Study Suggests 30-Case ‘Proficiency’ Threshold for TAVR

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Taking the first steps toward determining the learning curve for performing transcatheter aortic valve replacement (TAVR) via the transfemoral route, a new study shows that proficiency gradually increases up to about 30 cases and then plateaus. At this point, there were significant reductions in procedural times, radiation dose, and contrast volume. The study was underpowered to detect differences in clinical outcomes across the learning curve.

The findings were published online December 21, 2011, ahead of print in JACC: Cardiovascular Interventions.

For the retrospective single-center study, researchers led by David R. Holmes Jr, MD, of the Mayo Clinic (Rochester, MN), analyzed data from 44 consecutive patients who underwent transfemoral TAVR as part of the PARTNER trial between November 2008 and May 2011, sorting them into tertiles according to the order in which the cases were performed. All patients received the Edwards Sapien valve (Edwards Lifesciences, Irvine, CA).

Baseline characteristics among the tertiles were similar, with the exception that patients in tertile 1 were older (P = 0.016) but were less likely to be obese (P = 0.019) or suffer from sleep apnea (P = 0.023).

Procedural Gains Clear by Last Tertile

The learning curve was assessed by measurement of intraprocedural process parameters. Significant decreases were seen in cutdown-to-sheath, cutdown-to-valvuloplasty, valvuloplasty-to-valve, and fluoroscopy times as well as contrast volume. Concomitant decreases in radiation doses were also observed across the tertiles (table 1).

Table 1. Procedural Characteristics by Tertile

Plotting of these values showed decreased variation with a plateau at approximately 30 cases; after that, results were relatively consistent.

Taking a “holistic approach to the learning curve,” Dr. Holmes and colleagues write, “We believe the reasons for improvement are multifactorial, including refinement of procedural techniques, patient selection, and coordination of patient care among all the caregivers.”

They note that while the study was not powered to determine clinical outcomes, patient selection plays a critical role in ensuring positive short- and long-term results.

Fuel to the Fire

In an editorial accompanying the article, Peter C. Block, MD, of Emory University Hospital (Atlanta, GA), writes that while this study “begins to give us some insight” into questions about the TAVR learning curve, “the data allow a peek into the near future that may be either troubling, or not.”

He notes that given the recent US Food and Drug Administration approval of the Edwards Sapien valve, “the Mayo data should add fuel to the fire of what happens now.” Dr. Block calculates that approximately 7,500 TAVR cases will need to be performed around the country in the near future to enable all operators to meet the learning curve.

“We know nothing about how proficiency, once achieved, will be maintained—particularly by low-volume operators. If there were innumerable [TAVR] candidates out there for the proposed [TAVR] sites, it would not be an issue, but there are not,” he writes, adding that it may take more than a year for some site operators to become ‘proficient’ in low-volume hospitals.

Beyond Competency

“Quibbling” with Dr. Block’s assessment, Stephen G. Ellis, MD, of the Cleveland Clinic (Cleveland, OH), stressed the difference in qualifications for an expert center versus a proficient one.

“What the Mayo Clinic article is dealing with is how easily or how quickly the physicians were able to deliver the device,” he said in a telephone interview with TCTMD. “Obviously that’s important. But what happens if something goes wrong? You have to be able to manage complications, and that’s where a truly expert site distinguishes itself from a merely competent site.”

More specifically, Dr. Ellis said his center was able to salvage several potentially fatal complications because his team had enough experience to know how to deal with each situation. Thus, he argued, while the competency cutoff could remain at 30 cases, the expert cutoff would need to be closer to 100.

“There are gradations of competence and expertness, and to truly be able to manage some of the infrequent but life-threatening complications, you’re going to have to do lots more cases than the 30 cutoff that the Mayo Clinic suggests,” he said.

Lastly, Dr. Block observed that because of the Mayo Clinic’s reputation for excellence, their results would likely be representative of other, similar institutions, but every center has its own processes and rules, and the 30-case threshold may vary.

Study Details

The median age for all patients was 83 years and the mean STS score was 9.6. Half of the patients were men, 68% had CAD, and 55% had hypertension.

Five patients (11%) died by 30 days. Causes of death included acute aortic valve thrombosis, large ischemic/embolic cerebrovascular accident, sudden cardiac death, severe retroperitoneal bleed, and acute hypoxic respiratory failure.

 

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Sources:
1. Alli OO, Booker JD, Lennon RJ, et al. Transcatheter aortic valve implantation: Assessing the learning curve. J Am Coll Cardiol Intv. 2011;Epub ahead of print.

2. Block PC. Lessons from the learning curve. J Am Coll Cardiol Intv. 2011;Epub ahead of print.

 

 

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