred patients] across all quartiles.”

Overall, 81% of operations were repairs rather than replacements, but there were differences based on hospital volume. The repair rate was 63.8% at the lowest-volume and 84.5% at the highest-volume centers (P < 0.0001). And among patients who underwent repair, it was more likely to be done with a minimally invasive or robotic approach at the highest-volume centers (37.0% vs 8.0%; P < 0.001).

The primary outcome of the study was operative mortality, and this was inversely related to procedural volume at both the hospital and surgeon level. The same pattern was seen for the secondary outcomes of 30-day mortality/morbidity (bleeding, stroke, prolonged ventilation, renal failure, and wound infection) and 1-year mortality. There were no significant differences between volume groups in terms of 1-year rates of reoperation or heart failure rehospitalization.

Outcomes by Surgical Volume






OR (95% CI)

Hospital Level

     Operative Mortality

     Mortality/Morbidity, 30 days

     Mortality, 1 year










2.08 (1.48-2.93)

1.35 (1.15-1.60)

1.64 (1.32-2.03)

Hospital Level

     Operative Mortality

     Mortality/Morbidity, 30 days

     Mortality, 1 year










2.27 (1.69-3.04)

1.72 (1.50-1.97)

1.60 (1.32-1.93)

When assessing volume on a continuous basis, there remained inverse associations between volume at the hospital or surgeon level and operative mortality and 30-day mortality/morbidity. In addition, higher volumes were associated with increases in the rate of successful mitral valve repair (residual MR ≤ mild/1+).

Boosting Repair Rates

In a panel discussion following Badhwar’s presentation, James Gammie, MD (University of Maryland Medical Center, Baltimore), asked how the field can improve mitral valve repair rates, noting that one out of five patients is still getting a replacement according to these new data.

Badhwar responded by saying that training has recently stimulated more surgeons to want to learn mitral valve repair and how to do it better. “I think simplicity needs to be the focus in mitral valve repair, as all surgeons and cardiologists realize there can be very complex procedures being performed and yet excellent coaptation can be achieved through modified, simplified techniques,” he said.

Repair rates have improved over the past 10 years, Badhwar noted, adding that the number of surgeons and hospitals equipped to do mitral valve repair is larger than once thought. “So access to having quality outcomes and successful repair is now likely larger than what was previously estimated,” he said. About 82% of the US population lives within a referral region that provides access a center with an annual volume of at least 40 cases per year, he pointed out.

Responding to that figure during the press conference, Ajay Kirtane, MD (NewYork-Presbyterian/Columbia University Irving Medical Center, New York, NY), said that even though patients have access to a program like that, there’s no guarantee that’s where they’ll be sent for treatment.

Michael Mack, MD (Baylor Scott and White Heart Hospital, Plano, TX), added that even if patients get sent to the right program, it doesn’t mean they’ll get treated by a high-volume surgeon, noting that the volume-outcome relationship in this study was seen for both hospitals and surgeons. “I just think that means that we’re moving more and more to the age of super-subspecialization, and that there are procedures that are generalist cardiac procedures that most surgeons can do well,” Mack said. “Mitral valve surgery is one of those that should be super-specialized.”

Adnan Chhatriwalla, MD (Saint Luke’s Mid America Heart Institute, Kansas City, MO), then raised the idea of specialization among hospitals within a geographical area, where each center would take the lead for a particular procedure. “We can get less competitive about this stuff so that we can really get the volume and expertise we need to provide the best outcomes to patients,” he said.

That’s an important point, one that a forthcoming multisocietal document will make, Bonow said: “Whether that has an impact on the geopolitics of referral is unclear, but we think that’s an important statement to make.”

Todd Neale is the Associate News Editor for TCTMD and a Senior Medical Journalist. He got his start in journalism at …

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  • Badhwar V. The mitral valve surgery volume-outcome relationship in the United States. Presented at: TCT 2019. September 27, 2019. San Francisco, CA.

  • Badhwar reports no relevant conflicts of interest.