Percutaneous treatment of aortic valve stenosis
ABSTRACTAortic valve replacement via open heart surgery, although still the standard treatment for severe symptomatic aortic valve stenosis, is not an option for many patients with severe symptoms, and these patients are often left with suboptimal strategies such as medical management or balloon valvuloplasty. But over the last 5 years improvements in percutaneous approaches to implantation of prosthetic aortic valves have made it a potential therapeutic option for these patients. Technical and device issues are being refined, and percutaneous aortic valve replacement is showing promise in ongoing clinical trials.
KEY POINTS
- Aortic stenosis is the most common valvular condition, affecting 3% of the general population; its incidence and prevalence are increasing as the population ages.
- Many patients with severe aortic valve stenosis are considered too high-risk for standard surgical valve replacement but may be candidates for percutaneous valve replacement.
- Of the approaches now undergoing refinement, the most promising is retrograde (ie, femoral arterial) placement of the Edwards SAPIEN valve or the CoreValve.
- The technology is still evolving, and the learning curve is substantial, yet cautious enthusiasm about percutaneous aortic valve replacement is justified.
PUTTING THE DATA IN PERSPECTIVE
As noted in this review, a number of factors make a strong case for timely aortic valve replacement: the aging population, the increase in incidence and prevalence of aortic stenosis,1,3,4,27,40 the multiple comorbidities in older patients, and the eventually aggressive natural course of aortic stenosis.1,3,4,27,40–43 Yet current standards dictate not to proceed with standard surgical aortic valve replacement in patients who are truly asymptomatic and who have normal left ventricular systolic function,1,40 mainly because the risks of surgical valve replacement outweigh the benefits in this population.1,40 Aortic valve surgery carries a risk of early death of 15% for patients ages 80 to 84 and of 18% for patients age 85.3,9,10,12,43–45
These figures seem high when compared with death rates of 12% in recent studies of percutaneous valve replacement in similar patients.11,23,30,33 The rates become lower as the learning curve improves.11,21,23,27,30,33 Thus, as the design of aortic valve prostheses and the techniques to implant them are refined and tested for safety, the risk-benefit balance may change in favor of earlier intervention in aortic stenosis with a percutaneous approach.11,21,27,46 Some experts believe that in 10 years 10% to 30% of patients undergoing conventional valve replacement will be candidates for a percutaneous approach.
Of the techniques used to date, the retrograde approach seems most amenable to widespread acceptance, given its inherent advantage of being faster and easier.11,21,30 Limitations with the retrograde approach seen in earlier trials—challenges and complications associated with large-bore arterial vascular access, difficulty traversing the aortic arch with bulky devices, and the inability to cross the stenotic aortic valve to deploy the prosthesis even after balloon valvuloplasty11,21,30—are correctable with refinements in the devices and in technique.
New types of prosthetic aortic valves entering early human studies are improving on current devices, for example, by using collapsible, inflatable valve frames for retrievability before final deployment.
Surgical aortic valve replacement remains the gold standard treatment for patients with symptomatic aortic stenosis. And while studies of percutaneous aortic valve replacement show great promise for this less-invasive treat-men, enthusiasm about percutaneous aortic valve replacement should be tempered by an awareness of persistent limitations of this approach, such as vascular and mechanical complications and operator inexperience, which still need attention.
