Experience, High Volume Improve Mitral Valve Procedural Outcomes

Roxanne Nelson, RN, BSN

September 28, 2019

SAN FRANCISCO — Both operator experience and volume are paramount when it comes to procedure success and reducing complications for mitral valve procedures, findings from two new studies suggest.

In the first paper, which looked at operator experience with MitraClip (Abbott), optimal procedural success was higher among operators with experience of greater than 50 cases than among those with 1 to 25 cases (75.1% vs 63.9%; P < .001).

The associations between operator experience and patient outcome remained statistically significant after adjustment for patient characteristics, which suggests that case selection is unlikely to explain these results, reported lead study author, Adnan K. Chhatriwalla, MD, Saint Luke's Mid America Heart Institute, University of Missouri-Kansas City.

In the second study, which looked at the association of volume to outcomes for mitral valve surgery, an inverse volume-outcome relationship for surgeons and hospitals was observed for successful repair of primary mitral regurgitation (MR), 30-day operative mortality, and 1-year mortality.

"These findings may further inform guideline-directed efforts to define access to experienced hospitals and surgeons for primary mitral insufficient or complex mitral valve disease," said lead author, Vinay Badhwar, MD, executive chair, WVU Heart & Vascular Institute; Gordon F. Murray professor and chair, Department of Cardiovascular & Thoracic Surgery, West Virginia University, Morgantown.

The findings from both studies were presented here at the Transcatheter Cardiovascular Therapeutics (TCT) 2019 Conference, and the study by Chhatriwalla et al was published online September 27 in the Journal of the American College of Cardiology.

MitraClip

Transcatheter mitral valve repair (TMVr) using the MitraClip is an established therapy for patients with MR and has been commercially available in the United States since 2013. When used appropriately, MitraClip is associated with improvements in symptoms, quality of life, and survival.

Because it is a relatively novel procedure, it requires a very specific and complex skill set for both the operator and echocardiographer to ensure the most optimal results while reducing the risk for complications, the authors write. Procedural success of TMVr with MitraClip has been defined by acceptable reduction in MR and the absence of major procedural complications, and success in some postmarket registries has been reported as higher than 90%, with a good safety profile.

However, procedural success varies, and complications, including death and device detachment, can occur.

"It requires a unique operator skill set and navigation of the right and left atria, mitral valve apparatus, and left ventricle," explained Chhatriwalla. "The relationship between operator experience and procedural outcomes has not been fully characterized."

Using data from the Society of Thoracic Surgeons/American College of Cardiology (STS/ACC) Transcatheter Valve Therapy (TVT) registry, Chhatriwalla and colleagues examined the association between individual operator experience and clinical outcomes of TMVr with MitraClip.

A total of 14,923 TMVr device procedures were performed by 562 operators at 290 sites between November 2013 and March 2018 and were included in the analysis. Procedures were categorized according to individual operator case sequence (1 to 25, 26 to 50, and >50).

Operator case number was also analyzed as a continuous variable that allowed for visual estimation of the "learning curve," Chhatriwalla explained. If two operators with different levels of case experience  were working together, the case was categorized based on the higher case number.

The patient cohort was primarily elderly, with a median age of 81 years, and had a high prevalence of comorbidities: diabetes mellitus (27.6%), prior cardiac surgery (33.8%), prior myocardial infarction (26.6%), prior percutaneous coronary intervention (30.6%) and prior coronary artery bypass grafting (27.5%).

Most had 3+ or 4+ MR (92.9%) and degenerative mitral disease (86.3%), and the median STS-predicted risk for mortality was 5.7% (3.4%, 9.2%) for mitral valve repair, and 8.7% (5.5%, 13.3%) for mitral valve replacement.

Optimal procedural success (≤1+ residual MR without death or cardiac surgery) increased as operator experience increased and was observed across the three categories: 63.9%, 68.4%, and 75.1% (P < .001). At the same time, procedural time and procedural complications declined.

Rates of acceptable procedural success, defined as residual MR of 2 or less without death or cardiac surgery, also increased with operator experience, but the authors note that these differences were smaller (91.4%, 92.4%, and 93.8%; P < .001). However, these associations remained significant in adjusted, continuous variable analyses.

Procedural complications were lower in the higher categories of operator case experience, and, along with procedural time and success, improvement became evident after approximately 50 cases. Continued improvements were observed up to 200 cases.

"A procedural learning curve does exist for transcatheter mitral valve repair with MitraClip, and these findings are independent of mechanism of mitral regurgitation," said Chhatriwalla. "These findings have important implications as to the level of training and experience necessary to achieve optimal outcomes in this challenging patient population."

In a panel discussion of the paper, held during a press briefing, Michael Mack, MD, from Baylor Scott & White Health in Dallas, Texas, explained that as a rule of thumb, the more complex the procedure, the greater the volume-outcome relationship. "For simple procedures there isn't any reason to travel across the country or across the state to get tertiary center care."

"It isn't just the operator," he added. "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."

Mack said he believes these findings and thinks that they are 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."

Pinak Shah, MD, director of the cardiac catheterization lab at Brigham and Women's Hospital, Boston, Massachusetts, explained that this reflects his own clinical experience.

"I think it took about 50 to 60 cases before I understood what was going on, and it's not just the technicalities of the procedure," he said. "Another thing is that I think the average interventional cardiologist doesn't necessarily understand the mitral valve that well, so there's a lot of learning curve in understanding the anatomy of the mitral valve and how it becomes dysfunctional."

He added that 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."

Mitral Valve Surgery

In the second study, Badhwar and colleagues looked at the association of volume to outcome for mitral valve surgery, which has not been defined by contemporary national clinical data.

Their objectives were to assess volume of MV repair or replacement, assess 30-day and 1-year outcomes, and, importantly, define the MV surgery volume-outcome relationship at the hospital level and surgeon level.

Their study included a total of 55,311 patients with primary MR, 1111 hospitals, and 3137 surgeons, across all 50 US states. They used the Centers for Medicare & Medicaid Services to gauge 1-year outcomes. 

When looking at the patient characteristics in lowest vs highest quartiles, hospitals in the lowest quartile tended to have a higher percentage of uninsured patients (4.04% vs 2.35%), black/Hispanic patients (14.8% vs 10.2%), and class III/IV symptoms (31.9% vs 23.8%).

"Importantly, in the entire contemporary cohort, 81% is the overall repair rate for primary mitral value insufficiency," said Badhwar. "But when breaking it down, from highest to lowest quartile, it was nearly 90% for the highest while the lowest was closer to 60%."

The highest quartile also had a much higher percentage of performing minimally invasive surgery and using robotic technology (8.0% vs 37.0%; P < .001).

For hospital level outcomes, a higher annual procedural volume was associated with improved 30-day risk-adjusted operative mortality rate and a successful MV repair rate with an inflection point of about 75 cases.

For surgeons, the inflection point was about 35 cases per year for the same two outcomes.

Overall, 148 hospitals (14%) met the threshold of 75 cases per year, and 303 surgeons (13%) performed at least 35 cases annually.

"Super-Subspecialization"

Commenting on the presentation, Ajay J. Kirtane, MD, SM, associate professor of medicine at Columbia University Irving Medical Center and director of the cardiac catheterization laboratories at New York-Presbyterian Hospital, New York City, noted that "we really need these data because we have so many other pieces pointing to volume, repair rates, and technical success, which is clearly related to volume. We have many low-volume centers and low-volume operators, and this ties it together."

Kirtane, who moderated a press conference held ahead of the presentation, emphasized the importance of "getting the word out."

"Just because you live in an area that has a good program doesn't mean that you are going to get referred to that program," he said, adding that advocacy is very important, as is addressing the disparities shown in the study.

Mack pointed out that "even if you get to the right surgeon, you may not get to the right program. As was shown, there was an operator-volume outcome in addition to the institution, and I think that means that we're moving more and more to the age of super-subspecialization."

Badhwar has no disclosures. Chhatriwalla disclosed being a proctor for Edwards Lifesciences and Medtronic and serving as a speaker for Abbott Vascular, Edwards Lifesciences, and Medtronic.

Transcatheter Cardiovascular Therapeutics (TCT) 2019 Conference. LBA STS REGISTRY and STS/ACC TVT REGISTRY. Presented September 27, 2019. 

J Am Coll Cardiol. Published online September 27, 2019. Abstract

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