Development & Growth of TAVR in the U.S.

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 - David R. Holmes 2013
David R. Holmes, Jr., MD, MACC

Since the FDA’s approval of transcatheter aortic valve replacement (TAVR) in 2011, improvements and scientific evidence have continued to mount.

A central component of the regulatory process in the U.S. is the development of a National Registry (TVT Registry) containing data on all patients undergoing this procedure.  Under the leadership of the American College of Cardiology (ACC), the Society of Thoracic Surgeons (STS), the STS/ACC TVT Registry has come to fruition with support from the Duke Clinical Research Institute in data analytics, the FDA and the Centers for Medicare & Medicaid Services. Capturing data from all patients treated with this approach allows for a complete picture of the risks and benefits of the approach and data analysis for outcome assessment. It also fulfills regulatory mandates, and offers the potential to identify and implement new proposals and protocols to further expand the field and extend the benefits to broader patient groups.  

At the present time, more than 3,000 patient records have been accumulated for analysis. While only one manufacturer has been involved, the federal mandate has been to have this registry be “generic” in order for it to capture all patients undergoing TAVR irrespective of which company and which device was utilized. The structure and function of the STS/ACC TVT Registry has been formalized and codified for data elements, scope and standard operating procedures both for regulatory and industry as well as scientific purposes. Proposals now have been formulated and submitted for new patient groups and alternative access approaches and collaborations with other international registries have been initiated.

In addition, a wealth of scientific information has accumulated over the past year. This information relates to longer-term outcomes, increased knowledge about complications such as vascular or cerebrovascular complications with approaches to either prevent or mitigate them, introduction of new patient groups such as valve-in-valve, and new strategies such as alternative access approaches including direct aortic access.  

The FDA announced that it granted an investigational device exemption (IDE) to the ACC and STS to conduct a study assessing alternative access approaches for TAVR. The goal behind the study is to expand the field and extend the benefits of TAVR to broader patient groups. Moving forward, this should be a model for specialty societies, industry and federal regulators aligning efforts to ensure appropriate patient access to a new technology in a cost-effective and evidence-based way.

The specific issue of paravalvular aortic regurgitation has also been of great concern. Paravalvular leak has been associated with increased morbidity and mortality during follow up in multiple studies. It may relate to several factors including prosthesis/annulus mismatch with undersizing, or the presence of large rigid calcific nodules that prevent full expansion of the prosthesis. There are multiple avenues to address this, including the introduction and testing of new devices aimed at minimizing this with the use of circumferential “skirts,” as well as the use of larger devices.  

Measurement of annular dimensions is complicated because the annulus is more oval than round.  Echocardiographic studies may foster the use of prostheses which are somewhat smaller than ideal.  Application of alternative imaging modalities and the availability of 29 mm devices in selected cases have been associated with decreased paravalvular aortic regurgitation, improving outcome. Other technological advances such as the development and testing of smaller catheter sizes have been associated with a reduction in vascular complications and have facilitated the use of percutaneous applications with percutaneous closure devices, avoiding the need for surgical cut downs of the access site.

The field of TAVR continues to advance rapidly. The application of advanced technology, the presentation and publication of new trials and more optimal matching of devices and patients will allow full utilization of the attributes of this transformational technology. For  updates and clinical guidance on TAVR, visit CardioSource.org/TVT.

Dr. Holmes is past president of the ACC.