JAMA Viewpoint: TAVR Promise Must Be Weighed Against Risks, Limitations

Broad use of transcatheter aortic valve replacement (TAVR) in Europe and recent approval in the United States for inoperable patients have created high expectations for the procedure among individuals with severe aortic stenosis, including many who are younger and at lower risk. But this enthusiasm must be counterbalanced by careful assessment of the serious complications associated with the “transformative technology,” contends a Viewpoint article published in the August 8, 2012, issue of the Journal of the American Medical Association.

Chintan S. Desai, MD, and Robert O. Bonow, MD, both of Northwestern University Feinberg School of Medicine (Chicago, IL), highlight the challenges of determining TAVR appropriateness in patients based on surgical risk, age, and comorbidities.

Worrisome Complications

A major concern with TAVR, they say, is the potential for stroke, both in the short- and long-term. Though the cause is likely embolism of atherothrombotic debris from the aorta or the native valve, “the optimal stroke prevention strategy has yet to be determined,” Drs. Desai and Bonow report.

In addition, differences in antiplatelet use between the PARTNER trial and the FRANCE 2 registry “underscore the current variations in clinical practice and indicate that the most effective antiplatelet strategy remains uncertain. The question of whether anticoagulation with an oral vitamin K antagonist or direct thrombin inhibitor is more effective than dual antiplatelet therapy also remains unanswered,” they observe.

Another complication gaining attention is the development of heart block requiring permanent pacemaker implantation, the authors write. However, this occurs at a much higher rate with the CoreValve prosthesis (Medtronic, Minneapolis, MN) compared with the Edwards Sapien device (Edwards Lifesciences, Irvine, CA), and only the latter is currently available in the United States.

More recently, paravalvular aortic regurgitation has “arisen as a major determinant of poor postprocedural outcome,” the authors say. In the PARTNER 1A trial, moderate to severe regurgitation was seen in 12% of patients receiving TAVR compared with 0.9% receiving surgery, but registry studies suggest that the rate could be even higher in clinical practice, the authors explain. This is worrisome since even mild paravalvular regurgitation has been associated with increased mortality. “Possible mechanisms for [the complication] include malposition, undersizing, underexpansion, and malapposition of the prosthesis,” they add.

Drs. Desai and Bonow say that further research is warranted to “determine whether improved preprocedure imaging to optimize prosthesis size, greater attention to advantageous prosthesis deployment, or new device design will be successful in minimizing the frequency and severity of aortic regurgitation after TAVR.”

Tempering Consumer Expectation

Ultimately, all of these complications “provide reason for pause in the rush to expand the patient population eligible for TAVR,” the authors argue, because so much is still unknown regarding the extent of adverse outcomes outside of the clinical trial setting, where patients may not receive optimal care.

“Due to the complexity of patients with severe aortic stenosis and of the procedure, a team-based approach involving physicians and nurses experienced in TAVR is necessary to achieve the magnitude of benefit observed in the PARTNER trial and also to minimize complications,” they write.

As word-of-mouth spreads, patients requiring valve replacement will inevitably prefer a percutaneous approach to surgery, the authors suggest. However, “it is essential for clinicians to temper increasing consumer expectation for TAVR with a frank discussion emphasizing that the time has not yet come for TAVR in patients who fulfill criteria for aortic valve replacement and have low surgical risk.”

There is already evidence of “indication creep” in countries where TAVR has been approved the longest, and this is cause for concern, Drs. Desai and Bonow write, adding that clinicians have a duty to clearly explain the proven benefits of surgery in both the long and short term for patients at low surgical risk.

“As with all new technologies, it is essential that patient and physician expectations must be balanced with a realistic assessment of potential benefits, risks, and outcomes to provide the optimal therapy for severe aortic stenosis,” they conclude.

CMS Keeps ‘Indication Creep’ in Check

In a telephone interview with TCTMD, Ted Feldman, MD, of Evanston Hospital (Evanston, IL), said “this is a glass half empty, glass half full” viewpoint. “While I think the intent of the editorial is cautionary in a very appropriate way, the balance is that we have a therapy for a group of patients that has had no option in the past and we probably have a good therapy for patients for whom surgery is very high risk.”

Dr. Feldman noted that “everybody in the field agrees” with the admonition that TAVR not be promoted in low-risk surgical patients. However, the challenge lies with deciding how to proceed with “a borderline patient,” he commented.

Indication creep does not currently seem to be a problem in the United States, Dr. Feldman indicated. “We don’t know who’s being treated nationally with the commercial release, but my impression based on discussion with my colleagues is that the level of comorbidity of the patients being treated in the commercial use of the device in the United States remains very high,” he said, adding that the Centers for Medicare and Medicaid Services (CMS) reimbursement requirement that a TAVR candidate be declared inoperable by 2 surgeons “makes it clear to practitioners in the United States what the standard is.”

Without the CMS restrictions, “this discussion might be different,” Dr. Feldman concluded.

 

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Source:
Desai CS, Bonow RO. Transcatheter aortic valve replacement for aortic stenosis: Balancing benefits, risks, and expectations [viewpoint]. JAMA. 2012;308:573-574.

 

 

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