M-TEER Outcomes at 1 Year Best at Hospitals With High Mitral Surgical Volumes

Transcatheter edge-to-edge repair for primary mitral regurgitation (M-TEER) can be safely performed at centers with a low volume of surgical mitral valve repair, but new data suggest that hospitals with more surgical outcomes see better M-TEER outcomes at 1 year.  

While there was no difference in the risk of death in the hospital or at 30 days with M-TEER when done at low-, intermediate-, and high-volume surgical centers, that equivalence didn’t hold up at 1 year..

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“In the short term, there's not a lot of connection between a center's complex mitral valve surgical volume and the performance of M-TEER,” senior investigator Sreekanth Vemulapalli, MD (Duke University Medical Center, Durham, NC), told TCTMD. “What becomes really important is the 1-year outcomes, and that's where we do see an association between complex mitral valve surgical volume and M-TEER performance in terms of mortality and heart failure hospitalizations.” 

The big question, said Vemulapalli, is how to square the discordant early and late outcomes across centers with low and high surgical volumes.

“At these centers that are doing higher volumes of complex mitral valve surgery, either there's some sort of better postprocedural care or follow-up that's happening in the long term, or there's a difference in patient selection that is not captured by simple patient demographics,” he said. “It could be that centers that do more complex surgery are intervening with M-TEER at an earlier stage of disease.”

For example, M-TEER at those centers may be done in patients with more preserved left ventricular ejection fractions or in those with less structural damage to the myocardium. In fact, Vemulapalli noted that the median LVEFs of those treated at high-volume surgical centers tended to be slightly higher than those treated at low- and intermediate-volume surgical sites (57% vs 55% vs 55%, respectively).

Benjamin Hibbert, MD, PhD (Mayo Clinic, Rochester, MN), who wasn’t involved in the study, said he is  surprised somewhat by the data, noting that two-thirds of M-TEERs for primary MR in the US are being performed at centers with low surgical volume. Despite that, the overall results are really good, he said.

“When you look at the technical performance of the clip, TEER success is exactly the same across all of the centers and the complication rate was actually higher in the high-volume centers,” he told TCTMD. “Then, when you look at the outcomes, I agree they're slightly better in these high-volume mitral valve surgical centers [at 1 year], but the differences are small. They’re statistically significant because they have 40,000 patients, but we’re talking about differences of about 1%.”

While the conclusions of the paper are correct, the study also shows that centers performing fewer mitral valve surgeries “are getting excellent technical results and the patients are doing comparatively well to these high-volume centers,” said Hibbert.

Apples and Oranges

The new study, published recently in Circulation: Cardiovascular Interventions, with lead author Paul Grayburn, MD (Baylor Scott and White Research Institute, Plano, TX), included 41,834 patients with primary mitral regurgitation (MR) treated at 500 hospitals who were part of the American College of Cardiology/Society for Thoracic Surgeons (ACC/STS) TVT Registry and STS Adult Cardiac Surgery Database.

To TCTMD, Vemulapalli said the analysis is not like traditional studies comparing outcomes based on operator/institutional volume. Instead, it’s about understanding “systems of care” around the treatment of primary MR. He noted that the national coverage determination from the US Centers for Medicare & Medicaid Services requires on-site cardiac surgery—20 or more mitral valve surgeries per year, of which at least 10 must be repairs—for M-TEER programs to operate.

“That was one rationale for looking at this question,” he said. “The other is this overlying idea of valve centers of excellence. The question is: is there any sort of connection between the performance of mitral valve surgery and the performance of M-TEER?”  

Of the 500 surgical sites, 66.4% were low volume (fewer than 25 mitral valve repairs annually), 20.4% were intermediate volume (25 to 49 mitral valve repairs), and 13.2% were high volume (50 or more mitral valve repairs annually). Surgical mitral valve repair was defined as a leaflet resection or artificial chords with or without annuloplasty.

M-TEER success was 54.6% and did not differ by hospital surgical volume. In-hospital or 30-day mortality with M-TEER was 3.5%, a rate that also did not differ across centers with varying surgical volumes (3.4%, 3.4%, and 3.9% at low-, intermediate-, and high-volume surgical sites). When adjusted for clinical and demographic data, the relationship between surgical volumes and early mortality with M-TEER was not statistically significant (P = 0.552).

The rate of hospital readmission for heart failure (HF) at 30 days was 2.8% and did not differ by surgical volume. Readmission at 1 year was 9.4% overall, and this was significantly lower at high-volume centers (9.2%, 10.8%, and 8.6% at low-, intermediate-, and high-volume repair sites). In the restricted cubic spline analysis, the relationship between HF readmissions at 1 year and surgical volume was statistically significant (P = 0.015).

Regarding mortality at 1 year, the overall rate was 15.0% with M-TEER. After adjustment, the restricted cubic spline analysis for mortality was statistically significant, with lower rates of death at 1 year among higher-volume surgical centers (P = 0.027).

Results More Pronounced in Secondary MR?

In terms of whether M-TEER should be relegated to hospitals that also do a high volume of mitral valve repair surgeries, Vemulapalli said there is a need to balance patient access, noting that the absolute magnitude of the difference in outcomes at 1 year is relatively small.

“We're talking about a few percentage points in terms of mortality and hospitalization,” he said. “Now, if it was me, I would be willing to travel to go to the center that would give me absolutely the lowest rate of repeat hospitalization and mortality, but balancing access, that's an individual decision at a patient level.”

Still, Vemulapalli believes these new data support the concept of valve centers of excellence. “It does seem to be that it’s making a difference, whether it's in selection or in care afterwards,” he said, referring to the better outcomes at high-volume surgical sites.

Interpreting the results, Hibbert agreed that the difference in late outcomes likely reflects more comprehensive systems of care at sites with high surgical volumes, a category used here as a proxy for valve centers of excellence, and has little to do with TEER operators.

“At Mayo, when you get a MitraClip, you don't just have me doing your MitraClip, there’s a whole system,” he said. “As opposed to getting a procedure done and then going home, you’re getting follow-up from nurse practitioners and [physician assistants] who are experts in following patients with mitral valve disease. You’re integrated into a cardiac rehab program. We’ll never know with this type of data, but I’m willing to bet that's probably where the difference lies. Patients are getting more comprehensive care at these higher-volume centers.”  

Hibbert agreed that patient access to TEER is important, adding it might be best to reserve valve centers of excellence for more complex cases since centers with low surgical volumes are getting excellent technical results and comparable early outcomes. Instead of thinking about only treating patients at these top-notch centers, understanding the systems of care that appear to be making a difference in late outcomes is important so these practices can be adopted elsewhere.

Importantly, the present analysis is focused solely of primary MR, so it’s difficult to extrapolate the results to secondary MR. Vemulapalli pointed out that secondary MR requires a host of different subspecialists, including a good heart failure team with advanced therapies.

“The entire ecosystem around care is different,” he said. “Additionally, the level of evidence for surgical interventions in secondary MR is vastly different than in primary. Having said that, I would speculate that if a similar study was done for secondary MR, we might find the same things, but to an even greater degree. If we think that what we've seen here is related to patient selection and postprocedural care, that’s going to become, in my view, even more important in patients with substantial myocardial disease as most secondary MR patients have.”

To TCTMD, Hibbert agreed, noting that ancillary HF care, including comprehensive follow-up, is even more important in secondary MR. Like Vemulapalli, he suspects the differences across surgical volumes might be even more pronounced in functional MR.