Aortic valve stenosis (AVS) involves thickening and progressive immobility of the aortic valve. This restricts blood flow from the left ventricle to the aorta. AVS most frequently involves an anatomically normal three-leaflet aortic valve and is less frequently due to either a congenitally abnormal bicuspid aortic valve or to the late consequence of rheumatic fever. Since AVS predominantly afflicts the elderly, its prevalence is increasing. In fact, AVS currently ranks among the top five Medicare cardiac diagnoses. AVS is slowly progressive and has a long asymptomatic period. However, the prognosis turns grim once the cardinal triad of symptoms occur, including:
Progressive shortness of breath.
Anginal-like chest discomfort.
Lightheaded or fainting spells.
In such cases, the average survival without aortic valve replacement (AVR) is between 1 and 2 years.
Improved Surgical Treatments for AVS
Until recently, the only treatment for AVS has been surgical AVR. Unfortunately, the morbidity and mortality related to this open-heart surgery in elderly patients can be prohibitive and has prompted the development of less invasive non-surgical, catheter-based technologies to replace the aortic valve. Recently, the FDA has approved a new balloon-expandable stent-mounted bovine pericardial valve (SAPIEN, Edwards Life Sciences) for the treatment of symptomatic severe AVS in patients who are considered to be at either high or prohibitive risk for surgical AVR. The valve represents a significant advance in that it’s delivered via femoral arterial access and does not require cardiopulmonary bypass.
“There is hope that TAVR will continue to emerge as a viable alternative to surgical AVR in patients at high surgical risk.”
In the Placement of Aortic Transcatheter Valves (PARTNER) trial, transcatheter AVR (TAVR) demonstrated a highly significant improvement in survival through 2 years followup when compared with standard care in patients who were not deemed candidates for surgical AVR. Further study with the balloon-expandable stent-mounted bovine pericardial valve demonstrated that TAVR was non-inferior to surgical AVR with respect to mortality and other key clinical endpoints through 2 years follow-up in patients at high risk for surgical AVR.
More Data Coming on TAVR Devices
The PARTNER II trial has been launched to evaluate the relative safety and efficacy of next generation TAVR devices. These devices offer physicians two key potential advantages: they are smaller caliber, and they appear to be easier to use. In addition, they can be delivered via a small incision below the left breast (apical access) or by making an incision adjacent to or via limited sternal incision (direct aortic access). The PARTNER II trial will provide more data regarding the safety and efficacy of these next generation devices that may support FDA approval and expansion of current indications for their use to include moderate- to high-risk surgical AVR candidates as well as apical and direct aortic access.
The initial results of the PARTNER II trial are expected in 2013. In early clinical trials, TAVR approaches have been associated with a more rapid recovery when compared with surgical AVR. The major complications associated with TAVR have been stroke and vascular access related. These issues are being actively investigated with respect to the use of embolic protection devices, large vessel percutaneous closure devices, and smaller profile vascular sheaths. As research continues, there is hope that TAVR will continue to emerge as a viable alternative to surgical AVR in patients at high surgical risk. In the future, it’s possible that TAVR will become the procedure of choice for high-risk surgical candidates.
Readings & Resources (click to view)
Leon MB, Smith CR, Mack M, et al. Transcatheter aortic-valve implantation for aortic stenosis in patients who cannot undergo surgery. N Engl J Med. 2010;363:1597-1607.
Makkar RR, Fontana GP IIb/IIIa, Jilaihawi H, et al. Transcatheter aortic-valve replacement for inoperable severe aortic stenosis. N Engl J Med. 2012;366:1696-1704.
Kodali SK, Williams MR, Smith CR, et al. Two-year outcomes after transcatheter or surgical aortic-valve replacement. N Engl J Med. 2012;366:1686-1695.
Reynolds MR, Magnuson EA, Lei Y, et al. Health-related quality of life after transcatheter aortic valve replacement in inoperable patients with severe aortic stenosis. Circulation. 2011;124:1964-1672.
Webb JG, Wood DA. Current status of transcatheter aortic valve replacement. J Am Coll Cardiol. 2012;60:483-492.
Humphries KH, Toggweiler S, Rodes-Cabau J, et al. Sex differences in mortality after transcatheter aortic valve replacement for severe aortic stenosis. J Am Coll Cardiol. 2012 Jul 10 [Epub ahead of print].