Learning Curve Exists for MitraClip, Volume-Outcomes Data Hint

SAN FRANCISCO, CA—Operators who have performed more transcatheter mitral valve repairs (TMVRs) with the MitraClip (Abbott) are able to get better procedural results, according to data from the Society of Thoracic Surgeons/American College of Cardiology (STS/ACC) TVT Registry.

Greater experience was associated with shorter procedures, improved procedural success, and fewer in-hospital complications, Adnan Chhatriwalla, MD (Saint Luke’s Mid America Heart Institute, Kansas City, MO), reported here at TCT 2019. Improvements flattened out after about 50 procedures, but there were still gains associated with increasing experience up to about 200 MitraClip implantations.

Chhatriwalla told TCTMD that those associations remained after adjustment for baseline patient characteristics, which indicates that case selection does not explain the findings. “So we think we’re identifying the true procedural learning curve,” he said.

During a panel discussion following Chhatriwalla’s presentation, Francesco Maisano, MD (University Hospital Zürich, Switzerland), acknowledged the learning curve but highlighted the acceptable results achieved even early on in an operator’s MitraClip experience. “This is probably something that you would not see in surgery, for instance,” he said.

“On the other hand, the learning curve goes beyond 200 cases, and I believe that that is the case,” Maisano added. “With my background as a surgeon, I know that a surgeon who has done 1,000 repairs is better than a surgeon who has done 500. So still there is a learning curve and this is something that has to be underlined. You need to build centers of excellence where you can get . . . better outcomes, but on the other hand I’m also impressed by the fact that even in the very early stage you get reasonable results, so this is important for the access of this therapy to a larger population.”

Speaking at a press conference, Robert Bonow, MD (Northwestern University Feinberg School of Medicine, Chicago, IL), said this is important in the context of an expected increase in the number of patients who will undergo MitraClip implantation for secondary mitral regurgitation (MR) in heart failure. The COAPT trial showed a significant benefit of the MitraClip in this setting, leading to an expansion of MitraClip’s indication by the US Food and Drug Administration.

There have been multisocietal attempts to define procedural volume thresholds for the MitraClip “because clearly there’s a volume threshold above which you get very good results,” Bonow noted. “So the learning curve issue is important as we expand this now to more sites in the United States to provide access for patients.”

These data might also provide some insight into the discrepant results of COAPT and MITRA-FR, a French trial that failed to show a benefit of MitraClip implantation for functional MR; COAPT investigators were more experienced than the MITRA-FR investigators. “That may explain why the patients treated in France had higher degrees of residual mitral regurgitation with time, and it maybe also explains why the clinical results were better in COAPT,” Bonow said.

Experience Matters More for ‘Optimal’ Results

MitraClip implantation is a complex procedure and therefore experience with performing it might be expected to have an influence on results. Indeed, a prior study by Chhatriwalla’s group showed that centers with higher MitraClip volumes provided better outcomes and fewer complications.

An association between individual operator experience and procedural results for the MitraClip has not been established, however.

For this new study, published simultaneously online in the Journal of the American College of Cardiology, Chhatriwalla and his colleagues turned to the STS/ACC TVT Registry. The analysis included 14,923 MitraClip procedures performed by 562 operators at 290 sites between November 2013 and March 2018. The vast majority of patients (92.9%) had 3+/4+ MR, and 86.3% had degenerative disease.

In terms of case experience, 549 operators had done 25 or fewer, 230 had performed 26 to 50, and 116 had performed more than 50. Those with more experience were more likely to use multiple clips and to deploy clips in the A2-P2 and A3-P3 segments and less likely to deploy clips in the A1-P1 location. Postprocedural mitral valve gradients did not differ based on operator experience.

Experience came into play, however, when looking at procedural success. For acceptable results (≤ 2+ residual MR without death or a need for cardiac surgery), procedural success was high regardless of experience, but it increased from 91.4% for operators with 25 or fewer cases to 93.8% for those with more than 50 (P < 0.001).

The association was even stronger when the goal was “optimal” results (≤ 1+ residual MR without death or a need for cardiac surgery). There, procedural success was 63.9% in the least experienced operators and 75.1% for the most experienced (P < 0.001).

Asked about the relatively low proportion of procedures resulting in “optimal” procedural success, Chhatriwalla said that wasn’t surprising because treatment with the MitraClip involves a trade-off between reducing MR through clipping and still allowing the leaflets to open. “Really what we’re showing is that after you gain more experience, you’re able to better strike that balance,” he said.

Similar patterns were seen for procedural time, which fell from 145 to 99 minutes across experience groups, and procedural complications, which declined from 9.7% to 7.3% across groups (P < 0.001 for both). The reduction in complications was driven by lower rates of cardiac perforation and blood transfusion, with no differences in stroke, single leaflet device attachments, transseptal complications, urgent cardiac surgery, or in-hospital mortality.

Those associations remained significant in adjusted, continuous-variable analyses, which revealed a lessening of gains at around 50 procedures but continued improvements beyond that. The etiology of MR did not affect the results.

“These findings have important implications as to the level of training and experience necessary to achieve optimal outcomes in this challenging patient population,” Chhatriwalla said during the press conference.

What Are Experienced Operators Doing Better?

Chhatriwalla told TCMTD that operators who have performed more MitraClip implantations might be taking the time to get the clip in just the right position, whereas earlier on in an operator’s experience simply grabbing the leaflets was, at the time, considered a success.

He said it’s important to note, however, that getting to mild residual MR—rather than moderate residual MR—has been shown to make a difference in terms of mortality and rehospitalizations for heart failure.

Therefore, it’s important for less experienced operators to learn and improve their patients’ outcomes by partnering with those who have performed more of the procedures, Chhatriwalla said, noting that MitraClip cases are almost exclusively two-person procedures.

Less experienced operators might also want to consider passing on more challenging cases to colleagues with greater experience, he said, acknowledging that egos and institutional politics might get in the way. “I would say that the ideal is that people should feel comfortable going to more experienced operators and centers with the tougher cases,” Chhatriwalla suggested.

At the press conference, several panelists pointed out that successful MitraClip implantation involves a multidisciplinary team and not just a skilled operator. “It isn’t just the operator. It’s the patient selection, it’s the type of etiology of the valve that’s being treated, and it’s the intraprocedural imaging that’s absolutely critical to getting this done,” Michael Mack, MD (Baylor Scott and White Heart Hospital, Plano, TX), said. “So I do believe the findings. I think they’re real. I think that this is a superb analysis. And I would say I have four MitraClip programs in our healthcare system and we are seeing issues that are related to early experience in low-volume programs.”

Interventional cardiologist Pinak Shah, MD (Brigham and Women’s Hospital, Boston, MA), added that beyond the technicalities of the device and the procedure, there is a learning process for some operators regarding the mitral valve. “I think the average interventional cardiologist doesn’t necessarily understand the mitral valve that well, so a lot of the learning curve [for me] was understanding the anatomy of the mitral valve and how it becomes dysfunctional,” Shah said. “This is probably one of the most complicated things that we do in the cath lab and really requires a good multidisciplinary approach, not just with imagers but I think with surgeons as well.”