Indications

Aortic valve replacement (AVR) is indicated in all symptomatic patients with severe AS (2006 ACC/AHA Valvular Heart Disease Guidelines, Class I recommendation, Level of Evidence: B). Despite this recommendation, a significant number of elderly patients (up to one third) do not undergo AVR because of comorbidities, including advanced age and the associated increased morbidity and mortality with surgery. Additionally, many elderly patients that are suitable surgical candidates will refuse surgery because they perceive themselves as “too old” to survive open AVR. Transcatheter aortic valve replacement (TAVR) is a promising alternative to surgical AVR in those patients deemed high risk for surgery (Table 17-2).

^{Table 17-2} Indications for TAVR

Transcatheter Valves

There are two catheter-implantable valves commercially available overseas. They are the balloon-expandable Edwards SAPIEN valve and the self-expanding Medtronic CoreValve (Fig. 17-1). The Edwards SAPIEN valve was studied in the PARTNER trial, which completed randomized enrollment in fall 2009. The Medtronic CoreValve randomized trial started enrollment in December 2010. The initial international experience and the results of PARTNER cohort A and B suggest that outcomes compare favorably with conventional valve surgery in selected patients. In November 2011, the Edwards SAPIEN valve was FDA approved and became commercially available in the United States for PARTNER cohort B (inoperable) patients.

Figure 17-1 Left, Photograph of the Edwards SAPIEN transcatheter heart valve, which consists of a stainless steel stent with bovine pericardial tissue leaflets sewn onto the balloon-expandable stent. Right, Photograph of the Medtronic CoreValve transcatheter aortic valve system, which consists of a nitinol-based frame with porcine pericardial tissue leaflets affixed to the self-expanding stent.

Patient Selection

A thorough clinical evaluation of the patient is performed with special attention to vascular access and potential sources of complications. The evaluation includes history and physical examination, laboratories, chest radiograph, electrocardiogram, transthoracic echocardiography, pulmonary function testing, carotid ultrasound, right and left cardiac catheterization, coronary angiography, and computed tomography angiography (CTA) of the chest, abdomen, and pelvis. The CTA is performed to assess aortoiliac patency, dimensions, and tortuosity. Occlusive peripheral arterial disease, small vessels (<7 mm), and excessive tortuosity are characteristics that would preclude a transfemoral approach since the delivery systems for the SAPIEN valve are currently 22F and 24F sheaths for the 23-mm and the 26-mm valves, respectively. The second-generation Edwards valve, SAPIEN XT, is comprised of a cobalt chromium frame and allows for an 18F delivery system. Patients with unfavorable aortoiliac characteristics can have TAVR via a transapical approach with the Edwards valve. The advantage of the CoreValve system is the smaller 18F profile of its delivery system, but CoreValve can be delivered only in a retrograde fashion. If femoral access is not available, CoreValve may be delivered from subclavian and carotid approaches.

Risk of mortality is calculated using a validated scoring method such as the EuroScore or Society of Thoracic Surgeons (STS) score. Online calculators are available for both scores. These scores take patient characteristics (e.g., age, acuity, pulmonary function, renal function, neurologic function, type of surgery) to calculate risk of mortality and morbidity. An STS score of >10% mortality was an inclusion criterion in the PARTNER trial.