Transcatheter Aortic Valve Implantation (TAVI)

aortic valve
Aortic Valve. SCIEPRO/Getty Images

Transcatheter aortic valve implantation (TAVI) is a 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 new procedure, it is approved in the United States and the European Union for the treatment of certain high-risk patients with severe aortic stenosis.

In aortic stenosis, the aortic valve becomes partially obstructed, which forces the heart to work much harder to pump blood to the body. Eventually, untreated aortic stenosis leads to edema, dyspnea, heart failure, and (often) death.

While symptoms can be managed for a time using medical therapy for heart failure, no medicine can relieve the mechanical obstruction of aortic stenosis. The only really effective treatment is to surgically replace the diseased aortic valve with an artificial valve. Unfortunately, the standard method of aortic valve replacement requires a major open-heart surgical procedure, and, especially in the elderly patients who most typically develop aortic stenosis, it is a procedure that carries significant risk.

The TAVI procedure has been developed as a potentially lower-risk approach to replacing the aortic valve.

How Are TAVI Devices Inserted?

Two TAVI devices are FDA approved in the United States - the Edwards SAPIEN valve, and the Medtronic CoreValve). Both devices work similarly: The artificial valve is attached to a collapsed wire frame, which is attached to a 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 by blowing up a balloon. This allows the artificial valve to open up, 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 improved 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. TAVI-related strokes are embolic strokes.

A later 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 often-unavoidable trauma caused by inserting the sizable and relatively rigid valve mechanism into often-diseased arteries. 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 TAVI

At present, TAVI is approved by the FDA only for patients with severe aortic stenosis who are deemed to be at extremely high risk for standard, open-chest aortic valve replacement.

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.

Sources:

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.

Nishimura RA, Otto CM, Bonow RO, et al. 2014 AHA/ACC guideline for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol 2014; 63:e57.

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