What Will You Need to Start a TAVR Program?
- Volume 20 - Issue 7 - July 2012
- Posted on: 7/3/12
- 0 Comments
- 8528 reads
In early November, the U.S. Food and Drug Administration approved the first transcatheter valve for the treatment of inoperable aortic stenosis, the Sapien valve (Edwards Lifesciences). Clearly, this is one of the most exciting advances in interventional cardiology in the last decade. The procedure is called the transaortic valve replacement (TAVR) or implant (TAVI) and is usually done percutaneously via the femoral arteries or may be performed by a transapical surgical approach. The percutaneous insertion of an aortic valve to replace open-heart surgery is, of course, highly appealing to anyone contemplating open-heart surgery. The enthusiasm surrounding TAVR continues, especially with recent numerous presentations and publications demonstrating the effectiveness of the procedure and the clinical benefits seen in the first series of treated patients. I cannot wait for TAVR to come to my hospital and I am sure many of you are eager as well. However, while I have these hopes, I am not holding my breath, since my hospital system and current staffing limit us from becoming a “first-round draft pick” for a TAVR program site, with the requirements as described below.
The TAVR numbers
It is important to realize that TAVR is not the same as percutaneous coronary intervention (PCI) and will not sweep into every cath lab in the country the same way stenting swept across the nation and the world. There are major differences in operators’ teams, techniques, and facilities that must be noted. Let’s start with the procedure numbers. There are about 1,000,000 coronary angiograms/year with 400,000 stent procedures/year in the United States. There are 100,000 aortic valve surgeries/year, with about 15,000 suitable for TAVR. We should recognize that there are many more hospitals (and operators) wishing to do the procedure than the small number of patients with aortic stenosis will permit. TAVR will have to be centralized to maintain the necessary operator experience and resources to have good outcomes.
Who should be doing TAVR?
A recently released consensus document from The Society for Cardiovascular Angiography (SCAI), the American Association for Thoracic Surgery (AATS), the American College of Cardiology Foundation (ACCF), and the Society of Thoracic Surgeons (STS), a multi-society expert consensus statement entitled “Operatory and institutional requirements for transcatheter valve repair and replacement: Part 1 TAVR”1 describes the requirements for operators and institutions starting or maintaining a transcatheter valve program. The document focuses only on the transcatheter aortic valve replacement (TAVR) and proposed requirements to “enable institutions and providers to participate responsibly in this new and rapidly evolving field.”
From these recommendations1, “The critical cornerstone for establishing a transcatheter valve program is the formal collaborative effort between interventional cardiologists and cardiac surgeons. This element is essential for establishing a transcatheter valve program. No one individual, group, or specialty possesses all the necessary skills for best patient outcomes.”
The bottom line is that you are going to need a team (and need to play like a team) and as Dr. Tommaso notes, “there are going to be a lot of people around the [cath] table”. A full description of TAVR and its integration into clinical practice is provided in another expert consensus paper on the subject.2 While surgeons do not necessarily have catheter skills, their expertise at vascular access and repair is critical to the success of the procedure at this time. Unique situations will also require surgical expertise such as the transapical valve insertion approach or alternative vascular access such as subclavian arterial catheter introduction.
In addition, physicians involved in TAVR should possess “extensive knowledge of valvular heart disease, hemodynamics, appropriate diagnostics, and optimal medical therapy, the application and outcome of invasive therapies, and procedural and perioperative care.” While not specifically described, there should be a principal team leader or co-leaders who take ownership of the program and guide the institution in making the resources available. Table 1 summarizes operator and hospital experience requirements.
What does the hospital and cath lab need to do TAVR?
The recommendations also indicate that a TAVR hospital should have an active valvular heart disease program with at least two surgeons experienced in valvular surgery.1,2 The hospital should have a high quality cardiac catheterization laboratory or hybrid operating room (OR)/catheterization lab, and high quality noninvasive cardiovascular imaging, including echocardiography, vascular imaging, and computed tomography. The post-procedure intensive care should be similar to that of the post-operative care units for open-heart surgery.
The cardiac catheterization laboratory alone may be a suitable implantation site for TAVR. The “2012 American College of Cardiology Foundation/Society for Cardiovascular Angiography and Interventions Expert Consensus Document on Cardiac Catheterization Laboratory Standards Update” describes the specifications for a hybrid cath Lab/OR.3 Though preferable, a hybrid room is not a prerequisite at this time. However, TAVR facilities should plan for a hybrid OR/cath lab equipped with a fixed radiographic imaging system with flat-panel fluoroscopy offering catheterization laboratory-quality imaging. A biplane unit may be advantageous, particularly for complex structural (or congenital) heart disease. The implantation suite must have a sterile environment that meets OR standards.
Noninvasive imaging should have high quality transthoracic and transesophageal echocardiographic (TTE, TEE) capabilities with echocardiographers experienced in valvular heart disease. Access to 3D echocardiography is highly desirable. Since TAVR, at this time, uses large diameter (18-26 French) catheters introduced from the femoral approach, procedural planning will involve a vascular laboratory with specialists capable of performing and interpreting basic and complex vascular studies. Similarly, a critical part of the procedural planning also involves assessment not only of peripheral and coronary vasculature, but also the aorta, aortic root and aortic valve ring. High quality computed tomography (CT) imaging and CT specialists who can acquire and interpret cardiac and vascular CT studies are essential.
How many procedures are needed to qualify to start a TAVR program?
Since TAVR is so new, there are no specific guidelines on how many procedures are needed before a clinical center/operator becomes proficient in TAVR. However, since this is a highly complex procedure, TAVR should be performed only in centers that currently and routinely perform large volumes of surgical aortic valve operations (See Table 1).
What kind of screening for TAVR patients should be performed?
Current recommendations4 include patient-related selection criteria with one or more of the criteria listed in Table 2. Valve severity is assessed by echocardiography and in some cases, must be confirmed by direct hemodynamic measurements. Hemodynamic evaluation will be particularly valuable in patients with low-gradient, low-flow aortic stenosis common in patients with low ejection fraction.
Since most TAVR candidates are elderly with multiple coronary artery disease (CAD) risk factors, CAD evaluation is mandatory. This evaluation includes coronary angiography and in some patients, multislice coronary CT (MSCT). MSCT is helpful, especially in patients with high-risk features during the pre-assessment process (e.g. renal failure, co-morbidities of lungs or other medical problems.)
After clinical, valvular severity, and CAD screening, further information is needed for the planning of TAVR valve type and size to be used, based on the assessment of the aortic annulus. This evaluation is critical since a valve > 27 mm or < 18 mm will be unsuitable for any TAVR. Assessment of the aortic root is performed with echocardiographic or CT imaging. It is generally believed that the assessment of the size of the aortic annulus by MSCT, TEE, and transthoracic echo is largest in the following order of magnitude: MSCT > TEE > TTE.
There are specific aortic anatomic features that differentiate which valve type can be used. An annulus between 23 and 26 mm would favor a CoreValve (Medtronic), and a size between 23 and 25 mm might favor the next-generation Sapien XT (Edwards Lifesciences).4
After aortic root assessment, evaluation of the peripheral (femoral, iliac, abdominal aorta) arteries is needed, since the type of device and the delivery method is dependent on large and relatively pliant vessels. Peripheral angiography gives an idea of vessel tortuosity and the degree of vascular calcification. Contrast-enhanced MSCT provides better vessel imaging and adds the cross-sectional vessel anatomy, often with 3D reconstruction facilitating procedural planning. Non-contrast enhanced MSCT can be used as an alternative imaging modality in patients with chronic kidney disease or contrast allergy. Magnetic resonance imaging (MRI) is most informative when performed with gadolinium, but should be used cautiously, since gadolinium nephrotoxicity is similar to that of regular contrast agents.
Contraindications to TAVR
There will be many patients in whom TAVR cannot be performed, because of clinical, functional, or anatomic conditions. In these cases, either surgery or conservative therapy should be considered. Currently, most contraindications are the same exclusion criteria used in the initial TAVR trials and the PARTNER (Placement of AoRTic TraNscathetER Valve) randomized trial. These contraindications are listed in Table 3.