Transcatheter aortic valve implantation (TAVI) is a new, minimally invasive approach to replacing diseased aortic valves. In TAVI, an artificial aortic valve is implanted by means of a sophisticated catheterization procedure. While TAVI is still considered a largely investigational procedure, it is approved in the United States and the European Union for the treatment of certain high-risk patients with severe aortic stenosis.
How Are TAVI Devices Inserted?Two different companies are developing TAVI devices - Edwards (the SAPIEN valve) and Medtronic (the CoreValve). Both devices work similarly: The artificial valve is attached to a collapsed wire frame, which in turn is attached to the catheter. The catheter is inserted into a blood vessel (usually, the femoral artery near the groin), and is advanced to the area of the aortic valve. When in position, the wire frame is expanded, allowing the artificial valve to open and to begin functioning.
What Are The Results With TAVI?Early studies with TAVI were limited to patients with severe aortic stenosis who were deemed too sick to have the open-heart surgery necessary for "standard" aortic valve replacement.
In these very sick patients, those who were randomized to receive TAVI had a significantly reduced mortality rate and significantly reduced symptoms after one year, compared to those who received medical therapy alone. However, patients randomized to TAVI had a 5% incidence of major stroke, compared to only 1% in medically treated patients.
A more recent study compared TAVI to standard aortic valve replacement in 690 patients with severe aortic stenosis. The mortality rates, stroke rates, and symptom improvement were similar at one year in both groups. Those treated with TAVI had more major complications to the blood vessels, and those treated with open-heart surgery had more bleeding complications, and more post-operative atrial fibrillation.
What Are The Complications With TAVI?While TAVI is a minimally-invasive procedure, it still carries significant risks. The two most frequent and serious risks are serious damage to the major blood vessels, and stroke. Both of these complications are due to trauma caused by inserting the sizable and relatively rigid catheter-valve mechanism into often-diseased arteries, and manipulating this mechanism into its proper position. As a result of such complications, the risk of death with TAVI is around 6% within 30 days of the procedure.
Recent evidence suggests there is a steep "learning curve" associated with performing the TAVI procedure. In particular, the risk of serious complications seems to be highest during the first 30 TAVI procedures a doctor performs.
The companies that are developing TAVI devices continue to work on improving the technology, in an attempt to reduce the risks associated with their use. For the present, however, the risks remain substantial.
Current State of TAVIAt present, TAVI (the SAPIEN device only, at this point) is approved by the FDA only for patients whose severe aortic stenosis is deemed to be "inoperable." That is, it is approved for patients who are judged to be unlikely to survive open-heart surgery without major complications, and whose only other choice is for medical therapy - which is notoriously ineffective in treating severe aortic stenosis.
If TAVI is recommended for either you or a loved one, you should make sure the procedure is going to be performed by a doctor who has had substantial experience with this technique.
In the future it is likely that TAVI will become an approved alternative to open-heart surgery for at least some patients with significant aortic stenosis who are not yet "too sick" for the standard open-heart surgery. But given the complications that, so far, are associated with TAVI, we are not there yet.
Zajarias A, Cribier AG. Outcomes and safety of percutaneous aortic valve replacement. J Am Coll Cardiol 2009; 53:1829.
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.
Smith CR, Leon MB, Mack MJ, et al. Transcatheter versus surgical aortic-valve replacement in high-risk patients. N Engl J Med 2011; 364:2187.