Introduction
By George W. Vetrovec, MD, MACC
Editorial Team Lead, Invasive Cardiovascular Angiography & Interventions collection on ACC.org
Richmond, VA

Guidelines, Clinical Statements and Appropriate Use Criteria remain useful and significant products to guide clinical patient management. While often over interpreted as "rigid" documents dictating practice, they in fact offer a very well researched guide to help physicians in appropriate patient management. That said, no guideline can be entirely built on unequivocal evidence as the weighted significance of different trials as well as incompletely understood or studied issues all have to be "interpreted" by experts ideally clearly noting the areas of controversy or limited scientific rigor.

Thus guideline documents are ultimately the combined wisdom of the expert writing group filtered by external reviewers. But the reality is that writing committees are limited in size, and many expert clinicians are not involved in the writing. Depending on the guideline, there is always some "second guessing" by the clinical community about various aspects of new guideline statements. Evolving fields like transcatheter aortic valve replacement (TAVR) are particularly challenging because of the rapidly changing technology and even patient candidates—a true moving target.

In an attempt to offer selected clinicians not involved in the actual writing process a forum to comment on new guidelines, I invited a number of practice and academic "user" physicians to comment on the just released TAVR decision pathway. These individuals were asked to provide 2-4 paragraphs with optimally 1-3 references to support their comments. This is not intended to support a "rant" against guideline statements but rather to elicit thoughtful comments on the positives, possible negatives, areas with limited clarity in an attempt to have a useful dialogue for other practitioners.

This is an experiment. I appreciate the work of the contributors whose comments follow. I trust this will provide a useful discourse regarding the application of these guidelines to clinical practice.

Feedback is appreciated, and, if this commentary is deemed valuable, this collection will approach future guideline releases in a similar format.

Less May Indeed Be More
By Larry S. Dean, MD, FACC, MSCAI
University of Washington School of Medicine
Seattle, WA

The 2017 expert consensus decision pathway on TAVR recently published in the Journal of the American College of Cardiology is a welcome addition to this body of literature, offering an update on the current state of TAVR for the treatment of severe aortic stenosis (AS). As stated in the document, "expert consensus documents are intended to provide guidance for clinicians in areas where evidence may be limited, new and evolving, or lack sufficient data to fully inform clinical decision-making." TAVR clearly meets the intent of such a document, and the document does provide guidance to the field. The authors should be commended for their work, which discusses and distills a very large body of recent literature.

That said, the document seems too expansive for the cardiovascular practitioner not directly involved in TAVR or the primary care physician seeing such patients because much of the document is focused on descriptions of valve types, procedural details, anesthesia approaches, and other nuance, which distracts from many of the concise pathway outlines. Of course the degree of detail depends on the intended audience, but it could be argued that those who perform these procedures and have established heart teams do not need the detail provided. One could also argue that the target audience wasn't addressed or that the document was produced to speak to a larger audience, which unfortunately has the potential to dilute the message and make it a less useful to the practitioner, whether he or she is involved directly with the procedure or seeing such patients for initial evaluation.

Finally, the notion that guidelines with subsequent expert consensus documents can functionally bridge knowledge gaps in clinical care, especially in rapidly moving fields like structural heart disease intervention, should perhaps be rethought as well. Although it is true that guidelines take much longer to produce than expert consensus documents, the time needed to produce documents of this breadth is not trivial. It has only been a few years since last examined, but it may be time to relook at the process of generating such documents with the purpose of making them even more timely and therefore more reflective of current practice, which should make them of greater use to the practitioner caring for patients with similar diseases. This is especially true given the rapid dissemination of information via electronic means and is of keen importance considering the vast array of information available on the web that, rightly or wrongly, clinicians and patients use to assess approaches to care. Fully moving into the digital age by embracing its ability to present complex content in ways not possible with static typeface and leveraging content to the learner's advantage seems a logical next step. Although somewhat nascent, the work being done by the MAGIC group¹ could help inform the future of such documents.

Some Difficult Decisions Overlooked
By Ted Feldman, MD, MSCAI FACC FESC
Evanston Hospital
Evanston, IL

This 2017 ACC expert consensus decision pathway for TAVR has the "goal of expert consensus… to develop clinical policy based on… opinion in areas which important clinical decisions are not adequately addressed by the available existing trials" with brief decision pathways and key points. This task, to fill the gap between guidelines and real practice in a rapidly developing field, is daunting. This review provides a high-level overview and may be of greatest utility to readers involved with new or less-experienced TAVR programs.

There are several practical points that are not covered by this decision pathway. Difficult decisions are part of regular TAVR heart team discussion and encompass risk stratification, computed tomography (CT) assessment, vascular access, and minimizing intraprocedural risk.

One current problem in risk assessment is The Society of Thoracic Surgeons (STS) Predicted Risk of Mortality (PROM) score between low and intermediate risk. Although most of the literature classifies intermediate risk as STS PROM >4%, the recent Food and Drug Administration approval for the SAPIEN 3 (Edwards Lifesciences Inc.; Irvine, California) valve for intermediate risk references STS PROM >3%.² The low-risk TAVR trials being conducted by both Edwards and Medtronic thus face a gap from STS PROM 3% to STS PROM 4%, and the inclusion of patients in low-risk trials versus treatment in the commercial pathway requires judgment by the heart team.^3,4 Informed patients may resist a discussion of surgical aortic valve replacement as an alternative if they know their own STS risk and understand the current approval language for intermediate risk. Trial experience is helpful for risk assessment. Age >90 years has become a descriptor of high risk in some trials.

CT assessment of the aortic valve complex and to define catheter access has become standard. Several software packages specifically designed for TAVR are now available for annulus and vascular image analysis. It is important for TAVR operators to be able to use these software programs independently because readings by imaging specialists who are not proceduralists often overlook important nuances. Annulus measurements are often on the borderline between valve sizes, and repeated measurements are necessary to make a best choice of valve size and to understand how to manage decisions during and immediately after valve deployment.⁵

CT analysis has also had an important impact on planning vascular access. In addition to the basic assessment of access vessel dimensions, calcification, and tortuosity, the location of the femoral bifurcations relative to the female head can be seen. This allows femoral puncture with little or no X-ray contrast, which is important because depressed renal function is common in the TAVR population. Contrast savings may also by realized by using transthoracic echocardiography for assessment of paravalvular leak in TAVR procedures with conscious sedation, obviating the need for contrast aortography post valve deployment.

Bicuspid etiology for AS is an increasingly frequent issue as lower-risk patients are being evaluated. Bicuspid etiology represents an off-label indication, but many such patients have been treated in practice and in trials. The so-called "functional" bicuspid, highly calcified anatomy has most frequently been treated. The incidence of paravalvular leak and aortic root rupture are high for bicuspid AS, and the sizing algorithm is different. Better results in this subset are being seen with some next-generation TAVR platforms.⁶

Missing Guidance on Institutional and Heart Team Requirements
By Zachary Gertz, MD, FACC
Medical College of Virginia at VCU Health
Richmond, VA

The ACC's expert consensus decision pathway for TAVR is a helpful document for clinicians considering TAVR for their patients. The many considerations identified during patient evaluation, although probably too thorough to be applied uniformly, should prove very useful when physicians work up individual patients. Similarly, the procedural guidance provides a useful reference for physicians performing the procedure. The authors rightly point out what is clearly known and what areas require further research. Given the scope of the document, there is little to quibble with from a technical standpoint. However, the authors have chosen not to address other considerations regarding the TAVR procedure, with major implications.

As with many other procedures, there is a strong correlation between procedural volume and outcomes. Registry data from both national and international registries show that increasing case volume is clearly associated with reductions in death and other major cardiovascular complications. Data presented at the ACC 2016 Scientific Sessions showed that complications continued to decline up through the 400th case at TAVR centers. The Centers for Medicare & Medicaid Services (CMS) coverage decision for TAVR mentions a requirement to perform at least 20 cases per year, but at this low threshold an institution could take 20 years to reach the level of safety and success that higher-volume institutions reach within a few years. It is unknown whether the authors believe that a center's volume should be considered in determining whether a program is started or continues.

Similarly, the authors are silent on other heart team requirements dictated by CMS. The coverage decision requires two cardiac surgeons to independently evaluate each patient. Given the evidence of benefit for TAVR over surgical aortic valve replacement, do the authors consider this a valid requirement? If a patient clearly has severe symptomatic AS and an STS PROM >4%, is the opinion of the surgeon more valid than that of the cardiologist? This "Two-Surgeon Rule" does not exist for stenting in coronary disease or even for transcatheter mitral valve repair with the MitraClip (Abbott Vascular; Santa Clara, CA), a procedure that requires a patient be deemed "prohibitive" surgical risk. Furthermore, given the increasingly percutaneous nature of the procedure, is one cardiologist sufficient?

With ongoing studies of the use of TAVR in low-risk patients, the procedure is only likely to spread. And although a checklist of useful pre-, peri-, and post-procedure considerations is necessary and useful, guidance on institutional and heart team requirements may prove equally important in the years to come.

An Up-To-Date Comprehensive Resource
By Howard C. Herrmann, MD, FACC
Hospital of the University of Pennsylvania
Philadelphia, PA

This ACC expert consensus document was developed to provide clinicians with practical information, point-of-care checklists, and decision algorithms for the use of TAVR in adults with severe, symptomatic valvular AS. A unique aspect of this document is the publication of checklists for four aspects of care, including pre-procedure assessment of the severity of AS, the use of imaging modalities, the TAVR procedure, and post-procedure care. As with many valvular disease documents, emphasis was placed on individualized risk assessment, incorporating an integrated approach with frailty, co-morbidities, and the multidisciplinary heart team shared decision-making.⁷

Some important aspects of current TAVR care are not addressed, including how to practically incorporate frailty and co-morbidities into decision-making; how to deal with leaflet thrombosis,⁸ paravalvular regurgitation, and new conduction disease; and how long-term durability concerns might influence the choice of therapy. Although practitioners of TAVR may find this document too general and primary care doctors may find it too detailed, it is an up-to-date comprehensive resource of TAVR information and can serve as a framework for incorporation of future data.

Excellent Procedural Guidelines: Patient Selection Remains an Increasingly Complex Activity
By Michael J. Lim, MD, FACC
St. Louis University Medical Center
Saint Louis, MO

The ACC recently released an expert consensus decision pathway for TAVR.⁹ Although not a separate "guideline" for this relatively new procedure, it remains consistent with the most recent update of the Valvular Heart Disease Guidelines from 2014.7 In reading this document, the first question that comes to mind is "why do we need another document?" The authors state that their purpose is to "develop clinical policy based on expert opinion in areas which important clinical decisions are not adequately addressed by the available clinical trials." As such, it is clear that TAVR has grown tremendously and become much more frequently performed; therefore, the concept of addressing important clinical decisions is certainly justified. However, TAVR growth has been largely directly dependent upon the key clinical trials mainly due to the direct link that these trials have to CMS reimbursement for the procedure in a way that few other new cardiovascular technologies have ever been linked. Thus, the purported lack of available clinical trials concept may not be as large of a need as other areas (e.g., treatment of mitral regurgitation).

The document presents the reader with multiple tables and algorithms outlining critical steps in the process of care for a patient with AS, key issues surrounding pre-procedural work-up and planning, as well as procedural steps and potential complications. These tables and figures are the real value of this document because they nicely and succinctly summarize the process for all health-care providers to understand, from the valve centers that can use these to further refine their approach and assure that it fits the current standard to the non-implanting physicians who can better understand the issues that surround the complex work-up and decision-making involved in this "new" procedure. A critical supposition for these, however, is the fact that these represent the "ideal" patient with degenerative calcific AS who is able to undergo an extensive outpatient evaluation. Issues with far less robust clinical trial data, including patients with bicuspid AS, prosthetic valve stenosis, or multivalvular disease do not fall within many of these tables and are only mentioned briefly within the text.

A key area in the care of TAVR patients remains the heart team discussion. Although there has never been a disagreement to this standard, there is surprisingly very little that is specific and standard regarding what this really involves or entails, taking on the form of everything from a formal classroom presentation of patients very similar to a cancer center tumor board to a "virtual discussion" among the cardiac surgeon, interventional cardiologist, patient, and referring physician as a greater part of routine clinical practice. The document falls short of providing any detail or guidance as to best practice despite the fact that this is an area in which clinical trials do not provide much insight. Furthermore, along the same lines, the concept and definitions of "futility" and "frailty" are also discussed because they remain critical to the patient selection for TAVR. Although there is a rather comprehensive list of frailty objective scores that can be calculated, there remains little specific guidance to the heart team as to "best practice."

Finally, outside of the algorithms and checklists provided, the document excellently summarizes the key elements that differentiate low, intermediate, high, and prohibitive risk. Because these risk elements remain keys to patient selection and institutional reimbursement, the succinct summary presented remains highly clinically relevant but consistent with the 2014 Valvular Heart Disease Guidelines.

References

1. BMJ Rapidrecs for Transcatheter aortic valve implantation versus surgical aortic valve replacement for severe aortic stenosis in low-intermediate risk patients (MAGIC Group website). October 1, 2016. Available at: https://www.magicapp.org/app#/guideline/1294. Accessed January 30, 2017.
2. FDA approves expanded indication for two transcatheter heart valves for patients at intermediate risk for death or complications associated with open-heart surgery (FDA website). August 18, 2016. Available at: http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm517281.htm. Accessed January 30, 2017.
3. Medtronic Transcatheter Aortic Valve Replacement in Low Risk Patients (ClinicalTrials.gov website). 2017. Available at: https://clinicaltrials.gov/ct2/show/NCT02701283. Accessed January 30, 2017.
4. The PARTNER 3 - Trial - The Safety and Effectiveness of the SAPIEN 3 Transcatheter Heart Valve in Low Risk Patients With Aortic Stenosis (P3) (ClinicalTrials.gov website). 2017. Available at: https://clinicaltrials.gov/ct2/show/NCT02675114. Accessed January 30, 2017.
5. Khalique OK, Hamid NB, White JM, et al. Impact of Methodologic Differences in Three-Dimensional Echocardiographic Measurements of the Aortic Annulus Compared with Computed Tomographic Angiography Before Transcatheter Aortic Valve Replacement. J Am Soc Echocardiogr 2016 Dec 6 [Epub ahead of print].
6. Yoon SH, Lefèvre T, Ahn JM, et al. Transcatheter Aortic Valve Replacement With Early- and New-Generation Devices in Bicuspid Aortic Valve Stenosis. J Am Coll Cardiol 2016;68:1195-205.
7. Nishimura RA, Otto CM, Bonow RO, et al. 2014 AHA/ACC guideline for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol 2014;63:e57-e185.
8. Dangas GD, Weitz JI, Giustino G, Makkar R, Mehran R. Prosthetic Heart Valve Thrombosis. J Am Coll Cardiol 2016;68:2670-89.
9. Otto CM, Kumbhani DJ, Alexander KP, et al. 2017 ACC Expert Consensus Decision Pathway for Transcatheter Aortic Valve Replacement in the Management of Adults With Aortic Stenosis: A Report of the American College of Cardiology Task Force on Clinical Expert Consensus Documents. J Am Coll Cardiol 2017 Jan 4 [Epub ahead of print].

Keywords: Algorithms, Anesthesia, Aortic Valve, Aortic Valve Stenosis, Aortography, Conscious Sedation, Constriction, Pathologic, Coronary Disease, Echocardiography, Mitral Valve, Mitral Valve Insufficiency, Physicians, Primary Care, Risk Assessment, Thrombosis, Tomography, Tomography, X-Ray Computed, Transcatheter Aortic Valve Replacement, X-Rays, Angiography

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