TAVR Learning Curve, Annual Volume Back in Spotlight

Patrice Wendling

September 17, 2018

Transcatheter aortic valve replacement (TAVR) has a distinct learning curve, with greater operator experience associated with incremental improvements in procedural and clinical outcomes, including 30-day all-cause mortality, according to a large international registry study.

Results show that 30-day mortality rates are significantly worse in low-volume centers, which perform fewer than 50 TAVR cases a year, than in high-volume centers, which perform more than 100 cases a year (8.8% vs 3.9%; P = .003).

"One can argue whether it's 150 or 200 cases with regard to training," but "one thing in my opinion is clear: not every hospital or center should be doing it and not every interventional cardiologist should be doing it," senior author Asim Cheema, MD, St Michael's Hospital, Toronto, told theheart.org | Medscape Cardiology.

The study results, published in JACC: Cardiovascular Interventions on September 10, add to the ongoing debate about the need for procedural volume requirements for TAVR programs.

In an updated multisociety consensus document published in July, the performance measure for TAVR centers shifted from procedural volume to the quality of patient outcomes, but still states that existing programs should perform at least 50 TAVRs per year, or 100 in the previous 2 years.

Days later, a Medicare advisory committee was split over the continued use of volume requirements for new and continuing TAVR programs and operators, despite hours of testimony from hospital officials and industry experts.

Obviously, hospitals and physicians would like to offer the therapy to their patients where they practice, said Cheema, but TAVR is still a rapidly evolving field and requires a unique skill set that is a mix of interventional cardiology and interventional vascular practice.

The investigators wanted to understand whether experience affects the outcomes of "people getting the therapy at different centers, by different operators who do not have the same volume," and also how many procedures operators need to perform "before they offer this therapy to their patients," he said.

With that goal, the investigators examined data on 3403 patients who underwent TAVR from January 2005 to January 2016 at 16 large academic teaching sites in North and South America and Europe. Mean age of the patients was 82 years, 77% underwent transfemoral TAVR, and a balloon-expandable valve was used in 59% of the procedures.

For the learning-curve analysis, TAVR cases from each center were grouped by operator experience. In all, 33.5% of the procedures were performed by initial operators (1 to 75 cases), 22.9% by early operators (76 to 150 cases), 16.1% by intermediate-experience operators (151 to 225 cases), 10.4% by high-experience operators (226 to 300 cases), and 17.0% by very high-experience operators (>300 cases).

The unadjusted risk for mortality was significantly higher in the initial (9.6%; P < .001) and early (7.9%; P = .002) experience groups than in the very high-experience group (3.3%).

On multivariate analysis, TAVR procedural volume was independently associated with 30-day mortality, major bleeding, and major adverse cardiac events (P < .0001 for all).

Adjusted 30-day mortality was higher for operators with experience up to 225 cases (odds ratio [OR], 3.83 initial; OR, 2.41 early; OR, 2.53 intermediate) than for those with more than 300 cases.

The early safety end point — a composite of death, stroke, major bleeding, vascular complications, surgical conversion, and renal failure — was significantly worse in all the lower-experience groups than in the very high group, but continued to improve beyond the 225-case volume.

For the volume analysis, 2205 patients were placed into three groups, with 25.8%, 50.8%, and 23.3% of cases performed at low (<50 cases), moderate (50 to 100 cases), and high (>100 cases) annual volume centers, respectively.

On multivariate analysis, low annual volume was independently associated with higher risks for all-cause mortality (OR, 2.70; P = .002) and the early composite safety end point (OR, 1.60; P = .003).

Cheema declined to cite a specific volume threshold that operators or programs must achieve, and said that interventional cardiology and heart teams have learned a lot from the TAVR experience. There are more proctors, they are easily available, and CT is incorporated to identify the best valve for a particular patient.

"All these things put together have made the procedure safer and will continue to do so; however, to say that these things would obviate the need for a minimum volume or a certain experience, I personally do not agree with," he explained.

The investigators note that there are many low-volume centers, with fewer than 50 procedures a year, in the United States and around the world, and that "this trend is likely to continue, with potential utilization of this technology in lower-risk patients."

Reached for comment, lead author of the multisociety document and chair of the Society of Thoracic Surgeons (STS)/American College of Cardiology (ACC) TVT registry, Joseph Bavaria, MD, University of Pennsylvania, Philadelphia, said, "The bottom line from my perspective, especially as this relates to national healthcare policy in the United States, is that this paper corroborates two major components of the document that was just published in JACC a couple of weeks ago by the four cardiovascular societies."

He noted that international data on TAVR — whether it is from Michigan State University, the TVT registry, or Europe — all show that there is a significant learning curve of around 80 to 100 cases. As a result, when the writing committee updated the 2012 multisociety document, they stipulated that a new TAVR program needs a lead operator who has 50 primary TAVRs and another 50 secondary or assisting TAVRs.

"If you look at the data pretty closely, the inflection point for mortality comes somewhere between 25 and 50 cases per year as annual volume, so this corroborates the 50 number almost perfectly," said Bavaria.

Finally, he said, this study supports the practice of referring alternate access procedures to experienced centers.

The data, however, need to be put into the context of the tightrope between access and quality, but with 587 TAVR sites, the United States has more TAVR sites than any other country in the world, Bavaria said.

"I think these data and our recommendations will protect the Medicare population, to a certain extent, from really bad operators," he said. "But I don't think it will go to exclusive centers of excellence. That can be too restrictive. I think we've created a good balance, and this paper kind of corroborates our attempt to balance these two really important public health concepts."

John D. Carroll, MD, from the University of Colorado School of Medicine, Denver, who is a member of the multisociety document writing committee, writes in an accompanying editorial that the results "suggest that there is a danger of lowering TAVR quality by doing away or relaxing volume requirements."

This, he suggests, would create many new centers, starting a new learning curve, and result in more low-volume centers.

"Therefore, despite the efforts of many parties to use training and proctoring to eliminate the TAVR learning curve, it continues to exist and needs to be acknowledged as new centers start TAVR programs," he said.

Carroll observed that the study of access is more complex than that of quality and includes socioeconomic factors, the ability of primary care physicians to identify aortic stenosis, and other broad factors that lead to disparities in care.

"Until a definitive study shows access is a major problem in the United States, as well as other countries, we must emphasize quality of care with reasonable access, rather than taking the McDonald's strategy of saturation of markets for business reasons," Carroll concludes. "Our patients deserve better."

Cheema and first author Anthony W.A. Wassef have disclosed no relevant financial relationships. Bavaria's institution is part of the Edwards Lifesciences' PARTNER 2 and 3 trials and Medtronic's Low Risk SAVR-TAVR trial. Carroll reports being a member of the steering committee of the STS-ACC TVT registry; is a local site investigator for PARTNER 2 trial and the Low Risk SAVR-TAVR trial; and is a member of the data and safety monitoring board for the Tendyne trial.

J Am Coll Cardiol Intv. 2018;11:1669-1679 and 1680-1683. Full text, Editorial.

Follow Patrice Wendling on Twitter: @pwendl. For more from theheart.org | Medscape Cardiology, follow us on Twitter and Facebook.

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